Re: Interference-SSTC

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

Original poster: "Jan Florian Wagner by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jwagner-at-cc.hut.fi>

Hi Matt,

> I am getting shocked bad with the Al enclosure grounded to house ground.

Is that with the SSTC running? With streamers and all?

I get similar jolts from my (properly) mains & RF grounded power TV
flyback driver - it is about 3mm arcs from case to finger, when standing
on a concrete floor and touching the case and running at about 80W...

There isn't much to do except for NOT standing on concrete floor. ;o)

> I have the 3rd prongs wire connected to the Al box that houses the PSU
and 555 
> circuit.The Al heatsink and MOSFET are outside.

Probably miswiring? Is the Al enclosure _really_ on the ground prong? Zero
ohms from anywhere on the case to the ground prong?

> I am getting a reading of 122volts AC from enclosure to heatsink and the 
> power is off!

120VAC at power being OFF... 
Are you really absolutely sure that you have your power switch on the
_live_ prong? 


Other thing, if you have no insulator between your mosfet and heatsink,
then the heatsink will be connected to the metal plate on the back of the
mosfet. That's usually also the mosfet drain. So it is at +160VDC. 
That's with power being ON.

The +160VDC on the heatsink is one more reason to put it out of reach, and
also not to connect it to the grounded Al case.

Not to mention that the mosfet gate may pick up some reather bad vibes
from the HV RF streamers, and it may decide to drop deap at some point...;o)


>I am using a variac for in power. 

A variac doesn't protect you much against anything, really. 

You'd need an additional mains isolation transformer. (ok if the variac
specs say that your variac is/contains also an isolation transformer, then
you're off fine). Just don't ground any part of the isolation xfmr
secondary.


cheers,
 - Jan

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