how can test the stator insulation and mylar coating?

[geraldfryjr]

One of the IRF510 FET's gave out today.
I'm not sure why as the thing has been working perfectly and was used for many stator coating stress tests and arc tests with no problems at all.

I did go through many of them while devolping the power supply.
This sets me back abit,So now the search is on for some better FET's or maybe a revamp of the drive system.
Everything else is working fine and I will pop in a new one to verify this.

The IRF510 is a weaker type of FET and is fun to work with but it is not worth the money that Radio Shack charges for it although I did make it work in this circuit.

I will post my results after I replace it and start working on a better output circuit and/or FET replacement.

Oh, The Fun of R&D !!!

Cheers!
jer

[geraldfryjr]

I got the power supply back running today.
It took just one FET to do it.
I couldn't find any thing out of the norm to cause the failure.
I thought that maybe the drive got to high on the gates but they weren't,so I just replace the bad FET.

While I had it apart I did try a IRFZ42 in place of the the bad FET using the installed 1K resistors as a load with the output transformer disconnected and it worked as well.
Although it did show a slightly lower gain but a nicer output waveform than the IRF510 in which was expected due to the much lower on resistance (RDSon).

A slight tuning of the gate drive transformers primary will probably be all that is needed to make it perform properly.
I wasn't in the mood to re-tune it at this time.
Should another one fail I will look more deeply into the situation.

So, Let the Testing Resume !!!!

Cheers!

jer

[alexberg]

FET has died and it ought to die due to shoot through...

[geraldfryjr]

I had thought about that,alexburg,
But is that really possible being that the output stage is configured as a classic class B pushpull linear amplifier?

I am suspecting that some high voltage may have crept in from the ground side off of the stepup transformer driving the ESL panel because I forgot to use some isolation resistors to the panel when I hooked it up.

Also it is possible that a charge could have built on the surface of the plastic panel used to mount the amplifier board and on the panels high voltage section is encased in.
I was thinking that I may need to add some static shields.

Some times the thing seems be to energizes even on the ground side as can feel when I touch the voltage adjust or the ground case as the high voltage gets into everything above about 10Kv or so.

I found this to be true as well when I was working on the feedback circuit and was very surprised that the opamps could survive in this condition as the whole thing was energized with a small high tension.

All of that went away for the most part once I had it properly mounted in its case.

It is not doing this now and the case and Voltage control now seems to be cold
.
It may very well have been a bad solder connection on one of the three ground wires coming off of the High voltage section.
Everything is star grounded to the main amplifier board including the case and earth ground.

The control boards power is are daisy chained from the star point on the main amplifier board and are common grounded to the case through the mounting screws as well so they are well protected too.

I can sit here and draw arcs off of it all day with no issues.
But when I hooked up the ESL (that was insulated from the top of my desk with a pane of glass) it would reset my computer every time it arced in the panel.

Now I know I shouldn't have its power source common to my sensitive electronics but nothing was affected until I hooked up a panel for some breakdown testing!


Hmmmmmm...........

jer

[geraldfryjr]

Here is a source of high voltage power supplies and stuff as well as some ready made transformers and core pieces that might work in the power supply that I had designed or could be used to create some thing similar.
Also some little supplies that may be used for ESL bias supplies.

Very cool stuff!

Some expensive and some very reasonable prices,


High Voltage Transformers

Enjoy !!

jer