Hi Audioguru, many years since my last post, I hope everything runs very well!!!
Of course, in your example, when you switch off the refrigerator the processor stops sending signal to IGBT module so it protects the output. My doubt is what happen when everything is running and you disconnect the compressor to test Vac output, in theory processor stops signal to IGBT module because there is no feedback and as I said if you give power to unit with no load connected you can damage IGBT module (message from manufacturer).