Explanation: If the time angle displacement between currents and space angle displacement between winding axis are not equal, the magnitude of resultant MMF wave is always zero. 7. A 3 phase star connected winding is fed from symmetrical 3 phase supply with their neutrals connected together. If one of the 3 supply lines gets disconnected, then the revolving MMF wave will have a ___________
A. Constant amplitude but sub synchronous speed
B. Varying amplitude but synchronous speed
C. Constant amplitude but super synchronous speed
D. Varying speed and a speed fluctuating around the synchronous speed
Answer:A
Explanation: If the time angle displacement between currents and space angle displacement between winding axis are not equal, the magnitude of resultant MMF wave is always zero. 7. A 3 phase star connected winding is fed from symmetrical 3 phase supply with their neutrals connected together. If one of the 3 supply lines gets disconnected, then the revolving MMF wave will have a ___________
A. Constant amplitude but sub synchronous speed B. Varying amplitude but synchronous speed C. Constant amplitude but super synchronous speed D. Varying speed and a speed fluctuating around the synchronous speed
Explanation: With one supply phase disconnected, a rotating MMF wave of varying amplitude is produced, but at a speed fluctuating around the synchronous speed. 8. In case of the 3 phase winding with delta or star connection without neutral, if one of the supply lines gets disconnected, then the MMF becomes __________