OK, I've added the 25A SSR but am not sure it is the right device to use to switch the linear supply. Here's why . . .

The SSR is connected to the e-stop circuit to cut or supply power to the driver power suppliers. To test it out I tried it on the driver supplies one at a time. When I just connected it to the SMPS (30V) it all worked fine (on the one time I tried it). But when I connected it to the linear power supply (750VA coil, 40,000uF caps, 72V output) the MCB tripped (6A type D). Previously on the couple of times I tried it without the SSR it did not trip.

I'm now convinced that the SSR is not the right switching device for linear supplies due to the high inductance of the load, but I'd welcome a second opinion. I've been hesitating using a contactor because they all seem to be 24V and my box runs 12V. But I now think it is the only way so I'll have to modify all the 12V items to work with 24V. I did look at 12V to 24V DC-DC convertors but didn't like the idea of running it for extended periods to hold the contactor closed. Plus, I think they give out electrical noise?

So to convert the box to 24V needs a resistor for the 12V LED, and either resistors for the mechanical relays, or most likely swap them out for 24V versions. The pump and lights are 12V each so I can add them in series and switch both at once (instead of independently).

So the big question is what current rating of contactor do I need to switch the big linear supply (X,A,Y axes) and the SMPS (Z axis)? I'm guessing many tens of amps at least? The inrush current on this linear supply is quite high I suspect but the online calculations for current spec seem very involved. Does anyone have an idea of what to use? I don't want to run it for a bit then burn it out.

Thanks