High-frequency lumped parameter winding model of a synchronous servo drive

For servo drives a precise measurement of the stator currents is mandatory. It is common practice to neglect winding capacitances in most servo drive designs. But on the contrary, for precise current measurement these capacitances are a crucial factor since they form resonant circuits with the stator inductances. This paper proposes a lumped parameter model of moderate order for the high frequency winding effects. The theoretical results are verified by experiments with a synchronous servo motor. The capacitive currents induce torque fluctuations with the stator frequency in the control. The effects of the capacitive currents on the control quality of a servo drive are discussed at the end of the paper.