magnetic chuck control

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engineman

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Mar 11, 2010, 8:56:34 PM3/11/10
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have an Electro-Matic magnetic chuck control that I plan to sell.
It is rated at 115 volts AC in and 115 volts DC out at 50 watts 50-60
HZ.
It's like new and I'm going to try Craigslist first and if no results,
then eBay.
Do any of you guys have an idea what my asking price should be?

Engineman

Don Foreman

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Mar 11, 2010, 11:24:20 PM3/11/10
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It sounds like just a bridge rectifier, which can be had for well
under $5. Cost to replicate with box, switch, line cord and suitable
connector would probably be under $20.

DoN. Nichols

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Mar 12, 2010, 11:58:07 PM3/12/10
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Also a capacitor to minimize ripple, and a resistor to limit
turn-on surge. A DPDTCO switch does the job of selecting between AC and
CD output, as well as turing it off.

This is exactly what is in the base of the small surface grinder
which I have -- and it had an even simpler circuit before I "improved"
it. It had not a bridge, but a single Selenium rectifier, and a SPDTCO
switch. The original capacitor was marked 8 uF, and actually *measured*
something like 0.001 uF or less. I replaced it with about a 200 uF cap,
which is total overkill, but is what I had on hand in the proper voltage
range.

Enjoy,
DoN.

--
Email: <dnic...@d-and-d.com> | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

Don Foreman

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Mar 13, 2010, 12:44:22 AM3/13/10
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On 13 Mar 2010 04:58:07 GMT, "DoN. Nichols" <dnic...@d-and-d.com>
wrote:

>On 2010-03-12, Don Foreman <dfor...@NOSPAMgoldengate.net> wrote:
>> On Thu, 11 Mar 2010 17:56:34 -0800 (PST), engineman
>><engin...@aol.com> wrote:
>>
>>> have an Electro-Matic magnetic chuck control that I plan to sell.
>>>It is rated at 115 volts AC in and 115 volts DC out at 50 watts 50-60
>>>HZ.
>>>It's like new and I'm going to try Craigslist first and if no results,
>>>then eBay.
>>>Do any of you guys have an idea what my asking price should be?
>>>
>>>Engineman
>>
>> It sounds like just a bridge rectifier, which can be had for well
>> under $5. Cost to replicate with box, switch, line cord and suitable
>> connector would probably be under $20.
>
> Also a capacitor to minimize ripple, and a resistor to limit
>turn-on surge.

Since the spec is 115 VAC in, 115 VDC out, there can't be much of a
ripple-reduction capacitor, if any. A cap charges to the peak voltage
of 163 volts each half-cycle, decays according to the cap size and
load current but the avg DC voltage will always be > 115VDC because
(neglecting diode drops) the avg DC voltage is 115 with no cap at all.
A substantially inductive load like a magnetic chuck wouldn't have
much current ripple anyway. There's also no turn on surge; dI/dt is
limited by the inductance of the load and steady state current is
determined by the load's resistance.

Martin H. Eastburn

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Mar 13, 2010, 1:02:57 AM3/13/10
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Glad you got the Selenium rectifier out of there - when it fails,
a poisonous gas is released! Rather nasty in the small shop.
The 8uf cap was an electrolytic type and dryed out - becoming an insulator
almost.

Martin

Steve Lusardi

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Mar 13, 2010, 4:04:32 AM3/13/10
to
Very, very dangerous these things.....losing hold power on a magnetic chuck when in use can be very exciting indeed. I am afraid
that if I really needed to use one of these things, the circuit would be anything but simple. I would absolutely make certain
there would be enough hold time to get the wheel off the work in an emergency.
Steve

"engineman" <engin...@aol.com> wrote in message news:3ebed554-2c4e-449f...@t17g2000prg.googlegroups.com...

Karl Townsend

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Mar 13, 2010, 7:54:03 AM3/13/10
to

"Don Foreman" <dfor...@NOSPAMgoldengate.net> wrote in message
news:m19mp598smiuinnei...@4ax.com...

Just curious, there's also a spring loaded "reverse" switch to de magnetise
on these chucks. Are they just switching the + and - leads in there?

Karl


Ned Simmons

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Mar 13, 2010, 10:49:07 AM3/13/10
to
On 13 Mar 2010 04:58:07 GMT, "DoN. Nichols" <dnic...@d-and-d.com>
wrote:

>On 2010-03-12, Don Foreman <dfor...@NOSPAMgoldengate.net> wrote:


>> On Thu, 11 Mar 2010 17:56:34 -0800 (PST), engineman
>><engin...@aol.com> wrote:
>>
>>> have an Electro-Matic magnetic chuck control that I plan to sell.
>>>It is rated at 115 volts AC in and 115 volts DC out at 50 watts 50-60
>>>HZ.
>>>It's like new and I'm going to try Craigslist first and if no results,
>>>then eBay.
>>>Do any of you guys have an idea what my asking price should be?
>>>
>>>Engineman
>>
>> It sounds like just a bridge rectifier, which can be had for well
>> under $5. Cost to replicate with box, switch, line cord and suitable
>> connector would probably be under $20.
>
> Also a capacitor to minimize ripple, and a resistor to limit
>turn-on surge. A DPDTCO switch does the job of selecting between AC and
>CD output, as well as turing it off.
>
> This is exactly what is in the base of the small surface grinder
>which I have -- and it had an even simpler circuit before I "improved"
>it. It had not a bridge, but a single Selenium rectifier, and a SPDTCO
>switch. The original capacitor was marked 8 uF, and actually *measured*
>something like 0.001 uF or less. I replaced it with about a 200 uF cap,
>which is total overkill, but is what I had on hand in the proper voltage
>range.

It's probably more elaborate than that. Electro-matic makes these
chuck controllers.
http://www.em-chicago.com/chuck_controls.htm

In the dim past, they made the "Neutrofier" electromechanical chuck
controllers, which were crazy electromechanical clockwork affairs.
I've helped a customer repair the Neutrofier on their Blanchard
grinder a couple times. I wish I had taken a photo of it; I can't find
one online.

--
Ned Simmons

Ned Simmons

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Mar 13, 2010, 11:02:58 AM3/13/10
to
On Sat, 13 Mar 2010 10:49:07 -0500, Ned Simmons <ne...@nedsim.com>
wrote:

>I wish I had taken a photo of it; I can't find
>one online.

See patent numbers:

2229104
3401313

--
Ned Simmons

Don Foreman

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Mar 13, 2010, 11:15:29 AM3/13/10
to

My guess is that it applies AC thru a PTC thermistor to apply a
diminishing AC current.

Ignoramus4212

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Mar 13, 2010, 11:42:50 AM3/13/10
to
On 2010-03-13, Ned Simmons <ne...@nedsim.com> wrote:
>
> It's probably more elaborate than that. Electro-matic makes these
> chuck controllers.
> http://www.em-chicago.com/chuck_controls.htm
>
> In the dim past, they made the "Neutrofier" electromechanical chuck
> controllers, which were crazy electromechanical clockwork affairs.
> I've helped a customer repair the Neutrofier on their Blanchard
> grinder a couple times. I wish I had taken a photo of it; I can't find
> one online.
>

i have a neutrofier control and if any one is interested, I can take a
lot of pictures.

i

john

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Mar 13, 2010, 11:48:42 AM3/13/10
to

I have a Netrofier control on one of my bigger surface grinders. You
can adjust the dc voltage to the magnet to regulate the amount of
holding power to the piece. When you are ready to take the piece off
you release it with the control applying ac voltage to the chuck in
diminishing pulses of about one second duration. The process takes
about 10 seconds. I think I have the manual on the unit in my files.
Blanchard grinders use them a lot.

Walker also makes magnetic holding equipment. They are nice units. I
have replaced several of the old tube type controls with them and they
work flawlessly.

http://walkermagnet.com/products-and-services/products-and-services.html

I think the last one I did was for a 8x 24 inch magnet and the price was
about 450.00. They are just a two wire and ground hookup to the magnet
and plug into 110 volt outlet. To order you supply the model or size of
the magnet and they will supply the right control.

John

Ned Simmons

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Mar 13, 2010, 12:24:52 PM3/13/10
to
On Sat, 13 Mar 2010 11:48:42 -0500, john <amd...@intergrafix.net>
wrote:

>
>I have a Netrofier control on one of my bigger surface grinders. You
>can adjust the dc voltage to the magnet to regulate the amount of
>holding power to the piece. When you are ready to take the piece off
>you release it with the control applying ac voltage to the chuck in
>diminishing pulses of about one second duration. The process takes
>about 10 seconds. I think I have the manual on the unit in my files.
>Blanchard grinders use them a lot.

The mechanical Neutrofier I worked on has a big rotary switch that
sequences a number of polarity reversals and voltage reductions of the
DC magnet supply. As far as I know the magnet never sees AC.

>
>Walker also makes magnetic holding equipment. They are nice units. I
>have replaced several of the old tube type controls with them and they
>work flawlessly.
>
>http://walkermagnet.com/products-and-services/products-and-services.html
>
>I think the last one I did was for a 8x 24 inch magnet and the price was
>about 450.00. They are just a two wire and ground hookup to the magnet
>and plug into 110 volt outlet. To order you supply the model or size of
>the magnet and they will supply the right control.

Thanks, I'll try to remember that if the Neutrofier becomes
uneconomical to repair. The last time they called me the problem was
in the commutator under the chuck, not the controller.

--
Ned Simmons

Ned Simmons

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Mar 13, 2010, 12:29:50 PM3/13/10
to

If the price is right and it happens to match my customer's chuck,
they might be interested. My recollection is that the magnet is 240VDC
at around 3A. It's on a 30" or 36" Blanchard grinder. Is it a
mechanical unit or one of the more modern replacements?

--
Ned Simmons

Ignoramus4212

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Mar 13, 2010, 12:44:26 PM3/13/10
to
On 2010-03-13, Ned Simmons <ne...@nedsim.com> wrote:
> On Sat, 13 Mar 2010 10:42:50 -0600, Ignoramus4212
><ignora...@NOSPAM.4212.invalid> wrote:
>
>>On 2010-03-13, Ned Simmons <ne...@nedsim.com> wrote:
>>>
>>> It's probably more elaborate than that. Electro-matic makes these
>>> chuck controllers.
>>> http://www.em-chicago.com/chuck_controls.htm
>>>
>>> In the dim past, they made the "Neutrofier" electromechanical chuck
>>> controllers, which were crazy electromechanical clockwork affairs.
>>> I've helped a customer repair the Neutrofier on their Blanchard
>>> grinder a couple times. I wish I had taken a photo of it; I can't find
>>> one online.
>>>
>>
>>i have a neutrofier control and if any one is interested, I can take a
>>lot of pictures.
>
> If the price is right and it happens to match my customer's chuck,
> they might be interested. My recollection is that the magnet is 240VDC
> at around 3A. It's on a 30" or 36" Blanchard grinder. Is it a
> mechanical unit or one of the more modern replacements?
>

Ned, you can email me at ichudov AT algebra DOT com if you have any
questions.

Igor

Karl Townsend

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Mar 13, 2010, 3:52:07 PM3/13/10
to
...

>>Just curious, there's also a spring loaded "reverse" switch to de
>>magnetise
>>on these chucks. Are they just switching the + and - leads in there?
>>
>>Karl
> My guess is that it applies AC thru a PTC thermistor to apply a
> diminishing AC current.

that's the trouble with asking a EE a question. You don't understand the
answer <VBG>

Karl

john

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Mar 13, 2010, 4:58:48 PM3/13/10
to


If I remember right they use a magnetic amplifier type system to
regulate the AC voltage going to the magnet. Its been a number of years
ago ant to my recollection the transformer was bad on the one I was
fixing. I just rewound the transformer and put it back in service.

I learned winding transformers when I was a kid building high power ham
transmitters. The old Dumont TV transformers were great for getting
1500 vdc for a pair of 811's.

John

engineman

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Mar 13, 2010, 9:40:02 PM3/13/10
to
I took some photos of the device.
Can anyone tell from these whether the switch feeds in AC or reverses
the polarity to demagnatize?
Don, it is a little more elaborate than you speculated, it has a choke
coil also.
The cap is .001MFD


http://picasaweb.google.com/engineman69/DropBox?authkey=Gv1sRgCJf25e2Q6aiGiQE#

Engineman

> John- Hide quoted text -
>
> - Show quoted text -

Lloyd E. Sponenburgh

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Mar 13, 2010, 9:55:14 PM3/13/10
to
engineman <engin...@aol.com> fired this volley in news:ceb8d5a7-88fa-
4ee0-a365-5...@k2g2000pro.googlegroups.com:

> Can anyone tell from these whether the switch feeds in AC or reverses
> the polarity to demagnatize?
>

You can't "reverse the polarity to demagnatize" an electromagnet. If
current is flowing, it's magnetized. If it happens to be wound for AC,
it will be constantly reversing polarity at 60Hz, anyway. If it's wound
for DC, reversing the direction of current flow merely reverses the
magnetic poles.

OTOH, as suggested, if the chuck were wound for AC, and the power supply
were set up to supply a rapidly diminishing AC voltage to the magnet, it
would eventually settle down to nearly zero flux.

This is necessary, because suddenly breaking the current can leave the
poles magnetized even after current is stopped.

Your power supply apparently has two selenium rectifiers (of old). That
would suggest a full-wave-center-tapped DC configuration. But I don't
really see that ferro-magnetic thingy as a regular transformer. It looks
more like a center-tapped choke or an autoformer. The choke would be to
take out the "buzz" of AC, and make the chuck run more quietly. There is
a small cap on the control board. It might be there to suppress switch
arcing, or it could be used as a fly-back to suppress quick-break
magnetization of the chuck, or it could be a little bit of filtering to
take out more buzz.

The label sez... 115DC out 115AC in. So there's not much voltage
"transforming" going on in the choke/autoformer/transformer.

LLoyd

John

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Mar 14, 2010, 12:08:24 AM3/14/10
to


the selenium rectifiers look like they are hooked up as a full wave
center tapped rectifier system, but the wires on the secondary also go
out to the switch. I would imagine they are just using the ac to feed
the magnet while you remove the part from the magnet rather than on
other control units that actually demagnetize the part and magnet


John

DoN. Nichols

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Mar 14, 2010, 12:11:59 AM3/14/10
to
On 2010-03-13, Karl Townsend <karltown...@embarqmail.com> wrote:

[ ... mag chuck info snipped ... ]

> Just curious, there's also a spring loaded "reverse" switch to de magnetise
> on these chucks. Are they just switching the + and - leads in there?

Usually -- they just switch from DC to AC into the coil, which
weakens the attraction, and as you pull the workpiece away, the AC field
slowly decreases removing the permanent magnetism otherwise potentially
left in the workpiece. In the case of mine, it has no spring return, so
you can lift the workpiece away at leisure.

Ideally -- you would have a circuit which caused a steadily
decreasing AC voltage to demagnetize everything and then just go away.
You might be able to do it with just a good quality charged capacitor
switched onto the coil, which would ring for a few cycles and this may
be what you have with the momentary switch.

DoN. Nichols

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Mar 14, 2010, 12:16:24 AM3/14/10
to
On 2010-03-14, engineman <engin...@aol.com> wrote:
> I took some photos of the device.
> Can anyone tell from these whether the switch feeds in AC or reverses
> the polarity to demagnatize?

Certainly *not* the latter -- that would just re-magnetize it
with the opposite polarity -- still magnetized.

> Don, it is a little more elaborate than you speculated, it has a choke
> coil also.
> The cap is .001MFD
>
>
> http://picasaweb.google.com/engineman69/DropBox?authkey=Gv1sRgCJf25e2Q6aiGiQE#

Hmm ... perhaps the ringing capacitor discharge which I
postulated in the other article I just posted.

Don Foreman

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Mar 14, 2010, 12:19:06 AM3/14/10
to
On Sat, 13 Mar 2010 18:40:02 -0800 (PST), engineman
<engin...@aol.com> wrote:

>I took some photos of the device.
>Can anyone tell from these whether the switch feeds in AC or reverses
>the polarity to demagnatize?
>Don, it is a little more elaborate than you speculated, it has a choke
>coil also.
>The cap is .001MFD
>
>
>http://picasaweb.google.com/engineman69/DropBox?authkey=Gv1sRgCJf25e2Q6aiGiQE#

I'm wondering if the thing that looks like a choke might be a
transformer used to apply low-voltage AC for degaussing. There are
only three terminals in view on the choke/xfmr thingy, but all three
of them are more than halfway from center of coil to outside of coil.
That makes me wonder if there isn't another winding whose terminals
aren't visible in the photos.

That's about all I can deduce from the photos.

There could still be a PTC thermistor in there. They've been around
about as long as color TV has. They were used with the degaussing
coils that demagnetized the picture tube upon turnon.


Don Foreman

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Mar 14, 2010, 12:23:28 AM3/14/10
to

Ask easier questions! <G>

Wanna beer?
Hot enough for ya?
Cold enough for ya?
Ja git chur deer?
How 'bout them Vikings, eh?
Been catchin' enny?
Waddya usin fer bait?

Don Foreman

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Mar 14, 2010, 12:30:59 AM3/14/10
to
On Sat, 13 Mar 2010 12:24:52 -0500, Ned Simmons <ne...@nedsim.com>
wrote:

>On Sat, 13 Mar 2010 11:48:42 -0500, john <amd...@intergrafix.net>


>wrote:
>>
>>I have a Netrofier control on one of my bigger surface grinders. You
>>can adjust the dc voltage to the magnet to regulate the amount of
>>holding power to the piece. When you are ready to take the piece off
>>you release it with the control applying ac voltage to the chuck in
>>diminishing pulses of about one second duration. The process takes
>>about 10 seconds. I think I have the manual on the unit in my files.
>>Blanchard grinders use them a lot.
>
>The mechanical Neutrofier I worked on has a big rotary switch that
>sequences a number of polarity reversals and voltage reductions of the
>DC magnet supply. As far as I know the magnet never sees AC.

That makes sense and explains the electromechanical stuff. Polarity
reversals are by definition AC. This is a (very retro) way to achieve
AC excitation that diminishes in magnitude over a period of time.

pent...@yahoo.com

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Mar 14, 2010, 5:26:53 AM3/14/10
to

Difficult to sort out from the photos.

The two rectifiers are clearly AC in at the centre and DC out
at the ends. Since the the ends of the two rectifier stacks are
strapped together they are configured as a full wave bridge
rectifier with output to the magnetising coil.

The outer wires of the iron cored component connnect to bridge
rectifier AC input so this must be a transformer - it cannot be a
choke.

It looks as if there are only three leadouts. The AC input is
connected to the centre tag and RH tag(connection at rectifier
centre tag) so this makes it an autotransformer - possibly 2:1
stepup for a 230V magnetising coil.

This sounds pretty unlikely unless it is of European origin.
However the nameplate lists both 60 and 50 HZ operation so
clearly European supplies are a possibility. 230V operation would
simply need moving the yellow wire from centre to LH tag.

Jim

Ned Simmons

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Mar 14, 2010, 8:58:51 PM3/14/10
to
On Sat, 13 Mar 2010 23:30:59 -0600, Don Foreman
<dfor...@NOSPAMgoldengate.net> wrote:

>
>That makes sense and explains the electromechanical stuff. Polarity
>reversals are by definition AC. This is a (very retro) way to achieve
>AC excitation that diminishes in magnitude over a period of time.

Is it likely that the simulated low frequency AC is necessary to get
that big magnet to change polarity, and that regular 60Hz is fine for
a smaller chuck? This chuck is 30 or 36 inches in diameter and
probably weighs 1000 to 1500 lbs. I had a chance to ponder its weight
when I crawled under it to check the continuity thru the slip rings
and windings.

--
Ned Simmons

Lloyd E. Sponenburgh

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Mar 14, 2010, 9:00:03 PM3/14/10
to
Ned Simmons <ne...@nedsim.com> fired this volley in
news:q31rp5tppob446ti1...@4ax.com:

> Is it likely that the simulated low frequency AC is necessary to get
> that big magnet to change polarity, and that regular 60Hz is fine for
>

nah... there are magnets the size of a bus that work on 60Hz.

LLoyd

Martin H. Eastburn

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Mar 14, 2010, 9:56:59 PM3/14/10
to
I suspect it is an isolation transformer first off and then
has various taps to adapt to a full wave.

I can't see it well - so if the switch is DC to grip and AC
on the windings - it might demag the unit while 'off'.

Big time guess - have no idea what the PCB is doing...

Martin

Martin H. Eastburn

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Mar 14, 2010, 10:05:33 PM3/14/10
to
Yep - used a monster monster for semiconductor maga hits.

Semi had iron in it - a big NO NO for most fabs - a bad contaminant.

It had a massive metal core that 'focused in cone shape pole.
The pole face was an 300mm wafer diameter.

The real problem- where to use it - without ripping walls down.. :-)

Loading dock. It was put there by a massive Hyster forklift that
could tilt its wheels in order to make tighter turns.

Moved the loading dock people to another dock. :-)

Martin

DoN. Nichols

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Mar 15, 2010, 12:31:08 AM3/15/10
to
On Sat, 13 Mar 2010 14:52:07 -0600, "Karl Townsend"
<karltown...@embarqmail.com> wrote:

>...
>>>Just curious, there's also a spring loaded "reverse" switch to de
>>>magnetise
>>>on these chucks. Are they just switching the + and - leads in there?
>>>
>>>Karl
>> My guess is that it applies AC thru a PTC thermistor to apply a
>> diminishing AC current.
>
>that's the trouble with asking a EE a question. You don't understand the
>answer <VBG>

Well -- to give a partial answer at least:

1) PTC Stands for "Positive Temperature Coefficient" --
when cold the resistance is much lower than when hot.

2) If the cold resistance is low enough and the hot resistance
is high enough, it can start out with high current when first
switched on, and over a fairly short time decrease to a much
lower current as the resistance increases.

This sort of thing was used to degauss color TV tubes when the
set was first switched on without continuing to apply an AC magnetic
field strong enough to cause wiggling of the image as you watch. (If
you switch the set off and back on fairly quickly, you would probably
see just that as the PTC resistor heats up again. The presumes that the
circuit is designed to drop all power to the PTC and degaussing coil
once the current drops below a certain value.

Don Foreman

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Mar 15, 2010, 12:34:15 AM3/15/10
to
On Sun, 14 Mar 2010 19:58:51 -0500, Ned Simmons <ne...@nedsim.com>
wrote:

>On Sat, 13 Mar 2010 23:30:59 -0600, Don Foreman


><dfor...@NOSPAMgoldengate.net> wrote:
>
>>
>>That makes sense and explains the electromechanical stuff. Polarity
>>reversals are by definition AC. This is a (very retro) way to achieve
>>AC excitation that diminishes in magnitude over a period of time.
>
>Is it likely that the simulated low frequency AC is necessary to get
>that big magnet to change polarity, and that regular 60Hz is fine for
>a smaller chuck? This chuck is 30 or 36 inches in diameter and
>probably weighs 1000 to 1500 lbs.

Yes, if AC excitation voltage is limited to 115VAC. A large
inductance may not accept enough current to demagnetize at 115VAC, 60
Hz.

pent...@yahoo.com

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Mar 15, 2010, 5:01:19 AM3/15/10
to

Difficult to sort out from the photos.

ty

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Oct 25, 2021, 12:18:06 AM10/25/21
to
replying to Ned Simmons, ty wrote:
need one thats 13 amps 110 vdc output 4000 watts for my blanchard sg.

--
for full context, visit https://www.polytechforum.com/metalworking/magnetic-chuck-control-228438-.htm


Michael Terrell

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Nov 6, 2021, 5:01:13 PM11/6/21
to
On Monday, October 25, 2021 at 12:18:06 AM UTC-4, ty wrote:
> replying to Ned Simmons, ty wrote:
> need one that's 13 amps 110 VDC output 4000 watts for my blanchard sg.
Do you really think that he's waited over 11 years for this?
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