Design of a high-voltage GTO chopper for traction drive

A chopper operating at 4000 V and 800 A RMS using two large series-connected GTOs (4500 V, 2500 A) is designed. The series connection of GTOs is considered, including criteria for the selection of GTOs, design of snubbers, and adaption of GTO controls. The advantages and drawbacks of the strategies used are discussed. Detailed experimental results concerning the GTOs´ commutations and the snubber circuits are presented. The influence of important parameters, such as the load current on the transient voltage distribution on the GTOs is discussed. Because series connection of GTOs is liable to be used in the high-voltage converters of rail traction systems, two industrial realizations are proposed