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I have tried to find specific info on this scenario with no luck The situation is this; Off grid power system 12v battery store runs 12v lights etc. and an inverter for things difficult to run or convert. I have a relay which energizes from the generator output and disconnects the inverter (so I'm not trying to push two unsynchronized ac signals in the same circuit) The theory seems good, but I have managed to fry two inverters and I think this is due to a quick on/off switching of the relay as the generator powers down causing spikes and knocking out the output stages of the inverter. It would be good to isolate the inverter completely, i.e 12v input side and ac output side- but I feel like a debouncing type circuit is needed on both relays Any ideas/suggestions as to the simplest (and cheapest!) way of sorting this would be greatly appreciated.

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I believe that what you might really need is a changeover contact then neither grid/AC nor inverter output can be connected together. When AC resumes the relay, in sequence, disconnects the inverter and milli seconds later reconnects the AC to the load.

There may also be another problem that you haven't considered and that is when you disconnect the inverter output when it's supplying a high current to the load. This may cause some back emf (due to the inverter output filter) and this may "hurt" the inverter.

Anyway, it's worth trying the changeover relay and if it still gives problems then you'll have to find a way of ramping down the inverter output voltage to a safe level before disconecting and reconnecting the AC.

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  • \$\begingroup\$ Thanks Andy.The intention would be to not have anything powered by the inverter when the generator is started- so hopefully that's not a problem. The switch on the inverter could be changed for a relay though? I appreciate your time to answer the question. \$\endgroup\$ – Cornishwoodsman Nov 13 '14 at 14:04

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