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: inductive ballasting of x-ray unit
Date: Oct 28, 9:42 am
Poster: Don Harris

On Oct 28, 9:42 am, Don Harris wrote:

>Well, I have tried a form of inductive ballast for my transformer with good results. I used a trashed 15 kV, 30 mA neon transformer(one side was blown though), and shorted the outputs to ground. I run the hot primary lead to the x-ray unit through the 120-volt winding of a big variac, and have the NST between the variac wiper and one side so I can regulate how much ballasting is going on. The results look good. I can regulate the transformer power from seeing just thin crackly blue sparks to a thick orange arc by turning up the ballast variac. I believe I should be limited to about 500 watts this way. Perhaps I will have to add another NST in parallel to my arsenal to get enough power for the fusor out. Anyway, I feel secure that I can arc the x-ray unit all I want with this sort of ballasting. Unlike Richard's setup, I don't believe I have room in the tank for a big power resistor without major rearrangements. But since I will be using my Maxwell, 50 kV 50 uF cap for filtration I might have to stick a resistor in line anyway to keep from having a slight explosion problem (no kidding). It will most likely be in its own oil-filled tupperware bin. Any helpful suggestions will be considered!


I wound a choke coil to limit the current on a "pole Pig-Utility transformer". This is what the people in the neon industy do to limit power to the transformer. They use the "Pole Pig" to bombard the inside of a partialy evacuated tube with high voltage and current to heat the tube walls to drive out occluded gasses (easier than oven baking for long tubes), and then pull a low vacuum to extracact the gasses before they can recombine with the tube walls.

The choke coil was about 500 turns of 12 gauge wire on a sliding iron core that was about 18" long. Of course you would have to scale you choke to something that was appropriate for the XRay unit. You simply pull the core out more or less to increase the max current. In my case I was measueing the heat of the Neon tubing as I adjusted the current. You guys could watch those litte Neutrons!

By using a variac to set the max voltage and the choke coil to limit the max current you would have
complete control of you HV output. Hope this is helpful. Some day If I can get my shop buit I'm going to join the "Neutron Gang".

If you don't want adjustable current limiting your idea with the shorted NST's is much simpler.