Speed Control of a DC Compound Motor

A compound motor is a combination of a series and a shunt-wound motor.

The Speed-torque characteristics for a compound motor

Speed Control of a DC Compound Motor

Speed is controlled by variable resistors in the shunt field and armature circuit. The series winding may be arranged that it aids the shunt field (cumulative compound) or opposes it (differential compound).

Cumulatively compounded motors are similar in characteristics to series motors, while differential compounded motors are similar to shunt motors as shown in the figure below:

Starting a DC Compound Motor

The compound motor is started with the help of a dc face-plate starter.

Applications of DC Compound Motors

Compound motors are used in applications where a wide speed range is needed but the differentially compounded types are rarely used as they tend to be unstable. The cumulatively compounded types are suitable for heavy machine tools.

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