DC MOTOR-Various types of DC Motor

 

 TYPES OF D.C. MOTORS 
Like generators, there are three types of d. c. motors characterised by the connections of field winding in relation to the armature viz. : 

(i) Shunt-wound motor in which the field winding is connected in parallel with the armature(See Fig. 4.41. The current through the shunt field winding is not the same as the armaturecurrent. 

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
relativey small with the armature current. 

(2)Series-wound motor in which the field winding is connected in series with the armature 
(See Fig. 4.51. 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 rums 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. 

(ii) Compound-wound motor which 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 (like generators). When the shunt field winding is directly connected across  
the armature terminals (See Fig. 4.61, it is called short-shunt connection. When the shunt
winding is so connected that it shunts the series combination Of armature and series field
(See Fig. 4.71, it is called long-shunt connection.