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Old 6th Mar 2021, 9:33 am   #1
Diabolical Artificer
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Join Date: Jul 2009
Location: Sleaford, Lincs. UK.
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Default EHT PSU Question.

If you have a butchers at the attached schematic, page here - http://www.chambonino.com/construct/constwire2.html you'll see he's stacked several PSU's/rails on top of one another to get 2.5kv DC (and 750v DC).

Questions - 1) He's using 1000v rated bridge rectifiers, surely there's a problem exceeding the BR's PIV rating further up the stack/at the top - 2.5kv DC + AC peak or is that 2.5v DC + AC ripple?

2)He's stacking different AC RMS rated windings, IE 3 x 185v RMS & 5 x 260v AC RMS - is there a problem mixing different DC rails from a voltage sharing angle as regards the caps? He's using 100k sharing R's on all caps/rails

3) Is this a better way to implement a EHT PSU? Say one 1170v AC (or two) winding/s with one or two bridge rectifiers, that or series connect the various windings, rectify in one go, cap stack the same. What are the advantages/disadvantages of each approach?

4) From a safety POV would it be better to split the supply in two, EG +/- 1250v? 1250v still lethal but not as bad as 2.5kv. I think there'd be an issue with phase splitter & other stages, EG Vg2 750v, 813 cathodes would be at - 1250v, so Vg2 would be -500v with respect to ground/chassis mains earth = problem with OP of IP stage being referenced to 0v/gnd? Think I may be getting a bit lost there...

5) Lastly, there's no choke on the 2.5kv rail, only on the 500v rail... I've read about putting the choke in the ground so the choke isn't floating at EHT.If one did this, IE choke in the ground, could you also use a choke at 500v? Again,may getting muddled there...

TFL, Andy.
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