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

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mab1 Senior Member Joined: 10/02/2015 Location: United Kingdom Posts: 238	Posted: 01:02pm 25 Dec 2022         KeepIS said   I assume this HF inverter to be something like a "pure sine wave" 24/48vdc to 240Vac unit with a Hi frequency DC inverter generating around 360v-390v DC feeding a DC to AC PWM IGBT output stage and a large inductive filter for 230v AC. (No big Transformer) Sounds about right: the start surge limitation is the amount of energy stored in the 360v capacitors - if they’re big enough the starting capability would be fine.   Quote   Strangely, I have a $680 made in China 5kW/10kW surge inverter just like this. It's a 24v inverter and it starts a big 25 year old massive 2.5hp air Compressor that was the bane of every work site if put on any kind of extension lead - used to burn out the motor from slow startup/stalling. The peak startup current in to the inverter of the above unit is 480A @ 26V. Expensive DC clamp meter with a slow decay hold function, a late model DC clamp meter and my own DC 600Amp clamp used to monitor the Load current with special peak hold coding for catching any glitch on the displayed graph at very high sample rates.   It also starts our 2.5HP heavy induction motor Band-Saw at 410A surge, huge Bench grinder (induction), 2KW through wall workshop Vacuum, Air conditioner, Cloths dryer, small Oven, all workshop lighting computers, an so on, and until recently, a small 2.4kW water heater.   Now from what I have read, this should have destroyed itself, and I thought so to, but it is what it is. I could not believe it could start that Compressor, had to go back and look to make sure it wasn't on mains. Well 2.5hp is not that big for a 5/10kw inverter: my 5+ year old powerjack lf 24v 8kw/32kw (actually has 2×1kva transformer so nowhere near 8kw) will start a 4hp induction motor pressure washer. Actually, due to my ageing, small lead acid battery, my startups are now limited by the battery itself.   Quote   I want something that is not a ticking time bomb, hence my desire to build a Low frequency inverter, which is supposed to be the best with these kinds of induction load. But I see things like, you should soft start with these induction loads? seriously? you mean like a brownout condition? The Air compressor and Band-saw are just going to love that. I think it's more that you have to soft start the inverter when using a large toroidal tx; obviously it is desirable to soft start big loads but not practical for many.