Types of DC Motors and their Characteristics

Types of DC Motors and their Characteristics

1. Types of DC Motors

1. D.C Shunt Motor

In shunt wound motor the field winding is connected in parallel with armature. 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. Therefore, shunt field current is relatively small compared with the armature current

2. D.C Series Motor

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

 2. D.C Compound Motor

Compound wound motor has two field windings; one connected in parallel with the armature and the other in series with it. There are two types of compound motor connections

1. Short-shunt connection

            2. Long shunt connection

1. Short-shunt connection

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

2. Long shunt connection

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

2. D.C Motor Characteristics

1. D.C Shunt Motor

a. Torque versus Armature current

Ta is proportional to Ia

b. Speed versus Armature current

c. Speed versus Torque

2. D.C Series Motor

a. Torque versus Armature current

Ta is proportional to Ia2

b. Speed versus Armature current

c. Speed versus Torque

3. D.C Compound Motor