240v to 75kv transformer, shell type? Double winding? Need sum help please!!!!!

Hello! So I found this transformer the other day, it's a 240v to 75kv here where it's gets interesting, it's a shell type, with two separate transformers I'm guessing. It has a input for 240v on each end, it has 1-5 taps but 1 is not used 2 is phase 3 is neutral 4 is earth and 5 is not used. It only has condanuity between 2 and 3 on 240v side. On the high voltage side it has only one output and no condanuity to the core or anywhere, So I'm confused. I'm wanting to make it in to a high voltage Jacobs ladder setup. I have a varic that is 240v and goes from 1v up to 280v on the wiper side it is motor driven. Can I arc between the two hv posts? Also both transformers are have the same phase in parallel. Please help me!!!!! Thanks! 

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nz dude (author) 2 years ago

here is my Jacobs ladder I just finished, that's a big size boc lighter to compare size, it's a monster hahaha arc on!!!

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Would to find of them myself...

If it is still working the HV output is between the two posts.

It will have a very high resistance and a cheap digital multimeter might fail to show anything, an anlog tester should show you the high resistance.

You should always limit the arc to a shorter distance than the post to prevent over arcing inside the winding.

As a rule of thumb (if there is no data sheet available) I keep the max arc lenght 20-25% shorter than the distance between the HV terminals.

Of course you can create much longer arcs but you should have a spark gap of the said distance on the HV output, once the air is ionised you still get massive, long arcs.

Driving it throuch the vraic should be no problem if it is rated for the use of motors and transformers, if in doubt you can put a RC filter between it.

One thing you must be aware of is that those transformers are totally deadly if you get into into contact with the HV output!

You might also want to consider a current limiting resistor on the 240V side to prevent overheating during long term use as the arc acts like a short to the transformer when pulling it really long.

I use 250-1000W halogen lamps for it, sometimes a combination in parallel if I need more power.

nz dude (author)  Downunder35m2 years ago

thanks man, the transformer itself is from a dielectric oil breakdown down tester. The varic also was the factory one that was connected to the transformer when I found it, and guess what, they work!!! There is a resistor across the 240v input of the varic. Yup I know this tranny is deadly as I'm a hv electrical fitter here in New Zealand. No cheap meters round here I use a fluke 87v also have a 3phase hoki power anyliser . So can I wire it all up to a Jacobs ladder smaller thn the gap between the posts? Il post sum pics of the varic.

I don't see a problem apart from the insane power levels, will look great once working.

Just make sure you have a suitable spark gap fittet and all should be going smooth.

Please upload a video of the working setup when done!

nz dude (author)  Downunder35m2 years ago

insane power level alright lol, I'm going to be using two 1000mm long 2mm by 6mm soild copper rods as the Jacobs ladder standing off on two 100kv insulators mount on a 1000mm long piece of wood. Will up load a video to YouTube or sumthing this avo

nz dude (author) 2 years ago

here the varic il will be using to control my input voltage to transformer

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nz dude (author) 2 years ago

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nz dude (author) 2 years ago

here's sum photos

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