Thread: HV regulation.
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Old 27th Oct 2019, 9:23 am   #31
Diabolical Artificer
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Join Date: Jul 2009
Location: Sleaford, Lincs. UK.
Posts: 4,707
Default Re: HV regulation.

Having issues with the shunt regulator, it's not working as it should. I'm using two VR150/30's in series, so should get about 300v +/- 10v right? I'm getting 340v only 20v ish difference from HT loaded - 356v.

I'll own to some confusion about how to work out the dropping resistor value, I thought it was load current + a bit for the reg valves, which is 5mA - 40mA each. So by that reckoning 300/0.030 = 10k, that's 5mA each valve 20mA load I. Tried this, VR valves struck, glowed, voltage out 340v ish. So tried 5k, same, at one point tried 33k and also tried two R's, one to the bottom VR, one on top, same result.

If in doubt read the manual. I have an STC application report which covers the subject so had a read. It says your basic formula to determine Rs = Vi-Vs/Is+IL ... Vi is Vin, Vs is stabilised voltage, Is is VR current and IL is load current. Did the maths, got 1k6 as the result, used two 3K3's, same %*&!? result - 340v.

Another issue I had was the VR's valves flickering after the thing had been powered for about 10mins but I think this was down to dodgy resistors failing in my circuit.

I remember when I first got these valves, I tried powering them and they worked. I also tried two other VR150's, same result.

Andy.
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