Types of DC Motors | Series, Shunt, and Compound

Like DC generators, there are different types of DC motors characterized by the connections of the field winding in relation to the armature. They are

1. Shunt Wound DC Motor
2. Series Wound DC Motor
3. Compound Wound DC Motor
   1. Short Shunt Connection
   2. Long Shunt Connection
4. Permanent Magnet DC Motor
5. Separately Excited DC Motor

Shunt Wound DC Motor

The current through the shunt field winding is not the same as the armature current. Shunt field windings are designed to produce the necessary m.m.f. by means of a relatively large number of turns of wire having high resistance.

Series Wound DC Motor

A series-wound DC motor is one type of dc motor in which the field winding is connected in series with the armature.

Therefore, series field winding carries the armature current. Since the current passing through a series field winding is the same as the armature current, series field windings must be designed with much fewer turns than shunt field windings for the same m.m.f. 

Therefore, a series field winding has a relatively small number of turns of thick wire and, therefore, will possess a low resistance.

Compound Wound DC Motor

The compound-wound DC motor which has two field windings: 

• one connected in parallel with the armature 
• the other in series with it. 

There are two types of compound motor connections (like generators). 

1. Short Shunt Connection
2. Long Shunt Connection

Short Shunt Compound DC Motor

When the shunt field winding is directly connected across the armature terminals, it is called short-shunt connection. 

Long Shunt Compound DC Motor

When the shunt winding is so connected that it shunts the series combination of armature and series field, it is called long-shunt connection.

The compound machines (generators or motors) are always designed so that the flux produced by shunt field winding is considerably larger than the flux produced by the series field winding. Therefore, the shunt field in compound machines is the basic dominant factor in the production of the magnetic field in the machine.

Permanent Magnet (PMDC) motors

The stator is a permanent magnet, so the motor is smaller in size.

A disadvantage is these motors are only used for low torque applications.