# 3 pulse center switching which possibilities?

#### akhu

Joined Jan 3, 2021
39

What must be changed so that voltage on R can be regulated wiht the condition that the losses are minimal. And how does this regulation work ?

Does some got an idea ? My idea was to replace the diodes to thyristors is this possible ?

#### KeepItSimpleStupid

Joined Mar 4, 2014
4,370
http://www.vesco-usa.com/CV-8_Manual.pdf#page=113

This device actually uses a tube to regulate a high voltage ~15 kV at 1.5A DC. The transformer essentially has 3 separate primaries. Input was 208V 3 phase at about 60 Amps. Taps were available to set the line voltage. Your talking like 30 kW of power.

It's effectively a linear regulator that wastes power in the tube. Fan cooling was used.

if you were doing it today, regulating or pre-regulating the 208V coming in with phase-angle firing or use IGBT's

See: https://www.power-mag.com/pdf/feature_pdf/1461163294_Woifspeed_Feature.pdf

and

31295016605783.pdf

#### akhu

Joined Jan 3, 2021
39
Wow so many informations. Thank you a lot.

But If we want to stay at the circuit above, so we have two possibilieties.

Which one would you prefer?

phase-angle firing or use IGBT's

And what is about my first idea to using a thyristor?

#### KeepItSimpleStupid

Joined Mar 4, 2014
4,370
I think it depends on what your regulating. You haven't mentioned line voltages or power. If your controlling a furnace that's one thing. What I sent you was the power supply for 30 kW electron beam that I fixed a few times at work.

Anytime you do phase angle firing into a transformer you need current limit. I haven't quiet figured out the nuances to make current limiting work. You also have to keep firing the triac because it turns off at v(t)=0 and I(t)=0.
If your regulating power, your inital table of 0-100% should be proportional to V^2; Voltage then V, an incadesent load (Tungsten) then the same thing applies.

Your also doing 2 half cycles, so if v(t)=sin(wt). The w is omega, so the integral of v(t)^2 gets to be proportional to power, ut it'd kind of inverse. 5% might be 8ms and 10% might be 7ms. When to fire based on a zero cross. The numbers are for illustration only.

Two SCR's are supposedly better than a triac and I'm not sure why. You can fire them at the same time for something unique and I forget what that is. It might turn off the load.

#### akhu

Joined Jan 3, 2021
39
I think it depends on what your regulating. You haven't mentioned line voltages or power. If your controlling a furnace that's one thing. What I sent you was the power supply for 30 kW electron beam that I fixed a few times at work.
- How long does it take (weeks, days) to develope such a complicated circuit what you send me above ?

- And what I want to regulate is at first only the line voltage.

Two SCR's are supposedly better than a triac and I'm not sure why. You can fire them at the same time for something unique and I forget what that is. It might turn off the load.
Okay and what would happen when I insert 3 SCR's instead of 3 diodes ?