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AC Motor hook-up
October 14, 2005 2:48 PM   Subscribe

I need help figuring out how to hook up an AC electric motor. I want to animate a Halloween project.

It's a General Electric appliance motor, scavenged years ago from an old washing machine. The thing is, it's got three pairs of wires coming from it (blue-white, green-pink, and yellow-red) see pic. There are markings on it that tell me:

model: 5KH45DR92X
HP: 1/3
RPM: 1725
V: 115
CY: 60
A: 6.4
Code: R NTR3
PC: 12A

Which wires should I hook to hot and neutral? What are the other ones for? I don't want to play randomly with line voltage....
posted by Daddio to Technology (9 answers total)
There is hopefully a wiring diagram somewhere on the service plate. Often, you will attach the hot, neutral and ground to some of the wires, and wire other pairs together. Other times, you might wire 2 wires to hot, 2 to neutral, 2 to ground, etc. Do each of the wires have a small metal clasp on them with a number or a letter?

Also, you may already know this, but to use it for some kind of animation you're probably going to have to slow it way down using either gears or pulleys. 1725 RPM is in the slow side for an electric motor but still pretty fast in general.

If this motor is not clearly labeled, you can probably buy an equivalent at an electrical salvage yard for $5 or something.
posted by RustyBrooks at 2:55 PM on October 14, 2005

Can you get a clear pic of the plate that has all the data on it?
posted by RustyBrooks at 2:58 PM on October 14, 2005

I can't get a clear shot of the plate, but there's only text, no diagram. The wires all terminate with a fitting that slides onto a spade connector, but they don't seem to be marked.

Yeah, I know I'm going to have to slow it down. First, though, I have to get it to move!
posted by Daddio at 3:03 PM on October 14, 2005

I don't have a motor in front of me, but I suspect you could figure out which leads were which using a multimeter. If one of the sets is ground, then you should have infinite resistance between it and the other leads (I think). Hot and neutral should have a smallish finite resistance between them. This is kind of conjecture on my point. Neutral and the case of the motor might have a non-zero resistance between them. If you can figure out which one is ground, it shouldn't matter terrible much if you get neutral and hot switched. It's not a great idea if the motor was designed to be run with a very particular wiring, but I don't think it'll necessarily be a problem.
posted by RustyBrooks at 3:15 PM on October 14, 2005

The ground -should- have infinite resistance between the wire end and the motor casing.
posted by odinsdream at 4:07 PM on October 14, 2005

The ground -should- have infinite resistance between the wire end and the motor casing.

Are you sure? My understanding is that ground is generally connected to the housing to prevent electrical shock should the housing accidentally contact a "hot" component--which would mean that ground would be the only component with essentially zero resistance between it and the casing, while the other two wires would have no continuity with the casing.
posted by musicinmybrain at 4:18 PM on October 14, 2005

I measured the resistance between each pair of wires, and between each wire and the motor case. I made up a neat little table using HTML but on preview it got hosed, so here're the results in non-tabular form:

Zero resistance between blue/white, pink/green, red/green, and red/pink. All other pairs of wires have infinite resistance, and there is infinite resistance between each wire and the motor casing.

I don't think that any of the six wires are ground.
posted by Daddio at 4:44 PM on October 14, 2005

You need a wiring diagram for it and you most likely need two large capacitors that were probably bolted to the back of the washing machine. One is for power-factor correction, the other is a start capacitor. The former will reduce the supply current a LOT and the motor probably won't even run without the latter.

Two of the contacts are probably a centrifugal switch that opens when the speed is high enough, thereby disconnecting the start capacitor. The other contacts are likely to be separate connections to stator and rotor windings (does it have a commutator or not?).

It's unlikely that there are ground wires, there will probably be a point where a ground wire bolts directly onto the frame.

But really. Wiring diagram very necessary.

It's probably simpler for you to go to a salvage yard and get a $5 1/4HP blower motor with the start capacitor and everything pre-wired onto it; that will have only a pair of wires you directly connect to power. If they're nice, they might give you a couple $ off for donating the washing machine motor.
posted by polyglot at 11:13 PM on October 14, 2005

Ok, you've convinced me. I'll go look for a salvage electric motor, with a wiring diagram.

Thanks, all.
posted by Daddio at 6:20 AM on October 15, 2005

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