AC commutator motor

Thread Starter

strantor

Joined Oct 3, 2010
5,158
I took apart a failed angle grinder the other day. I saw brushes, so I figured "oh, it must be DC, so I will check the rectifier" - there was no rectifier. I have learned of a new type of motor! I checked here and I see it's a "AC commutator motor" (Single phase series motor )- but I don't understand from reading that, how does it work? it seems to me like that motor is exactly the same as a DC motor, yet works on AC? If you were to put AC through a DC motor (which is how I perceive this motor to operate) I would think it would oscillate at 60HZ or just burn up.
 

Thread Starter

strantor

Joined Oct 3, 2010
5,158
Oh, I think it get it; since the current flowing through the armature is the same current flowing through the field, no matter where the current is (along the AC waveform, peak pos, peak neg, etc) the magnetic field of the armature is offset from the magnetic field of the field by the same degree (set by the commutation).
Is that right?
If so, does that mean I can run any ol DC series motor on AC?
 

Thread Starter

strantor

Joined Oct 3, 2010
5,158
Check this out; http://en.wikipedia.org/wiki/Electric_motor#Universal_motors

A vacuum cleaner or sewing machine are two things that use them.
Ah, so the only difference is the core:
the use of AC to power a motor originally designed to run on DC would lead to efficiency losses due to eddy current heating of their magnetic components, particularly the motor field pole-pieces that, for DC, would have used solid (un-laminated) iron.
Thanks shortbus
 
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