Power Supply concept for 6" Tesla Coil / Tesla Coils / Forums

Forums

4hv.org :: Forums :: Tesla Coils

« Previous topic | Next topic »

Power Supply concept for 6" Tesla Coil

1 2 next

Move Thread

LAN_403

sparky

Wed Jun 20 2007, 06:29AM

Registered Member #530 Joined: Sat Feb 17 2007, 07:56AM
Location: Victoria BC, Canada
Posts: 178

I am coming up with a list of ways of getting at least 7.5 kVA for my 6" Tesla Coil. I have thought about using:

a. 2 PT units in parallel - 3kVA 14.4kV run at 7.5 kVA
b. a Pole Distribution Unit - 10 KVA 14.4kV
c. using 4 MOTs in series W/ DC voltage doubler circuit

....I'm curious about using "c" - anyone ever try rectifying 4 MOTs in series? Nearly 20 KVDC @ 7 kW.... that would be interesting to cram into an RSG driven tesla coil. I guess I'm following Roger Smiths idea of using MOT powered DC X 2 .... anybody here ever try this???

Any thoughts on this? I could save big money and not have to worry about truckin' around a 260 lbs transformer.... though I must admit I'd like to buy a Pole Transformer!

J. Aaron Holmes

Wed Jun 20 2007, 07:03AM

Registered Member #477 Joined: Tue Jun 20 2006, 11:51PM
Location: Seattle, WA
Posts: 546

The DC resonant charging topology is probably more like what you'd want for your MOT idea. The common two-capacitor voltage doubler circuit would cut your break rate in half, since it would take a full cycle to charge both caps.

If you have the MOTs and not the PTs, I guess go with what you've got and try the MOT stacking. I doubt if I could be bothered to deal with MOTs in a SGTC circuit (they're great for VTTCs, though!), but for some people MOTs are all that's easy to come by.

PTs are great, tough little units that are pleasant to work with. Well, *sometimes* they're little. I have a truly little 750VA PT that I can lift with one hand, and it's been pushed to 3kVA for short spurts. The 750VA and 1.5kVA 14.4kV PTs are just about the ultimate SGTC transformers out there, IMO, for their scalability and portability. 3kVA PTs are monsters, and are hard to come by. Often times these weigh as much as pigs (or more!) due to the extremely oversized cores generally employed for improved voltage regulation. A single 3kVA PT should survive short 7.5kVA runs no problem.

But if you think you'll go up from 7.5kVA, and if you don't mind dealing with a 250lb PT, AND if you're going to go to the trouble or expense of fetching a large transformer, a 10kVA pig is probably a better buy.

Play safe!

Regards,
Aaron, N7OE

sparky

Wed Jun 20 2007, 01:48PM

Registered Member #530 Joined: Sat Feb 17 2007, 07:56AM
Location: Victoria BC, Canada
Posts: 178

Thanks for the heads up Aaron! I am curious about DC Charging topology...however I'll try sticking with plain ol' AC first. I found a massive source for transformers so I'll be looking soon...

Dr. Drone

Wed Jun 20 2007, 02:34PM

Registered Member #290 Joined: Mon Mar 06 2006, 08:24PM
Location:
Posts: 1673

Hazmatt_(The Underdog)

Wed Jun 20 2007, 08:48PM

Registered Member #135 Joined: Sat Feb 11 2006, 12:06AM
Location: Anywhere is fine
Posts: 1735

There's a Pulse transformer up for sale on ebay right now:

If you're looking for a real challenge, you could rewind it for your purposes, provided that it has an iron core, its kinda hard to tell from the picture.

You 'could' rewind it for the output you're looking for. I planned on rewinding a 3180 VAC 24KVA transformer several years ago, but still haven't gotten around to that even though I have 90% of what I need, it's a pretty big undertaking! And considering the price of copper has gotten silly, you'd probably be much better off scavenging for transformers.

I was planning this before I got my little 1.5 KVA PT, although coming across a PT is kinda rare where I'm at.

sparky

Thu Jun 21 2007, 12:29AM

Registered Member #530 Joined: Sat Feb 17 2007, 07:56AM
Location: Victoria BC, Canada
Posts: 178

Actually copper has gone way way down... at least in Canada. My 1/2" X 50' copper tubing roll was $80 down from $120 with tax. Well I found MOTs and several 20:1 units at a junk shop - all in good shape I might add.... but I think I might just stick will plain ol' AC. I'm waiting to head south for my loot :)

J. Aaron Holmes

Thu Jun 21 2007, 05:50AM

Registered Member #477 Joined: Tue Jun 20 2006, 11:51PM
Location: Seattle, WA
Posts: 546

sparky wrote ...

Actually copper has gone way way down... at least in Canada. My 1/2" X 50' copper tubing roll was $80 down from $120 with tax. Well I found MOTs and several 20:1 units at a junk shop - all in good shape I might add.... but I think I might just stick will plain ol' AC. I'm waiting to head south for my loot :)

South, eh? Stopping by Seattle, per chance? Pretty soon, the utilities around here are going to catch the paranoia germ everybody else has. Better stock up now!

That's a good price for that tubing (compared to what *I've* seen). Better stock up on that, too!

Cheers,
Aaron, N7OE

sparky

Thu Jun 21 2007, 06:00AM

Registered Member #530 Joined: Sat Feb 17 2007, 07:56AM
Location: Victoria BC, Canada
Posts: 178

Paranoia germ...??? Really??? Damn the hydro utilities guys are pretty cool up here then. They'll sell me anything they got! No restrictions unless its too heavy to haul :) No paranoia here! By heading South, I meant Southern BC --- I live in central part of BC here. I'll be heading back to Victoria in a week.

J. Aaron Holmes

Thu Jun 21 2007, 06:07AM

Registered Member #477 Joined: Tue Jun 20 2006, 11:51PM
Location: Seattle, WA
Posts: 546

sparky wrote ...

Paranoia germ...??? Really??? Damn the hydro utilities guys are pretty cool up here then. They'll sell me anything they got! No restrictions unless its too heavy to haul :) No paranoia here! By heading South, I meant Southern BC --- I live in central part of BC here. I'll be heading back to Victoria in a week.

Excellent! Once I blow up my present lot of trannies, I'm heading for the border!!

I look forward to hearing details of your spoils.

Yes, paranoia is taking over "down here"; I must be the only person I've talked to recently (and I talk to myself a lot

) who's had luck just buying stuff off the local power utilities. It used to be easy everywhere, so I'm told, but not so lately. Of course, if you're willing to buy a brand new one, it's a lot easier to get somebody to listen to you!

Cheers,
Aaron, N7OE

Paul Benham

Thu Jun 21 2007, 12:33PM

Registered Member #570 Joined: Wed Mar 07 2007, 03:41PM
Location: Winchester Uk
Posts: 42

Four MOT's where two are in series, center grounded, with another two in parallel with the first two works well. I use a full wave doubler with resonant charging and it goes really well. It is a lot of building though compared to a PT or pig. I am at around 5kVA at the moment.

Cheers,

Paul.

1 2 next

Moderator(s): Chris Russell, Noelle, Alex, Tesladownunder, Dave Marshall, Dave Billington, Bjørn, Steve Conner, Wolfram, Kizmo, Mads Barnkob