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Maximum speed variation in synchronous motor is
10%
50%
0%
100%
0%
A synchronous motor is a constant speed motor because its rotor speed is locked to the frequency of the supply current. The motor operates at a speed exactly equal to the synchronous speed (NsтАЛ) regardless of the load applied, until it reaches its pull-out torque.
A synchronous motor is a constant speed motor because its rotor speed is locked to the frequency of the supply current. The motor operates at a speed exactly equal to the synchronous speed (NsтАЛ) regardless of the load applied, until it reaches its pull-out torque.
NsтАЛ=P120fтАЛ тАФ Synchronous speed formula
╬ФN=NsтАЛтИТNrтАЛ=0 тАФ Speed variation definition
The synchronous motor works on the principle of magnetic locking between the stator revolving magnetic field and the rotor poles. Since the stator magnetic field rotates at a constant synchronous speed NsтАЛ=P120fтАЛ, and the rotor poles are locked to this field, the rotor must rotate at exactly the same speed. Consequently, the speed variation from no-load to full-load is zero.
Synchronous motors are 'constant speed' machines.
The rotor poles 'lock' into the rotating magnetic field created by the stator.
Speed remains invariant with load changes up to the pull-out torque limit.
They are distinct from induction motors, which exhibit slip.
Constant speed operation
Ability to control power factor
Requires DC excitation for the rotor
Not self-starting without auxiliary methods
Power factor correction
Constant speed industrial drives
Ball mills and compressors
The inherent lack of slip is why synchronous motors do not experience speed variation as a function of torque.
Options like 10%, 50%, or 100% describe various types of speed regulation in different motor classes (e.g., DC series motors have high speed variation).
C is correct тАФ The speed of a synchronous motor is strictly constant, locked to the supply frequency, resulting in 0% speed variation.
Always remember that 'Synchronous' in electrical engineering is synonymous with 'Constant Speed'тАФunlike induction motors, which depend on slip for torque production.