For the Brushless Guru's

[Z06jim]

After lot's of $$$$$$$$, I've decided I really need to find some good diagnostic techniques for controllers and motors other than a "smoke" test.

There appears to be an issue with the cheaper (less expensive) motors with the wires as the exit the case and wearing holes in the insulation shorting to the case. This is corrected by inspection and heat shrink, but what else can be measured on these motors? Resistance, output at a given rpm, etc?

An 8Xl that was giving problems with heat was opened and one strand was broken inside and touching the rotor. Go figure.. just cut the strand, hope it works better now.

Any way to test a controller without plugging into a motor?



Right now I have;
3 controllers that need repair
2 blown UBEC's
2 Motors that are suspect

Any comments???

[BrianG]

You shouldn't get smoke unless your motor is pulling more current than the ESC can supply, or using too high voltage - in other words using parts beyond their ratings. I always like at least 20% headroom for current. So, if a motor pulls 100A, I would choose a 120A ESC, but that is purely my choice, not any rule of thumb.

I've also heard about the motor wires breaking insulation, but there are things you can do to help that. I used shoe-goo at the wire exits to keep the wires in place and prevent them from chafing on the can edge. It also keeps dirt out of the motor. Also, support the wires so they won't bounce around.

No matter what, there are going to be occasional issues in any product line. Something like that can be returned for warranty as long as there isn't obvious evidence of abuse.

An ESC needs to be hooked to a motor to work. A sensorless ESC uses back-EMF feedback from the motor to determine rotor position. No motor, no positioning. Without a motor, at best, you'd only be able to see PWM voltage coming across each phase with an o-scope, but you'd have to use a floating ground o-scope input because the voltages are in relation to each phase, not a common ground. But this won't test anything under load, which is where problems will come about. You could pick up a really high wind motor, like a 26 turn motor so there will be a real load, but won't draw as much current.