Re: Offline Cockroft-Walton

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Mike Harrison by way of Terry Fritz <teslalist-at-qwest-dot-net>" <mike-at-whitewing.co.uk>




On Sat, 03 May 2003 07:04:18 -0600, you wrote:

 >Original poster: "Jolyon Vater Cox by way of Terry Fritz 
<teslalist-at-qwest-dot-net>" <jolyon-at-vatercox.freeserve.co.uk>
 >
 >Dear List,
 >Would it not be possible to use a Cockcroft-Walton multiplier to derive a
 >HV DC supply from ordinary domestic mains voltage WITHOUT the need for a
 >high voltage transformer, as these are often difficult to find.
 >
 >I understand that with multipliers of this type, the current available on
 >the HV side is limited  this is often considered a disadvantage but maybe
 >this is a good thing.
 >In any case, can't the output current be increased by having the lower
 >capacitors in the "ladder" connected in parallel and the upper capacitors
 >connected in series?
 >
 >Also, with regard to possible safety hazard of having HV supply directly
 >connected to mains, could this not be mitigated by use of an isolation
 >transformer between the multiplier and mains supply,
 >only isolation transformers seen to be a lot more common and readily
 >available than high voltage transformers appear to be.

Yes it can be done, but it's not very efficient for seriously high voltages.
Air ionisers sometimes work like this.

It's usually best to boost the input voltage up a bit before starting 
though - one trick is to use a
few cheap low-voltage transformers, e.g. 4 12v transformers : the first set 
up for mains in 12V out.
Connect the 12V sides of the other 3 in parallel to the output of the 
first, then the secs in
series, giving 3x mains out. (If you're not worried about isolation, you 
couls also connect the
output in series with the mains.

Isolation isn't always necessary for safety - a couple of resistors can 
limit mains current to a
pretty low level without having too much impact on your HV