D.C. Motor Characteristics

There are three principal types of d.c. motors viz., shunt motors, series motors

and compound motors. Both shunt and series types have only one field winding

wound on the core of each pole of the motor. The compound type has two

separate field windings wound on the core of each pole. The performance of a

d.c. motor can be judged from its characteristic curves known as motor

characteristics, following are the three important characteristics of a d.c. motor:

(i) Torque and Armature current characteristic (Ta/Ia)

It is the curve between armature torque Ta and armature current Ia of a d.c.

motor. It is also known as electrical characteristic of the motor.

(ii) Speed and armature current characteristic (N/ia)

It is the curve between speed N and armature current Ia of a d.c. motor. It is very important characteristic as it is often the deciding factor in the selection of the motor for a particular application.

(iii) Speed and torque characteristic (N/Ta)

It is the curve between speed N and armature torque Ta of a d.c. motor. It is also

known as mechanical characteristic.