1 or 2 dedicated 120VAC circuits for my CNC?

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18 Nov 2022 03:41 #257002 by spumco
Sorry if I wasn't clear, or didn't simplify enough.  I get it - learning curve.

So... here's a suggestion.  Make a list of all components - spindle, PSU's, lights, disco ball, ect.  Write down all the amps they can pull.  that'll tell you if your 20A breaker can handle the load.

I suspect that if you're using a 60V PSU for the motor drives, you're using a stepper based system.  Those don't vary in load - i.e. pull more amps under higher cutting forces.  They pull the same amps no matter what.  What'll trip your breaker is - maybe - your spindle.

Still don't know exactly what you're using for a spindle and how it's powered. Knowing that detail would be helpful.

And if I'm following you correctly, you want/intend to run a new, dedicated 20A circuit for the CNC.  Yes - that's a good idea.

 
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18 Nov 2022 04:22 #257004 by Sray69
Yeah I should probably do some math on the circuit but my concern as mentioned is the other shop tools/machinery (miter saw, table saw, drill, planer, LinuxCNC PC, etc) that are on the same circuit. I won't be running them to often while the CNC is running but because the CNC can run for hours, there may be times that I need to. I just want to steer clear of tripping the circuit if I do. It usually isn't the running amps from those pieces of machinery but the startup amps are killer at times. I trip shit from time to time, especially with my table saw. So in order to avoid having issues I just plan to run the CNC on its own circuit. BTW, my router is a Dewalt DWP611.

From what you guys have said, running a separate 20amp circuit to the CNC is not a bad idea. Thanks!
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18 Nov 2022 17:18 #257048 by spumco
Knowing the router helps, thanks.

The Dewalt shows a 7A load on the sticker.  Assuming you run a separate 20A circuit off your wall box, that leave you with ~10A plus a little overhead.

This depends, of course, on what your 60V PSU pulls, but I think you can get away with what I suggested earlier - having a relay-controlled 120v socket on the CNC control box to power the router motor. 

The result would be a very handy/tidy setup.  Single power cord from CNC box to a dedicated 20A receptacle, and a receptacle on the side of the CNC box to power the router motor.  It would certainly be user-friendly to have LCNC be able to turn on/off the router.

And having a separate circuit for the CNC means if you start up a table saw or some other big load that won't trip your CNC unless the offending equipment pulls your whole house main breaker down.

 
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18 Nov 2022 20:45 #257064 by Sray69
I agree with everything you said. The total amps including the router (7A), 60V PSU (8A), 24V PSU (1.8A) total 16.8A. I have another small 12V PSU in my cabinet as well but I cannot find any input amps/current specs for it. I assume it is probably not much more than 1A. So that would put it at 17.8A. That seems a little tight.

Like I said in a previous comment, I have two slots open in my panel. I am thinking while I am going to the trouble of running one circuit, I might as well run the second circuit at the same time. That way I can run the router and the cabinet fan from one circuit and the rest of the CNC cabinet on the other. That way I have a lot of headroom if needed down the road.

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18 Nov 2022 22:52 #257075 by arvidb
Do your power supplies really draw 8 A (that would be almost a kilowatt or 16 A at 60 V) and 1.8 A (~200 W or 9 A at 24 V)? Or did you just (wrongly) add the output side current capabilities?

If the latter, the real 120 V current draw would be (60V×8A + 24V×1.8A)/120V < 4.5A (let's say 5 A including some inefficiency), or ≈12 A including the router. And that is if everything is running at max capacity.

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19 Nov 2022 00:24 #257080 by Sray69
Here are the specs as they are listed.
60V PSU
Input voltage range AC: 85-145V
Input current: 8A

24V PSU
Input Voltage (VAC): 85 to 264
Maximum Input Current (A): 1.8

Maybe I am not reading it correctly.
 

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19 Nov 2022 00:31 #257081 by Sray69
Here are the Output specs:
60V PSU
Output voltage: +60 V
Rated Current: 20A
Current range: 0.5-20 A

24V PSU
Primary Output Voltage (VDC): 24
Output Current (A): 2.5
Maximum Output Power (W): 60

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19 Nov 2022 00:36 #257082 by arvidb
Then you are reading it correctly... kind of. If they only list a single input current and a wide range of input voltage like that, then I assume that the rated input current is at the lowest input voltage (i.e. worst case). So actual input current at 120V would be 85×8/120 or 5.7 A for the 60 V supply at full load.

Is there a power rating on your supplies? Or a specified max output current?

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19 Nov 2022 00:45 #257083 by arvidb
Ok, we wrote simultaneously. So for the output specs:

Your 24 V supply kind of makes sense: 24V×2.5A = 60W, effective input current should be 60W/120V = 0.5A (plus some wasted heat). If it has no power factor correction I guess the real/reactive current could be much worse though. I'd still feel comfortable derating it for 120V: 1.8A/120V×85V = about 1.3 A.

The 60 V supply is weird. 20 A at 60 V is 1200 W. That would be >14 A at 85 V! So I have no idea what their thinking was there.

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19 Nov 2022 00:52 #257084 by Sray69
Unfortunately the 60V PSU I purchased from Alibaba and the spec sheet is a little messy, like most documentation from China. Because they offer many different models with different specs on the same product page, they don't pay much attention when they are creating the individual spec sheets. My spec sheet is for a 120VAC PSU but there are references to the 240VAC model. And my model is 1200W but there is reference to the 1500W model. So not the most reliable spec sheet. But here is a link to the one they provided me. I hope it answers the questions.

60V PSU Spec Sheet

The 24V PSU is a:

Mean Well MDR-60-24 DIN-Rail Power Supply 24V 2.5 Amp 60W
 

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