Stepped compound voltage control circuit of battery in combination with field-control DC motor driving circuit

In a stepped compound voltage power supply and field control for a DC motor driving circuit having at least one field winding, an armature, and a stepped compound voltage supply which includes a plurality of power supply sets arranged to be switched between parallel and series connections to provide the steps, the improvement wherein:

• the field winding is connected to said stepped voltage supply by means of a solid state switch connected in series with said stepped voltage supply and selected from the group consisting of a linearly adjustable resistance and an on-off switch arranged to pulse modulate the voltage supply output, and wherein the field control further comprises means for controlling the solid state switch and therefore the field intensity manually or by means of a controller responsive to inputs including feedback of the armature current, said means for controlling the solid state member switch control of motor speed over a greater range of speed than is provided solely by a supply of stepped voltages to the armature.