A series-wound electric motor is disclosed in which a triac or thyristor is placed in series with the armature winding and one of the field coils. Two control voltages and a reference voltage can be tapped off various points on the electric motor. By utilizing appropriate control circuitry, the current in the armature winding may be turned on and off, while current flow through the field coils can continue to flow. In this fashion, the speed of the motor can be accurately regulated within a permissible range of operating speeds, while maintaining a high efficiency comparable to the efficiency of an unregulated series-wound motor.