Fun with 770V

[GBD]

Intended to post this a while back, but didn't get around to it.




Right now its still sitting in my garage (as it was for the past month lol), running off a 120V/600V control tranny and a variac.

Ive designed a battery operated (lead acid) charging system, however haven't had the time to build and test it.. whenever (IF) time permits over the next few weekends Ill see where it goes.

Its pretty straightforward, half bridge driving a transformer with feedback to a logic driven discrete gate driver, secondary side voltage limit to cut off power.

 

[Tech_Junkie]

HMMM, I have a 4KV cap. Wonder what kind of arc I can pull from it.

 

[GBD]

That would depend on your resistance value.
with a 4KV cap, Id imagine it to be a pulse capacitor and have very low capacitance, so unless connected to its charging source, you won't get very long lasting arcs (before needing to recharge).
Its worthwhile to try though, DC arcs are silent and very cool in apperance.

Its tons more fun to short them out

 

[Tech_Junkie]

This is an older one full of PCBs. So I dont want it blowing up all over the place.

 

[GBD]

Fair enough.
Pulse caps in general are designed to take that kind of abuse, frequently and repeatedly.
Lytics on the other hand... if the ones I got weren't designed for inverter/high current use, they could very well explode.

 

[Fiddy]

Make a what happens when a PCB capacitor explodes video and post it up here

 

[Tech_Junkie]

Make a what happens when a PCB capacitor explodes video and post it up here

I'd send it to you to do it, but its almost the size of a loaf of bread, and weighs about 2 kilos. So shipping to OZ would be expensive. If you want to pay shipping its all yours. :beer:

 

[Hiemal]

GBD, why on earth did you decide to go discrete with your PWMing?

Wouldn't it have been slightly easier using a PWM chip?

And TJ, that sounds like a purty pulse capacitor. Where'd you get it from out of curiousity?

 

[Tech_Junkie]

And TJ, that sounds like a purty pulse capacitor. Where'd you get it from out of curiousity?

Flea market for under $4. This guy always has antique HV, Ham, PC, assorted electronics, ect. He always gives me deals. I bought a missile trajectory simulation board off him once. It had ~40 micro switches, and pots for different angles, speed, ect. $5 :wave:. I bought 300 assorded vacuum tubes, some from a radar set up, $20. I have piles of stuff.

I love the flea market.

You want the cap? Pay shipping and it yours.

 

[GBD]

GBD, why on earth did you decide to go discrete with your PWMing?

Wouldn't it have been slightly easier using a PWM chip?

Easier? yes. you can slap a UCC pair in there. From my past experience though, Ive grown to hate UCCs and other GD ICs with a great passion. unrelaible, more suseptive to RF interferance, can't push out any decent current (100ma or so for the majority) and expensive, since the bridge devices im using have trumendous gate charge, ICs capable of driving them would already cost far more then its worth to bother with (ex: IXYS drivers).

That whole discrete driver is simple in design, costs less to build then PWM chips, and Ive never had a failiure before with it, so Im sticking to what works best for me.

Note to self: find more storage space for caps...not sure if Ill be able to fit all of them in the car next run.

 

[Hiemal]

What? UCC37322x series of gate drive IC's are perfect, and provide a whopping 9 amps of peak gate drive current...

I don't know what gate drive ic's you're talking about though, they sound like absolute crap anyway!

And, I wasn't talking about the gate drive IC, I was talking about your oscillation method. A PWM chip is a bit easier and more user friendly than discretes. If something breaks, you replace the chip. Discretes, not so easy at all.

To TJ; Do you have any idea what kind of capacitance it has? And, what kind of vacuum tubes do you have? I have a small collection of my own going on; I plan on building an amplifier eventually.

 

[Fiddy]

I'd send it to you to do it, but its almost the size of a loaf of bread, and weighs about 2 kilos. So shipping to OZ would be expensive. If you want to pay shipping its all yours. :beer:

Yuk PCB's i dont want your carcinogenic loaf

Wire it into a welder or similar and let electrons sought it out`!

 

[Sigurthr]

I've got about 30 Valves (tubes) myself and too would like to build an amp with them eventually. I have some really nice 6146 transmitter pentodes as well, I'd REALLY like to make an amp with them. Darned things require 400VDC @ ~100mA plate power though! The grids run on 200VDC, and the heater requires 6.3V @ 1200mA. Building a power supply for it would be harder than building the amp itself!

 

[GBD]

What? UCC37322x series of gate drive IC's are perfect, and provide a whopping 9 amps of peak gate drive current...

I don't know what gate drive ic's you're talking about though, they sound like absolute crap anyway!

And, I wasn't talking about the gate drive IC, I was talking about your oscillation method. A PWM chip is a bit easier and more user friendly than discretes. If something breaks, you replace the chip. Discretes, not so easy at all.

Ah, I misread to what you refered to, but since on the topic; 9A peak current doesn't really mean much with its pulse lenth, sure it will work for low gate charge fets, but with the bricks im using its useless. All they are really good for is to drive a highside driver, adding extra parts to the system and additional propogation delay with the UCC acting as a medium from the logic input and the highside, while the delay is neglegible for such a low switching speed as in this application, it definatly adds up when you up the frequency. so why not skip all of it together and go for a simple logic driven discrete driver?

As per the second part, I would agree there, an IC could be better, but IMO thats user preferance, I see it easier and cheaper to replace discretes then ICs. (unless you aren't the type to enjoy desoldering/soldering)

EDIT: G'night, gotta work tommorow

 

[Hiemal]

I've got about 30 Valves (tubes) myself and too would like to build an amp with them eventually. I have some really nice 6146 transmitter pentodes as well, I'd REALLY like to make an amp with them. Darned things require 400VDC @ ~100mA plate power though! The grids run on 200VDC, and the heater requires 6.3V @ 1200mA. Building a power supply for it would be harder than building the amp itself!

I've got a pair of EL34's, a 6L6, and a 811A for power toobs. For smaller ones I got a 8FQ7, and a few other various ones that need not mentioning.

Gonna use two stage small one, then maybe the pair of EL34's for the driving stage... or the 811A, I don't know. I need to build the chassis first.

Also, you can use step up transformers (like the ones you'd use internationally) to power tubes. Though, I've got a nice 120 vAC to 440/220 vAC multitapped transformer I'm going to use for the amplifier...



And, I'm sorry GBD for not even really commenting on your cap bank! It's pretty nice! Also, why not use copper over aluminum? You'd get a bit more power output that way.

 

[GBD]

My hobby budget is limited .. and copper isn't cheap lol, so scrap AL works.
the car needed money put into it with repairs and stuff... stupid ringlands.

Once I find the time and spare funds....mucho copper will be needed.

The goal is to provide enough instantanios power to a TI-84 calculator to seccessfully devide by zero.