Contactor coil: 50 Hz vs. 60 Hz
DaveC
for 50 Hz only.
If I install it in N. America, what's the implication? Is the hold-in
magnetism less than if it were 60 Hz? Just noisy?
Please don't ask or suggest other sources. This is a very specific device and
I've not been able to locate other than this.
Thanks,
Dave
Rich Grise
Plug one into 60 Hz and find out what happens. It will probably work just
fine. The Mfr only rated it for 50 because they weren't expecting
international sales.
Are you allowed to tell us why it has to be such a narrow menu of choices?
Thanks,
Rich
Andrew Gabriel
DaveC <inv...@invalid.net> writes:
> I may be able to obtain a very small 2-pole 240 vac contactor I need rated
> for 50 Hz only.
>
> If I install it in N. America, what's the implication? Is the hold-in
> magnetism less than if it were 60 Hz? Just noisy?
Yes, the hold-in force will be proportionally less. If the
coil impedance was due entirely to the inductance, it would
be 50/60ths of the force. However, part of the current limiting
is done by the coil resistance, and that won't change so the
reduction in hold-in force will actually be less than this.
The pull-in force before the magnetic core is closed also
depend on the impedance and resistance, but the impedance
will be lower, and thus the pull-in force will be reduced by
even less.
The pull-in force usually has to overcome a faily weak return
spring. The hold-in force has to overcome a stronger contact
pressure spring. Providing both these conditions are still met,
you should be OK. Ideally, you should check that you have a
reasonable working margin by testing the coil at lower
voltage. If you don't, then the contactor might fail to
close properly on minimum supply conditions which could cause
it to burn out.
I would not expect it to be more noisy if it closes properly.
Noise would be an indication that is isn't closing properly.
Of course, you void all waranties and certifications by
operating it outside of it's specified ratings. The
manufacturers advice should be sought, but unless you are
buying lots of them, they probably won't commit other than
to say it's at your own risk.
--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]
petrus bitbyter
"DaveC" <inv...@invalid.net> schreef in bericht
news:0001HW.CA807E14...@news.eternal-september.org...
As we have very limited information about this device and its usage, I can
only suggest two possible solutions:
- The easy one: Just try it out.
- Build a piece of electronics that converts your 60Hz to 50Hz.
Dimensions of that electronics depend on the required current.
petrsu bitbyter
Spehro Pefhany
<snip>
A side effect of reduced holding force can be that it is more
sensitive to opening due to external vibration in the wrong axis (and
especially so when the input voltage is on the low side). That could
cause malfunction of whatever it's connected to and premature failure
of the contactor. This might not be so easy to test without a shaker
table etc., but it should be considered if the operating conditions
involve vibration (including vibration from another nearby contactor).
Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
sp...@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
John Fields
---
Not knowing the specifics about the coil makes predicting what will
happen at 60Hz difficult.
However, assuming that the inductive reactance and resistance of the
coil will remain constant at 50 and 60Hz means that the impedance of
the coil at 60Hz will be 1.2 times (60Hz/50Hz) what it is at 50Hz.
Consequently, the current in the coil at 60Hz will be about 83% of
what it is at 50Hz.
If that turns out to be a problem, a higher drive voltage could be
used in order to increase the current, namely 1.2 times 240V; 288V.
That could easily be accomplished using a transformer to boost the
240V mains to 288V, like this: (View with a fixed pitch font.)
240AC>-----+--+
| |
oP||S
R||E
I||Co
| |
| +-----> \
| > 288AC TO COIL
240AC>-----+--------> /
The transformer would need a 240V primary, a 48V secondary, and a VA
rating greater than or equal to the contactor coil's rating.
If you go here:
http://www.signaltransformer.com/content/split-bobbin-with-isolation
and select the input as 115/230 and the output as 48, you'll wind up
with 5 transformers rated at from 6 to 400 VA, one of which would
surely work.
Also, many manufacturers make similar transformers, and Digi-Key and
Mouser stock quite a few.
--
JF
NT
> On Sun, 28 Aug 2011 23:21:56 -0700, DaveC <inva...@invalid.net> wrote:
> >I may be able to obtain a very small 2-pole 240 vac contactor I need rated
> >for 50 Hz only.
>
> >If I install it in N. America, what's the implication? Is the hold-in
> >magnetism less than if it were 60 Hz? Just noisy?
>
> >Please don't ask or suggest other sources. This is a very specific device and
> >I've not been able to locate other than this.
>
> Not knowing the specifics about the coil makes predicting what will
> happen at 60Hz difficult.
>
> However, assuming that the inductive reactance and resistance of the
> coil will remain constant at 50 and 60Hz means that the impedance of
> the coil at 60Hz will be 1.2 times (60Hz/50Hz) what it is at 50Hz.
no, only the L component of the impedance will be 1.2 times as high.
> Consequently, the current in the coil at 60Hz will be about 83% of
> what it is at 50Hz.
>
> If that turns out to be a problem, a higher drive voltage could be
> used in order to increase the current, namely 1.2 times 240V; 288V.
>
> That could easily be accomplished using a transformer to boost the
> 240V mains to 288V, like this: (View with a fixed pitch font.)
>
> 240AC>-----+--+
> | |
> oP||S
> R||E
> I||Co
> | |
> | +-----> \
> | > 288AC TO COIL
> 240AC>-----+--------> /
>
> The transformer would need a 240V primary, a 48V secondary, and a VA
> rating greater than or equal to the contactor coil's rating.
these are the kind of 'solutions' that happen when people dont put the
relevant numbers to things.
NT
IME relays pull in at in the region of half rated voltage, and dc
ratings are typically about half the voltage of the ac rating, which
gives an idea of how much current is determined by L and how much by
R. Running your relay on 220v 60Hz it will work fine. Contact closing
speed will be slightly slower. Margin will be reduced, but its only
being reduced from enormous to slightly less enormous, so its a non-
issue except in very unusual situations. The vibration tolerance of
the contacts will be little affected in practice; if your environment
is harsh enough to shake the relay contact open, then you've got
bigger worries than contacts crackling.
If instead you meant you would use it on 110v 60Hz, then dont. But you
could use diodes to get a higher dc voltage and use that.
NT
cbarn...@aol.com
Finally someone comes up with the correct answer.
John Fields
wrote:
>On Aug 29, 3:03 pm, John Fields <jfie...@austininstruments.com> wrote:
>> On Sun, 28 Aug 2011 23:21:56 -0700, DaveC <inva...@invalid.net> wrote:
>> >I may be able to obtain a very small 2-pole 240 vac contactor I need rated
>> >for 50 Hz only.
>>
>> >If I install it in N. America, what's the implication? Is the hold-in
>> >magnetism less than if it were 60 Hz? Just noisy?
>>
>> >Please don't ask or suggest other sources. This is a very specific device and
>> >I've not been able to locate other than this.
>>
>
>> Not knowing the specifics about the coil makes predicting what will
>> happen at 60Hz difficult.
>>
>> However, assuming that the inductive reactance and resistance of the
>> coil will remain constant at 50 and 60Hz means that the impedance of
>> the coil at 60Hz will be 1.2 times (60Hz/50Hz) what it is at 50Hz.
>
>no, only the L component of the impedance will be 1.2 times as high.
---
Well, that's true, so let's just see how far off I was, by using a
real-world example.
I have an old P&B MR5A here with a 240V 50/60Hz coil.
The coil has a resistance of 4800 ohms, and an open inductance of 14.5
henrys, so it has an impedance of 6616 ohms at 50 Hz, and 7270 ohms at
60 Hz.
7270 - 6616 = 1.1, so my error was 1 part in 11, or a little less than
10%
I can live with that.
---
>> Consequently, the current in the coil at 60Hz will be about 83% of
>> what it is at 50Hz.
>>
>> If that turns out to be a problem, a higher drive voltage could be
>> used in order to increase the current, namely 1.2 times 240V; 288V.
>>
>> That could easily be accomplished using a transformer to boost the
>> 240V mains to 288V, like this: (View with a fixed pitch font.)
>>
>> 240AC>-----+--+
>> | |
>> oP||S
>> R||E
>> I||Co
>> | |
>> | +-----> \
>> | > 288AC TO COIL
>> 240AC>-----+--------> /
>>
>> The transformer would need a 240V primary, a 48V secondary, and a VA
>> rating greater than or equal to the contactor coil's rating.
>
>these are the kind of 'solutions' that happen when people dont put the
>relevant numbers to things.
---
Well, your tone is certainly insulting, while the solution remains
valid, but since the voltage into the coil will only be 11% low, the
transformer secondary will only have to supply 26V instead of 48.
In reality, 24V will be fine.
--
JF
Ian Field
"NT" <meow...@care2.com> wrote in message
news:c89fedd0-49ca-49fe...@n12g2000yqh.googlegroups.com...
-----------------------------------------
I'd have accepted the figures as near enough and the transformer with
stacked 48V secondary (wired as an autotransformer) as a convenient way to
do the job.
Even if the figures aren't correct to the nth decimal place, they're
probably within tolerance.
John G
And actually practical!
Not the wild theoretical solutions that are often way way over the head
of the original inquirer or so impractical as to be useless.
--
John G.
NT
> On Mon, 29 Aug 2011 07:28:53 -0700 (PDT), NT <meow2...@care2.com>
> Well, your tone is certainly insulting, while the solution remains
> valid, but since the voltage into the coil will only be 11% low, the
> transformer secondary will only have to supply 26V instead of 48.
>
> In reality, 24V will be fine.
The relay has a voltage margin of around 50%, the mains supply wont
vary more than 10%, so the transformer is of no use.
NT
NT
> On Mon, 29 Aug 2011 07:28:53 -0700 (PDT), NT <meow2...@care2.com>
> Well, your tone is certainly insulting,
yes, my apologies.
NT
cbarn...@aol.com
> cbarn24...@aol.com wrote on 30/08/2011 :
> > Finally someone comes up with the correct answer.
>
> And actually practical!
> Not the wild theoretical solutions that are often way way over the head
> of the original inquirer or so impractical as to be useless.
>
> --
>
Oh they don't do practical here! It's rare for them to get it right
either, this thread is no exception. Some of them even advertise their
place of work! I wonder how much business that has cost them.
Spehro Pefhany
<meow...@care2.com> wrote:
>On Aug 29, 7:21 am, DaveC <inva...@invalid.net> wrote:
>> I may be able to obtain a very small 2-pole 240 vac contactor I need rated
>> for 50 Hz only.
>>
>> If I install it in N. America, what's the implication? Is the hold-in
>> magnetism less than if it were 60 Hz? Just noisy?
>>
>> Please don't ask or suggest other sources. This is a very specific device and
>> I've not been able to locate other than this.
>>
>> Thanks,
>> Dave
>
>IME relays pull in at in the region of half rated voltage, and dc
>ratings are typically about half the voltage of the ac rating, which
>gives an idea of how much current is determined by L and how much by
>R. Running your relay on 220v 60Hz it will work fine. Contact closing
>speed will be slightly slower. Margin will be reduced, but its only
>being reduced from enormous to slightly less enormous, so its a non-
>issue except in very unusual situations.
Well, high ambient temperature and low input voltage. May not be that
unusual. I've seen it happen more than once, particularly in
industrial situations where ambient temperatures can be relatively
high.
I even had to wire an autotransformer into a domestic elevator control
panel because the designer ignored the necessity of allowing for
voltage drop when the drive motor started, which caused chattering of
the AC contactor even in a climate-controlled 22°C environment.
> The vibration tolerance of
>the contacts will be little affected in practice; if your environment
>is harsh enough to shake the relay contact open, then you've got
>bigger worries than contacts crackling.
Since the OP didn't describe the environment.. it may or may not be.
For aircraft work (yes, some is 60Hz) it would be a really good idea
to check. If it's sitting on a subpanel with the control cabinet
bolted to the floor rather than to an OBI punch press, not a big deal.
>If instead you meant you would use it on 110v 60Hz, then dont. But you
>could use diodes to get a higher dc voltage and use that.
>
>
>NT
David Lesher
>I may be able to obtain a very small 2-pole 240 vac contactor I need rated
>for 50 Hz only.
>If I install it in N. America, what's the implication? Is the hold-in
>magnetism less than if it were 60 Hz? Just noisy?
It will be happy. If it were a 60Hz on 50, it would not be as happy.
--
A host is a host from coast to coast.................wb8foz@nrk.com
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433
David Lesher
>I have an old P&B MR5A here with a 240V 50/60Hz coil.
>The coil has a resistance of 4800 ohms, and an open inductance of 14.5
>henrys, so it has an impedance of 6616 ohms at 50 Hz, and 7270 ohms at
>60 Hz.
What's the inductance while closed?
DaveC
> could use diodes to get a higher dc voltage and use that.
> NT
No, there are models for both 115 and 230 in both 50 and 60 Hz flavors. Here
in N. America these are difficult to get so I may have to settle for the 50
Hz models, ordered from Europe. Hence my query.
Thanks,
Dave
DaveC
> Since the OP didn't describe the environment.. it may or may not be.
> For aircraft work (yes, some is 60Hz) it would be a really good idea
> to check. If it's sitting on a subpanel with the control cabinet
> bolted to the floor rather than to an OBI punch press, not a big deal.
> Spehro Pefhany
It's usually in old (60's & 70's) V-belt driven letterpress type printing
presses (think "clamshell" press). No vibration at the controls.
Thanks,
Dave
DaveC
Interesting. Good to know. It's stuff like this I learn here that I wouldn't
otherwise know.
Cheers,
Dave
John Fields
<wb8...@panix.com> wrote:
>John Fields <jfi...@austininstruments.com> writes:
>
>
>>I have an old P&B MR5A here with a 240V 50/60Hz coil.
>
>>The coil has a resistance of 4800 ohms, and an open inductance of 14.5
>>henrys, so it has an impedance of 6616 ohms at 50 Hz, and 7270 ohms at
>>60 Hz.
>
>What's the inductance while closed?
---
16 henries, but that measurement was made by closing the armature
manually.
If there's any real interest I can measure it energized.
--
JF
John Fields
wrote:
>IME relays pull in at in the region of half rated voltage, and dc
>ratings are typically about half the voltage of the ac rating, which
>gives an idea of how much current is determined by L and how much by
>R.
---
IME, most relays (with either AC or DC coils) are guaranteed to pull
in at about 80% of their rated coil voltage, so I'm at a loss trying
to understand what you meant by: "dc ratings are typically about half
of the ac rating."
Can you elaborate, please?
---
>Running your relay on 220v 60Hz it will work fine.
---
Knowing nothing about the contactor, other than that it's specified to
energize when 240V 50Hz is placed across the coil, your imprimatur is
premature.
---
>Contact closing speed will be slightly slower. Margin will be reduced,
>but its only being reduced from enormous to slightly less enormous,
>so its a non-issue except in very unusual situations.
---
It seems you've forgotten that when the armature makes, and the
magnetic circuit is closed, the inductance of the coil will rise.
Such being the case, the current in it will diminish, reducing the
hold on the armature and making the contacts more likely to chatter.
---
>The vibration tolerance of
>the contacts will be little affected in practice; if your environment
>is harsh enough to shake the relay contact open, then you've got
>bigger worries than contacts crackling.
>If instead you meant you would use it on 110v 60Hz, then dont. But you
>could use diodes to get a higher dc voltage and use that.
---
Interesting conjecture.
Something like this?
+-----+
120AC>--|~ +|----+
| | |
| | [COIL]
| | |
120AC>--|~ -|----+
+-----+
Since the coil has an impedance of about 6600 ohms at 50Hz, then the
current through it will be:
E 240V
I = --- = ------- = 0.036A = 36mA
Z 6600R
Then, since the coil has a resistance of 4800 ohms, the DC voltage
across it required to force 36mA through it would be:
E = IR = 0.036A * 4800R ~ 174V.
The peak voltage out of the bridge would be:
E = RMS * sqrt(2) = 120 * 1.414 ~ 170V.
Pretty close, but at 120Hz, the reactance of the coil would increase,
limiting the current to something less than the 36mA needed to close
the armature.
However, the reactance of the coil will smooth the current and the
addition of a capacitor in parallel with the coil will remove some of
the ripple and allow the coil to see more nearly pure DC.
Here's a simulation showing both ways:
Version 4
SHEET 1 880 680
WIRE -144 16 -304 16
WIRE 112 16 -144 16
WIRE 448 16 288 16
WIRE 704 16 448 16
WIRE -304 80 -304 16
WIRE 288 80 288 16
WIRE 448 80 448 64
WIRE 480 80 448 80
WIRE 592 80 560 80
WIRE 704 80 704 64
WIRE 704 80 672 80
WIRE -144 112 -144 80
WIRE -112 112 -144 112
WIRE 0 112 -32 112
WIRE 112 112 112 80
WIRE 112 112 80 112
WIRE -144 160 -144 112
WIRE 112 160 112 112
WIRE 448 160 448 80
WIRE 544 160 448 160
WIRE 704 160 704 80
WIRE 704 160 608 160
WIRE -304 224 -304 160
WIRE -144 224 -304 224
WIRE 112 224 -144 224
WIRE 288 224 288 160
WIRE 448 224 288 224
WIRE 704 224 448 224
WIRE -304 272 -304 224
WIRE 288 272 288 224
FLAG -304 272 0
FLAG 288 272 0
SYMBOL ind -128 128 R270
WINDOW 0 32 56 VTop 0
WINDOW 3 5 56 VBottom 0
SYMATTR InstName L1
SYMATTR Value 15
SYMBOL voltage -304 64 R0
WINDOW 3 24 104 Invisible 0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V1
SYMATTR Value SINE(0 170 60)
SYMBOL diode -160 16 R0
WINDOW 0 4 -52 Left 0
WINDOW 3 -28 -24 Left 0
SYMATTR InstName D1
SYMATTR Value MUR460
SYMBOL diode 128 80 R180
WINDOW 0 1 119 Left 0
WINDOW 3 -33 84 Left 0
SYMATTR InstName D2
SYMATTR Value MUR460
SYMBOL diode 96 160 R0
WINDOW 0 3 89 Left 0
WINDOW 3 -27 118 Left 0
SYMATTR InstName D3
SYMATTR Value MUR460
SYMBOL diode -128 224 R180
WINDOW 0 2 -28 Left 0
WINDOW 3 -31 -57 Left 0
SYMATTR InstName D4
SYMATTR Value MUR460
SYMBOL res -16 128 R270
WINDOW 0 32 56 VTop 0
WINDOW 3 0 56 VBottom 0
SYMATTR InstName R1
SYMATTR Value 4800
SYMBOL ind 464 96 R270
WINDOW 0 32 56 VTop 0
WINDOW 3 5 56 VBottom 0
SYMATTR InstName L2
SYMATTR Value 15
SYMBOL voltage 288 64 R0
WINDOW 3 24 104 Invisible 0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V2
SYMATTR Value SINE(0 170 60)
SYMBOL diode 432 16 R0
WINDOW 0 4 -52 Left 0
WINDOW 3 -28 -24 Left 0
SYMATTR InstName D5
SYMATTR Value MUR460
SYMBOL diode 720 80 R180
WINDOW 0 1 119 Left 0
WINDOW 3 -33 84 Left 0
SYMATTR InstName D6
SYMATTR Value MUR460
SYMBOL diode 688 160 R0
WINDOW 0 3 89 Left 0
WINDOW 3 -27 118 Left 0
SYMATTR InstName D7
SYMATTR Value MUR460
SYMBOL diode 464 224 R180
WINDOW 0 2 -28 Left 0
WINDOW 3 -31 -57 Left 0
SYMATTR InstName D8
SYMATTR Value MUR460
SYMBOL res 576 96 R270
WINDOW 0 32 56 VTop 0
WINDOW 3 0 56 VBottom 0
SYMATTR InstName R2
SYMATTR Value 4800
SYMBOL cap 608 144 R90
WINDOW 0 0 32 VBottom 0
WINDOW 3 32 32 VTop 0
SYMATTR InstName C1
SYMATTR Value 10µ
TEXT -298 246 Left 0 !.tran .05
If the relay is spec'ed as "must make" at 80% of rated current through
the coil (~29mA), then note that with a 10µF cap in parallel with the
coil the relay will _always_ make using full-wave rectified 120V 60Hz
mains.
--
JF
NT
wrote:
> On Mon, 29 Aug 2011 07:25:23 -0700 (PDT), NT <meow2...@care2.com>
> wrote:
>
> >IME relays pull in at in the region of half rated voltage, and dc
> >ratings are typically about half the voltage of the ac rating, which
> >gives an idea of how much current is determined by L and how much by
> >R.
>
> ---
> IME, most relays (with either AC or DC coils) are guaranteed to pull
> in at about 80% of their rated coil voltage, so I'm at a loss trying
> to understand what you meant by: "dc ratings are typically about half
> of the ac rating."
>
> Can you elaborate, please?
When relays have dual ratings for ac and dc, its normal for the dc
voltage rating to be half the ac voltage rating.
> >Running your relay on 220v 60Hz it will work fine.
>
> Knowing nothing about the contactor, other than that it's specified to
> energize when 240V 50Hz is placed across the coil, your imprimatur is
> premature.
I really dont agree. I do know the basics about relays, and one
normally finds that pull-in occurs at around 50% rated voltage. The OP
is welcome to test theirs to see if it behaves the usual way.
> >Contact closing speed will be slightly slower. Margin will be reduced,
> >but its only being reduced from enormous to slightly less enormous,
> >so its a non-issue except in very unusual situations.
>
> It seems you've forgotten that when the armature makes, and the
> magnetic circuit is closed, the inductance of the coil will rise.
I dont know why you think I've forgotten it. What's relevant here is
inductance in the closed position.
> Such being the case, the current in it will diminish,
true with all relays under all ac conditions. Theyre designed to work
that way.
> reducing the
> hold on the armature and making the contacts more likely to chatter.
No, its exactly how theyre designed to operate.
> >The vibration tolerance of
> >the contacts will be little affected in practice; if your environment
> >is harsh enough to shake the relay contact open, then you've got
> >bigger worries than contacts crackling.
> >If instead you meant you would use it on 110v 60Hz, then dont. But you
> >could use diodes to get a higher dc voltage and use that.
>
> Interesting conjecture.
Where's the conjecture? I get the feeling you could do with bringing
your skills up to speed on relays.
> Something like this?
>
> +-----+
> 120AC>--|~ +|----+
> | | |
> | | [COIL]
> | | |
> 120AC>--|~ -|----+
> +-----+
That would work.
> Since the coil has an impedance of about 6600 ohms at 50Hz, then the
> current through it will be:
>
> E 240V
> I = --- = ------- = 0.036A = 36mA
> Z 6600R
>
> Then, since the coil has a resistance of 4800 ohms, the DC voltage
> across it required to force 36mA through it would be:
>
> E = IR = 0.036A * 4800R ~ 174V.
You're not saying where you got those figures from. Typically dc
rating is half ac rating.
> The peak voltage out of the bridge would be:
>
> E = RMS * sqrt(2) = 120 * 1.414 ~ 170V.
>
> Pretty close, but at 120Hz, the reactance of the coil would increase,
> limiting the current to something less than the 36mA needed to close
> the armature.
The effect of the relay's inductance, when run off a BR, is simply to
smooth the current flow somewhat. Mean current remains much the same.
So we're looking for 120v rms, which is what the BR would deliver.
> However, the reactance of the coil will smooth the current and the
> addition of a capacitor in parallel with the coil will remove some of
> the ripple and allow the coil to see more nearly pure DC.
and overheat the relay by increasing its rms dc voltage to above 120v.
NT
petrus bitbyter
"NT" <meow...@care2.com> schreef in bericht
news:9eae9570-949f-4798...@j1g2000yqn.googlegroups.com...
"The relay has a voltage margin of around 50%" How do you know? FAIK the op
did not supply this numbers.
petrus bitbyter
David Lesher
Well anytime you run transformers {Be they two fixed windings,
or one fixed and one rotating aka motor, or one fixed &
one sliding aka solenoid or relay....} on LESS than design
frequency, worry. Lower frequencies need more iron.
I'm not sure the slightly less pull-in power will be relevent but
it's possible.
If you do pursue the "make DC and use that..." approach; don't forget
you need to limit the holdin current. One technique is a cap in parallel
with a resistor.
Jeffrey Angus
> Well anytime you run transformers {Be they two fixed windings,
> or one fixed and one rotating aka motor, or one fixed&
> one sliding aka solenoid or relay....} on LESS than design
> frequency, worry. Lower frequencies need more iron.
Hasn't anybody read the original question?
He wants to know if a 50 Hz relay coil will work at 60 Hz.
Jeff
--
"Everything from Crackers to Coffins"
Rich Grise
> On 8/30/2011 10:38 AM, David Lesher wrote:
>> Well anytime you run transformers {Be they two fixed windings,
>> or one fixed and one rotating aka motor, or one fixed&
>> one sliding aka solenoid or relay....} on LESS than design
>> frequency, worry. Lower frequencies need more iron.
>
> Hasn't anybody read the original question?
>
Yeah. It was answered some days ago.
Guess you gotta be quick. ;-)
Cheers!
Rich
Rich Grise
> On Tue, 30 Aug 2011 02:58:19 +0000 (UTC), David Lesher
>>
>>>I have an old P&B MR5A here with a 240V 50/60Hz coil.
>>
>>>The coil has a resistance of 4800 ohms, and an open inductance of 14.5
>>>henrys, so it has an impedance of 6616 ohms at 50 Hz, and 7270 ohms at
>>>60 Hz.
>>
>>What's the inductance while closed?
>
> manually.
>
> If there's any real interest I can measure it energized.
>
interested in seeing your experimental results, but that's just because
I like seeing experimental results. ;-)
Cheers!
Rich
Jeff Liebermann
wrote:
>Hasn't anybody read the original question?
Nope. With 5 groups in the distribution, I just assumed the original
question to not be worth reading. Besides, some of the groups appear
to be write-only, where nobody (including me) reads the original
question.
>He wants to know if a 50 Hz relay coil will work at 60 Hz.
Well, if it's too much of a risk trying it and checking if it will
explode, there are plenty of 50 to/from 60 Hz converters available for
a small fortune:
<http://www.50hz.com/Rotary/rotary.htm>
If sufficiently low power, one could probably just build a converter
from two motors and a suitable gearbox.
Jeff (part of the problem) L.
--
Jeff Liebermann je...@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
David Lesher
>On 8/30/2011 10:38 AM, David Lesher wrote:
>> Well anytime you run transformers {Be they two fixed windings,
>> or one fixed and one rotating aka motor, or one fixed&
>> one sliding aka solenoid or relay....} on LESS than design
>> frequency, worry. Lower frequencies need more iron.
>Hasn't anybody read the original question?
I have.
>He wants to know if a 50 Hz relay coil will work at 60 Hz.
And that's my point; if it were the other way, he SHOULD worry.
John Fields
wrote:
>On Aug 30, 12:39 pm, John Fields <jfie...@austininstruments.com>
---
I disagree.
Since the relay is open when power is applied to the coil, it's the
open inductance (and the resistance, of course) which will determine
how much current will flow through the coil, that current being what
generates the magnetic field to start the armature on its way.
Then when the relay closes, the closed inductance comes into play and
holds the armature in place until the current through the coil is
reduced to a point where the armature's return spring overcomes the
weakened magnetic field, allowing the armature to open.
---
>> Such being the case, the current in it will diminish,
>
>true with all relays under all ac conditions. Theyre designed to work
>that way.
>
>> reducing the
>> hold on the armature and making the contacts more likely to chatter.
>
>No, its exactly how theyre designed to operate.
>
>
>> >The vibration tolerance of
>> >the contacts will be little affected in practice; if your environment
>> >is harsh enough to shake the relay contact open, then you've got
>> >bigger worries than contacts crackling.
>> >If instead you meant you would use it on 110v 60Hz, then dont. But you
>> >could use diodes to get a higher dc voltage and use that.
>>
>> Interesting conjecture.
>
>Where's the conjecture? I get the feeling you could do with bringing
>your skills up to speed on relays.
---
Perhaps.
---
>> Something like this?
>>
>> +-----+
>> 120AC>--|~ +|----+
>> | | |
>> | | [COIL]
>> | | |
>> 120AC>--|~ -|----+
>> +-----+
>
>That would work.
---
Not in all cases, certainly.
---
>
>
>> Since the coil has an impedance of about 6600 ohms at 50Hz, then the
>> current through it will be:
>>
>> E 240V
>> I = --- = ------- = 0.036A = 36mA
>> Z 6600R
>>
>> Then, since the coil has a resistance of 4800 ohms, the DC voltage
>> across it required to force 36mA through it would be:
>>
>> E = IR = 0.036A * 4800R ~ 174V.
>
>You're not saying where you got those figures from.
---
The P&B MR5A I talked about in an earlier post, which has a 240V
50/60Hz coil, a coil resistance of 4800 ohms, an impedance of ~ 6600
ohms at 50 Hz, an open inductance of 14.5 henrys, and a closed
inductance of 16 henrys
---
>Typically dc rating is half ac rating.
---
But I don't think "typical" is what we're after since we want
something that will _always_ work.
Since current is what's doing the work, my real-world example shows
that 240V 50 Hz RMS impressed across a load with an impedance of 6600
ohms will force 36mA RMS of current through the load.
Then, since it's current that's doing the work, 36mA of DC through the
coil should accomplish the same thing.
---
>> The peak voltage out of the bridge would be:
>>
>> E = RMS * sqrt(2) = 120 * 1.414 ~ 170V.
>>
>> Pretty close, but at 120Hz, the reactance of the coil would increase,
>> limiting the current to something less than the 36mA needed to close
>> the armature.
>
>The effect of the relay's inductance, when run off a BR, is simply to
>smooth the current flow somewhat.
---
Yeah, I know, said so earlier, and posted a simulation showing the
ripple.
---
>Mean current remains much the same.
>So we're looking for 120v rms, which is what the BR would deliver.
---
But, what it won't deliver is the worst-case voltage required over the
interval required to guarantee the armature will close.
---
>> However, the reactance of the coil will smooth the current and the
>> addition of a capacitor in parallel with the coil will remove some of
>> the ripple and allow the coil to see more nearly pure DC.
>
>and overheat the relay by increasing its rms dc voltage to above 120v.
---
There's no such thing as "rms dc voltage", and if the relay is
designed to operate on AC with a certain RMS current in its coil, how
can it possibly overheat if that current is DC?
---
--
JF
NT
wrote:
> "NT" <meow2...@care2.com> schreef in berichtnews:9eae9570-949f-4798...@j1g2000yqn.googlegroups.com...
experience with various relays
NT
NT
> On Tue, 30 Aug 2011 05:11:20 -0700 (PDT), NT <meow2...@care2.com>
>
> Since the relay is open when power is applied to the coil, it's the
> open inductance (and the resistance, of course) which will determine
> how much current will flow through the coil, that current being what
> generates the magnetic field to start the armature on its way.
yup
> Then when the relay closes, the closed inductance comes into play and
> holds the armature in place until the current through the coil is
> reduced to a point where the armature's return spring overcomes the
> weakened magnetic field, allowing the armature to open.
yes. I guess in theory both matter, one determines closing behaviour,
the other ensures the relay doesnt overheat. In practice though the
margins are very large, and its normal to simply fix holding current
to suit the relay, and not worry about closing current, which will be
so close as to make no real world difference in all but exceptional
circumstances. But yes, we can consider both if need be.
> Not in all cases, certainly.
I'd like to see you find one single electromechanical relay that wont
work for.
> >> Since the coil has an impedance of about 6600 ohms at 50Hz, then the
> >> current through it will be:
>
> >> E 240V
> >> I = --- = ------- = 0.036A = 36mA
> >> Z 6600R
>
> >> Then, since the coil has a resistance of 4800 ohms, the DC voltage
> >> across it required to force 36mA through it would be:
>
> >> E = IR = 0.036A * 4800R ~ 174V.
>
> >You're not saying where you got those figures from.
>
> ---
> The P&B MR5A I talked about in an earlier post, which has a 240V
> 50/60Hz coil, a coil resistance of 4800 ohms, an impedance of ~ 6600
> ohms at 50 Hz, an open inductance of 14.5 henrys, and a closed
> inductance of 16 henrys
> >Typically dc rating is half ac rating.
>
> But I don't think "typical" is what we're after since we want
> something that will _always_ work.
This 2:1 ratio normally is good for relays, and the OP can check his
to see if it conforms to that. If it does, the thing will always work
when subject to this formula.
FWIW, when ac is applied you get puling force plus vibration. With dc
there is no vibration component when its closed, so less holding
current is needed. How much less I've really no idea.
Some relays are fast movers capable of 100s of Hz, some are slow. Ac
relays can always work on dc, but dc ones often dont work ok on ac.
> Since current is what's doing the work, my real-world example shows
> that 240V 50 Hz RMS impressed across a load with an impedance of 6600
> ohms will force 36mA RMS of current through the load.
>
> Then, since it's current that's doing the work, 36mA of DC through the
> coil should accomplish the same thing.
> ---
>
> >> The peak voltage out of the bridge would be:
>
> >> E = RMS * sqrt(2) = 120 * 1.414 ~ 170V.
>
> >> Pretty close, but at 120Hz, the reactance of the coil would increase,
> >> limiting the current to something less than the 36mA needed to close
> >> the armature.
>
> >The effect of the relay's inductance, when run off a BR, is simply to
> >smooth the current flow somewhat.
>
> ---
> Yeah, I know, said so earlier, and posted a simulation showing the
> ripple.
> ---
>
> >Mean current remains much the same.
> >So we're looking for 120v rms, which is what the BR would deliver.
>
> ---
> But, what it won't deliver is the worst-case voltage required over the
> interval required to guarantee the armature will close.
Re ripple: If the relay is designed to run on ac 50 or 60Hz, its
designed and rated to live with the current and force variations that
go along with that, 100-120 times a second. Running it on rectified
mains will only serve to reduce the current variations through the
cycle, it wont cause the relay any issues.
Re rms voltage: With my 2:1 figures, rectified 120v is spot on. With
your 174v figure, 120v is well within the 50% margin. Of course for
some uses that margin would need to be confirmed by testing before
production, and reconfirmed if a new relay type is used. Or as you
say, a cap could be added. Or for off brand consumer goods, in it
goes, relays are good for it.
> >> However, the reactance of the coil will smooth the current and the
> >> addition of a capacitor in parallel with the coil will remove some of
> >> the ripple and allow the coil to see more nearly pure DC.
>
> >and overheat the relay by increasing its rms dc voltage to above 120v.
>
> There's no such thing as "rms dc voltage",
RMS can be applied to any and every waveform, dc included. Its very
relevant when working with rectified ac, semismoothed or unsmoothed.
> and if the relay is
> designed to operate on AC with a certain RMS current in its coil, how
> can it possibly overheat if that current is DC?
With the same current it wont, with higher curren ti will. IIRC you
proposed using 174v rms, that would be ok on your specific relay, but
not a universal solution.
NT
The Ghost In The Machine
> > >> WIRE -144 16 -304 16
> > >> WIRE112 16 -144 16
> > >> WIRE448 16 288 16
> > >> WIRE -304 80 -304 16
> > >> WIRE288 80 288 16
> > >> WIRE448 80 448 64
> > >> WIRE480 80 448 80
> > >> WIRE592 80 560 80
> > >> WIRE704 80 704 64
> > >> WIRE -144 112 -144 80
> > >> WIRE -112 112 -144 112
> > >> WIRE0 112 -32 112
> > >> WIRE112 112 112 80
> > >> WIRE -144 160 -144 112
> > >> WIRE112 160 112 112
> > >> WIRE448 160 448 80
> > >> WIRE544 160 448 160
> > >> WIRE704 160 704 80
> > >> WIRE -304 224 -304 160
> > >> WIRE -144 224 -304 224
> > >> WIRE112 224 -144 224
> > >> WIRE288 224 288 160
> > >> WIRE448 224 288 224
> > >> WIRE -304 272 -304 224
> > >> FLAG -304 272 0
> > >> FLAG288 272 0
>
> read more »
YES A-NT-MAN BUT THE RMS REFERS TO THE AC WAVEFORM NOT THE DC OUTPUT.
HENCE THERE IS NO SUCH THING AS RMS DC VOLTAGE.
PATECUM
TGITM
John S
>
> YES A-NT-MAN BUT THE RMS REFERS TO THE AC WAVEFORM NOT THE DC OUTPUT.
> HENCE THERE IS NO SUCH THING AS RMS DC VOLTAGE.
> PATECUM
> TGITM
Actually, RMS DC voltage is a redundant expression since DC is RMS.
NT
> On 8/31/2011 1:06 PM, The Ghost In The Machine wrote:
>
>
>
> > YES A-NT-MAN BUT THE RMS REFERS TO THE AC WAVEFORM NOT THE DC OUTPUT.
> > HENCE THERE IS NO SUCH THING AS RMS DC VOLTAGE.
> > PATECUM
> > TGITM
Root Mean Square does not imply an ac waveform, its jsut most commonly
used for ac waveforms. Every stable waveform has an rms value, even
perfect dc.
> Actually, RMS DC voltage is a redundant expression since DC is RMS.
I realised it was perhaps not the best phrasing. But... would the dc
component be the average V or the rms?
NT
Jeffrey Angus
> I realised it was perhaps not the best phrasing. But... would the dc
> component be the average V or the rms?
DC would be the RMS value. Because, RMS means "This is what the DC
value would be."
Ian Field
"Jeffrey Angus" <grend...@aim.com> wrote in message
news:j3m408$fqf$1...@dont-email.me...
> On 8/31/2011 2:33 PM, NT wrote:
>> I realised it was perhaps not the best phrasing. But... would the dc
>> component be the average V or the rms?
>
> DC would be the RMS value. Because, RMS means "This is what the DC
> value would be."
Years ago when I needed more power from a soldering iron I used to feed the
240VRMS through a rectifier/reservoir to get aproximately 320VDC.
Spehro Pefhany
wrote:
>On Aug 31, 7:11 pm, John S <soph...@invalid.org> wrote:
Generally, in electronics, "DC component" is defined as the average
value (say, over a period of a periodic waveform). So a 1V peak sine
wave sitting on top of 1VDC would have DC component of 1.0V.
A 1V peak sine wave has a DC component of 0.
The RMS value is the heating value- a 1 ohm resistor with 1VDC across
it will dissipate 1W. A 1 ohm resistor with 1.414V peak sine wave
across it (1 V RMS) will dissipate 1W.
A 1 ohm resistor powered with a 1V peak sine wave sitting on top of
1VDC will dissipate a bit more than 1 watt (RMS value is sqrt(3/2) if
you want to get analytical about it, so about 1.22W).
John S
DC is all of the following: Average, Peak, RMS, Mean, Mode, and most
anything else.
John S
Paul Conners
> value (say, over a period of a periodic waveform). So a 1V peak sine
> wave sitting on top of 1VDC would have DC component of 1.0V.
> A 1V peak sine wave has a DC component of 0.
>
> The RMS value is the heating value- a 1 ohm resistor with 1VDC across
> it will dissipate 1W. A 1 ohm resistor with 1.414V peak sine wave
> across it (1 V RMS) will dissipate 1W.
>
> A 1 ohm resistor powered with a 1V peak sine wave sitting on top of
> 1VDC will dissipate a bit more than 1 watt (RMS value is sqrt(3/2) if
> you want to get analytical about it, so about 1.22W).
Thank you SP. Amid all the chest-pounding and playground antics here I can
actually learn something.
Don Kelly
"NT" wrote in message
news:acc067aa-0f17-4b7b...@s12g2000yqm.googlegroups.com...
yup
NT
-----------------------
I sense a bit of cross confusion in this thread.
a)Do not the AC/DC ratings refer to the contact rating rather than the coil
rating? As with any switch, there is a big derating of contacts designed for
AC use but applied to DC- Example a typical 120V 15 A light switch would
fail at 15A 120V DC- it might work at 15A, 12V. Older switches with good
snap contacts do much better.
You indicate experience for the factor of 2:1- but is this something that
translates across the AC/DC barrier?
b) John indicates 174VDC giving 0.036A would be OK- for closing. However
when closed, the holding current will be 0.031A and this is the steady state
current that is involved in heating when the relay is closed. For DC the
voltage would need to be about 150VDC [ (174*0.031/0.036)^2]. So it
remains to be seen if that is sufficient to close the relay. According to
you- it would be more than adequate. From John's 80% criterion it is
inadequate.- so point (c).
c) The peak force is related to the square of peak flux For AC, this is
proportional to (Vrms/f)^2 independent of the magnetic medium. The magnetic
medium determines the corresponding peak current. While a DC current of
0.036A corresponds to an rms current of the same magnitude, and the average
force is the same, at that current, as the average force in the AC case, it
is well below the peak force (about a factor of 2, ). This may have have a
bearing on the relay's operation- just a conjecture.
Don Kelly
cross out to reply
Michael A. Terrell
RMS = 'Roy? Mouthy & Stupid.'
--
You can't have a sense of humor, if you have no sense.
Ralph Barone
wrote:
but not peak to peak...
NT
No, I'm talking about coil voltage ratings.
> You indicate experience for the factor of 2:1- but is this something that
> translates across the AC/DC barrier?
I'm not 100% clear what you mean there. In short, many relays only
have one coil voltage rating, and its for just one of either ac or dc.
The various ones I've seen that have coil 2 ratings, one for ac one
for dc, have consistently had the dc coil rating be half the ac
voltage rating.
> b) John indicates 174VDC giving 0.036A would be OK- for closing. However
> when closed, the holding current will be 0.031A and this is the steady state
> current that is involved in heating when the relay is closed. For DC the
> voltage would need to be about 150VDC [ (174*0.031/0.036)^2]. So it
> remains to be seen if that is sufficient to close the relay. According to
> you- it would be more than adequate. From John's 80% criterion it is
> inadequate.- so point (c).
>
> c) The peak force is related to the square of peak flux For AC, this is
> proportional to (Vrms/f)^2 independent of the magnetic medium. The magnetic
> medium determines the corresponding peak current. While a DC current of
> 0.036A corresponds to an rms current of the same magnitude, and the average
> force is the same, at that current, as the average force in the AC case, it
> is well below the peak force (about a factor of 2, ). This may have have a
> bearing on the relay's operation- just a conjecture.
>
> Don Kelly
> cross out to reply
Peak force would come into play when dealing with stiction, but a
relay would have to be on its very last legs for stiction to be
significant in practice.
NT
John Fields
wrote:
>On Aug 31, 1:36 am, John Fields <jfie...@austininstruments.com> wrote:
>> On Tue, 30 Aug 2011 05:11:20 -0700 (PDT), NT <meow2...@care2.com>
>> wrote:
>> >On Aug 30, 12:39 pm, John Fields <jfie...@austininstruments.com>
>> >wrote:
>> >> On Mon, 29 Aug 2011 07:25:23 -0700 (PDT), NT <meow2...@care2.com>
>> >> wrote:
>>
>> >> >IME relays pull in at in the region of half rated voltage, and dc
>> >> >ratings are typically about half the voltage of the ac rating, which
>> >> >gives an idea of how much current is determined by L and how much by
>> >> >R.
>>
>> >> ---
>> >> IME, most relays (with either AC or DC coils) are guaranteed to pull
>> >> in at about 80% of their rated coil voltage, so I'm at a loss trying
>> >> to understand what you meant by: "dc ratings are typically about half
>> >> of the ac rating."
>>
>> >> Can you elaborate, please?
>>
>> >When relays have dual ratings for ac and dc, its normal for the dc
>> >voltage rating to be half the ac voltage rating.
---
But, in this case, the OP has a relay which isn't dual-rated, but
rated only for 240V 50Hz.
---
>> >> >Running your relay on 220v 60Hz it will work fine.
>>
>> >> Knowing nothing about the contactor, other than that it's specified to
>> >> energize when 240V 50Hz is placed across the coil, your imprimatur is
>> >> premature.
>>
>> >I really dont agree. I do know the basics about relays, and one
>> >normally finds that pull-in occurs at around 50% rated voltage. The OP
>> >is welcome to test theirs to see if it behaves the usual way.
>>
>> >> >Contact closing speed will be slightly slower. Margin will be reduced,
>> >> >but its only being reduced from enormous to slightly less enormous,
>> >> >so its a non-issue except in very unusual situations.
>>
>> >> It seems you've forgotten that when the armature makes, and the
>> >> magnetic circuit is closed, the inductance of the coil will rise.
>>
>> >I dont know why you think I've forgotten it. What's relevant here is
>> >inductance in the closed position.
>>
>> I disagree.
>>
>> Since the relay is open when power is applied to the coil, it's the
>> open inductance (and the resistance, of course) which will determine
>> how much current will flow through the coil, that current being what
>> generates the magnetic field to start the armature on its way.
>
>yup
---
"yup"?
Strangely, your pretentiously authoritative "yup" seems designed to
denigrate my critique as if you knew you were wrong and tried to
assign the guilt to me.
---
>> Then when the relay closes, the closed inductance comes into play and
>> holds the armature in place until the current through the coil is
>> reduced to a point where the armature's return spring overcomes the
>> weakened magnetic field, allowing the armature to open.
>
>yes. I guess in theory both matter, one determines closing behaviour,
>the other ensures the relay doesnt overheat. In practice though the
>margins are very large,
---
I don't understand; what margins are you talking about?
---
>and its normal to simply fix holding current
>to suit the relay, and not worry about closing current, which will be
>so close as to make no real world difference in all but exceptional
>circumstances. But yes, we can consider both if need be.
---
Again, I'm confused.
If, as you say, it's normal to simply fix holding current to keep from
overheating the coil [by using the impedance of the coil as a current
limiter, once it's closed] then, since the strength of the magnetic
field varies, in an inverse square law kind of way, as a function of
the distance between the pole pieces, there's the very real worry
about the spacing of the pole pieces which will guarantee closure.
---
>> >> Such being the case, the current in it will diminish,
>>
>> >true with all relays under all ac conditions. Theyre designed to work
>> >that way.
---
By God, maybe, but to us mortals the change in impedance is
serendipitous and all we can do with it is to work out the "must
close" to "must open" hysteresis.
---
>> >> reducing the
>> >> hold on the armature and making the contacts more likely to chatter.
>>
>> >No, its exactly how theyre designed to operate.
---
Are you saying that a variable current in the coil won't react against
the holding force of the armature's return spring?
---
>> >> >The vibration tolerance of
>> >> >the contacts will be little affected in practice; if your environment
>> >> >is harsh enough to shake the relay contact open, then you've got
>> >> >bigger worries than contacts crackling.
>> >> >If instead you meant you would use it on 110v 60Hz, then dont. But you
>> >> >could use diodes to get a higher dc voltage and use that.
>>
>> >> Interesting conjecture.
>>
> >Where's the conjecture? I get the feeling you could do with bringing
>> >your skills up to speed on relays.
>>
>> ---
>> Perhaps.
>> ---
>>
>> >> Something like this?
>>
>> >> +-----+
>> >> 120AC>--|~ +|----+
>> >> | | |
>> >> | | [COIL]
>> >> | | |
>> >> 120AC>--|~ -|----+
>> >> +-----+
>>
>> >That would work.
>>
>> Not in all cases, certainly.
>
>I'd like to see you find one single electromechanical relay that wont
>work for.
---
Well, I'm certainly not going to spend any portion of the rest of my
life searching for that reclusive gem but, in the same vein, I invite
you to find any electromechanical relay with a guarantee that its
must-close voltage is half of its nominal energization voltage.
---
>> >> Since the coil has an impedance of about 6600 ohms at 50Hz, then the
>> >> current through it will be:
>>
>> >> E 240V
>> >> I = --- = ------- = 0.036A = 36mA
>> >> Z 6600R
>>
>> >> Then, since the coil has a resistance of 4800 ohms, the DC voltage
>> >> across it required to force 36mA through it would be:
>>
>> >> E = IR = 0.036A * 4800R ~ 174V.
>>
>> >You're not saying where you got those figures from.
>>
>> ---
>> The P&B MR5A I talked about in an earlier post, which has a 240V
>> 50/60Hz coil, a coil resistance of 4800 ohms, an impedance of ~ 6600
>> ohms at 50 Hz, an open inductance of 14.5 henrys, and a closed
>> inductance of 16 henrys
>
>> >Typically dc rating is half ac rating.
>>
>> But I don't think "typical" is what we're after since we want
>> something that will _always_ work.
>
>This 2:1 ratio normally is good for relays, and the OP can check his
>to see if it conforms to that. If it does, the thing will always work
>when subject to this formula.
---
You keep saying that ratio is "normal", but when a manufacturer
specifies the "must make" voltage as 80% of the relay's rated voltage,
then the voltage across the coil must never be allowed to fall below
that when the relay is being energized.
If it's allowed to fall below that point, then even though the relay
may make, its ON delay and bounce specs will no longer be valid, with
the increased bounce time certainly being detrimental to the relay's
lifetime.
---
.
.
.
---
But that 50% margin is bogus since any manufacturer's guaranteed "must
make" voltage is far higher than 50%.
---
>Of course for
>some uses that margin would need to be confirmed by testing before
>production, and reconfirmed if a new relay type is used. Or as you
>say, a cap could be added. Or for off brand consumer goods, in it
>goes, relays are good for it.
>
>
>> >> However, the reactance of the coil will smooth the current and the
>> >> addition of a capacitor in parallel with the coil will remove some of
>> >> the ripple and allow the coil to see more nearly pure DC.
>>
>> >and overheat the relay by increasing its rms dc voltage to above 120v.
>>
>> There's no such thing as "rms dc voltage",
>
>RMS can be applied to any and every waveform, dc included. Its very
>relevant when working with rectified ac, semismoothed or unsmoothed.
>
>> and if the relay is
>> designed to operate on AC with a certain RMS current in its coil, how
>> can it possibly overheat if that current is DC?
>
>With the same current it wont, with higher curren ti will. IIRC you
>proposed using 174v rms,
---
No, I merely added a capacitor across the output of _your_ proposed
full wave rectified 120 VRMS 60Hz source (170V peak) in order to get
smoothed DC closer to the relay's must-make current.
---
>that would be ok on your specific relay, but
>not a universal solution.
---
???
Take a look at the sim again:
--
JF
cbarn...@aol.com
> On Tue, 30 Aug 2011 10:55:10 -0500, Jeffrey Angus <grendel...@aim.com>
> wrote:
>
> >Hasn't anybody read the original question?
>
> Nope. With 5 groups in the distribution, I just assumed the original
> question to not be worth reading. Besides, some of the groups appear
> to be write-only, where nobody (including me) reads the original
> question.
>
That must be the explaination as to why so much crap has been written
on this thread!!
John Fields
---
The addition of your three turds to this punchbowl certainly isn't
helping, is it?
--
JF
Jeff Liebermann
<jfi...@austininstruments.com> wrote:
>The addition of your three turds to this punchbowl certainly isn't
>helping, is it?
Hmmm.... 5 newsgroups.... where's my soap box?
Usenet, blogs, forums, and mailing lists are much like a trash
dumpster. At the bottom of every dumpster is a gem. All one needs to
do is dig through mountains of garbage in order to find it[1]. I try
to include some of those gems in my postings, no matter how far off
topic. As a general rule, one should not write anything that one
would not personally want to read.
In this case, there are some common indications of articles not worth
reading. My list includes:
1. One line replies. These are usually devoid of any thought,
substantiation, or useful detail.
2. Massive crossposting. This suggests that the OP hasn't bothered
to research the topic before asking, usually resulting in a question
with insufficient detail necessary for a productive answer.
3. Large numbers in the line count. This suggests that the author
has included massive quotes from the previous discussion, usually
automatically reformatted into an unreadable mess. Best to skip to
the next message in the thread, which usually includes the one line
the author has added.
4. URL only. Invariably, it's spam or self promotion.
5. All CAPS in the Subject line. That's usually spam, but sometimes
is from someone that can't type. Occasionally, it's used for its
original purpose as shouting. Unless you're into emotional content,
it's not worth reading.
6. Change of Subject line. The author doing that, instead of
starting a new topic, is usually a Usenet lawyer, more interested in
form than content. In most cases, the change of topic doesn't do much
as few readers bother to read the header. Some readers will
optionally start a new thread when the subject line changes. These
are probably worth reading, but with some suspicion as to the
motivations of the author.
7. Unsubstantiated offers of truth. These are declarations of fact
or truth based solely on the reputation or authority of the author. My
assumption is that the author usually can't prove his point if pressed
and therefore supplies no substantiation. This is difficult because
many well known authorities on a topic are too busy to lecture on
Usenet and will often assume the reader will automatically accept
their point of view based on their reputation. Personally, I don't
care what someone things. I want to know why.
[1] The few times I've asked a question on Usenet, only a small
percentage of the replies were genuinely useful. When I asked a
really complex question, with considerable detail and background,
there were no replies.
NT
> On Wed, 31 Aug 2011 09:38:16 -0700 (PDT), NT <meow2...@care2.com>
> wrote:
> >On Aug 31, 1:36 am, John Fields <jfie...@austininstruments.com> wrote:
> >> On Tue, 30 Aug 2011 05:11:20 -0700 (PDT), NT <meow2...@care2.com>
> >> wrote:
> >> >On Aug 30, 12:39 pm, John Fields <jfie...@austininstruments.com>
> >> >wrote:
> >> >> On Mon, 29 Aug 2011 07:25:23 -0700 (PDT), NT <meow2...@care2.com>
> >> >> wrote:
> >> >> >IME relays pull in at in the region of half rated voltage, and dc
> >> >> >ratings are typically about half the voltage of the ac rating, which
> >> >> >gives an idea of how much current is determined by L and how much by
> >> >> >R.
>
> >> >> ---
> >> >> IME, most relays (with either AC or DC coils) are guaranteed to pull
> >> >> in at about 80% of their rated coil voltage, so I'm at a loss trying
> >> >> to understand what you meant by: "dc ratings are typically about half
> >> >> of the ac rating."
>
> >> >> Can you elaborate, please?
>
> >> >When relays have dual ratings for ac and dc, its normal for the dc
> >> >voltage rating to be half the ac voltage rating.
>
> ---
> But, in this case, the OP has a relay which isn't dual-rated, but
> rated only for 240V 50Hz.
We know that. I also know from observation of various mfr specs that
ac relays are normally happy on half the voltage at dc. The relays
I've seen the dual ratings on havent been significantly different to
others.
> >> >> >Running your relay on 220v 60Hz it will work fine.
>
> >> >> Knowing nothing about the contactor, other than that it's specified to
> >> >> energize when 240V 50Hz is placed across the coil, your imprimatur is
> >> >> premature.
>
> >> >I really dont agree. I do know the basics about relays, and one
> >> >normally finds that pull-in occurs at around 50% rated voltage. The OP
> >> >is welcome to test theirs to see if it behaves the usual way.
>
> >> >> >Contact closing speed will be slightly slower. Margin will be reduced,
> >> >> >but its only being reduced from enormous to slightly less enormous,
> >> >> >so its a non-issue except in very unusual situations.
>
> >> >> It seems you've forgotten that when the armature makes, and the
> >> >> magnetic circuit is closed, the inductance of the coil will rise.
>
> >> >I dont know why you think I've forgotten it. What's relevant here is
> >> >inductance in the closed position.
>
> >> I disagree.
>
> >> Since the relay is open when power is applied to the coil, it's the
> >> open inductance (and the resistance, of course) which will determine
> >> how much current will flow through the coil, that current being what
> >> generates the magnetic field to start the armature on its way.
>
> >yup
>
> "yup"?
>
> Strangely, your pretentiously authoritative "yup" seems designed to
> denigrate my critique as if you knew you were wrong and tried to
> assign the guilt to me.
Yup just means yes, it indicates agreement. Nothing else.
> >> Then when the relay closes, the closed inductance comes into play and
> >> holds the armature in place until the current through the coil is
> >> reduced to a point where the armature's return spring overcomes the
> >> weakened magnetic field, allowing the armature to open.
>
> >yes. I guess in theory both matter, one determines closing behaviour,
> >the other ensures the relay doesnt overheat. In practice though the
> >margins are very large,
>
> I don't understand; what margins are you talking about?
The coil v/i margins, the difference between what works and the
nominal voltage rating
> >and its normal to simply fix holding current
> >to suit the relay, and not worry about closing current, which will be
> >so close as to make no real world difference in all but exceptional
> >circumstances. But yes, we can consider both if need be.
>
> ---
> Again, I'm confused.
>
> If, as you say, it's normal to simply fix holding current to keep from
> overheating the coil [by using the impedance of the coil as a current
> limiter, once it's closed] then, since the strength of the magnetic
> field varies, in an inverse square law kind of way, as a function of
> the distance between the pole pieces, there's the very real worry
> about the spacing of the pole pieces which will guarantee closure.
a design question for the relay manufacturer perhaps, its a non-issue
for us
> >> >> Such being the case, the current in it will diminish,
>
> >> >true with all relays under all ac conditions. Theyre designed to work
> >> >that way.
>
> ---
> By God, maybe, but to us mortals the change in impedance is
> serendipitous and all we can do with it is to work out the "must
> close" to "must open" hysteresis.
One seldom need worry about the must open rating. The must close and
wont overheat points are what counts in 99.9% of applications.
> >> >> reducing the
> >> >> hold on the armature and making the contacts more likely to chatter.
>
> >> >No, its exactly how theyre designed to operate.
>
> ---
> Are you saying that a variable current in the coil won't react against
> the holding force of the armature's return spring?
I'm saying it already taken into account in teh design of the relay,
its an ac relay. All we need do is give it enough current, but not too
much.
I'm talking about what relays actually do in the real world. Reality
and mfr specs often dont match.
I have to say that is false. Its fairly normal engineering practice to
use parts outside of mfr's specs so long as their effectiveness in
such conditions is verified, they can reasonably be counted on to
continue to operate satisfactorily, and so long as the level of
reliability that gives is sufficient for the app. And in this case the
OP has good motivation to do so.
> If it's allowed to fall below that point, then even though the relay
> may make, its ON delay and bounce specs will no longer be valid, with
> the increased bounce time certainly being detrimental to the relay's
> lifetime.
On delay specs are seldom critical. If they are then of course you'll
hit the coil with full rated v - or as I used to do at times, much
higher for a small fraction of a second to get it switching faster.
Bounce specs, again whether its ok depends on the app, and effect on
lifetime depends on whats being switched, and what lifetime is in fact
required of the part.
> But that 50% margin is bogus since any manufacturer's guaranteed "must
> make" voltage is far higher than 50%.
Its not bogus at all. If you really want to settle this, take a pile
of random relays and test what v they actually do close at. Then we
can discuss why what you find and what the mfr says are different.
You're stuck on mfr spec when the situation is that the OP is strongly
motivated to use the part outside of its mfr spec. Engineers do that.
> >Of course for
> >some uses that margin would need to be confirmed by testing before
> >production, and reconfirmed if a new relay type is used. Or as you
> >say, a cap could be added. Or for off brand consumer goods, in it
> >goes, relays are good for it.
>
> >> >> However, the reactance of the coil will smooth the current and the
> >> >> addition of a capacitor in parallel with the coil will remove some of
> >> >> the ripple and allow the coil to see more nearly pure DC.
>
> >> >and overheat the relay by increasing its rms dc voltage to above 120v.
>
> >> There's no such thing as "rms dc voltage",
>
> >RMS can be applied to any and every waveform, dc included. Its very
> >relevant when working with rectified ac, semismoothed or unsmoothed.
>
> >> and if the relay is
> >> designed to operate on AC with a certain RMS current in its coil, how
> >> can it possibly overheat if that current is DC?
>
> >With the same current it wont, with higher curren ti will. IIRC you
> >proposed using 174v rms,
>
> No, I merely added a capacitor across the output of _your_ proposed
> full wave rectified 120 VRMS 60Hz source (170V peak) in order to get
> smoothed DC closer to the relay's must-make current.
fwliw I said use diodes, you came back with a FW BR. I dont think it
matters.
> >that would be ok on your specific relay, but
> >not a universal solution.
>
> ???
Your proposd BR+C delivers the right i for one specific relay. For
some relays it will fry them.
NT
John Fields
Snipped a lot of repetitious, self serving nonsense.
>> >> and if the relay is
>> >> designed to operate on AC with a certain RMS current in its coil, how
>> >> can it possibly overheat if that current is DC?
>>
>> >With the same current it wont, with higher curren ti will. IIRC you
>> >proposed using 174v rms,
>>
>> No, I merely added a capacitor across the output of _your_ proposed
>> full wave rectified 120 VRMS 60Hz source (170V peak) in order to get
>> smoothed DC closer to the relay's must-make current.
>
>fwliw I said use diodes, you came back with a FW BR. I dont think it
>matters.
---
Then show me your circuit.
Just in case you've forgotten, your suggestion was to use a 240V AC
relay using diodes and 120V mains.
---
>> >that would be ok on your specific relay, but
>> >not a universal solution.
>>
>> ???
>
>Your proposd BR+C delivers the right i for one specific relay. For
>some relays it will fry them.
---
Show me.
--
JF
John Fields
---
OK. :-)
First, in order to measure the coil's unexcited inductance, I set up
the experiment like this:
+---------+ R1 +-----+
| SINE OUT|--[30K]---+----|VERT |
| | | | |
| | [0.1µF] | |
| | | | |
| | [DUT] | |
| | | | |
| GND|----------+----|GND |
+---------+ +-----+
FUNCTION SCOPE
GRNERATOR
I then cranked up the generator's output to get a decent display on
the scope and changed frequency until I got a suckout on the scope.
That was at 110Hz so, since in a resonant circuit the reactances
cancel, the suckout was caused by the voltage divider formed by R1 and
the resistance of the coil.
The reactance of the cap at that frequency was:
1 1
Xc = --------- = ---------------------- = 14476 ohms ~ 14.5kohms
2pi f C 6.28 * 110Hz * 1e-7F
Then, since the reactances of the capacitance and the inductance are
equal (but of opposite sign) at resonance, we can find the inductance
with:
Xl 14500R
L = ------- = -------------- = 21 henrys
2pi f 6.28 * 110Hz
Next, I measured the coil's DC resistance, found it to be 4900
ohms,and in order to measure the coil's excited inductance, set up an
experiment, like this, in order to measure the coil current at 240V
60Hz:
0->120V
/
VARIAC / 0->480V 240V
+------+ / / /
120AC>--| HOT|--+ +--[AC AMPS]--+-------+
| | | | | |
| | P||S | |
| | R||E [DUT] [AC VOLTS]
| | I||C | |
| | | | | |
120AC>--|-NEUT-|--+ +-------------+-------+
+------+ BFT
I got 15mA with 240V across the coil.
Now, to find the impedance of the coil we can say:
E 240V
Z = --- = -------- = 16000 ohms.
I 0.015A
Then the inductive reactance of the coil will be:
Xl = sqrt(Z² - R²) = sqrt(2.56e8 - 2.4e7) ~ 15200 ohms
and, finally, the inductance:
Xl
L = ------- = 40.3 henrys
2pi f
TADA! ;)
--
JF
cbarn...@aol.com
> On Fri, 2 Sep 2011 05:47:43 -0700 (PDT), "cbarn24...@aol.com"
Well they might if you actually read them, I have actually given the
op the correct answer, I actually read the question. Of course your
free to ramble on about relays instead of contactors if you like.
cbarn...@aol.com
> Hmmm.... 5 newsgroups.... where's my soap box?
>
> Usenet, blogs, forums, and mailing lists are much like a trash
> dumpster. At the bottom of every dumpster is a gem. All one needs to
> do is dig through mountains of garbage in order to find it[1]. I try
> to include some of those gems in my postings, no matter how far off
> topic.
If it's off topic what use is it?
As a general rule, one should not write anything that one
> would not personally want to read.
>
> In this case, there are some common indications of articles not worth
> reading. My list includes:
> 1. One line replies. These are usually devoid of any thought,
> substantiation, or useful detail.
One liners often get straight to the point, many nonsence posts need
that kind of answer.
> 2. Massive crossposting. This suggests that the OP hasn't bothered
> to research the topic before asking, usually resulting in a question
> with insufficient detail necessary for a productive answer.
Most OPs havent done any research, if they had they wouldnt need to
post in the first place.
> 7. Unsubstantiated offers of truth.
Well they all unsubstantiated, some are accurate but most are not,
some are total nonsence.
These are declarations of fact
> or truth based solely on the reputation or authority of the author. My
> assumption is that the author usually can't prove his point if pressed
> and therefore supplies no substantiation.
He cant because he doesnt know what he's talking about mostly.
This is difficult because
> many well known authorities on a topic are too busy to lecture on
> Usenet and will often assume the reader will automatically accept
> their point of view based on their reputation.
They are only well known because they post alot, that doesn't make
them expert or an authority in any way.
Personally, I don't
> care what someone things. I want to know why.
Well google it then.
>
> [1] The few times I've asked a question on Usenet, only a small
> percentage of the replies were genuinely useful.
Your asking the wrong question then.
When I asked a
> really complex question, with considerable detail and background,
> there were no replies.
Who can be bothered to read all that? You need to get your question
consice, you need to independently verify any answer you get. This is
not the place to learn anything except maybe to do your research
somewhere else.
> --
> Jeff Liebermann je...@cruzio.com
> 150 Felker St #D http://www.LearnByDestroying.com
> Santa Cruz CA 95060http://802.11junk.com
> Skype: JeffLiebermann AE6KS 831-336-2558
John Fields
>On Sep 2, 3:04 pm, John Fields <jfie...@austininstruments.com> wrote:
>> On Fri, 2 Sep 2011 05:47:43 -0700 (PDT), "cbarn24...@aol.com"
>>
>> <cbarn24...@aol.com> wrote:
>> >On Aug 30, 6:59 pm, Jeff Liebermann <je...@cruzio.com> wrote:
>> >> On Tue, 30 Aug 2011 10:55:10 -0500, Jeffrey Angus <grendel...@aim.com>
>> >> wrote:
>>
>> >> >Hasn't anybody read the original question?
>>
>> >> Nope. With 5 groups in the distribution, I just assumed the original
>> >> question to not be worth reading. Besides, some of the groups appear
>> >> to be write-only, where nobody (including me) reads the original
>> >> question.
>>
>> >That must be the explaination as to why so much crap has been written
>> >on this thread!!
>>
>> ---
>> The addition of your three turds to this punchbowl certainly isn't
>> helping, is it?
>>
>> --
>> JF
>
>Well they might if you actually read them, I have actually given the
>op the correct answer,
---
Really?
Here are your previous posts to this thread:
Your first:
"Finally someone comes up with the correct answer."
Your second:
"Oh they don't do practical here! It's rare for them to get it right
either, this thread is no exception. Some of them even advertise their
place of work! I wonder how much business that has cost them."
Your third:
"That must be the explaination as to why so much crap has been written
on this thread!!"
Which of those gives the correct answer to the OP?
---
>I actually read the question.
---
More's the pity then, since you obviously didn't understand it.
---
>Of course your free to ramble on about relays instead of contactors if you like.
---
If you have any capacity for learning, you need to smart up on
reasoning and punctuation before you start talking about shit you know
nothing about.
Just to help you along, here's a clue:
All contactors are relays, but not all relays are contactors.
--
JF
John Fields
---
Another of the illiterati bums rears up and flaunts his midget
intellect while standing on soggy ground.
--
JF
whit3rd
> On Aug 29, 7:21 am, DaveC <inv...@invalid.net> wrote:
> > I may be able to obtain a very small 2-pole 240 vac contactor I need rated
> > for 50 Hz only.
> >
> > If I install it in N. America, what's the implication? Is the hold-in
> > magnetism less than if it were 60 Hz?
> If instead you meant you would use it on 110v 60Hz, then dont. But you
> could use diodes to get a higher dc voltage and use that.
NO NO NO!
DC excitation of an AC-rated coil is never a good idea.
DC coils and DC-activated relays are designed very differently
from their AC cousins.
cbarn...@aol.com
> ---
> Another of the illiterati bums rears up and flaunts his midget
> intellect while standing on soggy ground.
>
> --
> JF- Hide quoted text -
>
> - Show quoted text -
Thats an outstanding insult John, must have taken you a while to come
up with, or is it a quote you stole?
Ian Field
"whit3rd" <whi...@gmail.com> wrote in message
news:b625b3af-377a-429c...@glegroupsg2000goo.googlegroups.com...
vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
As long as you alter the voltage to take into account no inductive effect,
its probably not as bad as running a DC contactor with AC.
NT
If you want to go get some specs of other relays, you can. This is
starting to get silly.
John Fields
wrote:
>On Sep 2, 8:41 pm, John Fields <jfie...@austininstruments.com> wrote:
---
Translation: "I can do neither, but let me see what I can do to duck
out of here without losing too much face."
--
JF
whit3rd
> "whit3rd" <whi...@gmail.com> wrote in message
> NO NO NO!
> DC excitation of an AC-rated coil is never a good idea.
> As long as you alter the voltage to take into account no inductive effect,
> its probably not as bad as running a DC contactor with AC.
There's a subtle difference, though, in an iron pole piece that gets
permanently magnetized by repeated DC excitation, and the same
pole piece that gets AC and is repeatedly demagnetized. I'd worry
about the DC causing, maybe after weeks, a failure of a perfectly
good AC component.
The 'no inductive effect' means that only the wire resistance, not the
resistance plus inductance, limits field current. That means the
field current with DC isn't predictably proportioned to the field
current with AC (though THAT could be quickly tested).
Don Kelly
"NT" wrote in message
news:1151b7d1-43be-4a3c...@hb5g2000vbb.googlegroups.com...
NT
Thank you.
Possibly the DC rating is lower because of the lower impedance (In the
example, with the coil closed the resistance cited is about 60 % of the 60
Hz impedance and the same current is wanted.
NT
> On Sat, 3 Sep 2011 10:13:51 -0700 (PDT), NT <meow2...@care2.com>
translation: if you want to go teach yoursef, youre free to. I'm not
puting however many hours in for you for free.
cbarn...@aol.com
> On Fri, 2 Sep 2011 15:42:28 -0700 (PDT), "cbarn24...@aol.com"
Err the first, maybe you didnt read the post it was replying to.
> ---
>
> >I actually read the question.
>
> ---
> More's the pity then, since you obviously didn't understand it.
What do you think i didn't understand?
> ---
>
> >Of course your free to ramble on about relays instead of contactors if you like.
>
> ---
> If you have any capacity for learning, you need to smart up on
> reasoning and punctuation before you start talking about shit you know
> nothing about.
smarten up John
>
> Just to help you along, here's a clue:
>
> All contactors are relays, but not all relays are contactors.
No there not dopey.
The Ghost In The Machine
TRANSLATION: I'M JUST SAYING.
John Fields
wrote:
>On Sep 3, 6:50 pm, John Fields <jfie...@austininstruments.com> wrote:
---
You're the one who made the accusations, copycat, so it's up to you to
prove them.
The fact is, you can't, since you have no working circuit which isn't
a full-wave bridge yet uses more than one diode, and there is no relay
with a 240VAC coil which will fry when driven with perfectly rectified
and smoothed 120VAC.
If you had either you'd post proof but, instead, you choose to be
ignominious.
--
JF
John Fields
---
Goodbye, inept troll...
PLONK
--
JF
NT
> On Sat, 3 Sep 2011 17:57:46 -0700 (PDT), NT <meow2...@care2.com>
I havent made any accusations
> The fact is, you can't, since you have no working circuit which isn't
> a full-wave bridge yet uses more than one diode,
what are you talking about
> and there is no relay
> with a 240VAC coil which will fry when driven with perfectly rectified
> and smoothed 120VAC.
So your sample of one proves it for all relays? Do all have the same L/
R ratio?
> If you had either you'd post proof but, instead, you choose to be
> ignominious.
You get stupid and make personal insults, AND expect the person you
insult to spend time for you for nothing. No, it is not my job, like
everyone here I only write when I have time & feel like it, and its
not my concern whether you look stuff up or not.
John Fields
wrote:
>On Sep 4, 11:06 am, John Fields <jfie...@austininstruments.com> wrote:
---
OK, then, unsubstantiated claims.
---
>> The fact is, you can't, since you have no working circuit which isn't
>> a full-wave bridge yet uses more than one diode,
>
>what are you talking about
---
You don't know?
By claiming to use "diodes" the meaning is taken that more than one
will be used.
My request was simply to show the circuit.
Can you?
---
>> and there is no relay
>> with a 240VAC coil which will fry when driven with perfectly rectified
>> and smoothed 120VAC.
>
>So your sample of one proves it for all relays? Do all have the same L/
>R ratio?
---
Unless you can prove my claim is wrong, somehow, my claim stands
undefeated.
---
>> If you had either you'd post proof but, instead, you choose to be
>> ignominious.
>
>You get stupid and make personal insults,
---
PKB???
---
>AND expect the person you
>insult to spend time for you for nothing.
---
I really expect nothing from you, and you may find being called
ignominious insulting, but I was just stating a fact.
---
>No, it is not my job, like
>everyone here I only write when I have time & feel like it, and its
>not my concern whether you look stuff up or not.
---
Well, since it's not my job to do _your_ legwork, and you refuse to
back up what you claim to be true, this discussion is over.
--
JF
cbarn...@aol.com
> On Sat, 3 Sep 2011 20:01:00 -0700 (PDT), "cbarn24...@aol.com"
>
> - Show quoted text -
Yes night night, dont forget to take your meds
NT
> On Sun, 4 Sep 2011 06:50:56 -0700 (PDT), NT <meow2...@care2.com>
what a waste of time
ehsjr
Worth investigating, to me. JF gave a specific relay & numbers. I
tried to find a relay to support the idea that an AC/DC relay would
be happy with DC voltage about 50% of AC rating. Can you please
provide a reference?
Meanwhile, what I did find was an ap note from Tyco entitled
"Operating DC Relays from AC and Vice-Versa" .
http://relays.te.com/appnotes/app_pdfs/13c3250.pdf
It does not agree with the DC at ~50% of AC rating idea. It uses
the example of a KR series relay coil. Their example uses a 12
volt AC relay fed by DC. The example states that the "DC voltage
cannot exceed 9.8 volts", and "should not be lower than 7.35 volts".
Thus the DC range would be ~61%(minimum) to ~81% (maximum) of the
12VAC rating.
Extrapolating, it does agree with the idea of BR+C fed by 120 for
the 240 volt relay, insofar as the DC voltage:
~146VDC min to ~194VDC max, which makes the midpoint ~170VDC.
That's very close to ~168 from the BR+C
Regarding coil ratings, I've worked with DC relays, and I've worked
with AC relays, but I haven't worked with AC/DC coil relays, so
I can't speak from experience with them, and I haven't found
anything yet specifically dealing with that, other than the
link I found to Tyco. So a specific link or links would be
most helpful.
Thanks,
Ed
Jamie
its not just induction here. Inter pole windings help keep the AC coil
from chattering the armature. I am sure under DC operation, this may
effect the calculations.
There are some AC coil relays that do not do this and thus the 50%
voltage for DC should come close, but then again, DC R in the coil also
plays a role in this.
Jamie
ehsjr
Your post contains nothing specific and does not address
my question.
I am looking for a specific link or links that shows a datasheet,
ap note, or example of a relay that NT has in mind. Do you have one?
I want specifics, like John Fields posted; the specs that NT
said you could get: "If you want to go get some specs of other
relays, you can." The specs I have been able to find so far
do not demonstrate what NT was talking about, thus my post
asking for a reference.
Ed
Jamie
diode imbedded in them. The voltage ratings are the same. The coil is
actually of DC type.. They also have relays with shunt diodes built into
them, for those you need to insure the polarity is correct and are
strictly DC only.
We also deal with solenoids to operate in the same manner..
Scroll down and read about AC coils, I am sure if you're looking for
some more detailed information you can find it, but this will explain
some of the differences.
http://www.ehow.com/about_6498402_difference-ac-dc-relay-coil.html
Jamie
The Ghost In The Machine
First you tell him not to be anal then you lube him up really good
then you ram your howdy doody linkage , what's up kiddo?
BOOWAHAHA...I JUST HAD TO, YOU HAD TO:) LOL
MOST UNIVERSAL MODELS ARE SOMEWHAT ERRATIC & DUBIOUS.
EUROS AND AMERICANS WILL ALWAYS BE THEMSELVES, BEST CAN BE DONE IS PUT
TO USE A CONVERTER DEVICE HARMONIC WITH BOTH WAVES PHI's. OR FREQUENCY
TO OR FROM THE INSTINCTIVE DEVICE BE IT AC OR DC PLAIN COIL OR
CONTACTOR WHICH IS HIS CONUNDRUM.
PLEASE SEND YOUR ARGUMENTS TO WHO GIVES A FLYING FUCK.COM :-)
TGITM
Jamie
You must? You read and replied to it. It didn't concern you one bit how
ever, you were interested enough to push those fat fingers along while
burning all those calories sitting on your fat ass, just to post your
dumb shit..
You are taking up valuable space, move on and allow some one more
deserving to fill that gap.
Jamie
The Ghost In The Machine
FUCK YOU CUMSHOT..GO POP YOUR LOAD SOMEWHERE ELSE.
TELL YOUR FAT ASS FATHER I AM POSTING HIS NAME AS A REFERNCE ON A
HAUNTED HOUSE I HAVE MY EYES ON......BOOWAHAHAHAHA!
AND DONT ASK ME TO BILL THE GROUP FOR MY SERVICES EITHER.
THIS IS HOW WE DO IT.
PATECUM
TGITM
Jamie
jamie
John Fields
---
"Embedded."
Link?
---
>The voltage ratings are the same. The coil is
>actually of DC type..
---
If you're saying that half-wave rectified 12VAC will cause the
armature of a relay with a 12VDC coil to close, instead of chatter,
then I'd have to ask for proof since I have empirical evidence which
refutes your assertion.
Years ago, Larkin and I had the same argument here.
He took your position and lost the argument.
---
>They also have relays with shunt diodes built into
>them, for those you need to insure the polarity is correct and are
>strictly DC only.
---
What does that have to do with driving DC coil relays with rectified
AC, or driving AC coil relays with DC?
From my experience, those diodes are used in order to return the
coil's inductive turn-off transient to the positive supply in order to
keep E = LdI/dT from ruining a relay driver's day, and to save the
user the expense of an extra part and the PCB real estate needed for
its implementation.
---
> We also deal with solenoids to operate in the same manner..
---
Elaborate, please?
---
>Scroll down and read about AC coils, I am sure if you're looking for
>some more detailed information you can find it, but this will explain
>some of the differences.
>
>http://www.ehow.com/about_6498402_difference-ac-dc-relay-coil.html
>
>
>Jamie
--
JF
John S
> I may be able to obtain a very small 2-pole 240 vac contactor I need rated
> for 50 Hz only.
>
> If I install it in N. America, what's the implication? Is the hold-in
Hi, Dave -
Magnitisim is less.
Noisy depends on many things.
>
> Please don't ask or suggest other sources. This is a very specific device and
> I've not been able to locate other than this.
>
> Thanks,
> Dave
>
You should look at the manufacturer's specifications. The 50/60 Hz will
not matter much except for one thing: the coil current will be reduced
to ~50/60 of its nominal value (~83.3%) because of the coil inductance
(it has to do with total impedance, but this is a best guess without
knowing more about your contactor). Usually, the manufacturer will list
the minimum voltage the coil can handle.
At this point, my best guess is that the coil will suffer a 15% loss of
excitation voltage. If the mfr says that's too low, you may be in
trouble at low line.
Cheers,
John
Jamie
Never heard of core hysteresis?
>
>
>>They also have relays with shunt diodes built into
>>them, for those you need to insure the polarity is correct and are
>>strictly DC only.
>
>
> ---
> What does that have to do with driving DC coil relays with rectified
> AC, or driving AC coil relays with DC?
>
> From my experience, those diodes are used in order to return the
> coil's inductive turn-off transient to the positive supply in order to
> keep E = LdI/dT from ruining a relay driver's day, and to save the
> user the expense of an extra part and the PCB real estate needed for
> its implementation.
> ---
>
>
>> We also deal with solenoids to operate in the same manner..
>
>
> ---
> Elaborate, please?
> ---
>
>>Scroll down and read about AC coils, I am sure if you're looking for
>>some more detailed information you can find it, but this will explain
>>some of the differences.
>>
>>http://www.ehow.com/about_6498402_difference-ac-dc-relay-coil.html
>>
>>
>>Jamie
>
>
>
carry on with JL, I won't be another one of your imaginary conquest.
Not saying that don't know what your doing but you tend to over look
a few things that have been done in the field over the years.
Jamie
Jeff Liebermann
<jamie_ka1lpa_not_v...@charter.net> wrote:
>I was going to make a whole page for you to read, but I know how you
>carry on with JL, I won't be another one of your imaginary conquest.
--
Jeff Liebermann je...@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
The Ghost In The Machine
THEY DETECT CHANGES AND OPEN OR CLOSE RESPECTIVELY, SOMETHING LIKE
SEMICONDUCTORS.
NO MAGNETIC DISTORTION INVOLVED.
BOOWAHAHAHAHAA.....WELCOME TO THE FUTURE.
PATECUM
TGITM
The Ghost In The Machine
PLEASE HOLD YOUR ANAL EMANATIONS FOR THE REST ROOM, JAMIKA.
YOU STINK !
TGITM
The Ghost In The Machine
ehsjr
While I do appreciate your attempt to help, I must say it misses
the point.
I want a *specific* link to an *AC/DC* relay of the type *NT*
had in mind, or to an ap note or reference that discusses a relay
coil that is rated for *both* AC and DC as he indicated.
Do you have a link to what NT was talking about? Here's what
"The various ones I've seen that have coil 2 ratings, one for ac one
for dc, have consistently had the dc coil rating be half the ac
voltage rating."
responses. You mentioned a relay that will "do" DC because it
has an imbedded (sic) diode and say "The voltage ratings are the
same." That is *NOT* what NT said. He talks about the dc
coil rating being half the ac rating.
Ed
Michael A. Terrell
Jeff Liebermann wrote:
>
> On Thu, 08 Sep 2011 21:56:25 -0400, Jamie
>
> ?I was going to make a whole page for you to read, but I know how you
> ?carry on with JL, I won't be another one of your imaginary conquest.
> Ummm.... I'm JL. What am I missing?
--
You can't have a sense of humor, if you have no sense.
The Ghost In The Machine
wrote:
YOU SUCK.....STAY OFF USENET DUDE.
YOU'RE ON BORROWED WAVELENGTH AS IT IS.
GO HUNT DOWN SOME TERRORISTS OR DO SOMETHING HELPFUL INSTEAD.
CHANGE YOUR NAME, TRY COOKIE MONSTER.
BOOWAHAHAHAHA,.....YOU FINK !
PATECUM
TGITM
John Fields
>John Fields wrote:
>
>> On Thu, 08 Sep 2011 11:23:56 -0400, Jamie
>> <jamie_ka1lpa_not_v...@charter.net> wrote:
>>>Don't be anal, they make relays that will do AD/DC because they have a
>>>diode imbedded in them.
>>
>>
>> ---
>> "Embedded."
>>
>> Link?
>> ---
>>
>>
>>>The voltage ratings are the same. The coil is
>>>actually of DC type..
>>
>>
>> ---
>> If you're saying that half-wave rectified 12VAC will cause the
>> armature of a relay with a 12VDC coil to close, instead of chatter,
>> then I'd have to ask for proof since I have empirical evidence which
>> refutes your assertion.
>>
>> Years ago, Larkin and I had the same argument here.
>>
>> He took your position and lost the argument.
>
>Well, then he lost unfairly.
---
Instead of blathering on about something of which you obviously have
little knowledge, why not try it?
That is, get a few relays with DC coils, drive their coils with
half-wave rectified AC, and post back with the results.
---
>Never heard of core hysteresis?
---
Sure, but for relays it's usually defined as the difference between
the must-make and must-break voltage instead of this:
>>>They also have relays with shunt diodes built into
>>>them, for those you need to insure the polarity is correct and are
>>>strictly DC only.
>>
>>
>> ---
>> What does that have to do with driving DC coil relays with rectified
>> AC, or driving AC coil relays with DC?
>>
>> From my experience, those diodes are used in order to return the
>> coil's inductive turn-off transient to the positive supply in order to
>> keep E = LdI/dT from ruining a relay driver's day, and to save the
>> user the expense of an extra part and the PCB real estate needed for
>> its implementation.
>> ---
>>
>>
>>> We also deal with solenoids to operate in the same manner..
>>
>>
>> ---
>> Elaborate, please?
>> ---
>
>Why?. You don't understand why, I guess?
---
Well, although a case might be made for:
.AC>---[DIODE>]--+-------+
. | |K
. [COIL] DIODE
. | |
.AC>-------------+-------+
I've never heard of a DC solenoid being converted to AC by using a
shunt diode, have you?
If so, why not give us the benefit of your knowledge by elaborating on
the subject?
---
>>>Scroll down and read about AC coils, I am sure if you're looking for
>>>some more detailed information you can find it, but this will explain
>>>some of the differences.
>>>
>>>http://www.ehow.com/about_6498402_difference-ac-dc-relay-coil.html
>>>
>>>
>>>Jamie
>>
>>
>>
>I was going to make a whole page for you to read, but I know how you
>carry on with JL, I won't be another one of your imaginary conquest.
---
Aw... Poor baby.
Afraid of making and having to own up to an error, are you? ;)
---
> Not saying that don't know what your doing but you tend to over look
>a few things that have been done in the field over the years.
---
Like what, the development of latching relays with infinite gain? ;)
--
JF
Jamie
Is this what you're looking for ?
http://relays.te.com/appnotes/app_pdfs/13c3250.pdf
It explains operating AC coils on DC and AC coils using
the internal DIODES for shading rings design.
These are just some examples out there.
I don't know what "NT" had in mind, if this isn't what
you're after, than I'll stand down. ;)
Btw.
P&B got bought out, in case any one didn't know.
Jamie
Jamie
No error, you're the one with egg on the face loser, and this will be
my last to you. I will not be another JL stick for you to crack your
false sense of victory with.
http://relays.te.com/appnotes/app_pdfs/13c3250.pdf
Just because you haven't seen it or think it shouldn't be done means
every one else should bend over to your rule? Sorry sucker, this is why
people move on and those like yourself are left holding the bag.
And while your reading that doc, if you even do, the comment about
unfiltered DC where the armature might experience movement, they don't
say it will. That is because it depends on the mechanical design of the
relay and type of system in place.
Further more, I guess you've never seen the old trick of operating a
small DC relay with half wave to force the unit to slightly vibrate, not
enough to actually see it how ever, when doing this, you could force the
contact surface to keep themselves cleaner and thus cheap relays would
be used to pass reference signals through. This would be evident over
time from apparent ware on the contacts from mechanical movement and no
arc which would otherwise do the wetting process via the plasma process.
By and have a good life..
Jamie
Jamie
You know what's even funnier than your stupidity? Your lack of
ability to convey over what you really want to say in english,
it's hilarious..
Jamie
"Just for you:
SOME PEOPLE ARE LIKE SLINKIES. NOT REALLY GOOD FOR ANYTHING BUT
THEY BRING A SMILE TO YOUR FACE WHEN PUSHED DOWN THE STAIRS.
"
Jamie
> On Thu, 08 Sep 2011 21:56:25 -0400, Jamie
> <jamie_ka1lpa_not_v...@charter.net> wrote:
>
>
>>I was going to make a whole page for you to read, but I know how you
>>carry on with JL, I won't be another one of your imaginary conquest.
>
>
> Ummm.... I'm JL. What am I missing?
>
>
>
Absolutely nothing sir :)
Jamie
John Fields
<jamie_ka1lpa_not_v...@charter.net> wrote:
>No error, you're the one with egg on the face loser, and this will be
>my last to you.
---
Thanks, I'm looking forward to it!
--
JF
ehsjr
Geeeez. I posted that link in my _first_ post in the thread, and
you replied to that post. I guess you either didn't read the post
properly, or didn't understand it. The ap note does not agree with
the DC at ~50% of AC rating idea - details are given in that post.
>
> It explains operating AC coils on DC and AC coils using
> the internal DIODES for shading rings design.
Yup. To operate an AC relay on DC, (the Tyco ap note says
doing so is impractical, but that you can do it in an
emergency) you should install a residual and you must lower
the voltage below the AC rating. An AC rated coil needs DC
in excess of 61% of the ac rating on the minimum side, and
less than 82% of the ac rating on the maximum side, per the
example given in the ap note.
>
> These are just some examples out there.
>
> I don't know what "NT" had in mind, if this isn't what
> you're after, than I'll stand down. ;)
>
Ok.
Ed
Jamie
>>> I don't know how to make it clear enough for you to understand.
>>> While I do appreciate your attempt to help, I must say it misses
>>> the point.
>>>
>>> I want a *specific* link to an *AC/DC* relay of the type *NT*
>>> had in mind, or to an ap note or reference that discusses a relay
>>> coil that is rated for *both* AC and DC as he indicated.
>>>
>>> Do you have a link to what NT was talking about? Here's what
>>> he said:
>>> "The various ones I've seen that have coil 2 ratings, one for ac one
>>> for dc, have consistently had the dc coil rating be half the ac
>>> voltage rating."
>>>
>>> I _do not_ need generalizations, hand waving and condescending
>>> responses. You mentioned a relay that will "do" DC because it
>>> has an imbedded (sic) diode and say "The voltage ratings are the
>>> same." That is *NOT* what NT said. He talks about the dc
>>> coil rating being half the ac rating.
>>>
>>> Ed
>>
>>
>> Is this what you're looking for ?
>>
>> http://relays.te.com/appnotes/app_pdfs/13c3250.pdf
>
>
> Geeeez. I posted that link in my _first_ post in the thread, and
> you replied to that post. I guess you either didn't read the post
> properly, or didn't understand it. The ap note does not agree with
> the DC at ~50% of AC rating idea - details are given in that post.
>
Sorry, I didn't see that.
>>
>> It explains operating AC coils on DC and AC coils using
>> the internal DIODES for shading rings design.
No, that wasn't a hack as far as the diodes goes, that is a practical
design in a family of relays, We use large contactors with the dual
coil and diodes in them. You don't see this from the out side world but
they are incased in the encapsulation. Those particular types can have
DC going directly to them. It's just the way they are with obvious
reasons.
>
> Yup. To operate an AC relay on DC, (the Tyco ap note says
> doing so is impractical, but that you can do it in an
> emergency) you should install a residual and you must lower
> the voltage below the AC rating. An AC rated coil needs DC
> in excess of 61% of the ac rating on the minimum side, and
> less than 82% of the ac rating on the maximum side, per the
> example given in the ap note.
The app note is pointing equivalent power dissipation, as you
know relays will pull in at a lower current So I don't see a problem
here.
Why don't you put a few AC types on the bench and test them yourself?
I think you'd be surprised in what you find. Lab testing tells a lot
about what you can do.
The only problem I have found with this practice of using AC on DC is
that some AC units use material that has a high hysteresis and the
AC will help keep this down. They do this in cases where they don't use
the dual coil system. In DC operation, I've seen it over magnetize the
core and cause a little slow release on the contacts. But that may not
be such a big deal in most cases.
Have a good day.
Jamie
John S
I have an Essex contactor which was removed from my old A/C outside
unit. It has a 24VAC 50/60 Hz coil. I can make some measurements on it
if anyone is interested.
John S