Investigation of a dynamic braking scheme for switched reluctance motor drives

Switched reluctance motors (SRM) have the advantages of ease for manufacturing, low-cost, and robustness in withstanding centrifugal force. Therefore, they are particularly suitable for high speed applications. However, when running at high speeds, rapid braking becomes difficult since the rotor holds a large kinetic energy. Although applying negative torque can stop the motor effectively, it may also raise the DC link voltage to a critical level if a conventional AC-DC rectifier front is used. In this paper, the relationship between regeneration energy and DC link voltage is investigated, and an electric braking scheme employing multi-phase excitations is proposed. During braking, instead of regenerating back to the DC link, the excessive rotor kinetic energy is dissipated in the winding resistance. Therefore, the motor can stop safely in a short time. The proposed control scheme is verified experimentally with a four-phase SRM.