Circuit Function

[alan sailer]

I recently got a look inside an old Spellman 30kV powers supply and have a question about the HV side of the circuit.



The secondary inductor is a beautiful are core unit coupled to the primary inductor which is driven by a multiple transistor
circuit. I curious as to what the diode/capacitor circuit does. It seems like a multiplier but the out put of this circuit goes to a silicone rubber potted assembly that looks like it contains a tripler circuit (complete guess here). If the potted assembly is a tripler then it would need an AC input.

I'd try an simulate it but I only use LTSpice once every five years and have to relearn the whole process from scratch. Which normally takes a few hours.

[klugesmith]

Very interesting.  Looks like the HV winding connects to two voltage doublers, of opposite polarity, sharing a common node with "bottom" end of the winding and not Ground.   I think the result is a quadrupler with lower output resistance than other configurations using same capacitor values, and more balanced stress on the components.  DC output, which make the potted thing a mystery.

For purposes of discussion, can you give the C's and D's reference designator numbers?   Maybe even also identify the nodes (N1-N6 would do), a thing required for SPICE simulation before schematic entry was available. Thanks.

[alan sailer]

I'm not sure about the node labels but here are the parts.



Also a photo of the unit. It's so nice and clean.



I like old style structural electronics. The new electronics
can do amazing things but it looks like debris glued to a board.

[klugesmith]

Beautiful. Note anti-corona balls at the free ends of upper capacitors. Can we see picture of the primary coil? Does the unit work, or you want to make it work?

We definitely have a voltage doubler on each side, not very different from microwave oven power supply.  When top of HV winding is positive, current in D4 charges C2 negative-on-right.   When top of HV winding is negative, C2 voltage adds to that & charges C4 to double voltage negative-on-right through D3.   Etc.

>> I like old style structural electronics.

Me too.   Has design of electrical substations changed much in 21st century?  https://electrical-engineering-portal.com/7-design-diagrams-hv-substation-engineer

[alan sailer]

kugesmith,

Thanks so much. I'm not interested in making it work right now. I'll take a picture of the primary but it is not a simple single coil. Several taps etc.

The whole power supply was initially exciting but I soon realized that to make it work would require external signals., some sort of control module.
I have a homebrew 30kV power supply that isn't as fancy or well regulated as the Spellman but does the job. I don't really need another.

So if each side is a voltage doubler then the output is four times ref to ground? Also, since the caps are rated 15kV for the lowest, the input AC would be 7.5kV?

Times 4 gives the 30kV rated voltage.

This means that the black box is not a multiplier. I may break it part to see whats up.

Sorry if I seem too lazy to do the work with LTSpice. I always dread the process of figuring out how to run the program. I addition I am fighting medical/mental issues that make concentration more difficult than usual.

I also stop to admire HV substations. There is also an element of fear.

A short story about an event that has haunted me for years. The local highway high point is the Conejo Grade. Running across the top over the freeway are a series of high tension transmission lines. Back in the 80's I was driving home from work and saw a bunch of fire trucks around the base of one of the pylons. The next day I found out why. A group of kids decided to climb up the pylons for a look. They explored and were heading back when one kid stood up and got flashed. He lived for a while after but died of the burns. The idea of him sitting on the top of the pylon, in shock, waiting for the firemen to get him down has always terrified and saddened me. The kid wasn't hurting anyone and he died because of his mistake.

[alan sailer]

So I di tear open the black box. I found various smoothing, voltage monitoring stuff. Caps and resistors. Nice 40kV stuff.

If anyone is curious I can post a schematic. Otherwise the chances that the information will be useful to anyone are on the order of one over the half life of the proton.

[klugesmith]

What do they call that coil winding style, which strongly influences self capacitance?
Here's a specimen that has Christmas tree influences.

[MRMILSTAR]

The term that I've seen used for this type of winding is "basket winding".

[alan sailer]

mrmstar has it. The other terms are listed here,

https://dbpedia.org/page/Basket_winding

When I was going down the brain melting road of trying to make my own HV AC coils I bought the plans for something called the Gingery
Coil Winding Machine. It worked, sort of, with larger diameter wire.

But in the end it reminded me of sewing, which also drives me crazy. I want the stuff I'm working on to stay still...