Various aspects of home brew inverters

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Joined: 09/08/2007
Location: Australia
Posts: 4406
Posted: 09:13am 08 Jul 2018      

  poida said   just like what I am seeing..

Yes indeed.

The story behind all this is that commercial transformer designers are not charitable institutions, they make a living out of building good reliable transformers at absolute minimum rock bottom cost. To do that they come up with a design that uses minimum iron and the minimum copper by pushing the flux density and the temperature rise to the absolute safe (?) maximum.

A successful transformer designer will advertise his transformers as having maximum continuous power output at minimum dollars. The buyer never asks about no load idling power, because most commercial transformers go into some kind of equipment that usually draws fairly constant near full rated load power anyway.

So a commercial inverter designer is pretty much in the same boat. The transformer in his inverter will almost certainly be the most expensive single part, and he is trying to compete with other inverter manufacturers, and still make a profit.

Very often idling power is not even included in an inverters specifications, and that is deliberate. For something like a grid tie, it probably does not matter much anyway.
But if you are off grid and on a battery, no load power suddenly becomes of critical importance.

Now we are in a VERY different situation to the commercial inverter people.
We are winding out own transformers, often out of free or recycled junk.
We don't care about how big or heavy it is, or how much the core or the wire costs brand new.
We want to make something really nice that performs much more efficiently than some corporate bean counter scrooge would ever allow.

So just reverse engineering or copying commercial designs and thinking that must be the absolute ultimate is a very big mistake.
We can do very much better than that if we apply some well known theory and design our own transformers from scratch to do what we want it to do.

Transformer design has been perfectly understood for over 200 years. Micheal Faraday solved all of the design equations back in the age of sailing ships, muzzle loading guns and crude steam engines.
There are no mysteries, its not voodoo or magic.
Cheers,  Tony.