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Line Powered Voltage Multiplier for Capacitor Charging

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axi0m

New Member
Would it be advisable to power a simple voltage multiplier circuit such as the one below directly from line power (mains power)?

I need roughly 400 to 500VDC to charge my capacitor bank for some experiments, this schematic should theoretically put out 440VDC from a 110VAC line power outlet as the source, right?

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Thanks in advance for any help people! I appreciate your time.
 

marcbarker

New Member
To many people, this kind of question is like asking "does anyone know the best kind of string I can attach to the trigger of this here loaded gun?" !!

Then fresh noobies seeing a really simple 'power circuit' think "hey! that's gonna be my first ever circuit I'm going to build!" (not knowing how potentially lethal it could be!)

I believe some cheap mains-powered Ionisers use a similar circuit. And stungun weapons. But the big difference between those and this circuit in the OP, is Ionisers only produce less than a mA of current, which is on par with static electricity. I imagine there are current-limiting resistors.

Maybe you should consider current limiting resistors, or use smaller value capacitors to reduce the short-circuit (i.e. a person attached to the circuit) to a 'safe' (you decide what's 'safe', not me!) current.
 
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Hero999

Banned
Agreed use small capacitors to limit the output current.

It depends on what you want it for.

10nF Y2 rated capacitors would make safe to touch as you'll only get a small static shock but will take ages to charge even small capacitors and not even fully charge large electrolytic capacitors due to the leakage current.
 

crutschow

Well-Known Member
Most Helpful Member
The circuit can become instantly lethal if you accidentally interchange the neutral and the hot connections from the power line. Not recommended you do this circuit unless you use an isolation transformer.

Or better, just get a plate (tube) transformer with about a 400VAC output and rectify that.
 

marcbarker

New Member
In the UK our mains connectors can't be plugged in reversed.

Nevertheless, wise people appreciate that "neutral" wiring is far from neutral under some fault conditions! Foolish people think that 'neutral is always neutral'
 
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RODALCO

Well-Known Member
It works but limit the current.

I have built the circuit for a fly zapper by putting two transformers back to back and a 4 stage diode capacitor bridge.

In my case 240 / 12 -and- 12 / 240 volts (7.5VA) it provides galvanic isolation from the mains too.
 

bailey45

New Member
A single 30AC transformer wired backwards would create 480 VAC output. A 6K 5Watt resistor in series between line and the tranformer would limit the secondary current to 5mA.
 

Hero999

Banned
If the current is under a certain level (I think 1mA) the earth wire can be safely used as a return conductor.

marcbarker said:
Nevertheless, wise people appreciate that "neutral" wiring is far from neutral under some fault conditions! Foolish people think that 'neutral is always neutral'
Yes, relying on the neutral being 0V is bad because if it breaks somewhere in the wiring, it can become live.
 

mneary

New Member
Would it be advisable to power a simple voltage multiplier circuit such as the one below directly from line power (mains power)?
:eek: Somehow I think you knew what we would say. :D
 

RODALCO

Well-Known Member
The neutral is treated as a live conductor in the electrical industry, hence N cable has to be insulated to the same level as the Phase conductors.
 

marcbarker

New Member
The neutral is treated as a live conductor in the electrical industry, hence N cable has to be insulated to the same level as the Phase conductors.
I should hope so too! when the neutral return wire falls off, there's no return path, except maybe the person touching the 'neutral' wire in dis-belief that it's not neutral!

Interesting thing I discovered (in IEE regs) only recently, was that on permanent sites such as dwellings and commercial premises, the neutral must never be fused. However, at non-permanent installations, i.e. generator powered, the appliance neutral is fused as though it's another live.
 
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RODALCO

Well-Known Member
a Neutral should not be fused at a generator in an MEN system.

In Europe the Neutral is switched but not fused.
 

Hero999

Banned
If the neutral is fused, in a generator, before it's tied to earth I don't see the problem.

In double insulated appliances, it's perfectly acceptable to fuse the neutral since the only risk of short circuit is between the live and neutral not live and earth conductors.
 
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