ABSTRACT
Synchronous motors (SMs) are, in general, three-phase a.c. fed in the stator and d.c. (or PM) excited in the rotor. As the stator currents produce an m.m.f. traveling at the electric speed ω1 () ω 1 = 2 πf 1 https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315368573/146c4cdc-e01a-40c3-85d9-48bb00ff42e4/content/eqn10_1.tif"/> the rotor m.m.f. (or PM) is fixed to the rotor. The rotor electrical speed ωr is () ω r = ω 1 = 2 πnp https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315368573/146c4cdc-e01a-40c3-85d9-48bb00ff42e4/content/eqn10_2.tif"/> in order to obtain two m.m.f. waves at standstill with each other. It is a known fact that only in this situation is a nonzero average torque per revolution obtained.
