Stator
Voltage Control of
three phase induction motor
By stator voltage control :
•We
have,
•Torque is directly proportional to stator voltage square.
•The torque is directly proportional to speed so if torque will decrease speed
also decrease and if torque will increase speed also increase.
•So we
can control speed of three phase induction motor by varying stator voltage.
•This
method is suitable for application where load torque decreases with speed.
•This
method is sometimes used for small
motor fans.
•This
method is very easy and cheap but still use rarely.
•Because
by decreasing the voltage torque will reduce.
•But
to maintain power (P=VI) this will increase current in motor which will heat the motor which is not good it
causes losses.
•Also
the torque is proportional to square
of voltage so large voltage change is required for changing torque.
