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Testing a brushless motor for issues.

Testing a brushless motor for issues.

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Old 12-16-2013, 11:09 AM
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Default Testing a brushless motor for issues.

Have a Thunderpower 8.5T motor that is suspect making ESC go poof.

Anyone have a method for testing the motor without risking another ESC?

I have done the checks for a dead short between the windings, and haven't found a short or anything physically showing me it is bad.

backstory... My sons 22, ran 2 warmup laps, put of the starting grid, motor makes wierd long beep sound then poof, esc dead. Put a replacement board in esc, Motor made the same sound and poof goes esc again.

So for this one, and in the future, who has developed a reliable method to test them before risking an ESC?

thanks
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Old 12-16-2013, 11:15 AM
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Originally Posted by DsWright View Post
Have a Thunderpower 8.5T motor that is suspect making ESC go poof.

Anyone have a method for testing the motor without risking another ESC?

I have done the checks for a dead short between the windings, and haven't found a short or anything physically showing me it is bad.

backstory... My sons 22, ran 2 warmup laps, put of the starting grid, motor makes wierd long beep sound then poof, esc dead. Put a replacement board in esc, Motor made the same sound and poof goes esc again.

So for this one, and in the future, who has developed a reliable method to test them before risking an ESC?

thanks
Cut the loss and ditch the motor.

If it has warranty send it in. If not contact the manufacturer and see if they offer a trade in program or some other way to minimize the loss.
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Old 12-16-2013, 11:24 AM
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You can make some fairly simple measurements to see if the motor is good. First off, you should check the sensors to see that they are good. There are several tools out there to do this. Tekin ESC's do it with the lights. Another measurment you can do is to measure resistance from each phase to the case of the motor. This can be done with a simple ohm meter. The last check that you need to do (and you said you did this one) is a phase resistance check. This requires a meter that can measure fractions of an ohm and standard meters will not work. The three phase resistances should all be the same. If one is lower, it probably has some shorted turns.

By the sounds of it, you have a sensor problem and you are running a sensored only ESC.
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Old 12-16-2013, 12:04 PM
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An alternative to the low ohm meter (and actually more correct) is to use a LCR meter and measure the inductance of each coil. This should be done with the rotor removed and with the ESC wires removed from the can. The inductance of each coil should be within a couple % of the others.
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Old 12-16-2013, 09:19 PM
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Originally Posted by lbenton View Post
Cut the loss and ditch the motor.

If it has warranty send it in. If not contact the manufacturer and see if they offer a trade in program or some other way to minimize the loss.
It's not about the motor... it's about making sure a bad motor doesn't damage the ESC in the future...
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Old 12-16-2013, 09:21 PM
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Originally Posted by kufman View Post
You can make some fairly simple measurements to see if the motor is good. First off, you should check the sensors to see that they are good. There are several tools out there to do this. Tekin ESC's do it with the lights. Another measurment you can do is to measure resistance from each phase to the case of the motor. This can be done with a simple ohm meter. The last check that you need to do (and you said you did this one) is a phase resistance check. This requires a meter that can measure fractions of an ohm and standard meters will not work. The three phase resistances should all be the same. If one is lower, it probably has some shorted turns.

By the sounds of it, you have a sensor problem and you are running a sensored only ESC.
ESC isn't sensored only, but i tend to agree it might be a sensor board. thanls for the ideas, will do some more research on how to test the sensors.
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Old 12-17-2013, 03:56 AM
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Something like this maybe useful.

http://www.amainhobbies.com/product_...hecking-Widget
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Old 12-18-2013, 01:46 PM
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Another suggestion which I have used once before to verify a motor that I thought had an internal short:

Chuck the motor shaft in a drill press (ideally) or a drill (not as ideal) and turn on the drill motor, making sure any wires from the motor are not touching each other. If the motor is hard to keep from spinning when held by hand, that means a short in one or more poles. If it passed that test, then measure the voltage across each phase (pair of stator terminals: a-b, a-c, b-c) while the motor shaft is being turned by the drill motor. The voltages should be very close. If one is off (and I can't really say how much because it was a long time since I did this), then one phase is bad in some way.

I used a drill press for this test instead of another RC motor because I wanted something way more powerful than the RC motor so that it would not be bogged down by a short in the RC motor. Serious shorts are pretty obvious because the rotor will have a "gummy" feel.

BTW, a solder bridge across the motor's terminals will show up as a short in the motor and seriously affect the ESC.
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