Question

The purpose of providing dummy coils in a generator is
1. to enhance flux density
2. maximise voltage drop
3. to provide mechanical balance for the rotor
4. to reduce copper loss

Answer 1

Correct Answer - Option 3 : to provide mechanical balance for the rotor

• Dummy coils are used with wave-winding and are resorted to when the requirements of the winding are not met by the standard armature punching available in armature-winding shops.
• These dummy coils do not influence the electrical characteristics of the winding because they are not connected to the commutator.
• They are exactly similar to the other coils except that their ends are cut short and taped.
• They are there simply to provide mechanical balance for the armature because an armature having some slots without windings would be out of balance mechanically.