Rotational Iron Losses in Brushless Doubly Fed Machines

In this paper the rotational characteristics of the magnetic field in Brushless Double Fed Induction Machines (BDFIM) iron circuit is studied. The BDFIM has a complex magnetic field pattern which make its iron loss prediction difficult. This is due to the fact that BDFIM has two stator windings with different pole numbers which supply at different frequencies. In addition, the stator magnetic field contains excessive higher order field harmonics that make the conventional iron loss formulations not applicable to its iron loss predictions. A new iron loss formulation is proposed in this paper for the BDFIM that takes the rotational field and harmonic effects into account in the iron loss prediction. The proposed formulation is then verified using experimental tests on a prototype BDFIM with rotor open winding.