Renewable Energy Questions/Discussion > Automation, Controls, Inverters, MPPT, etc

Inverter Build Project.

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Pete:
Any clues Ross on why some inverters can handle load switching easily and others not.
I remember reading that PowerJack inverters can have problems and blow mosfets when switching from stand alone to mains inputs, and that PowerStar W7s were a bit more robust and handled it well. ( I think it was Oz that said that)
I am guessing that the transformer type may have had something to do with it.
Pete

rossw:

--- Quote from: Pete on September 28, 2020, 09:11:32 pm ---Any clues Ross on why some inverters can handle load switching easily and others not.
I remember reading that PowerJack inverters can have problems and blow mosfets when switching from stand alone to mains inputs, and that PowerStar W7s were a bit more robust and handled it well. ( I think it was Oz that said that)
I am guessing that the transformer type may have had something to do with it.
Pete

--- End quote ---

Not really, because I haven't delved into their bowels to find how everyone is doing it.
I have an expensive commercial unit specifically built and marketed to be "generator interactive", they go to great lengths to do the transition "gently" - when the inverter senses input on the generator input, it monitors the genset voltage and frequency and adapts its own output to match the same voltage, frequency and phase. Only then does it pull in the contactor. Once that is done, the inverter then GRADUALLY changes its output to transition the load across to the genset, and then GRADUALLY starts taking as much power as it is permitted to by the configuration (generator capacity less instantaneous load = available capacity) to charge the batteries.

It does the same thing in reverse when isolating from the generator.

I've never heard of any of this type of inverter suffering the kind of problems some have experienced with the chinese inverters, but I suspect that is largely by the design and perhaps partly by the choice of components.

As to why some inexpensive inverters survive and others don't, I could only guess (and probably be wrong!)

noneyabussiness:
Oz explained it the best somewhere here, toroidal transformers are electrically " stiff " and as ross said to switch over cleanly they need to match the phase and frequency and voltage etc. before changing over, PJ's don't as far as im aware.  There is a version that has a series resistor accross a relay setup to " soften " the change. The W7's did it ok because they used a E/I laminated core, which has enough " give " electrically that the mosfets etc. could survive the change over..

If you do a search,  OZ and Madness, by memory go into depth about it...

welshman:
This seems to be a very nice transformer..

it even has the ability to move the coils. there is a piece of aluminium, with some grub screws that is bent by the screws to fix the coils in place.

what would be the best option here? leave them as they are or move them closer?

It weighs 46.5KG.

Pete:
Most of the coupling between the coils will be via the magnetic circuit so I am not sure about whether moving the coils will make much difference.
If it were mine I would put some power onto it and measure the idle current, then move the coils and see if it makes any difference.
The main problem with that sort of transformer will be how much idle current it draws.
Pete

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