Single Phase to three signal generator.

Question

Hello everyone,
I am designing a low voltage power supply that will run single phase to three phase circuit and will be using ultrosonic frequency as its signal input. The current circuit design uses three operational amplifiers that has a 60 degress phase shift. I am encountering a problem with regards to the output amplitude of the three phase signals. It seems to have a decrease in the amplitude. I also used RC oscillator circuit in front of the op-amp to have a precise phase shift. I am asking for any suggestions or how to deal with this problem? Also, are there any concept that I can study to approach this problem? I am also thinking to apply DSP filtering to elimate the noise in the output. Thank you in advance.

shabaz · Accepted Answer

I'm not entirely sure what you're looking for, especially the ultrasonic bit! 
 A diagram would definitely help. 
 For the 3-phase generation portion, in theory that's quite easy using any microcontroller with PWM, and a simple filter to construct the waveforms from that: 
 /technologies/power-management/b/blog/posts/building-a-three-phase-mains-power-system-simulator 
 However you may have different requirements so it needs more info. (the microcontroller approach just mentioned only works at low frequencies, not ultrasonic).

genebren · Answer

It would appear from your schematic, that because the output of the first stage, feeds the input of the second stage, and the output of the second stage feeds the input for the third, the amplitude changes are being caused by a gain less that one in each stage. You could test this by increasing the resistance for R2, R4 and R6 to increase the gains. The gains appear to be about 0.5 right now, so you might want to double the resistance. Good luck

Single Phase to three signal generator.

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