Why is the DC armature on the rotor?


Joined Feb 12, 2009
Do not understand!

If English is not your first language, a picture will help!

Please explain more.

Thread Starter

Abel Assegid

Joined Nov 5, 2007
what I meant is..
We know that the rotating part of a DC motor holds the main winding and the stator holds the field winding. Couldn't it be the other way(field on the rotor and main winding on the stator)? If not why?

I hope this one is clear enough.


Joined Feb 28, 2009
The primary reason for placing the windings of DC motors on the rotor is that it is easier for the commutation to be implemented. There are brush type DC motors that have the magnets on the rotor and the windings in the stator. They are sometimes called "inside out" motors. The armature carries a complex brush rigging that has brushes for both slip rings for power to the rig and brushes that contact a fixed commutator arrangement. The primary advantage of that setup is lower inertia on the rotor, but the cost is in complexity.

For a standard AC induction motor, the elimination of brushes reduced the complexity of design as well as reducing cost.

An old saying is, "Whatever they tell you is not the whole truth and no matter what you think they are talking about, it is really MONEY!" The last part of that statement pretty well answers any design question.