Abstract: A power converter control system for use with a power converter of the type which comprises a plurality of cascade-connected converter units of which at least one converter unit is subjected to continuous control of its conduction phase angle and the remaining converter units are subjected to on-off control of their conductivity is arranged to include a master controller for instructing the number of the converter units to be rendered operative, a reversible counter operative to change its content in response to a phase controlling command applied to the continuously controlled converter unit indicating a maximum or minimum conduction phase angle or delayed phase angle in conduction, a unit change control unit for producing unit changing operation signals to be applied to the respective converter units for controlling the operation of the same, by using one of the binary bits derived from the counter without modification and decoding the remaining bits, and a comparing and identifying circuit which compares t

Abstract: A power converter control apparatus comprising continuously controlled converter units and on-off controlled converter units for effecting powering control and regenerative braking control of a DC motor, which is arranged to include a unit change circuit for generating unit changing operation signals in response to a command for instructing the number of the converter units to be rendered operative from a master controllerand conduction phase signals from a phase shifter. In accordance with the unit changing operation signals, the conduction phase signals from the phase shifter are applied as a gate signal to the continuously controlled converter units in response to a powering control or a regenerative braking command, while a minimum conduction phase signal is applied as a gate signal to the on-off controlled converter units in response to a powering control command signal and a maximum conduction phase signal including a commutation marginal angle in response to a regenerative braking command signal.

Abstract: A protective circuit for protecting a main d.c. circuit of the kind comprising a d.c. power source, a d.c. load, a contactor and a chopper. In the protective circuit, a resistor is connected in parallel with the series-connected contactor and load to permit continuous application of power supply voltage across the chopper. A circuit is connected to the connection point of the load and chopper to provide a signal synchronous with on-off of the chopper, and the output signal of this circuit and a signal corresponding to a chopper-on signal are applied to a logic circuit which provides the logical sum of these inputs for the detection of commutation failure of the chopper. The output of the logic circuit turns on a thyristor for deenergizing the contactor thereby disconnecting the load from the power source.