Hopefully? Another 48vdc-240vac Toriod Inverter build.

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poida Guru Joined: 02/02/2017 Location: Australia Posts: 1458	Posted: 11:53pm 14 Jan 2023         KeepIS said   Question: You mentioned re adjusting the resonance after fitting the choke. Wondering how did you did that, I initially used a precision generator and CRO to set the secondary CAP value. I doubt having the choke connected would make that static test for resonance change that much?   how I do it is drive the entire transformer, with choke in circuit at the two connections (I call them V1 and V2) made at the inverter board. I disconnect one from the board to remove any effect it may have. Today I checked it with the test inverter. The function generator is set to 3.5V p/p, 50 Ohm output. The output is connected to V1 and V2 with a 50 Ohm resistor in series. The CRO is connected to the function gen outputs, at it's BNC terminal. This test measures the choke + transformer + cap placed on the secondary and also it includes the effect of the small 240 -> 12V feedback transformer. The whole lot. It does resonate but the Q factor is rather small. I put the DSO in "HiRes" mode (this decimates large no.s of samples). This is to reduce the EMI my workbench is bathed in. 70 Hz   4.03 V 60 Hz   4.42 V 50 Hz   4.67 V 40 Hz   4.3 V 30 Hz   3.7 V The peak is around 50 Hz. The capacitor is 1.0uF The choke is 100uF. 8 1/2 turns on a double core (2 side by side) using the E70/33/32, N87 with 1mm or so gaps on the inner poles I tried this without the choke in circuit and the peak was the same. You are right, it does not make much difference.