Best way generate sine wave reference signals for PWM?

[sp_vibes]

I am trying to generate three sine waves 120 degrees out of phase with the option of changing the volts to hz ratio in a linear way i.e. when the amplitude of the sine waves change, the frequency must also change once a volt/hz ratio has been set.

Whats the best way to generate the sine waves?

These sine waves can then be used to create a pwm pattern when compared with a triangle wave.

 

[kchriste]

Sounds like a strange application. What are trying to build?
Are you going to use a microcontroler?

 

[sp_vibes]

Variable Speed Drive to run AC motor.

Just wondered how the reference sine waves were normally generated to be compared with a triangular wave to generate the pwm pattern to fire the inverter gating.

 

[kchriste]

Variable Speed Drive to run AC motor.

That makes sense.

Just wondered how the reference sine waves were normally generated to be compared with a triangular wave to generate the pwm pattern to fire the inverter gating.

The easiest method would be to use a motor control IC like the MC3PHAC from Freescale. I suspect that the MC3PHAC is just a preprogrammed microcontroler.