20kv Multiplier

[John Steaver]

hi, what kind of capacitors and diodes would I need to build a 20kv multiplier? how many stages and how much will it require to power it?
thanks - John

 

[Martaine2005]

Big ones!!
Why are you playing with fire, yet don't understand it?

 

[GPG]

how many stages

Depend on what you start with.

 

[John Steaver]

I know how it works I just want the materials to make one. thanks for video.

 

[duke37]

It depends on what you want.
What output do you want?
What is the power supply, voltage and current?
How much do you want to pay?

!000V diodes are fairly cheap and would be able to handle 250V input, Use fourty of these. 1N4007 would suffice at 50 or 60Hz.
The capacitors will need to be fourty 500V electrolytics for a reasonable output cuurent. With all these capacitors in series, there will be considerable restriction of the current. The 'bottom' capacitors could be bigger than the 'top' capacitors.

A high frequency supply will need faster diodes but could use un-polarised capacitors.

 

[John Steaver]

how much current would this produce and I only wish to produce 20kv. thanks

 

[John Steaver]

oh and with a low input voltage

 

[John Steaver]

oh also (haha sorry), could I just have bigger capacitors and diodes and have only 4 or 5 stages? it would be much easier. thanks again

 

[(*steve*)]

what is your input voltage and what is your output current requirement?

If your input voltage is 500VAC, then you would need 40 stages (at least) and the output current you could draw would typically be *very* low.

What do you want the 20kV for? if you don't know the current required then this may help us make an estimate.

 

[duke37]

Why go for a C/W multiplier?
If you want fewer stages, you will need higher input voltage, 5 stages will need an input of 4kV.
Look up the cost of high voltage diodes and capacitors.
Why go for the multiplier, I would go for parts out of a CRT colour TV. These often run from 12V, use a high frequency oscillator and a EHT winding to produce a high voltage with just a tripler for the output. The current available is very low.

The problem here is that if you get a dead TV, the fault may well be in the line output stage.

 

[John Steaver]

just an experiment. it will be my first with high voltages and I want to get it right. are you talking about the flyback transformer in the tv duke? and if its not any trouble could you give any advice about how to place the diodes and capacitors the right way. pictures would also be nice if its not to much trouble. thanks

 

[John Steaver]

Will it look something like this. its very bad haha.

 

[duke37]

You could look at the following
http://www.extremeelectronics.co.uk/electronic/cockcroft-walton-voltage-multiplier/

The capacitors should be in two stacks and the diodes will be cross connected between them.
You could look at a Tesla coil to get the voltage directly, this will be AC whearas the CFM produces DC.

 

[John Steaver]

what o u mean by 2 stacks? isn't that 2 stacks?

 

[duke37]

Your diagram is neither schematic or practical layout.
If it is a schematic, you should use the conventional capacitor symbol.
If it is a practical layout, you need to show how the capacitor stacks are built with high quality insulation support.

 

[John Steaver]

its more practical, I was to lazy too do symbols haha. by insulation do you mean put it in a plastic container and smear or cover it in oil? I heard of this because they say the diodes perform better in oil. thanks for sticking with me, I'm a pretty new to this and want to start small. thanks

 

[John Steaver]

oh and sorry I took so long my internet was out last night.

 

[Martaine2005]

its more practical, I was to lazy too do symbols haha. by insulation do you mean put it in a plastic container and smear or cover it in oil?

 

[duke37]

Glass is a good insulator but cannot be machined. It is often used for overhead electrical distribution.
Polyethelene is good and used for water pipes, it can be cut easily.
Bare glass fibre/resin printed circuit board is good but you may not find it big enough. Cheap PCB will often absorb water and will be very poor for high voltages.
Steer clear of oil, you will need very pure transformer oil and it is very messy.

Any material must have a very clean surface. Many detergents contain ionic solvents which can conduct electricity so the surface will need to washed in distilled water or pure IPA.

If you look at the pictures of the big CW generators, you will see the stacks with the capacitors separated with ceramic or glass insulators.

 

[John Steaver]

didn't think I needed to insulate so much when its a lot smaller than the large ones but ok, thanks for information