Abstract: The trackside control includes a trackside d.c. power supply applied initially at low voltage (of selectable polarity, to determine the direction of vehicle motion along the track) and then increased (preferably with constant voltage-increase rate) to maximum supply voltage, and a trackside electrical braking load (preferably capable of forcing down at constant rate the voltage applied to it from the vehicle motor).The motor has series and (separately excited) shunt field windings, and on-board sensing and switching circuitry which (a) in motoring, either forward or reverse, sets full series field in flux addition to limited shunt field (b) in coasting, maintains field winding switch settings, and (c) in electrical braking, sets full shunt field and reduces the now decompounding series field.

Abstract: A dynamic braking system for a D.C. traction motor which is driven from an asymmetric bridge rectifier having freewheel diodes to permit circulation of motor generated current. The system employs field reversal to ensure a generated (braking) current direction the same as for motoring and this facility permits injection current braking by phasing up the supply bridges when the motor is braking with full excitation. The brake resistance is in two parts one of which forms an uncontrolled arm of the bridge, this part of the resistance being shunted by a thyristor. Part way through an injection braking process the supply bridge is phased down, the resistance bridge arm shorted out and the supply bridge phased up again. Lower losses and greater braking efficiency result.