# PROBLEM WITH SCHMITT TRIGGER (HYSTERESIS CURRENT CONTROL)

Discussion in 'The Projects Forum' started by enricuzzo, Jan 31, 2016.

1. ### enricuzzo Thread Starter New Member

Jan 31, 2016
2
0
Hello everyone, I'm trying to simulate with Orcad Pspice a Three phase inverter with hysteresis current control.
I attached my circuit.
I did it with 3 non-inverting Schmitt trigger, setting ratio R2/R1 =30 so that, as the ideal opamp has +-15V output, I should have the hysteresis band width=1. The E generators have a gain=-1 so that they work as a Not port. The H generators have a gain=1 so I have voltage feedback. I put two vsin with offset, on the bottom, to see the band margins.
Well, currents through the loads should follow the vsin reference (setted on 50hz, ampl=6) with a ripple depending on the band widht, but It doesn't work: current through L1 is a sine curve among 0A, the one throug L2 is among 20A, and through L3 among -20A.
Can somebody help me?
Thanks.

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2. ### crutschow Expert

Mar 14, 2008
13,529
3,393
Sorry, but I really don't understand your problem.
What is a "hysteresis bandwidth"?
What are "E generators" and "H generators"?
And this makes no sense: "L1 is a sine curve among 0A, the one throug L2 is among 20A, and through L3 among -20A."

Perhaps you could find someone to help with your English.

3. ### enricuzzo Thread Starter New Member

Jan 31, 2016
2
0
Well, sorry.
1) Hysteresis bandwidth : I mean the distance between the lower and upper threshold.
2) E and H generators: voltage generators respectively voltage and current-controlled. In pspice they are E and H blocks.
3) L1 is a sine curve among 0A: i(L1) is a sinusoidal current with the average value in zero (a typical sine curve). i(L2) is the same with an offset of 20A, and i(L3) with an offset of -20A. And I don't know why.