Help identifying connections on Kyosan KE750 power supply
I'd be willing to bet that the J1 connector provides access to a pair of remote sense leads. These would be extended to the actual load so that the power supply can account for the voltage loss in the power leads. With up to 63A getting pumped out the voltage at the load could have dropped a fair bit. You can read more about how it works here:  http://power-topics.blogspot.com/2008/07/what-is-remote-sensing.html

Usually these kinds of arrangements have either a switch or a pair of jumper wires attached that tie the sense leads to the local output of the power supply but that doesn't seem to be present on that jumper block.