How to wire up a GEC 2 pole capacitor run motor

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How to wire up a GEC 2 pole capacitor run motor

This topic has 13 replies, 7 voices, and was last updated 24 August 2024 at 11:37 by Baron J.

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22 August 2024 at 12:59 #748415
Greensands
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@greensands
I have acquired a vintage single phase GEC 2 pole motor running at a nominal 2880rpm with a starting capacitor rated 40-50uf. The motor has 6 leads coloured Red, Black, Yellow and Green plus 2 White. A test meter check shows that the resistance between Red and Black leads gives 26.3 ohms and 42.8 ohms between leads Yellow and Green and I assume that the 2 White leads are connected to the capacitor.

Perhaps before making any serious mistakes someone could advise me on how the motor should be wired up to the mains.
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22 August 2024 at 22:13 #748464
Emgee
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@emgee
I believe the wire colours are blue and yellow which denotes the start winding. (not green)

Red and black will be the run winding.

The 2 white wires may possibly be across the centrifugal switch, check for resistance across the ends.

Emgee
23 August 2024 at 08:32 #748485
Clive Foster
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@clivefoster55965
Greensands

That motor looks vaguely familiar. Maybe 45 or so years ago I had one of similar size and wire colours with just GEC and a type number on the side and on indication of connections.

Fortunately I contacted GEC before letting the magic smoke out.

Turned out to be a 2 or 3 speed motor (can’t recall which) for industrial fan drive applications made as a special for an air conditioning system maker. Hence no type number. I gather special in such cases referred to mounting and shaft length configurations. Slightly whacky switching arrangement too if I recall right.

If it is a fan motor it’s not much use for anything else. Effectively they are a sort of two phase motor. They are designed for maximum efficiency at the rated speed but the torque characteristics are pants at driving a variable load. High current flow off load and when loaded enough to drag the slip outside the design range.

I put a lovely looking single speed fan motor on a drill in the days before I knew about such things. Cooked it in about 3 months. It would get stupidly hot spinning off load. Would get almost too hot to touch in the time needed to shift a job on the table over to the next hole.

Yes I knew I should have stopped the drill to reposition but what 19 year old is gonna do that. Rush headedness rules at that age. Probably hormonal.

Wouldn’t surprise me if my cooked motor was rated for a very limited number of starts before the excess heat generated in run up caused the windings to deteriorate. If it were basically designed to run 24/7 a couple of hundred starts would be overkill.

Clive
23 August 2024 at 09:47 #748507
John Doe 2
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@johndoe2
It’s definitely a single phase motor is it ?

I only ask because Blue, Yellow and Red remind me of the traditional three phase colours, I think ? and the Black could be the star/neutral point and the two Whites for a thermocouple or bi-metallic thermal switch perhaps ?

Just a thought – which is probably completely wrong – and which of course would not need a start capacitor 🙂
23 August 2024 at 10:26 #748508
Greensands
Participant
@greensands
I have checked for continuity across the two white wires and the resistance is zero ohms which suggests that the two wires may be connected to a centrifugal switch in its normally closed position but short of dismantling the motor I cannot be sure that this is the case.
23 August 2024 at 11:37 #748521
peak4
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@peak4
On 22 August 2024 at 22:13 Emgee Said:

I believe the wire colours are blue and yellow which denotes the start winding. (not green)

Red and black will be the run winding.

The 2 white wires may possibly be across the centrifugal switch, check for resistance across the ends.

Emgee

Looks about right to me, though I’m not an expert on GEC motors;
This is from a Brook catalogue

You could try spinning it up with a soft start variable speed electric hand drill and see if the contacts open twixt the two white wires.
In reality, it should probably fire up with just the run winding connected, though it might require a spin by hand in one direction.

Bill
23 August 2024 at 11:39 #748522
Baron J
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@baronj17589
23 August 2024 at 14:54 #748554
Greensands
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@greensands
The mystery deepens. I tried a test run wiring the motor according to the diagram shown above on the assumption that the 2 White wires were connected to an internal centrifugal switch but the result was some nasty blue smoke emerging from the ventilating grills and the motor getting very hot. Fortunately I was able to switch off at the mains before hopefully doing too much damage.

Opening up the two end plates reveals the two white wire leading to an external location in one of the end plates but for what reason I have no idea. The photos hopefully illustrate the situation.
23 August 2024 at 15:31 #748566
Baron J
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@baronj17589
Hi Greensands,

That device on the end frame is a thermal cutout, it should have a protective red plastic button over it.

Normally it would have mains voltage on it. Don’t touch it when power is on !

Simply applying power to red and black should allow the motor to be started just by spinning the motor shaft without making any other connections. Are you sure that the capacitor is OK and not shorted. The run winding will have a slightly higher resistance than the start one.

It is possible that the motor was damaged before you got it.

HTH.
23 August 2024 at 16:35 #748568
Greensands
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@greensands
On giving the spindle a twist the motor will quite happily run with the mains connected across the Red and Black. What i have seen done in the past under similar circumstances is to include a Normally-Off/Push-On hand switch to take the place of an internally fitted centrifugal switch to provide the necessary phase shift for starting and keep the two White leads out of circuit and disconnected.
23 August 2024 at 19:18 #748591
Baron J
Participant
@baronj17589
Hi Greensands,

If you now connect one capacitor lead to the red wire and the other capacitor lead to the blue wire and the yellow wire to black, the motor should start and run when you connect power to it.

If it runs the wrong way just swap the blue and yellow wires. Just keep an eye on the temperature for a while, just to check that its not overheating. Ignore the white wires.

I suspect that the motor is just a capacitor start and run, no centrifugal switch. If there is one you will hear it click as the motor slows down.
23 August 2024 at 22:25 #748600
noel shelley
Participant
@noelshelley55608
red / black should be the run windings. Blue/ / yellow start windings. White wires thermal cut out. I don’t think this type of motor has a centrifugal switch. capacitor across the start and run windings. Good luck. Noel.
24 August 2024 at 11:03 #748646
Greensands
Participant
@greensands
Thanks for all the info. In the absence of a centrifugal switch arrangement perhaps a wiring diagram showing a motor circuit with a permanently wired in capacitor would be of use.
24 August 2024 at 11:37 #748659
Baron J
Participant
@baronj17589
Hi Greensands,

The diagram that I posted above is quite correct, just ignore the CF switch.

“If you now connect one capacitor lead to the red wire and the other capacitor lead to the blue wire and the yellow wire to black, the motor should start and run when you connect power to it.”
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