Synchronous Motor for rotary Kilns Run
Synchronous Motor for the rotary Kilns Run at
Right Answer is:
Ultra Low speed
- 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.
- Modern electronic converters can produce very low frequencies, and synchronous motors of 10 MW range can be run at ultra-low speeds desirable in rotary kilns in cement plants and, as in its pioneering application, in ore or rock milling and crushing.