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kalee20 · 12th Feb 2018, 12:28 am

Actually, resistances sound about right!

2.3 ohms for the 10V portion, multiply by 20 to get approximately the resistance for the 200V portion (because it's going to be wound with the same wire gauge) gives 46 ohms, and that's roughly what you've got. There may still be a shorted turn, of course.

4kV at 10mA is 40W, and at 240V you'll draw 167mA ideally. So with your total primary resistance of about 50 ohms, you will lose 8.3V, about 3.5%, which is about right for a reasonably efficient transformer. If the secondary is designed to have the same percentage losses, you'll lose a total of 7% of input power. Much more resistance and you'd lose even more, which is not elegant unless the transformer is specifically designed to have an output which droops highly with load.

12th Feb 2018, 12:28 am	#12
kalee20 Dekatron Join Date: Feb 2007 Location: Lynton, N. Devon, UK. Posts: 7,077	Re: HV PSU Question Actually, resistances sound about right! 2.3 ohms for the 10V portion, multiply by 20 to get approximately the resistance for the 200V portion (because it's going to be wound with the same wire gauge) gives 46 ohms, and that's roughly what you've got. There may still be a shorted turn, of course. 4kV at 10mA is 40W, and at 240V you'll draw 167mA ideally. So with your total primary resistance of about 50 ohms, you will lose 8.3V, about 3.5%, which is about right for a reasonably efficient transformer. If the secondary is designed to have the same percentage losses, you'll lose a total of 7% of input power. Much more resistance and you'd lose even more, which is not elegant unless the transformer is specifically designed to have an output which droops highly with load.