Including slot harmonics to mechanical model of two-pole induction machine with a force actuator

A simple mechanical model is identified for a two-pole induction machine that has a four-pole extra winding as a force actuator. The actuator can be used to suppress rotor vibrations. Forces affecting the rotor of the induction machine are separated into actuator force, purely mechanical force due to mass unbalance, and force caused by unbalanced magnetic pull from higher harmonics and unipolar flux. The force due to higher harmonics is embedded to the mechanical model. Parameters of the modified mechanical model are identified from measurements and the modifications are shown to be necessary. The force produced by the actuator is calculated using the mechanical model, direct flux measurements, and voltage and current of the force actuator. All three methods are shown to give matching results proving that the mechanical model can be used in vibration control. The test machine is shown to have time periodic behavior and discrete Fourier analysis is used to obtain time-invariant model parameters.

► Two-pole induction motor has four-pole stator winding to suppress rotor vibration. ► Force on rotor comprised mechanical force, magnetic actuator force, and other magnetic force. ► The other magnetic force is included in the mechanical model. ► Parameters of the modified mechanical model are identified from measurements. ► Modified model is used to calculate forces in frequency domain.