Speed  Control of Three  Phase Induction Motors

Three  phase  induction motors are invariably used in the application where in speed in  required to be  constant  or adjustable speed for their efficient operation. Use of thyristor circuits has made  it possible  to control  and vary its  speed  over a wide  range. Followings  methods  are used to speed control 3-? induction motors:

a.Stator  voltage control methods

b.Frequency  control  methods

c. voltage and frequency  control methods

d.Stator current  control methods 

e.Static rotor  resistance control  methods

f.Slip  power  recovery  schemes