We run over 200 Dell Poweredge Server to support our business. We are about to conduct a mandatory electrical test that requires us to power down servers to critical systems. To avoid this we are planning on using a pair of synronised 125KVa generators. What I want to know is can I leave the normal feed from the main supply plugged into and running the server, bring up the generator supply and plug it into the alternative supply to the server and then remove the normal feed, without powering down the server. Whilst understanding that the supplies will not be in phase?