Abstract: A current source power converter for an electric motor is comprised by a combined controlled rectifier and chopper which is coupled to a controlled-current inverter by a dc reactor. In the motoring mode the combined rectifier and chopper functions as a phase controlled rectifier to control the current magnitude. In the dynamic braking mode a line switch is opened and a braking resistor placed across the rectifier output, and the combined rectifier and chopper is operated as a chopper to control the average voltage across the braking resistor and thus the current magnitude during braking.

Abstract: A three phase bridge inverter supplies rectangular wave currents to an inductive load and to capacitors connected in wye across the load for wave shaping as well as filtering and power factor correction. A commutating capacitor connected to the midpoint of the wye-connected capacitors is controlled by two auxiliary thyristors. The commutating capacitor voltage is sensed and an incoming thyristor is not fired until the voltage rises to a level sufficient to commutate the next thyristor in sequence. This commutation is independent of load inductance.

Abstract: A single phase controlled capacitive filter with a smaller, more efficiently used filter capacitor than conventional capacitive filters is connected between rectifier terminals and supplies voltage to an active load producing dc output voltage. The charge and discharge intervals of the filter capacitor are controlled by gate controlled thyristors or other devices such that discharge occurs when the instantaneous rectified line voltage falls below the dc output voltage. The filter capacitor during discharge is placed in series with the load or can remain in parallel with the load in a simpler arrangement.

Abstract: Full-wave and half-wave rectifier circuits are disclosed; the former circuit using two transistors and the latter circuit using one transistor. In both circuits transistors are connected in an inverted mode so that, for example, with an NPN transistor current flow is such that line current flows into the emitter and load current flows out of the collector. Furthermore, voltage blocking is performed by the collector-base junction instead of the emitter-base junction. High efficiency is achieved by controlling the transistor base current in response to the emitter current so that the base current is proportional to the emitter current and is also at an optimum magnitude so as to minimize circuit losses.

Abstract: A turn-off circuit for a gate turn-off thyristor (GTO) generates a ramped turn-off gate current pulse which, because of the increase in device storage time with anode current, has a peak magnitude approximately proportional to the anode current. The direct-coupled or transformer-coupled turn-off circuit employs a transformer controlled by a solid state switch with the secondary winding connected to return excess energy to a supply.