Electric Flight in Australia


Do I have to "run in" my electric motors?

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The quick answer is that if you have a brushed motor, "running in" is optional. But if you have a brushless motor you should NOT run it in.

"Running in" usually means running a motor for extended periods (about one hour), sometimes at low voltage, to seat the brushes. The theory is that the brushes will deliver the current more efficiently to the commutator if they are seated properly. I have tried this using a model train controller and connecting the motor directly to it using jumper leads. I cranked up the controller until it delivered 5 or 6 volts, and left the motor running for 20 minutes at a time. Any DC power source is suitable. You must be careful not to overheat the motor. If the motor gets hot, let it cool before proceeding with the process. That's why I used reduced voltage, so as to prevent overheating.

Some people advocate "running in" brushed motors under water. I have never tried this trick, but I do know it works.

I must also say that I have often used a brushed motor straight out of the box without running in, with no obvious detriment to the performance or life of the motor. That's why I say it is optional, particularly if the motor is used in a gearbox for almost continuous running at low amps (as in a sports cabin model). Why not run it in in the air?

If you are going to use an improved ferrite motor at high amps, then "running in" is probably a good idea.

Brushless motors do not need "running in" because they have no brushes. In fact, the only moving parts are the shaft and the bearings. But that is not why I said that you must not run them in. There is another reason; it is because you should not run a brushless motor without a load. Doing so can damage the motor and the controller. There are other complications - you should not run a brushless motor with a reduced number of cells, and you should not use an external power supply like you can with a brushed motor. The set-up of a brushless motor is highly specialised, and controllers are matched to motors; the correct feedback from the motor to the controller is necessary. I recommend that you set up brushless motors according to the manufacturers specifications, and do not vary the set-up for testing purposes. Test under real life conditions. Do not even use an ammeter in the line in a brushless set-up; rather use a clamp meter which is non-invasive.