Discussion
In polyphase induction motor, the speed higher than synchronous speed can be obtained by :
Answer: C
Speeds above synchronous speed are obtained by rotor slip power control.
An induction motor fed only from the stator can never reach synchronous speed, because it needs slip to induce rotor current. If a voltage of slip frequency is injected into the rotor circuit from an external source (as in slip power recovery and doubly fed arrangements), the rotor current can be maintained with negative slip, and the machine can run above the synchronous speed set by the supply.
Changing the supply frequency changes the synchronous speed itself, and the motor still runs a little below the new value. Reducing the supply voltage or adding rotor resistance only increases the slip, so both lower the speed.
Post your comment
Please log in or register to post a comment.
Examination Categories
- SSC Exams
- Banking Exams
- Teaching Exams
- Civil Services Exams
- Railways Exams
- Engineering Recruitment Exams
- Defence Exams
- State Government Exams
- Police Exams
- Insurance Exams
- Nursing Exams
- Other Government Exams
- NRA CET
- PG Entrance Exams
- Campus Placement
- MBA Entrance Exams
- CUET and UG Entrance
- Judiciary Exams
- Regulatory Body Exams
- Software Development