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Re: [TCML] 30kVA 3-Phase Variac

David,
yes, such variacs can be pushed to the extreme. For my 30kVA 3-phase columnar variac (45 amps per phase) I have all the manufacturer documents, including a diagram, in which the manufacturer tells you the short-time current capacity of this beast. It states for example the following: 

120 seconds 90 amps
60 seconds 108 amps
12 seconds 180 amps
6 seconds 225 amps

and so on. This gives you an idea of what such a transformer is capable of.

Regards,
Stefan
----- Original Message ----- From: "David Rieben" <drieben@xxxxxxx> 
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Wednesday, September 10, 2014 5:25 PM
Subject: Re: [TCML] 30kVA 3-Phase Variac



Stefan,
That's indeed some sweet toys that you have there. My prized possession (a far as variacs go) is the 4-stack 1256D Powerstat that is installed into my main power control panel cabinet for my big spark gap driven, Green Monster Tesla coil. I also picked it up "for a little of nothing" off eBay several years ago :-) At 28 amps rating per unit, it should be good paralleled for 112 amps continuous at 0 - 280 volts. At >30 kVA continuous capacity and weighing over 280 lbs (nearly 130 kilos), it's a bit overkill, even for my pole pig driven monster coil, but I love it, as I've never been able to detect notable warming of it above ambient temperature no matter how hard and long I've pushed it. Actually, I don't think my residential electrical service is capable of overworking this beast ;-)) 

David

Teslalabor <teslalabor@xxxxxxxxxxx> wrote:


Hi David,

it was "a little of nothing".
This variac was used in a theatre for dimming nearly hundred light bulbs.
Because the bulbs wasted a lot of (expensive) energy, the whole system was
replaced by LED systems, so the variac was not needed any more. So I took
the opportunity :-)
Yes, this variac is called a "columnar variac". Here in germany we have both types, also the circular shaped units. I have another columnar variac, which 
I will use in my current DC resonant project. This isn't even an
autotransformer, it has separated primary and secondary coils:

https://www.youtube.com/watch?v=5EKyaMFbCP4

And here is another circular shaped high power 3-phase variac in my variac
collection: It makes 0-440V @ 32Amps per phase (24kVA) and of course can
also be pushed far behind this powerlevel

https://www.youtube.com/watch?v=798JN1ZgHq4

Regards,
Stefan
----- Original Message ----- From: "David Rieben" <drieben@xxxxxxx> 
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Tuesday, September 09, 2014 7:08 PM
Subject: Re: [TCML] 30kVA 3-Phase Variac



Wow! Nice find. Did you have to come off a king's ransom to score this
beauty or were your able to get it for "a little of nothing"?
I see it's linear, as opposed to the more common circular shaped style (at 
least here in the US they are).

David
On Tuesday, September 9, 2014 6:31 AM, Teslalabor <teslalabor@xxxxxxxxxxx> 
wrote:



Hi all,

just wanted to show you my new 0-400V high-power variac, made a video of
it.
It's a motor driven 3-phase variac with a power rating of 30kVA. It has a 
nameplate rating of 45A per phase and can make twice the power for 2
minutes
(90Amps per phase, 60kVA).
2x2 Contactors per phase and so it even has balancing chokes between each pair of contactors on each phase. The contact-surface below them is silver 
coated, so it has a dark colour.

Video: https://www.youtube.com/watch?v=U5No4VBoM9A

Regards,
Stefan

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