What causes motor brushes to spark? - RC Groups
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Jun 27, 2001, 03:23 PM
jbourke's Avatar
It sparks because the voltage difference is enough that the electricity arcs from the brush to the commutator.

Its always a good idea to break in new motors, but it doesn't really make a big difference for a lot of them. Chances are that you would still get sparking even if you had broken the motor in.

The sparking is common and unavoidable in some situations, but can be minimized by proper motor timing. I don't have a lot of experience with the Master Airscrew unit, but my guess is that it is normal for it to spark at full throttle. Maybe someone else will chime in and give different advice.

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Jun 27, 2001, 03:26 PM
Registered User
SheldonYoung's Avatar
Mine do the same as well. Unfortunately, the timing isn't adjustable on these motors.
Jun 27, 2001, 03:29 PM
Registered User
rtideas's Avatar

I talked to MAS and they said I could break the motor in running it for 30 minutes to get the brushes to seat,

I conneced to d cells and removed the prop. Let it go at it for 30 minutes and it is much less noticeable.

Thanks for helping me understand.
Jun 27, 2001, 04:14 PM
York Electronics
Gary Warner's Avatar
The collapsing flux field (magnetic field) on the stator coil as the brush passes the comutator pad and disconnects that coil, causes an increase in voltage that resists the field collapse. The momentary spike in voltage is sufficient to cause an arc back to the passing brush. I'll let others tell you how to control it and the interference it causes.

Jun 27, 2001, 05:54 PM
Space Coast USA
hoppy's Avatar
Very nicely said Gary.
Jun 27, 2001, 07:31 PM
ὅπερ ἔδει δεῖξαι
Gerald's Avatar
Originally posted by Gary Warner:
The collapsing flux field (magnetic field) on the stator coil as the brush passes the comutator ...
Except that these permanent magnet brush-type motors do not have a stator coil. The stator would be the 'stationary' coil as for example in a wound field type motor. The permanent magnets in our motors provide the stationary field. You are of course referring to the 'rotor', or 'armature' coil.

A brushless motor however would properly be said to have a stator.

By the way, I found this nice little web page giving useful terminology and motor info for e-power newbies that you all might find interesting: http://www.csc.uvic.ca/~tyounger/hafh/rc/motorguts.html

[This message has been edited by Gerald (edited 06-27-2001).]
Jun 28, 2001, 01:33 AM
Registered User
rtideas's Avatar

What causes motor brushes to spark?

I have a new MAS electric flight pack. It's a 550 motor w/ a 3:1 reduction drive.

At full throttle, the brushes are sparking.

Do these motors need to be broke in?

How muxh damage does sparking do?