Similar to generators, DC motors are also classified into three types by the connections of field winding and they are:
- Shunt Wound Motor
- Series wound Motor
- Compound Wound Motor
Shunt Wound Motor
In shunt wound motor the field winding is connected in parallel with the armature winding as shown in the fig. the current through the shunt field winding and the armature will not be the same. In this type the field windings are designed to create the needed m.m.f by means of a moderately large number of turns of wire having high resistance. As a result, the current in the shunt field winding is smaller when compared with the armature current.
Series Wound Motor:
In Series wound motor the field winding is connected in series with the armature as shown in the fig. Thus, series field winding carries the armature current. In Series motor the current passing through field winding is same as that of armature current. Series field windings should be designed with abundant fewer turns than shunt field windings for constant m.m.f. As a result, a series field coil contains a comparatively tiny range of turns of thick wire and, therefore, can possess a low resistance.
Compound Wound Motor
The Compound wound motor has 2 field windings; one connected in series and another connected in parallel with the armature. Like Generator there are two types of compound motor connections. Once the shunt field winding is directly connected across the armature winding terminals as shown in fig-a it's referred to as short-shunt connection. When the shunt winding is therefore connected that it shunts the series combination of armature and series field as shown in fig-b, it's referred to as long-shunt connection.
Generally the compound machines either motor or generator are at all times designed so that the flux created by shunt field winding. Thus, the shunt field compound machine is the usual dominant factor in the production of the magnetic field in the machine.