Page 234 - Electrician - TT (Volume 1)

ELECTRICIAN - CITS

Change direction of rotation of dc motors
To change the direction of rotation, the direction of current either in armature or field circuit is to be changed.
In compound machines,if field currents are changed, change both series and shunt field currents, unless it will
inverse between cumulative or differential.

Tests on dc motors
Brake test – direct loading test
This method is used only for small motors with simple brake. It gives almost accurate results. In large motors, it
is difficult to dissipate the large heat at the brake. Lot of power is wasted.

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CITS : Power - Electrician & Wireman - Lesson 30-37 CITS : Power - Electrician & Wireman - Lesson 30-37