Page 232 - Electrician - TT (Volume 1)
P. 232
ELECTRICIAN - CITS
Regenerative braking – dc series
In shunt, used for overhauling loads- motor becomes generator. It is not possible in DC series motor without
modification, reversal of Iawould also mean reversal of the field and hence of Eb.However, this method is
sometimes used with traction motors, with special arrangements.
Speed control of dc motors
The governing equation
Eb
α N
Φ
Eb V Ia Ra
V Ia Ra
α N
Φ
Methods of speed control 1
α N
• Armature circuit resistance control
Φ
• Flux control by variable resistance in field circuit Losses
Input
output
Efficiency
• Applied voltage control
Input Input
VI [(I Ish) 2 Ra Wc]
VI
DC Series motor - armature diverter
DC Series motor speed control - field diverter
• Field diverter
• For speeds higher than normal
• Resistance in parallel to series field
219
CITS : Power - Electrician & Wireman - Lesson 30-37 CITS : Power - Electrician & Wireman - Lesson 30-37
