3 Phase from a single phase circuit design

[ringo888]

Hi Guys,

I'm trying to generate a 3 phase waveform from a single phase, this isn't high voltage (15VAC). I believe you can achieve this using oscillators but not sure of the circuit design, can anyone help?

Regards,
Ringo

 

[Prototyp_V1.0]

Must there be analog circuits or can you do digital counters+DAC?

 

[betwixt]

There are many ways to do this. You already have one phase, call it phase A. The other two phases are just time shifted copies of it. I'm assuming you are using 50Hz or 60Hz so delaying the other waveforms is not practical as the delay would be too long at such a low frequency.

You could consider phase locking an oscillator at 3 times input frequency then taking it's output through a 3-cycle ring counter. This will give you three reference signals which you can use to sync three single phase oscillators 120 degrees apart.

Or you could use a ROM/EPROM to look up points on three waveforms and then DACs to create the output voltages. This way ensures the phase is always accurate, if it needs to be locked to the input waveform, PLL the readout clock to the original.

Or by careful selection of RC networks, you could slew the original signal to provide the other two phases but you would have to compensate for the lower signals they provide by applying different amplification factors to them.

There are other ways....

Brian.

 

[FvM]

If the question is about fixed frequency sine waveforms, allpass phase shifters are the most simple way. It's basically sufficient
to generate a quadrature (90° phase shift) signal. Any phase can be represented by a linear combination of the quadrature
signals.