Homebrewed Electricity > Solar

What happens when you generate more than the inverters rating?

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Valalvax:
So, let's say I have a inverter rated at 500w, and I have 750w of panels, now normally I'd only be getting a small portion of that, but on a super sunny day I might actually be generating near the full 750w, what happens to the inverter? Does it just cap out at 500? Or do I let the smoke out?

boB:
Well, first of all, with your larger than necessary PV array, you will have a charge controller of some sort which will keep your
batteries from overcharging.  If you always have more charging energy than you can suck out by your inverter, you will just
always have a fully charged battery.

Any excess energy from the PV array will be wasted unless you have some way of using it.  (dump loads, etc)

A decent inverter will just limit its output power so it doesn't burn up.  If you overload the inverter AC output, it should
turn itself off.

boB

Rob Beckers:
Valalvax, to complete the story for grid-tie inverters (without batteries): All those inverters will limit the input current so that their output power is limited to the maximum they were designed to handle. For example, say your PV array is generating 350 Volt DC and could provide 10A of current at that voltage (making for 10 x 350 = 3.5kW), if it's a 3kW inverter it'll only draw about 8.6A on purpose, instead of "as much as the array will allow" (making for 8.6 * 350 = 3kW). That's the gist of it...

-RoB-

boB:
One more clarification...

If a PV array provides 10 amps at 350 volts, and the grid tie inverter can only use 8.6 amps, the grid tie inverter will (on purpose) operate
that PV array at a voltage higher than 350 volts to reduce the current and power.  The I/V  (current/voltage) curve of the PV array dictates
what current will be drawn at any particular loaded voltage.  Open circuit is of course 0 amps and is the highest voltage that will be seen
by the particular PV array.

0 amps times that high voltage (Voc) = 0 watts.

boB

Valalvax:
Thanks, the reason I was asking is because the inverter is a significant portion of the cost of any system, and if I buy 1kw worth of panels and an inverter today, then later want to increase my output, well, I'm not going to be getting 1kw all the time, so I could just buy more panels for a fraction of the cost of a total system upgrade and still get increased

I kind of figured that any non-Chinese inverters would be smart enough to do something to avoid dying, but figured it'd be smarter to ask first before letting a couple hundred dollars go up in literal smoke

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