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Forum Index : Electronics : Inverter building using Wiseguys Power board and the Nano drive board
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wiseguy Guru  Joined: 21/06/2018 Location: AustraliaPosts: 1290 |
Toroidal Transformers are not something I have much experience with especially with correct design values so maybe treat what I am suggesting with a grain of salt. My calculations of your cross section are 45 x 120 or 5400sq mm ? If I apply Oztules law, I understood that he said 2800sqmm = 1T/Volt, so your turns per volt should be 5400/2800 = ~1.9286. You used 118 turns which suggests an output of 227.57V ? He also suggested for lower flux that you should calculate for a 240 - 260V secondary when your desired output is 220V which is somewhere between 9% & 18% more turns. Using that theory if we assumed your 227.57 volts was the correct target your secondary turns should have been ~133T if I use 13% more turns (half way between the suggested increased turns%) ? If you have access to a proper wattmeter why not disconnect the transformer from the circuit and check its power draw from the mains (118T winding!!) - do not use RMS Volts and Amps calculations as they will be a long way from reality due to the inductive phase shift involved. That would be a good starting point. Whatever don't get distressed if the answer is a lack of turns. although not ideal you can add a few primary and secondary turns as required and still make it come good. Or maybe someone with real winding experience can chime in and give you more correct advice. Alternatively a quick test might be to adjust your output volts to around 200-205V and tell us what the idling current now is with the 12T chokes. I think the combination of choke inductance a bit low and transformer not at optimum is causing the high idling power? Edited 2026-05-27 09:57 by wiseguy If at first you dont succeed, I suggest you avoid sky diving.... Cheers Mike |
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phil99 Guru Joined: 11/02/2018 Location: AustraliaPosts: 3233 |
That is correct. Optimum Turns / Volt is a compromise that depends on usage requirements. More T/V = lower core loss, which is there all the time, but the extra resistance increases loss loss in the windings at high power. A transformer intended for a particular piece of equipment may spend most of its time near full power so you aim for lowest loss at full power. If that is what the maker thought it was for then that is what he made. A domestic inverter usually spends little time at full power so low idle loss is more important for minimizing total energy loss. |
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KeepIS Guru Joined: 13/10/2014 Location: AustraliaPosts: 2149 |
The other option, I think wiseguy mentioned, even if you only have one spare core of some type, wind enough turns around it to get another 20uH or so and connect it in series with one of the Inverter chokes, as you are only testing at idle, it should tell you if you need another turn or two in the existing chokes. NANO:Inverter V 8.2ks - Linux AvrDude GUI script V4.1 |
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