1 or 2 dedicated 120VAC circuits for my CNC?

I wanted to get opinions on whether it is worth it to provide 2 separate 120VAC circuits (from the panel) to my CNC? 

To start I will not be running a inverter/spindle. I will be starting with a router but do have plans to upgrade at some point. I know that running the logic from its own PSU is preferred but was wondering if there is any advantage to running two separate AC circuits? Or is running them off of separate PSU's/breakers good enough?

I only ask because I am planning to run a dedicated circuit to the CNC anyway, so running an extra is very little extra effort.

Thanks

tommylight wrote:

Sending two phases is OK, just in case you might need it later.
Sending 2 wires from the same phase is redundant, still might come in handy.
 

Well it is my understanding that residential power in the US is not 2 phase, although the 240V (single phase) coming in is split into two 120V phases (split phase).

With that said, I am talking about running two circuits, from two 20amp breakers in the panel to the CNC. I guess that would be running them both off the same phase. So there is no advantage in regards to keeping the noise from certain components separate from others by running separate circuits off the same phase? I know they all go back to the same panel. 

Shawn

No, there's no advantage noise-wise.  Two 20A 120vac circuits off the same breaker box is basically like running a single 40A 120V circuit with heavier conductors.

You can handle noise inside your control cabinet by keeping the AC stuff away from the DC stuff, adding filters and a line reactor upstream of the VFD (if you have one).  Line power comes in through main disconnect, through the main circuit breaker or fuse, then to a junction block.  The AC-DC PSU gets fed from that (with it's own breaker/fuse), then another (fused) branch through a line reactor & EMI filter to the VFD or servo drives (or other noisy component).

You can even add sheet metal paneling inside the cabinet (if you've got room) to shield radiated noise from noise-sensitive dc signal circuits.

Use shielded cable for all analog conductors, encoder cables, and the HV stuff like servo power cables and VFD to motor cables.  Ground all shielding per the component MFGR.

Use 24vdc for signaling and control circuits where possible - much more resistant to low voltage ripples/EMI than 5v circuits.

My setup is very basic to start. It is just a CNC router. I am designing my cabinet to where the 3 PSU's are all on one side of the cabinet separate from the low voltage.

I have a 60V PSU supplying the motors. A 24V PSU supplying the logic (Mesa). And a 12V PSU for the cabinet fan.

If I were to add a inline EMI filter, where would be the most effective place to install it? Or do I need one if I am not running a spindle at this time?

I have been meaning to ask about surge protection. Is that a necessary component as well?

Thanks

I assume you're running a separate spindle - like a Bosch Colt or some other manually-activated thing?   Otherwise it's not really a router...?

If you want to add a filter you can add it to the AC-in between the main circuit breaker and a distribution block (that your PSU's are fed from).

Unless you have some component that generates PWM noise, I don't see a need for an EMI filter or line reactor with the setup you've described.

For surge protection, don't bother.  The PSU's will take the hit and likely save your drives and other components.  You're better off spending time/money making sure you've got a good e-stop circuit and disconnect scheme.

spumco wrote:

I assume you're running a separate spindle - like a Bosch Colt or some other manually-activated thing?   Otherwise it's not really a router...?

If you want to add a filter you can add it to the AC-in between the main circuit breaker and a distribution block (that your PSU's are fed from).

Unless you have some component that generates PWM noise, I don't see a need for an EMI filter or line reactor with the setup you've described.

For surge protection, don't bother.  The PSU's will take the hit and likely save your drives and other components.  You're better off spending time/money making sure you've got a good e-stop circuit and disconnect scheme.

Perfect! Thanks!

Meant to ask... is there some reason you're going with a 120v system and not 240v?  Your PSU's should have a 120/240 switch to take different input voltages.

Going with 240 means a single cord/cable feeding the whole thing rather than two 120v cords (if I'm following your plan).

And if you're worried about where to plug the spindle motor in, if you use a 4-conductor cable from the outlet you can have a neutral line tied to your main house box... meaning you can install a 120v socket on the side of the CNC control box and plug the spindle in to that.  One leg of the 240 feeds the socket and return via the neutral. (4-conductor = L1, L2, N, Gnd)

Even better - have that socket controlled by a relay, with the relay coil tied in to your e-stop and/or mesa so you and LCNC can kill the power to the spindle motor socket during an emergency.

I understand using 120 for some systems... I'm doing an old Torchmate right now and using 120 for all the motion & control stuff so it can be plugged in anywhere.  But this is a special-use project.

spumco wrote:

Meant to ask... is there some reason you're going with a 120v system and not 240v?  Your PSU's should have a 120/240 switch to take different input voltages.

Going with 240 means a single cord/cable feeding the whole thing rather than two 120v cords (if I'm following your plan).

And if you're worried about where to plug the spindle motor in, if you use a 4-conductor cable from the outlet you can have a neutral line tied to your main house box... meaning you can install a 120v socket on the side of the CNC control box and plug the spindle in to that.  One leg of the 240 feeds the socket and return via the neutral. (4-conductor = L1, L2, N, Gnd)

Even better - have that socket controlled by a relay, with the relay coil tied in to your e-stop and/or mesa so you and LCNC can kill the power to the spindle motor socket during an emergency.

I understand using 120 for some systems... I'm doing an old Torchmate right now and using 120 for all the motion & control stuff so it can be plugged in anywhere.  But this is a special-use project.

Actually maybe I described what I was doing incorrectly. I am running 120V mainly because getting 240V to my machine at this time would be a hassle. What I meant is that I have two open spots (120V) in my electrical panel that I plan to run a dedicated 20A circuit to my CNC. The circuit that is currently in my CNC room is used by other shop tools/machinery (miter saw, table saw, drill, planer, LinuxCNC PC, etc). My thought was to run two separate circuits in order to hopefully provide cleaner power to the logic/low voltage side, but looks like that is not the case, but also I don't want to take the chance of tripping the breaker if I happen to over load the circuit while the CNC is running. If my thinking is incorrect, please let me know.

In the future I may change over to 240V once we move to our new property.

I am still learning how all this gets hooked up. I will have to dissect your comment to try to understand it correctly.
Thanks