Electronics > Beginners

does the stall current of a dc motor change depending on polarity?

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engineheat:
Hi,

I'm connecting a AA battery to a small DC motor. I'd like to know from a theoretical standpoint if the stall current and the current when the motor spins can change depending on the orientation (polarity) the battery is connected to the motor. Also like to know if it can change in practice due to manufacturing variations.

I'm doing some measurements with a meter but the reading are a bit unstable.

thanks

Kleinstein:
The stall current should not depend on the direction, as the motor is not turning, so no direction  :-DD for not turning.
The position of the brushes may not be symmetric. So some motors have a preferred direction. So the run current and speed can depend on the direction. However there are also motors that are symmetric for both direction - kind of a compromise for both.

Zero999:
To expand on the previous comment. When the motor is stalled, there's no back-EMF, so the only resistance present is due to the windings and brushes, which is independent of the supply voltage's polarity.

T3sl4co1l:
To first order, no.  There may be effects like stiction and commutator angle and such, but they should have only a small effect.

Tim

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