Power Supply concept for 6" Tesla Coil
sparky, Wed Jun 20 2007, 06:29AMI 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!
Re: Power Supply concept for 6" Tesla Coil
J. Aaron Holmes, Wed Jun 20 2007, 07:03AM
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
J. Aaron Holmes, Wed Jun 20 2007, 07:03AM
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
Re: Power Supply concept for 6" Tesla Coil
sparky, Wed Jun 20 2007, 01:48PM
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...
sparky, Wed Jun 20 2007, 01:48PM
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...
Re: Power Supply concept for 6" Tesla Coil
Dr. Drone, Wed Jun 20 2007, 02:34PM
Dr. Drone, Wed Jun 20 2007, 02:34PM
Re: Power Supply concept for 6" Tesla Coil
Hazmatt_(The Underdog), Wed Jun 20 2007, 08:48PM
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.
Hazmatt_(The Underdog), Wed Jun 20 2007, 08:48PM
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.
Re: Power Supply concept for 6" Tesla Coil
sparky, Thu Jun 21 2007, 12:29AM
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 :)
sparky, Thu Jun 21 2007, 12:29AM
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 :)
Re: Power Supply concept for 6" Tesla Coil
J. Aaron Holmes, Thu Jun 21 2007, 05:50AM
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
J. Aaron Holmes, Thu Jun 21 2007, 05:50AM
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 :)
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
Re: Power Supply concept for 6" Tesla Coil
sparky, Thu Jun 21 2007, 06:00AM
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.
sparky, Thu Jun 21 2007, 06:00AM
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.
Re: Power Supply concept for 6" Tesla Coil
J. Aaron Holmes, Thu Jun 21 2007, 06:07AM
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
J. Aaron Holmes, Thu Jun 21 2007, 06:07AM
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.
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
Re: Power Supply concept for 6" Tesla Coil
Paul Benham, Thu Jun 21 2007, 12:33PM
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.
Paul Benham, Thu Jun 21 2007, 12:33PM
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.
Re: Power Supply concept for 6" Tesla Coil
sparky, Thu Jun 21 2007, 02:23PM
Thats great to know Paul.... I guess I'd have to look for those power chokes and diodes. I wonder if MO diodes are alright for resonant operation. I know they work fine for doubling. Is it better to get those fast diodes???
I know older MO's came with those diode bricks rated at 17 kV 450mA or so.... I'd love to find a source for these :)
sparky, Thu Jun 21 2007, 02:23PM
Thats great to know Paul.... I guess I'd have to look for those power chokes and diodes. I wonder if MO diodes are alright for resonant operation. I know they work fine for doubling. Is it better to get those fast diodes???
I know older MO's came with those diode bricks rated at 17 kV 450mA or so.... I'd love to find a source for these :)
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