how to determine if DC mtr is PM

[paulmars]

Im told I can test using my dvm, but how?

Tks, >p

 

[Skogsgurra]

If you turn the rotor and measure a "substantial" voltage, then it is PM.

Substantial means that the voltage shall be close to nominal when running rated speed. And, say, 10 percent of nominal when running one tenth rated speed.

A motor with separate (or serial) excitation shows a lot less voltage.

It is, of course, also a good idea to look at the connections. If there are connections for an external field, it sure has one.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[paulmars]

thanks

 

[bklauba]

Another way is to turn the motor by hand, and then short it. If it is much harder to turn, it is a PM. Works for both brushed and brushless.