[Amps] How about this furnace?

[Peter Chadwick]

PA3DUV said:
>On the EU mainland 20 kW input @3 phase mains with 400 VAC between the 
phases will result in 17 A per phase. 
I reckon from am a standard house mains inlet one can run a 30 kW 
amplifier and use the dishwasher, microwave and cook a decent stir fry 
wok at the same time.<

and DF3KV said:
>In a 3-phase environment which is standard nowadays in
central Europe that is no problem at all, at 20KW input you
need 28A per phase.<
So guys, are you saying that on the Eu mainland, domestic properties are routinely provided with 3 phase mains?
They certainly aren't in the UK, and as far as I'm aware, not as a matter of routine in the US. I suspect a request for installation in domestic properties would meet with some questions, especially with our new UK 'nanny state' electrical regulations. Even my neighbouring farm only has single phase in the farmhouses.
The main supply to my house is fused at 100amps, (24kW at unity PF) although if you tried drawing that much, the voltage sag would hurt, as I'm on the end of the best part of 500 metres of overhead line from the transformer. It used be two phases from the transformer, but there's now 3 phases from a new transformer (it's fed from a an 11kV 3 phase overhead line) and two of them get to the pole outside my house. But only the neutral and 1 phase come in. To get 3 phases for the lathe and mill, I have a solid state inverter, although as it provides variable frequency, it provides variable speed, too.
But the other point that needs considering in the current draw is the amplifier power factor. If that was 0.8, the current goes up by 1.25 times for the same power.
And I still don't like the idea of the electricity bill!
As far as corona is concerned, don't bet on it. The Quad originated at HCJB because 10kW led to corona off the ends of the Yagi they tried. Some locations you may get away with it, but I've seen problems with 1kW at 500kHz into a shorter than usual antenna. On my 80 and 160m vertical, I've been rebuilding the tuner since I changed the beam on top to a Steppir and reduced the capacitive loading. I had a beautiful blue glow inside my 500pF 15kV vacuum variable - does anyone rebuild or repump those? - and building padding capacitors witrh 0.064inch thick glass produced impressive fireworks and pinholes in the glass around the edges of the metal electrodes - and broken glass. That was with less than 1kW!!! A 7.5kV peak vacuum variable will just do it (I hope): for 10kW, I'd be talking in terms of 20kV plus at the antenna terminal......
Incidentally, producing a suitable motorised mounting for the remote tuned vacuum variable has led to an enormous amount of swarf in the workshop: it just shows what can be achieved with economy and care! And a load of scrap metal where things didn't work out right. But that's another story............


73

Peter G3RZP