# Solid State Analog Phase Shifter

I have a single A/C source that I would like to phase shift into three different phrases, offset by 120 degrees, essentially resulting in something like below:

I've seen out in the real world, folks doing this type of conversion by powering a single phase motor, into a three phase generator. I'd like to find a way to do this using only solid state components; I don't see any reason why this is not possible (if it is not possible, please tell me why!)

So I'd like to design individual "PS1", "PS2" and "PS3" circuits. I've had some luck phase shifting voltage using capacitors (dumb example) but I haven't been able to figure out the math for how to calculate the right capacitor (or inductor) sizes to make this work. It seems like a simple 120 shift should be feasible but I'm stuck. What should a simple 120 degree phase shift circuit look like? What math should I poke around with to calculate component sizes?

• A solution using only passive components breaks down as soon as the load on the motor changes. What you need is a variable-frequency drive (VFD). Nov 25, 2022 at 18:04
• It is absolutely possible to generate three phase shifted copies of an input signal using solid state devices. The phase shift can be any amount from 0 to 360. Jonathan is assuming you are trying to drive a motor. If that is the case, for sure get a VFD. But if you just want to generate phase-shifted signals, you can look at the all-pass filter. You can also cascade RC filters to achieve phase shifts > 90 degrees. At the end, an op-amp can buffer and gain up the phase shifted signal so that all three phases are equal amplitude. Nov 26, 2022 at 2:02
• If the frequency changes, then using an all-pass or RC filters will not work. Nov 26, 2022 at 2:05
• @mkeith I think I'd get 120 degrees shift by making a 60-degree shift and inverting it. Or use a PLL to lock onto the signal, generate a 90-degree signal, then just use inverters and a resistor network to get whatever phase shift I want. Nov 26, 2022 at 3:05
• I am guessing that you are interested in power inputs and outputs, and not merely signal inputs and outputs. But I would like to know if that guess is correct. Nov 26, 2022 at 3:56