抄録
This paper discusses the efficiency of an induction motor when periodic fluctuation occurs in a load. A high-efficiency control method for induction machines achieves minimum copper loss by adjusting the excitation current depending on the load condition. When the load torque varies rapidly, the high-efficiency control method increases the copper loss because the transient current flows in the excitation current. This paper clarifies the boundary condition for high-efficiency control. When the load fluctuates faster than the boundary condition, high-efficiency control based on the effective value of the load torque is used. The copper loss under load fluctuation is analyzed in order to derive the boundary condition at which copper loss is minimized. Finally, the validity of the boundary condition is confirmed experimentally using a 3.7-kW induction motor.
