Semi-conductor Question
Bob Villa
the place of a starting relay or centrifugal cut-out for an AC motor.
Where do you find them? (I think I sent for one thru Popular Science
mag at the time)
Thanks
Pilgrim
<e6651839-0b72-4722...@h19g2000yqb.googlegroups.com>,
Bob Villa <pheeh...@gmail.com> wrote:
I don't know about a solid state version. But, there are
electro-mechanical versions that are quite common on motors less than
1 hp. They control the input to the start winding with a current
sensitive relay. When the motor is turned on the inrush current closes
the circuit to the start winding. When the motor gets up to speed and
the current drops to the run value the relay opens the circuit the the
start winding. I believe Klixon made them. You might try and google them.
CP
nesesu
> Many years ago (possibly 50) you could buy a module that would take
> the place of a starting relay or centrifugal cut-out for an AC motor.
> Where do you find them? (I think I sent for one thru Popular Science
> mag at the time)
> Thanks
Those relays are [were] commonly used on sealed refrigeration
compressor motors, so check out an appliance repair place or a heating/
air conditioning place.
Neil S.
ian field
"nesesu" <neil_su...@telus.net> wrote in message
news:518162d2-e047-4047...@s17g2000prh.googlegroups.com...
---------------------------------------------
Some fridge motors use a PTC thermistor instead of a current sensing relay -
once or twice I've successfully bodged motors with failed thermistors by
using the thermistor from a CRT TV degauss posistor.
Wild_Bill
as replacement parts for current-type start relays, typically for
refrigeration compressor motors (fractional HP).
Places like Johnstone, or other suppliers for HVAC service folks should have
numerous models to choose from.
You may need to know a motor's specs, at least the LRA locked rotor amps
rating, to be able to make an informed selection of starter devices.
The following is a post from rec.crafts.metalworking..
I bought a couple of used Dayton (1/3 HP) bench grinders recently, and found
some
Klixon current-type motor starter relays being used instead of centrifugal
switches for switching between Start and Run windings in these small
split-phase 120VAC induction motors.
http://www.sensata.com/klixon/motor-protector-3cr.htm
I mention these relays because they would be a suitable replacement for
damaged mechanical components or switch contacts related to centrifugal
switches.
These relays are the types used with refrigeration and air conditioning
compressors, and also completely suitable for other split-phase motors. They
have a heavy duty winding that the motor current passes thru, not a separate
coil like common relays.
When the power is turned on, the relay is pulled in, to make contact to the
Start winding.
The starting amperage of the motor is initially high, but it drops as the
rotor approaches Run speed, the relay drops out, connecting the line voltage
to the Run winding.
There are charts of different models of the SR start relays (in PDFs at the
link above), but I didn't find any type of selector guide for choosing what
the appropriate amp ratings would be for various HP ratings.
The models of Klixon SRs I was looking at were applicable for motors up to
15A (3CR series), and the next larger series of SRs were for up to 25A, so
these ratings would cover nearly all single phase split-phase motors
(capacitor start or non-capacitor start) used in a home shop environment.
One particular aspect of the SRs is that they are gravity-dependent, and
therefore need to be installed with the proper end pointed up.
Aside from that, they are highly reliable starting devices, rated for about
1 million cycles.
The specific ratings used for a 1/3 HP bench grinder motor use an 11A
pull-in (Start) spec and a 6A drop-out (Run) spec.
Of course, larger motors would use higher rated specs for pull-in and
drop-out currents, and the ratings vary in tenths-of-an-ampere (11.5A/6.3A,
etc).
--
Cheers,
WB
.............
"Bob Villa" <pheeh...@gmail.com> wrote in message
news:e6651839-0b72-4722...@h19g2000yqb.googlegroups.com...
Bob Villa
> I've seen 3-wire starters that were marked Solid State (triac, presumably),
> as replacement parts for current-type start relays, typically for
> refrigeration compressor motors (fractional HP).
>
> Places like Johnstone, or other suppliers for HVAC service folks should have
> numerous models to choose from.
> You may need to know a motor's specs, at least the LRA locked rotor amps
> rating, to be able to make an informed selection of starter devices.
>
> The following is a post from rec.crafts.metalworking..
>
> I bought a couple of used Dayton (1/3 HP) bench grinders recently, and found
> some
> Klixon current-type motor starter relays being used instead of centrifugal
> switches for switching between Start and Run windings in these small
>
> news:e6651839-0b72-4722...@h19g2000yqb.googlegroups.com...
>
> > Many years ago (possibly 50) you could buy a module that would take
> > the place of a starting relay or centrifugal cut-out for an AC motor.
> > Where do you find them? (I think I sent for one thru Popular Science
> > mag at the time)
> > Thanks
This was a totally solid state device...like a timed triac that cuts-
out after a half second.
ian field
----------------------------------
If the motor is low powered, ie not too much bigger than a fridge motor, you
can use a CRT TV degauss unit, there are 2 different types of the 3 pin unit
so you have to make sure you know which and wire it accordingly.
The most common type has 2 PTC elements - one is in series with the load
(degauss coil - (or start winding)) and delivers a short burst of current
which decays as the current through it heats it and causes its resistance to
rise.
The second PTC element is wired directly across the mains (after the on/off
switch) so that its self heating also heats the first PTC turning the
current fully off.
The less common type of degauss unit is a combination PTC/NTC pair, the PTC
would go in series with the load as before, the NTC in this case would be in
series with the run winding - the NTC element provides inrush current
limiting as it has a high resistance at room temperature, falling to a low
resistance as the current flowing heats it up.
Once again the self heating of the NTC heats the PTC and switches off its
current.
The downside is that degauss units take a few minutes to cool after the
motor is switched off.
Bob Villa
It is amazing to me that they aren't commonly available!
Meat Plow
Google --- PLC module.
HTH
--
Live Fast, Die Young and Leave a Pretty Corpse
Bob Villa
Not even close. This was a small (a little larger than a postage
stamp), simple device. I remember using one on a 5 HP motor that
wouldn't start. It was for a bakery mixing machine.
Meat Plow
Thermistor across the start cap?
ian field
"Meat Plow" <mhy...@yahoo.com> wrote in message
news:pan.2010.08...@hahahahahahahah.nutz.I.am...
Already suggested - he seems to be ignoring it.
Murata make a range of motor start thermistors (posistor).
By the look of the picture on the front of the catalogue they may be plug in
replacements for existing start winding solenoids.
Meat Plow
Back in my youth I went to school for HVAC and got a job with a family
owned company who installed Trane. I can remember installing hard start
kits. But my specialty was gas fired ammonia systems. Quite a few
residential and small office units around. Mostly 5 ton. Hell natural gas
was cheap back then. Our local gas company went on strike and I was
working on those things 24 hours a day it seemed. So freon-based systems
were not part of my routine except for the then emerging residential heat
pump units. But I do remember the solid state hard start kits.
I think this Villa dood is somewhat purposefully dense.
Bob Villa
wrote:
> "Meat Plow" <mhyw...@yahoo.com> wrote in message
There is no starting cap...it would take the place of a centrifugal
opening starting switch.
I'll Google posistor and see where that leads.
(thanks meathead for the comment-helpful indeed)
Meat Plow
Never got into actual motor repair except for taking apart 10/15 horse
230 volt single phase repulsion/induction motors, then having the rotor/
stator rewound, the com resurfaced or replaced. Other than that was a
simple plugin solid state replacement for a three pin residential AC
compressor. There were direct replacements or hard start replacements to
give the compressor a month or so longer useful life while the owner
scraped up the cash for a replacement.
ian field
-------------------------------------------------
AFAIK Murata claim "posistor" as a registered trademark, but the word has
found its way into common usage by TV engineers to describe the PTC degauss
units for CRTs.
ian field
Meat Plow
> http://www.murata.com/products/catalog/pdf/k99/k99e_l0725.pdf
Yeah I mistyped PLC for PTC a couple replies ago.
> >>> Google --- PLC module.
Still that doesn't replace a centrifugal clutch directly although you
could probably jury-rig one.
ian field
"Meat Plow" <mhy...@yahoo.com> wrote in message
news:pan.2010.08...@hahahahahahahah.nutz.I.am...
> On Tue, 24 Aug 2010 17:40:18 +0100, ian field wrote:
>
>> http://www.murata.com/products/catalog/pdf/k99/k99e_l0725.pdf
>
> Yeah I mistyped PLC for PTC a couple replies ago.
>
>> >>> Google --- PLC module.
>
> Still that doesn't replace a centrifugal clutch directly although you
> could probably jury-rig one.
"clutch"?!
Meat Plow
Well yeah a clutch, switch, kickout what the fuck ever you want to cal
it.
Bob Villa
wrote:
> http://www.murata.com/products/catalog/pdf/k99/k99e_l0725.pdf
I went to an electrician and this is what I got...
http://stearns.rexnord.com/products/Cat_902_table.asp
Thanks for the help guys!