though i synchronize the two sources before a switch.
I have on occasion pushed stop button on controller which transfers all without regard to phase alignment. Thats a fatal error
How do you guys do this? I know those with gensets just charge the battery but wondering if anyone else uses transfer relays
I'm not using PJ or similar (no insult intended) "low end, very basic" inverters.
My scenario is using commmercial "generator-interactive" inverters. When transitioning to generator mode, they initiate generator start based on various conditions (but typically SoC or DC volts). When generator input is detected, the inverter drifts its frequency to match the generator over a second or so, adjusts its output voltage to match the generator, and then drifts its phase to match the generator. When all three are "very close", a large contactor pulls in to join generator output and inverter output together with the load.
The inverter can then gently adjust its voltage/phase to gently transfer the output load to the generator, and indeed can go a little further to start pulling power from the generator to charge the batteries (using whatever headroom is left). Similarly, it can change it's output the other way to assist the generator allowing the pair to drive loads larger than either alone can.
When disconnecting, the contactor simply opens and 100% of the load is supplied from the inverter.
I've never had problems transferring to or from generator, the relay doesn't introduce a break (even briefly), and can be of a simpler "normally open" construction rather than change-over.