wrote:

Just wanted to get back to the group about this
AC motor that was running in reverse after being
disassembled and then put back together. It turns
out that reversing the brushes did indeed reverse
the direction of the motor. We can't argue with
success, but I still don't fully understand why
this is so. Can anyone please explain this to me?


** A regular DC motor is surrounded by a *permanent magne*t - right?

If you reverse the external connections to the rotor, it spins the other way cos the relationship between the fixed and moving magnetic fields is reversed.

With your " AC/DC" motor, the fixed field is provided by the same current that drives the rotor. When fed by an AC or DC supply, the fixed and rotor fields always *change polarity at the same time* so the rotation direction remains the same.

You have to go inside and reverse the connection to the field or rotor to effect a change.


.... Phil