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.

On Aug 27, 4:30 pm, John Doe <j...@usenetlove.invalid> wrote:
> Can all DC motor leads be reversed so the motor runs in the other
> direction equally well?
=================================
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 little
jumpstart on overcoming the L/R time constant in the windings?

On Mon, 27 Aug 2007 20:30:16 +0000, John Doe wrote:

> 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"?
>

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

John Doe wrote:
> 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.
>
>
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 Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html

On Mon, 27 Aug 2007 20:30:16 +0000, John Doe wrote:

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

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 of
polarity. Reversing the polarity will reverse both fields, leaving the
rotation unchanged.

2. Motors which aren't designed to be reversible may have the brushes
aligned for a specific rotation. Such motors will often run in
reverse, but with reduced efficiency and/or longevity.

3. If the motor has an integral cooling fan, it may not work (or not
work so well) in the opposite direction.

4. If the "motor" consists of embedded electronics along with the actual
motor, all bets are off.

On Mon, 27 Aug 2007 20:30:16 GMT, John Doe <jdoe@usenetlove.invalid>
wrote:

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

---
No.


--
JF

Jamie <jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote:

> John Doe wrote:

....

>> 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"?

> Well, I guess you answered your own question.

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