Main 3 phase power to CNC mill cabinet?

[Jake2465]

Tomorrow I will be putting some power to my mill and I see that the terminals I need to power on are right on that rotary switch that operators normally flip to turn a mill on or off.

This CNC mill is wired for the standard 200+V 3 phase power. My question here is does it matter what legs I put on those terminals? They are labeled "L1, L2, L3" and then there is a gound as well. There is no indication anywhere that I need to put the wild leg in any one of those terminals. My assumption is that I can simply go ahead and stuff the three lines in there and the only problem may be that the spindle runs backward. And if that happens, I can simply take any two of those wires and switch their terminals.

I have attached a picture of what my cabinet looks like. From what I can see, it looks to be a pretty typical setup.

 

[Flyinfool]

The power should not be wired direct to the switch, there should be a disconnect with fuses or breaker between the line power and the machines power switch. This is forsafety so that everything inside of the cabnet is dead when the machine is off. A bad switch could have power in unexpected places while you are in there working on things. I always turn the disconnect off to help prevent issues if a thunderstorm rumbles on by.

 

[Jake2465]

The power should not be wired directly to the switch, there should be a disconnect with fuses or breaker between the line power and the machine's power switch. This is for safety so that everything inside of the cabinet is dead when the machine is off. A bad switch could have power in unexpected places while you are in there working on things. I always turn the disconnect off to help prevent issues if a thunderstorm rumbles on by.

Correct, I have a triple fuse disconnect that is ready to be used for this. Actually, I had used a pigtail line for my other mill. If I got concerned about bad weather, I would shut the mill down and disconnect the pigtail from the wall. That way the mill had such an air gap that it would be impossible to get a high voltage strike.

 

[mksj]

Typically if there are and subsystems powered by 2 legs (single phase) of the 3 phase, like the transformer or other control systems then the wild leg would no want to be connected to those electrical devices the other 3rd leg would be needed for the VFD, drives, etc. The main cabinet power disconnect should be sufficient, but during electrical storms I also would switch off the power at the breaker box and also had an industrial surge protector at the service entrance. I never had an issue, but neighbor's w/o a surge protector lost appliances.

 

[Jake2465]

Typically if there are and subsystems powered by 2 legs (single phase) of the 3 phase, like the transformer or other control systems then the wild leg would no want to be connected to those electrical devices the other 3rd leg would be needed for the VFD, drives, etc. The main cabinet power disconnect should be sufficient, but during electrical storms I also would switch off the power at the breaker box and also had an industrial surge protector at the service entrance. I never had an issue, but neighbor's w/o a surge protector lost appliances.

That's a good point. It is likely that the only thing using all three legs is the VFD in that cabinet. That would mean that the ambiguity of the legs would only apply on the output side of the VFD to the spindle motor. That means I will need to chase those power wires in that cabinet and see where they go. As soon as I find one of those legs that seems to only go to the VFD, then I have my answer.