Testing a brushless motor

[ReddyWatts]

Someone asked me how to check their brushless motor without hooking it to a controller. I have heard that you can short two wires and turn it and feel a resisitance to check each winding. The guy tried it and said the magnets on his airplane motor were too strong for this to work by hand. So I had him use a variable speed drill and spin it, not to fast. He was reading 0.5 ac volts on each set of wires and nothing to the case. I told him it was ok, since he was getting the same reading between the windings and nothing to ground. He hooked it up to a controller and it was ok.

I guess you could run this test on a new motor before you run it and log your readings to get a reference for future tests on the condition of your windings and magnets. Different winding motors should have a different voltage output reading.

Does anyone have a bad brushless motor to try this on and give the results, Maybe one that burnt a controller? Anyone else have more ideas on testing these motors?

[SJFE]

I have one. I will try the drill volt meter test this evening.

[ReddyWatts]

Another idea!!!

Could you use this test to find the best motor, same brand and winding?

Compare your results from each motor to find the one with the best readings and equal on all windings???

I would think you would need to turn it clockwise, because of your rotor to coils relationship and output or would it make a difference on brushless???

[part time]

on brushless it should not make any diff which way its turned. all the timing is done electronicly instead of mechanicaly like brushed motors.

[ReddyWatts]

Voltage test

I tested a used Feigao 10XL motor tonight using my variable speed drill while running it wide open. This is what I measured with a digital AC meter across each of the leads. Guessing it was turning about 3600 rpm.

RED/GREEN 0.4756 VOLTS

RED/YELLOW 0.4758 VOLTS

GREEN/YELLOW 0.4757 VOLTS

No continuity reading from each winding to the case. I could not take a voltage reading from each lead to the case because of electrical interference from the drill.

I was really surprised at how close the readings from each winding are to each other. I think it is a good benchmark for future testing on this motor, if I am having any problems.

Do not let there be any cross pressure on the rotor from the drill. It effects the readings, keep it centered.

Do you think this is a good test or am I all wet?

[properchopper]

Testing

I chucked up a Nemsis 10XL that was in questionable condition in my drill press, holding the motor body in the rubber-insulated vice. At med speed [ I'm not sure of the rpm] each motor lead put out @ 3.0 VAC with ONLY the plus lead of the meter in use. I have no idea what this means. Any ideas ??

[ReddyWatts]

test

Proper, I was not able to take any voltage readings to one single winding wire to the case or other wise. My digital meter was going nuts. I think it is just induced electrical noise. I had to ohm each wire to the case with the drill unplugged to good test.

What voltage were you reading on each of the windings? I think that is a good test. Were they all equal?

I had to use some alligator clips to get a good connection on the winding leads for a consistant reading.

I think if you have a shorted single wind on a 10XL you should ATLEAST see a 10% drop in voltage on one of the readings. An open or shorted winding would not give a reading. If you have weak magnets, you should see al of the readings being lower.

[properchopper]

re

I'll do some more experimenting tonight ; gotta get to work. I was getting @ 3.1 VAC ; all wires were about the same.

[ReddyWatts]

IMO, I think this is as good a test or better than shorting the wires together and hand turning the rotor, but it will work for all brushless motors. Just use a drill to spin it and use a (true RMS) digital volt meter to compare each windings condition. The motor acts like a low power generator. You could also use an ammeter to compare readings on each winding output.