I'm trying to understand the concept of a floated voltage, and why it is needed in some cases. For my own case, I am using a variac connected to a rectifier to provide a DC voltage for a circuit, (charging a large capacitor for discharge). The circuit needs a ground connection, but connecting a ground to complete the circuit also grounds the rectifier, which I am told will damage the rectifier. (I do not fully understand why this is the case, and would like to find out more.)
But it was suggested to me to use an isolation transformer before the variac and to float the voltage, and in this way rectifier would be kept safe. I would like to know understand how this works.
(I am aware another option could be to add a switch and just disconnect the rectifier from the capacitor, but I am more interested in understand the above).