words per minute
4
Rahul_Tiwary
00:00
Speed
is confined to less than 5 percent slip, and the speed variation over that range is
more or less directly proportional to the load on the shaft of the motor. Even if the
slip could be made larger, the effi ciency of the motor wou ld become very poor,
since the rotor copper losses are directly proportional to the slip on the motor
(remember that PRCL = sPAG).
There are really only two techniques by which the speed of an inducti on
motor can be controlled. One is to vary the synchronous speed, which is the speed
of the stator and rotor magnetic fields, since the rotor speed always remains near
n,ync. The other technique is to vary the sli p of the motor for a given load. E:1.ch of
these approaches will be taken up in more detail.
The synchronous speed of an inducti on motor is given by