Guru
Joined: 13/10/2014
Location: AustraliaPosts: 1860
| Posted: 04:38am 13 Jan 2023 |
Well, I checked the transformer again, it was now 47Hz with the cap supplied with the inverter board, it was previously 76Hz.
I'm aware of the remanence in the transformer raised by wiseguy, I did what he did with the generator and series resistor to reset it just in case.
And I too needed only 1uf now to resonate it at 75hz, not 4uf which previously resonated it at 76Hz. I'm trying to remember if I checked the resonance BEFORE I had wound the test secondary, that might explain the difference?
So with just the 15uH choke, was 13uH in last post but I managed to fit one more turn, so 15uH choke gave me a perfect wave shape but with a tiny amount of HF switching noise, like a tiny staircase effect, idle current was 300ma.
With the other 40uH choke added in series, extremely clean waveform with only that slight flickering on the TRAILING slope just after the crossover.
However the idle current is now down to only 200ma, 11 watts?
EDIT: With the smaller CAP the big variac no longer makes any noise when running loaded or unloaded, but the choke and transformer now make a very faint hum
Edited 2023-01-13 16:15 by KeepIS