Hi,
I asked for advice a while ago, and now I have finished the control cabinet
and the ballast. Here are a few pictures:
https://photos.app.goo.gl/1veXfqtzqGanxEWm9
The ballast core weighs 110 kg, double the weight of the HV-transformer
core. I wanted a ballast that can´t saturate, it has an air gap of 2*10 mm.
A rotary switch in the cabinet shifts the current from 10 to 40 amps at 400
V. To limit the inrush current I have NTC-resistors, but it seems like the
ballast starts very softly anyway, I could start it with shorted output,
tapped for 16 amps, on a 10 amp fuse, so the inrush current seems very
reasonable. I have no variac, so a soft start is important.
To test the HV-transformer I used a Jacob´s ladder with about 35 amps at 400
V to the transformer primary. The JL was not very successful, it arced
internally in the plywood base, and I think the initial gap was to tight, so
that the arc reignited there before it had climbed very far. I also scared
myself when a tape holder, placed on top of the control cabinet, fell
suddenly to the floor from the ballast vibrations. There is a short video of
that incident among the pictures.
The HV-transformer has very low idle current draw, it was hard to measure
with my clip on type ammeter. It is less than a few hundred milliamps,
anyway. The tank leaked some oil at the gaskets to the LV and HV terminals,
the rubber gaskets had set a bit, so I had to retighten the bolts. As I lost
a couple of liters of oil, the oil level is now below one of the HV leads
above the transformer core. I have to refill that, I don´t want a power arc
inside the tank.
Next I will start with the rotary gap. I have a VFD unit in the cabinet,
which I hope will hold up to the TC environment. And in a distant future,
perhaps I will come to start with the TC itself...
Moving forward, but slowly...
Jan
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