Help with DC motor wiring

amdx · 2008-10-24T19:33:52+00:00

I built a gokart using a 28v 65a 2 hp shunt field motor. I used a series field motor controller. Note a mismatch. I noted an oddity with my voltmeter during the initial testing, but choose to ignore it. Please view the attachment of the wiring diagrams.The kart ran great with with wiring scenario A, we drove the heck out of it for 4 days.Then I got curious about the voltage oddity. After some testing and wire tracing I came up with the improper shunt connection in wiring scenario A. The shunt is connected to B+ on both ends, one end through a 20 ohm resistor.I corrected that with scenario B. The gokart did not run as fast so I dumped that scenario.Looking at scenario A, I noted the shunt has no battery current through it so I tried disconnecting it, as in scenario C.This was a mistake, the gokart shutdown twice in in 1/4 mile, the second time never to run again. The motor controller is defective, it gives an "overvoltage error code". Error codes are supposed to be self clearing but it doesn't.So the obvious answer is to get the motor controller repaired and reconnect as in scenario A.But scenario A is not really proper.I'm looking for a reason the controller popped and the best connection for this mismatch.Thanks, Mike

Oct 24, 2008 22 Replies

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amdx 17 years ago

Maybe, but A run great, I don't think it was residual magnetism.

Well, that would make the most sense, considering how good the motor ran. But that doesn't fit with the motor wiring plate. The 4 Lead shunt only has the shunt and CNPS or IP. The six lead compound has the shunt, the CPNS or IP and a series. I just don't see enough coils in the motor to be the six lead. It is evident the motor has been in a shop (alignment punch marks) so the motor wiring plate may not have any relevence. When I get a minute I'll run to the local motor shop and see if they can decipher it. Thanks, Mike

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Paul Hovnanian P.E. 17 years ago

See my other post. This appears to be a shunt field motor with a compensation winding, based upon your description and nameplate diagram.

It is possible that this motor will behave like a series motor if the shunt field is disconnected. In fact, this makes sense with respect to your initial description of its behavior. Series motors don't have a distinct maximum RPM as shunt field motors do. Under light load, the motor can continue to develop a small amount of torque in the forward direction where shunt field motors have a distinct point at which they cease to provide mechanical power out and, if driven from an external prime mover (or the inertia of the vehicle) will become generators, providing dynamic braking.

Paul Hovnanian mailto:Paul@Hovnanian.com ------------------------------------------------------------------ Parity on, dudes!

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Robert Monsen 17 years ago

at 30mph, your daughter needs a helmet!

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