As compared to three-phase induction motor the advantage of synchronous Motor in addition to its constant speed is

As compared to three-phase induction motor the advantage of synchronous Motor in addition to its constant speed is

Right Answer is:

Both 1 & 2

SOLUTION

Synchronous motors have the following advantages as compared to 3-phase induction motors:

  • A 3-phase induction motor always operates at a low lagging power factor. On the other hand, an over-excited synchronous motor can supply leading kVAR to improve the p.f. of the system while carrying its rated load
  • Synchronous motors are particularly attractive for low-speed drives (< 600 r.p.m.) because the p.f. can always be adjusted to 1 (through the change of d.c. field excitation) and the efficiency is high. On the other hand, at low speeds, 3-phase induction motors become heavy, costly, and have relatively low p.f. and efficiency.
  • For equal power and speed, the weight and cost of synchronous motors are less than those of 3-phase induction motors. This is particularly true for speeds below 300 r p.m
  • The starting torque of a synchronous motor can be made considerably greater than that of a 3-phase induction motor. The reason is that we can raise the resistance of damper winding (i.e. squirrel-cage winding) without affecting the speed and efficiency.
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