Design Method of Capacitor Network for Interior Permanent Magnet Synchronous Machine Drive

Abstract

This paper proposes a method to extend the constant torque speed region of the interior permanent magnet synchronous machines (IPMSMs). For a high power-density and large constant power speed region, IPMSMs utilize both the reluctance and magnetic torques. To generate enough reluctance torque, the input impedance of IPMSMs is inductive. This decreases the power factor of the inverter, so field-weakening current increases at high-speed region. For this reason, the operating area is limited and the conduction loss increases. This paper proposes the impedance cancelling method using a capacitor power network. In this way, the constant torque speed region of IPMSM is extended. So, the maximum output power increases. Also, the conduction loss decreases at the previously field-weakening region when the capacitor network is not used. The principles how the capacitor network operates are explained. To operate with the capacitor network, the design method and the control method are presented. To verify the theoretical results, experimental results are presented.