DC motors

Re: DC motors

Rick Christopherson

>Actually, you will probably find that it is a 3-phase, low voltage motor. These are commonly called brushless DC, or servo motors, and can be identified by having three power wires. (If there are also 4 smaller wires, then the motor also contains commutator sensors, which can fail too.) The motor could be shot, but more likely it is the driver board that is shot.

If you want to test the motor, find someone with a Variable Frequency Drive that has an adjustable output voltage. You can spin the motor on low voltage AC without needing the commutator sensors. These are only needed when the motor is powered from a DC controller.

Come to think of it, if it is a permanent magnet motor, then all you have to do to test the motor is to spin it with a drill and measure the voltage output from the three phases. If you're getting an output then the motor is probably good.

Re: DC motors - troubleshooting

Al Stokka - Cambridge, Iowa

>http://www.leeson.com/servicesupport/troubleshootingDC.htm

Re: DC motors

Justin Szeliga

>Thanks Rick- When I spin the motor it starts producing a voltage, then suddenly drops off to zero. I was thinking something was burned out inside.

Thanks

Justin

Re: DC motors

Rick Christopherson

>About the only thing I can think of is that there is an internal circuit breaker that is failing.

Although another alternative is that it really isn't a permanent magnet motor, and you are getting a voltage due to residual magnetism.

Re: DC motors

Rick in Colgate, Wi

>I'm in the process of repairing ours as I write this. There is some good resources at treadmilldoctor.com. Our motor quit working as well but the issue is the motor control board. You can test the motor by jumping it from a cordless drill battery, if it spins at all its ok.

My research has led me to believe that the motor control board components are not heavy duty enough to handle the motor loads and burn out.

Rick

Re: DC motors

Rick Christopherson

>The most likely failure on a motor control board is the power transistors (or SCR's) feeding the motor. These will be physically large transistors and probably connected to a heat sink.

Re: DC motors

Rick in Colgate, Wi

>On my board I have 2 zener diodes and one signal diode that are toast, hopefully thats all thats wrong!

You are correct about the power transistors, my board has 2 of them attached to the heat sink.

Rick

I was warned that on my

Don Henthorn

>board two green resistors could overheat to the point they would unsolder themselves. I installed a rather large computer fan that blows directly over them and have had no trouble.