Loss Analysis of Electric Motors in Hybrid Excavator

Kobelco Construction Machinery Co., Ltd. has launched a new 20 tonne hybrid excavator, equipped with two types of newly developed electric motors, namely, a permanent magnet type, flat, high-torque generator motor, and a compact high-output slewing motor. In an electric motor, iron loss and copper loss occur, and these losses increase as the internal temperature rises. Therefore, the challenge in making compact electric motors with high torque and high output is to release the heat generated inside the motors to the outside and to prevent their internal temperature from rising. A technique has been established for the coupled analysis of an electrical/magnetic circuit model and a heat transfer circuit model in an electric motor that enables an optimal design of the heat transfer path inside the motor, as well as making it possible to efficiently find an appropriate electromagnetic circuit for it. This has resulted in the development of electric motors with high torque density.