Chopper circuit for dynamic braking in an electric power conversion system

Abstract From the Canadian patent

An improved electrical circuit configuration for a chopper circuit is disclosed which is particularly adapted for use with an inductive load such as a braking resistor (38) of the type used in many rapid transit vehicles. Instead of connecting a di/dt reactor directly in series with the electronic switch of the chopper circuit, a di/dt reactor (84) is connected in series with the freewheeling diode (46). Using this configuration the, di/dt reactor (84) does not have to continuously handle the average current through the electronic switch (42) during the entire chopping operation. Hence, a much smaller lighter, and, less expensive di/dt reactor (84) can be utilized.