Why doesn't an ac motor need a commutator?
A DC motor requires a SPLIT RING commutator, whereas an AC motor uses a ring that isnt split (i.e full ring) An AC motor doesn't need a commutator because the current polarity is already alternating. This is the job of the split-ring commutator in a DC motor. DC motors chane the current polarity through roatiting section of the motor, whereas an AC motor does it through the stationary part.
a commutator mechanically switces the external terminals just when the polarity changes in time so that the external circuit maintains a one directional potential(either +ve or -ve)...theres no such a requirement for an ac circuit..the external voltage can(is supposed) to reverse polarity) so we dont need such an aid
I guess the answer is sometimes. I forgot about the universal motor the answer is right there induction motors, the largest group of ac motors do not need commutators. depending on whether they have wound or squirrel cage rotors, they may not even need slip rings.
an ac motor doesn't need a commutator because unlike the dc current a commutator is not needed to reverse the polarity of the current as it is already alternating, hence why it's called an alternating current. This is also because a dc motor works by changing the polarity of the current through the rotating part of the motor whilst the ac motor does the same thing but through the STATIONARY part of the motor. so there you go, hope that helped.... :) - nickie xx
