Anotherpower.com Forum

Renewable Energy Questions/Discussion => Automation, Controls, Inverters, MPPT, etc => Topic started by: frackers on December 13, 2016, 05:56:32 pm

Title: Powerjack UPS mode
Post by: frackers on December 13, 2016, 05:56:32 pm

Greetings all

Nearly finished my Ozinverter after some 18 months!! Just got to cut some holes in the case for the cooling fans.

Anyone who has seen my posts will know that I wound my own core and as a result of either poor insulation or suspect steel, I have a standby current that is a bit higher than I'd like.

As a result I've been thinking about cascading a lower power inverter going into the mains (UPS) input of the PJ and controlling the 2 inverters depending on load. The states I would expect to be:

• No or very small load, small inverter on, PJ off, power passes through PJ control board but otherwise doesn't do anything
• Load increases, PJ switched on and allowed to sync with small inverter, small inverter switches off after short delay, PJ handles the load
• Load decreases, small inverter is switched on, PJ switches off after short delay, back to the first case!!

It occurs to me that if the small inverter is also a PJ with the UPS function then the inverters could be cross connected to provide the mains sync and smooth transitions. I'm assuming that the high source resistance of the small inverter would be sufficient to prevent the big core on the PJ causing a problem and if the small inverter also uses an E core so it has a softer start then the switch back would be without drama.

So do I make sense and will it fly?

Title: Re: Powerjack UPS mode
Post by: oztules on December 14, 2016, 02:08:50 am

I would live with the 80 watts, and use the money for more panels.

Then turn you attention to  getting the idle current down a bit more.... try bigger inductor,  and when that fails.....more turns on the transformer to get the flux down, and so less magnetising current.... may need only ten or so extra turns on the secondary and primary to match, and the flux drop off may be enough to get you in range... ie more copper loss, and less iron loss.

Copper loss is only when you push it, iron loss is all the time.

For testing this out, just hook up wire will do, as you are only interested in the idle currents, and that will beonly 1.6a max on the primary, and nothing on the secondary.

If you are daring, you could simply change the staircase resistors ( bypass some) and this will get the voltage down say to 220 or 200v to test how well/much the flux change needs to be.

Complicating a simple system is the last resort....... I just would find another way.



..........oztules