isolation transformer for pulse charger

[wingman1776]

I have read every back post on here that I can find on build a pusle charger. Took me 3 days lol. I have decicied to build a transformer cap bridge type. I want this thing to be safe not just line voltage to the cap bridge. I am a plumbing heating a/c guy by trade and not real sure about the transformer to put in frount cap brige part of circut.

So this is my plan I found a medical isolation transformer 120V to 120V it is a round thing with lots of wire coming out of it. Then I was going to put a varic adjustable transformer 120V 12 amp. I have about 500 uf  total in run cap mixxed voltages rated between 370 - 440 volts and a 3 phaze 60 amp  1200 volt high voltage bridge rectifier nice big heat sink for it.

Now do I need the isolation transformer I definaly want the varic so I can control the voltage and the varic is fused to 20 amps. Will not having the isolation ransformer burn up my varic ? If I wire this properly will it work and be a safe ?


Moved to the proper section

[wooferhound]

Wouldn't the variac be an isolation transformer in itself ?

[rossw]

I've seen a lot of variacs in my time, but never seen an isolating one.

Variac and "auto-transformer" types are usually a single coil on a round former. The knob adjust the ouput tap.

Zero isolation. Arguably the most dangerous thing about using one of these devices is what happens if yo lose the neutral/ground side - you end up getting full mains potential on the output, even if the voltage was wound down to minimum!

[bob golding]

cant answer the question,but i do know variacs are not isolating.

a few possible variac wiring schemes.

http://instrumentation-central.com/Staco/PDFCutSheets/VT%20Schematic.pdf

cheers

bob golding

[Flux]

Variacs are not isolated they are autotransformers. If you want isolation then you need the isolation transformer. As long as the thing can handle the load and is rated for your mains voltage it will be ok. I have no idea if your medical thing is suitable as you gave no information. You can in theory isolate the supply to the variac or you can isolate the variac output. Variacs take a massive magnetising surge when switched on but that won't matter as long as you have fuses to stand it.

Whether it is safe is a completely different issue. Without isolation it could never be considered safe unless in the hands of someone with enough experience to know the risks. With isolation it is no more dangerous electrically than any other device but from the non electrical point of view you must form your own opinion. To work I believe you have to hit the battery with a lot of volts. If it is badly sulphated or it develops an open circuit to the plates then you may ignite explosive gas.

I have no belief that the inductive pulse things do any desulphating, I have never tried the capacitor discharge method so I can't say if it is effective. I regard it as something for experimenters and if you are aware of what you are doing then ok. Not something to leave in the hands of an inexperienced person.

Flux