- 3PH Regulator.GIF (23.16 KiB) Viewed 31750 times
I sorted to a way to replace the TIP120 and was going to post it. However, I found two problems with the rest of the circuit so I am attaching your circuit with the problems outlined.
The two transistors (any small NPNs) work like this. With the V+ line below the zener voltage, TR1 is cut off so TR2 is on, pulling the 330 resistors low and energizing the gates of the triacs. When the zener starts to conduct, TR1 turns on and TR2 turns off; the triac gates then have no drive.
All Ok so far, but then I looked at the rest of the circuit and spotted the two faults.
1. Any time when voltage on phase1 is more positive than phase2, the two bridge rectifiers will conduct as shown by the red path, taking V+ to over 200V. The zener and triacs will not control that in any way, so it would be disastrous for a battery connected there.Similarly for phases 2-3 and 3-1.
2. When TR2 is on, all three triacs have their gates enabled, so as soon as there is a difference in their anode and cathode voltages (either polarity) they will conduct. Looking at the circuit, as soon as there is a difference between phase1 and phase2, T2 and T3 conduct putting a short circuit between those two phases as shown by the blue path. The same with T1.
Once triggered, a triac will remain on until there is no voltage between anode and cathode, so the only way to control it would be to switch it on just before the zero crossover point, then it would switch off at zero crossover, ie. pulse width modulation. But that would be a whole new ball game.
I have Googled for ‘3phase battery charger’ but all I have found have been large commercial chargers. So I don’t think I can help you.
Perhaps another member may be able to help.