29-12-2021, 12:57 PM
I got around to finishing the EHT transformer this week. It has been a long time since I started it but just hadn't a lot of time to spend on it.
The laminations were quite rusty. I knew as they were, they wouldn't all fit back. So I removed the rust and in doing so removed the insulating layer. So I gave each lam a light dusting of black spray paint. It took a considerable length of time to do all that.
All that time I was considering how to wind the EHT winding. I was leaning towards building a multi section former for it as it would avoid having to use insulation between layers. But in the end I decided to wind it as it had been wound in a single section. I wound it with 0.08mm ECW and used Polyester tape between each layer. I built a former from Perspex. The inside width of the former work out at 25mm which was convenient as the tape width was also 25mm. It was a slow job. I would do a few layers in each session and a few sessions each day. I got it completed in 3 days.
After finishing the winding I dipped it in transformer varnish and while in the varnish placed it in a vacuum chamber. This helped the varnish to penetrate deep into the windings.
The heater winding for the EHT rectifier is also on this transformer. As it sits at EHT potential I though it prudent to replace it. It was replaced with some narrow 10kV wire that I had.
I reassembled it and everything seams to be OK.
I need to camouflage the new winding but I will leave that until the varnish fully hardens.
The photos below are of the painted lamination's, the former, part way through winding, the completed winding before dipping, My vacuum chamber made from a pot and perspex sheet and the last two are of the completed transformer.
Frank
The laminations were quite rusty. I knew as they were, they wouldn't all fit back. So I removed the rust and in doing so removed the insulating layer. So I gave each lam a light dusting of black spray paint. It took a considerable length of time to do all that.
All that time I was considering how to wind the EHT winding. I was leaning towards building a multi section former for it as it would avoid having to use insulation between layers. But in the end I decided to wind it as it had been wound in a single section. I wound it with 0.08mm ECW and used Polyester tape between each layer. I built a former from Perspex. The inside width of the former work out at 25mm which was convenient as the tape width was also 25mm. It was a slow job. I would do a few layers in each session and a few sessions each day. I got it completed in 3 days.
After finishing the winding I dipped it in transformer varnish and while in the varnish placed it in a vacuum chamber. This helped the varnish to penetrate deep into the windings.
The heater winding for the EHT rectifier is also on this transformer. As it sits at EHT potential I though it prudent to replace it. It was replaced with some narrow 10kV wire that I had.
I reassembled it and everything seams to be OK.
I need to camouflage the new winding but I will leave that until the varnish fully hardens.
The photos below are of the painted lamination's, the former, part way through winding, the completed winding before dipping, My vacuum chamber made from a pot and perspex sheet and the last two are of the completed transformer.
Frank
