Guru
Joined: 21/06/2018
Location: AustraliaPosts: 1156
| Posted: 07:48am 08 Jul 2022 |
Ok Today I re-tested for resonance with my transformers and got quite different and more believable results. I did find a clip-lead that was open circuit and another with a dubious crimp connection. Usually I dismantle and solder clip leads as I have never trusted their wire crimp connections, don't know how this one missed out. That must explain the crap results. The strange thing is that after working out the L from the resonance formula and adding capacitors etc all the calculations and measurements looked correct? Just goes to show, crap in = crap out..... (a bit like 1 = 2 -that sounds familiar hmmm)
The much better figures I got today is for resonance at 76 hertz = 6.7uF still high but only 36% of yesterdays calcs so I will set it at that.
An interesting discovery during the re-testing was that I got the same resonance with just one 240V winding as I did when both 240V windings were connected in parallel. This didn't make sense at first. Then I realised the 48V spwm windings were still connected in parallel. This effectively put the 2 x 240V windings in parallel - on the same core effectively if you think about it. If I had disconnected/separated the 48V spwm windings I would have got a much different result, but the connections were buried & not easy to access.
It is like winding two bifilar windings on the same core and discovering that with one winding you get the same uH value as with the other or with 2 windings connected as one, then they just have half the R value with the same number of effective turns & inductance. Probably useless information for most...
Now to get back to testing Poidas new codes, but with resonance now in check !
Edited 2022-07-08 19:26 by wiseguy