There is also a 54 V supply for the current limit circuit using the ACC card. The bridge for this is with the 3 axis drive bridges on the same heat sink.
There is a range for the 56 VDC supply for the axis. The 56 VDC is the minimum. I have seen many cases where people move the Z axis wire to the next higher tap on the 3 phase transformer to get less stalling. The high limit is about 65 VAC on this transformer. Any higher and you will blow the final drive transistors like candy.
When setting the current on these drives, the fuse is replaced with an amp meter and the static current is set to 8 to 8.2 amps. Funny thing though, the voltage will be about 9 VDC with respect to ground at this current. Run the axis at rapid and the current drop to about 2 amps and the voltage grows up to 56 Volts.
I guess you need a power supply that can provide 30 amps at 60 VDC in a reliable manner to be safe. I am assuming the drives you mention do not have their own power supplies built in.