Can all DC motors be reversed?

Question

Can all DC motor leads be reversed so the motor runs in the other direction equally well?

I have a 36 V DeWalt cordless drill motor that has a casing with a molded plus sign on it. Clearly they very much want the positive motor speed control lead to be attached at that terminal. But maybe that plus sign is just so that the worker will connect the wire to the right terminal so that the motor will turn in the right direction when the drill's switch is turned to "forward"?

Thank you.

BobG · Accepted Answer

=================================I think there is a slight 'timing' or a couple of degrees of 'advance'on the brushes in the preferred direction to give the current a littlejumpstart on overcoming the L/R time constant in the windings?

Rich Grise · Answer

The smart thing to do would be to get a voltmeter, clip it across the motor, and see what you get, forward and reverse.

Any permanent magnet motor should work like this, although as BobG mentioned, it might affect efficiency.

And no, "ANY" dc motor can't be reversed just by swapping the leads - for series wound "universal" motors, you have to swap either the field leads or the armature leads, but not both.

Hope This Helps! Rich

Tim Wescott · Answer

In theory one could build a DC motor that would jam the brushes or suffer other mechanical damage were it run in reverse.  Practically I would be very surprised to find one unless it were above 1HP output -- and even then I'd be surprised.-- Tim WescottWescott Design ServicesDo you need to implement control loops in software?"Applied Control Theory for Embedded Systems" gives you just what it says.See details at

Nobody · Answer

No.1. Motors which use coils for both rotor and stator (rather than using permanent magnets for one of them) will rotate the same way regardless ofpolarity. Reversing the polarity will reverse both fields, leaving therotation unchanged.2. Motors which aren't designed to be reversible may have the brushesaligned for a specific rotation. Such motors will often run inreverse, but with reduced efficiency and/or longevity.3. If the motor has an integral cooling fan, it may not work (or notwork so well) in the opposite direction.4. If the "motor" consists of embedded electronics along with the actualmotor, all bets are off.

John Fields · Answer

---No. -- JF

Jamie · Answer

Well, I guess you answered your own question.-- "I'm never wrong, once i thought i was, but was mistaken"Real Programmers Do things like this.

John Doe · Answer

...Not nearly as well as the reply authors. I'm schooled.

Jamie · Answer

You're schooled? what the hell is that suppose to mean?-- "I'm never wrong, once i thought i was, but was mistaken"Real Programmers Do things like this.

John Doe · Answer

Gecko/20030624 Netscape/7.1 (ax)

Can all DC motors be reversed?

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