On these motors the armature and field winding are connected to different voltage sources. The armature winding and the field winding therefor form independent circuits. The characteristics of such motors correspond to that of a self excitated shunt motors. Even on these motors the speed remains constant under changing loads. Another advantage is the wide speed range, which is achieved by controlling the armature voltage. The typical speed range on a self-ventilated is 10:1. Provided The excitation stays constant the motor speed changes proportionally to the armature voltage, the speed range can be increased dramatically by the use of forced-ventilation.
On these motors the armature and the field windings are connected to the same voltage source. Such shunt motors are mainly used as low voltage powered motors. An important characteristic of shunt motors is the constant speed under alternating loads. If the starting current has to be restricted, starting resistance is required.
Compound Wound DC Motors have a shunt winding so that these motors behave partly like a shunt motor and partly like a series wound motor. The most important features are:- optimum starting characteristics, greater starting torque than on shunt wound motors but lower than on series wound motors, better control of constant speed than on series wound but greater speed variation to that of shunt wound motors.
An important advantage of of series wound motors is the high starting torque, so these motors are particularly suitable for vehicular drives or lifting gear. On a series wound motors speed is dependent on load. On large motors the release of load can cause the motor to reach unacceptably high speeds.