New build with recycled parts on a ridiculous budget 120cm*60cm work area

[Davek0974]

I would not bother with pre-charge, this supply is not big enough to need it, as long as the rectifier is big enough to take the inrush as well as a slow-blow fuse in the input it should work fine.

Pre-charge is easy with a resistor in the output before the rectifier, maybe 10r 25W and a timer relay which shorts out the resistor after maybe 2s would do it but i wouldn't bother myself. Pre-charge is more used with supplies that have very large capacitors/higher voltages.

[Desertboy]

I would not bother with pre-charge, this supply is not big enough to need it, as long as the rectifier is big enough to take the inrush as well as a slow-blow fuse in the input it should work fine.

Pre-charge is easy with a resistor in the output before the rectifier, maybe 10r 25W and a timer relay which shorts out the resistor after maybe 2s would do it but i wouldn't bother myself. Pre-charge is more used with supplies that have very large capacitors/higher voltages.

[Desertboy]

Right wired up properly and tested 78.2v out so a little high what's the best way to reduce this voltage my AM882's 80v is max input.


I daren't plug it in to the AM882's.

Got it wired to a 13 amp switch finally so I can turn it on/off without killing power to pc.


Got a free enclosure some damage to the front but better than what I have, will transfer the AM88's and BOB's across PSU will stay in PC case.

[Davek0974]

Right wired up properly and tested 78.2v out so a little high what's the best way to reduce this voltage my AM882's 80v is max input.

If it were my supply i might unwind a couple of turns off the transformer secondary, but thats just me ;)

Not too many ways to fine tune the voltage really.

Maybe also look at an autotransformer in the primary circuit - a multi-tapped primary only transformer with the input going to the normal 240v tap and then take an output from the neutral and a tapping a little lower like 220v.

https://en.wikipedia.org/wiki/Autotransformer

Just an idea though. ;)

[Desertboy]

Or just run it at 78v's and hope ;) I turned it on off a few times and tested the voltage each time, and I noticed my input was 250v at the time it seems to vary at work from 238 to 250v this is the highest reading I've had so far and I think the max allowable is like 252v.

I need to check what the ac voltage going into the rectifier is didn't think that but was gutted as I was expecting to get something like Joe Harris 68v giving he has 25v output coils in series and I have 50v in parallel.

I wonder why I'm getting such a high reading is it because I have a high input voltage? This is mains fed, to an industrial unit, is it possible other things could affect voltage on the line? I'm going to have a dedicated line put in for the machine I seem to remember getting 240v when I was working on the 3 phase sockets (I tapped 1 phase for my plasma cutter)

Could I be getting a high reading because it's Saturday and the demand is lower on the estate?

[Davek0974]

Or just run it at 78v's and hope ;)

I wonder why I'm getting such a high reading is it because I have a high input voltage?

Yes, output is directly related to input, that is a very high input.

[Desertboy]

Yes, output is directly related to input, that is a very high input.

Will have to check Monday morning see what it reads.