Abstract: A high power semiconductor heat sink assembly comprising a semiconductor slice or chip and a heat sink structure. The heat sink structure comprises two spaced apart thermally and electrically conductive plates of for example aluminum between which the slice or chip is clamped. A device such as an O-ring is sandwiched between the plates so as to extend around the slice or chip and define a sealed compartment within which the slice or chip is located. An electrically non-conductive thermally conductive material such as a resin comprising alumina fills the space between the plates outside the compartment.

Abstract: A pulse controller for controlling the energization and regenerative braking of a DC electric motor. An electronic switch connects the motor to a power source during motor driving and controls motor current during regenerative braking, the switch being rendered alternately conductive and non-conductive during both driving and braking and the ratio of conductive to non-conductive periods being controlled. The conductive and non-conductive periods are interrelated such that, regardless of the ratio between the periods, during regenerative braking the switch alternates between its conductive and non-conductive states at a rate sufficient to automatically maintain the generated motor current within desired maximum and minimum limits.

Abstract: A field weakening circuit for an electric motor comprises a switching circuit the impedance of which is variable connected in parallel with a field winding of the motor. The switching circuit impedance is variable in dependence upon motor speed and current, either continuously or in a plurality of discrete steps, to control the current through the field winding.

Abstract: A control arrangement is described for dynamically braking a vehicle driven by an electric motor having a single field winding. The control arrangement comprises means for controlling the supply of power to the motor, a permanent magnet generator for mechanically coupling to the motor, and circuit closure means arranged to complete a circuit between the output of the generator and the field winding to dynamically brake the motor when the motor is de-energized by the controlling means.