Snubber energy recovery for a high power traction drive

This paper describes the development of a snubber energy recovery scheme for high power traction drives of around 2.5 MVA, with an operating DC link voltage in the region of 2.8 kV. The circuit is an extension of a low loss snubber circuit commonly used in traction drives. A significant part of the snubber energy is returned to the DC link by using a DC/DC converter which itself has an energy recovery snubber arrangement. The circuit has been examined in detail to ensure reliable operation under maximum current and maximum voltage conditions. Certain limitations of the proposed snubber are discussed. The operation of the energy recovery circuit was investigated by simulation with a computer model. The results of this simulation for operation of the recovery circuit operation with an inverter drive are presented and compared with experimental test results obtained from a 1.5 MVA inverter