At what load angle does a synchronous motor deliver its maximum power____________?
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Answer: C. 90°
Explanation
A synchronous motor delivers its maximum theoretical torque and power output when the load angle reaches 90 degrees. The power-angle equation dictates that power varies sinusoidally with the load angle, peaking at the sine of ninety degrees. Exceeding a ninety-degree load angle causes the motor to pull out of synchronism and stall immediately. The load angle, also known as the torque angle, is the mechanical phase displacement between rotor and stator magnetic fields. Maximum torque capability is known as the pull-out torque or breakdown torque of the synchronous machine. Operating beyond the maximum power angle destroys the stable magnetic linkage holding the rotor in synchronism.
45 degrees represents a normal operating load angle well below the maximum theoretical torque capacity of the machine. 60 degrees is a moderate load angle providing adequate safety margin before reaching pull-out conditions. 120 degrees exceeds the stability limit, resulting in loss of synchronism and immediate motor stalling.
- Subject
- Engineering
- Category
- Electrical Engineering
- Topic
- —
- Difficulty
- medium
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