120 degree phase shift.

Thread Starter


Joined Mar 4, 2014
my project is on v/f control of induction motor and i need to produce three phase sine wave independent of frequency. can any one suggest me a method for it.. ??
thank you.


Joined Jul 9, 2011
I can't remember when but I posted a huge circuit somewhere on this forum some time ago. You need a lot of components to do it with normal ICs.

This is usually done with a microcontroller.

For an AC induction motor you will want to be able to adjust some parameters like a voltage boost at low frequencies, ramp up and down. Ramp up limits startup current, ramp down will avoid increasing your bus voltage to much when the load drives the motor.

uC is the way to go.


Joined Feb 11, 2008
Could you use a simple phase shift oscillator with 3 cap stages and just take a tap from each cap stage? They might be different in amplitude but I think with some effort you could get it to make three sines each 120' apart.