D. C. Motor control system effecting changes in the connections of the armature and variations in current flow through the field

A d.c. motor control system comprising a pair of armature windings mounted on a single rotor or on a pair of mechanically coupled rotors, a field winding or windings, the system including switch means operable to effect a change in the electrical connections of the armature windings to a pair of electric supply terminals, and means for effecting variation of the current flowing in the field winding or windings, said switch means comprising a contactor, the contactor serving in one condition to place said windings in series with each other and in the other condition in parallel with each other, said means for effecting variation in the current flowing in the field winding or windings comprising an operator controlled member, and a field current controller of the chopper type, said field current controller receiving a first control signal from said operator controlled member and acting to reduce the current flowing in the field windings when it is required to accelerate the motor, a power amplifier being further provided intermediate the controller and the field winding, said system additionally including means for providing a field current signal representative of the field current, means for providing an armature current signal representative of the armature current, switch means operable to control said contactor, said switch means being operated to cause the contactor to connect said armature windings in the correct parallel or series mode when the armature and field current are at predetermined values.