Running a 220v AC/DC PSU from 3-Phase?

J

Jimustanguitar

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Hey, all. I'm working on a vintage Van Norman mill that runs on 'low voltage' 3-Phase power. A buddy who does a lot of automation saved me a 3-phase contactor from the dumpster at work, and I'm planning how to wire it up. The contactor runs on 24VDC from a power supply that says it will take 100-240VAC at 50/60hz. When I measured the voltage across the legs of my 3-phase plug, I recall having 120ish and 220ish VAC depending on which phases I measured across... If the power supply is just a simple rectifier circuit, would it "care" that I was feeding it with two legs of 3-phase? Is there any reason that I couldn't just use the electric that I already have on the machine instead of having to run a second extension cord from the wall?

OI4jvXc.jpg
 
It will work fine on 2 of the 3 phase legs. But I don't understand why you would get 120 between 2 of the 3 phase legs. That is strange.
 
JimDawson said:
It will work fine on 2 of the 3 phase legs. But I don't understand why you would get 120 between 2 of the 3 phase legs. That is strange.
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I think it was a measurement between two of the phases, not a single phase and ground... Maybe 220VAC 120deg off of another 220 has an average difference in the low 100's... It was a cheap multimeter, I'd check it more carefully before connecting it, to be sure.
 
Your 24 volt power supply is probably a switching type supply hence the wide input voltage range. No it won't care about the phases as long as the voltage is within the range.
Do you have 3-phase power there? Most homes don't by default.
Mark
 
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Phase-to-phase voltages on 3-phase Y system should all be the same. If you are measuring "120-ish" voltages along with 220V then your 120V measurement is a 220 phase to neutral voltage-- that is 220 / 1.73= 127 V. You should have at least 4 wires plus a ground entering your receptacle. You need to establish which are the 3 phases, which is the neutral, and phase sequence. On the odd chance that you running Delta, then it is possible that your 120 V is a center tap on one phase - in which case you have no grounding conductor, and you will need to install a ground fault detector/trip circuit. With respect to control voltages, you can derive power to your transformer either from a phase to phase connection or from a phase to neutral connection -- depending on the rated primary voltage of the control transformer you are planning to use. Moreover, the contactor pic you posted appears to be a DC output contactor and not a 3-phase contactor.
 
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Blackjackjacques said:
Phase-to-phase voltages on 3-phase Y system should all be the same. If you are measuring "120-ish" voltages along with 220V then your 120V measurement is a 220 phase to neutral voltage-- that is 220 / 1.73= 127 V. You should have at least 4 wires plus a ground entering your receptacle. You need to establish which are the 3 phases, which is the neutral, and phase sequence. On the odd chance that you running Delta, then it is possible that your 120 V is a center tap on one phase - in which case you have no grounding conductor, and you will need to install a ground fault detector/trip circuit. With respect to control voltages, you can derive power to your transformer either from a phase to phase connection or from a phase to neutral connection -- depending on the rated primary voltage of the control transformer you are planning to use. Moreover, the contactor pic you posted appears to be a DC output contactor and not a 3-phase contactor.
Click to expand...
BJJ, agree with most of your post but, to avoid confusion, the pic the OP put up is of his ac-24Vdc power supply not his contactor.
Cheers Tim

Sent from my SM-G950F using Tapatalk
 
TimSmith said:
BJJ, agree with most of your post but, to avoid confusion, the pic the OP put up is of his ac-24Vdc power supply not his contactor.
Cheers Tim

Sent from my SM-G950F using Tapatalk
Click to expand...
Correct. The earlier picture was just the power supply. This is the contactor.
JUqKT1y.jpg
riqtPyY.jpg
 
TimSmith said:
BJJ, agree with most of your post but, to avoid confusion, the pic the OP put up is of his ac-24Vdc power supply not his contactor.
Cheers Tim

Sent from my SM-G950F using Tapatalk
Click to expand...

My bad - thanks. Looking at it again, it clearly states "power supply"
 
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