A synchronous machine with its field winding on stator and polyphase armature winding on rotor. At steady state, which of the following is not true for its air gap field?
(a) stationary w.r.t. stator
(b) rotating at double the speed Ns w.r.t. rotor
(c) rotating in direction opposite to rotor
(d) rotating at Ns w.r.t. rotor
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This question is from Starting of Synchronous Motors topic in portion Synchronous Motors of Electrical Machines