Fusion Message Board

In this space, visitors are invited to post any comments, questions, or skeptical observations about Philo T. Farnsworth's contributions to the field of Nuclear Fusion research.

Subject: Re: x-ray transformer arcs (not for the faint of heart)
Date: Oct 23, 8:43 am
Poster: Richard Hull

On Oct 23, 8:43 am, Richard Hull wrote:


>I followed Richard's instructions for looking for corona, with leads from the transformer raw AC out about 6" from eachother above the oil. I brought the variac up and corona started forming, oil started climbing the leads due to the charge, and suddenly at about full 120 V in, a huge arc jumped between the leads. It must have got a full foot in total length before the wiper lead on this 8-amp variac vaporized (no big deal.) It was beautiful and loud and did not ruin my transformer luckily.

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I should have added that once you see corona...STOP!!! You really don't want to arc an Xray transformer. If you have corona at half of the variac or less you have a good transformer. That is good enough.
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>
>I was thinking, would I be able to limit the power drawn by an arc by putting a shorted microwave oven transformer in series with the primary of the xray unit to act like a magnetic shunt? Any recommendation for safety-ballasting this x-ray machine so it doesn't ruin stuff, including itself, in case of breakdown?

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I would imagine a neon sign transformer or any other shunted inductor in series with the primary would do, but I always include a large high watt resistor in series with the secondary (well insulated and isolated in the X-ray oil tank. (70k ohm 200 watt in my fusor.)

Richard Hull