Brushless DC motor dimensions

[jglmech]

Hi,

I am looking at replacing a brushed DC motor with a planetary gearbox with a similar brushless variety. So far all of the ones I found are much longer in length, and with a slightly smaller diameter. Is this extra length an inherent feature due to the control electronics?

Thanks

 

[Clyde38]

So far all of the ones I found are much longer in length, and with a slightly smaller diameter. Is this extra length an inherent feature due to the control electronics?

Not necessarily. Brushless motors do not have to include the drive electronics. They may have some type of rotor position feedback (encoder, hall switches for commutation, resolver etc.). This would not have to occupy any more room than the commutation system on the brush motor (commutator and brush rigging).

 

[TurbineGen]

How are you comparing these motors? Power output? kV (rpm/volt)? kT (Torque/Ampere)? Are you looking at slotless types or ones with a wound iron stator? Usually brushless motors can put out more power per unit weight than most brushed DC motors. What type of motor are you replacing? PM DC? Series DC?

As Clyde stated, brushless motor usually have sensors (in my experience they have been Hall effect) in the rear of the motor to sense rotor position, but these are often small and take up less room than the brushed motor commutator.

Do the motors you are looking at have the controller built into them? That would explain the longer motor.

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