robbins myers motor wiring

The motor is likely not made by Robins-Myers.

First, figure out which of the 3 wires is the centertap. That's Neutral.

Next, given the uF value of the cap, it sounds like a starting cap, NOT a run cap, so there has to be a centrifugal starting switch. Figure out which wire goes to the centrifugal switch. The cap goes from Hot to that wire. The remaining wire is Hot.

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Thanks for the input. This is an open frame type motor, meaning I can look inside both ends and there isn't a centrifugal switch in there. There is a thermal overload reset but thats it.

Right now I have the Blue and Red to lines and the Red and Yellow to the cap.

Appears to run, not extremely smooth. It is a new motor and really looks well made. I want to use it on a homemade cnc spindle. It is 3750 RPM, I didn't mention that before not the it matters for the wiring.

Thanks for your help

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You will need to use an ohm meter to check the windings' resistances, in a

3-wire PSC motor without a wiring diagram.

The readings should look like 2 identical windings in series (such as the secondary winding on a center-tapped transformer, for example).

0----------------0-----------------0 The readings should be 2 nearly identical resistances from the center tap. A 4th wire may be present for the case earth ground (usually always green, or green/yellow).

The PSC motors that I'm familiar with have all used capacitors of very low values (uF). Some smaller (up to 1/8 HP) PSC motors that I have, use caps with values ranging from 2uF to 20uF. The value you stated seems excessively large, and 460-525uF would be a value I would expect to find as the Start capacitor on a 3/4 to 1 HP split-phase motor.

Capacitors that have been designed/intended for use as Start caps, should not be subjected to constant voltage application. A constant voltage will destroy Start capacitors. In their intended usage (spilt-phase motors), Start caps are only subjected to voltage very briefly, until the rotor comes up to speed where the Run winding is used for powering the motor during operation.

This site has a clear diagram of a PSC motor (about halfway down the page).

-- Cheers, WB .............

Must be 3450, as 3750 would be above synchronous speed.

"110 Volts" implies a very old motor, which was a bit puzzling.

If there's no centrifugal switch there must have been an external relay to disconnect the start winding and capacitor.

Find out which is the run winding by measuring resistance and picking the lower of the two. That one goes across the AC line. The start winding goes across the line, in series with the capacitor, for a fraction of a second.

Alan

to

3750 RPM is an unlikely speed if it is an induction motor (which it probably is). You may want to re-check that. Does the motor have brushes?

Do you have a way to control the speed of the motor?

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Hey, Thanks for all the great info, its helps greatly.

I may have to put a start relay in if needed. I am an electronic technician and understand lots of stuff but sometimes these motors really get confusing since there doesn't appear to be a standard and also part numbers clearly marked on it and yet with the internet no documentation to go with it.

I do have to state, yes it is 120v clearly stamp on the plate and RPM 3520 But being an old timer from vacuum tube days I am surprised I did not say

117v ac instead of 110v.

I tried to post pictures of the name plate on the motor but I can't seem to find a method to do that here. I hope to try a timer relay to open cap after start or simply pull the wire after it starts. I know, I will be careful for all those who are about to tell me that is dangerous.

The nameplate also clearly states 450-522mfd 165v ac.

Earl

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Well, I have it running, now I need to find a starter relay for the cap.

Hooked it up with the yel wire to the cap, this wire came out of a Klixon temp reset. The other two winding also go to different terminals on the reset but then head straight for the windings and come out from the bottom of the motor.

If I hook one line to the other side of the cap along with the red or blue line of course the line not connected to the cap goes to nuetral. The motor starts right away but hums or vibrates and gets warm. I then pull the yellow line off the cap removing cap from circuit and motor run very smooth and cool. Switching red and blue line changes motor direction of course.

So everything is working fine, just need to find an external cap start relay.

Thanks much guys, I am on my way.

Earl

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Does that 'Klixon' have three terminals? If so, it is a thermal motor start circuit.

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Yes it does but it is a discontinued module and I can't find the data for it. I put it back together I think the number on it was DK 12-35

If you have some info on this I sure would like to figure that out.

There is only one wire the comes out of the motor which to a yellow wire and has T1 label on it. I connected to cap as stated earlier but it does not disengage the capacitor after the motor starts.

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Despite the motor being, or appearing to be new, it may be defective, which can't really be determined in many cases, with just a multimeter.

The P in PSC represents permanent.. meaning the capacitor is permanently in the circuit, unlike other types of motors. The capacitor in a PSC motor isn't swiched in, out, or otherwise.

The statement which includes "there doesn't appear to be a standard", is misplaced, since all PSC motors operate in the same way, and are wired the same way. Other types of motors are the same, for each particular type of motor, it's just a matter of correctly idenifying the correct motor type. If you can determine that your motor is a PSC motor, then wiring it should be a fairly simple matter.

You need an ohm meter, as the simplest method to determine which terminals (or wires) go where internally. Then you assign your wire colors to the appropriate connections. The only unexpected results would be that the motor runs in the opposite direction than desired. PSC motors are easily reversed once the internal connections are known. Figure 3 applies to PSC motors

If the resistance readings for the 2 windings aren't nearly identical, then the motor isn't likely to be a PSC motor. If the motor isn't a PSC motor, then it won't be easily reversed, so it probably won't work for your CNC application anyway.

It may be worthwhile to look for information for other motors that Robbins Myers uses for their products. If you find wiring connection diagrams for oher R-M fan/pump/other motors, one may match your motor. FWIW, the stated 3520 RPM isn't a common speed, but the value of the capacitor used with a PSC motor will effect the motor's speed (a certain amount).

As I was going to mention before, there is a lot of misleading electric motor info online, mostly created by confused/inexperienced people using incorrect terms where they don't apply.

There is a connecting Wiring Diagram pdf file below the deails/specs. This motor is a Robbins Myers PSC motor, incorrectly listed by Skycraft as a capacitor start motor.

-- Cheers, WB .............

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It does have a klixom KD12-35 and it has 3 terminal on it.

Two terminals connect to wires which head into the coils.

The third is a yellow wire mark T1 with I connect to one side of

the Cap. The other side of cap goes to either red or blue wire depending

on direction of rotation plus to one side of line.

It still does not disengage cap after start but if I remove the yellow wire from the cap after it starts it runs real smooth.

So either the Klixon is not working or it is not a dual purpose device. That model is obsolete and not available so I need an alternitive external relay to control it.

Any ideas?

Thanks

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Contact Sensata who now own the Klixon brand, or find a modern motor. These three terminal motor starters are a pain in the ass to find. Most have been obsolete for decades. The alternative is to design an electronic replacement. The two heavy terminals go to the bi-metalic switch, the small terminal is the heater. Its resistance is selected to give the proper start time, with a normal start current. They were used instead of a mechanically operated speed dependent switch.

Sensata claims to be able to supply almost every version ever built, so they should be able to give you the specifications.

snipped-for-privacy@sensata.com

Robbin Myers is still in business, but appears to have abandoned the small motor market.

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OK, thanks again for the info.

Yes I did go to klixon website and they show a picture of the unit but say it is obsolete and no data given.

I think I have decided to just build a simple 555 timer and drive a mechanical or solid state relay. The is the spindle motor for a small home built CNC machine I am building for my son and it was suppose to be done by Cristmas so I think I have spent too much time on this starter.

Thanks all for your help, at least I got the motor running and once I disconnect the cap it really runs very smooth. Will drive the machine very nicely. The computer will control the start logic, I will set for about

500 msec as a starting point.

Earl

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I find some nice fractional horse split phase motors in large photocopiers. They can be had for hauling them home and are a wealth of hardware and interesting parts. No one wants them, and I can keep a lot of the parts out of the landfill. It doesn't take long to strip one, and I have about 100 pounds of motors, stainless steel rods, bearings, gears and chain for mechanical projects. from the last half dozen large copiers. :)

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On Sun, 27 Dec 2009 04:05:06 +0000, e2w_at_earthlink_dot snipped-for-privacy@foo.com (wentzele) put finger to keyboard and composed:

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