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Topic: contactors and controlling single110 and 220v 3 phase power... (Read 2 times) previous topic - next topic


**crossposted from general**

Hey guys, I'm involved in a 5 axis cnc router build and we're working on electronics now while we wait for parts.  We need some major help with something that in theory should be simple, but until you do it...

We're using the pmdx series of breakout boards,
and we're using geckodrive stepper drivers powered by a 56vDC psu (110vAC)
and a 220v 3phase spindle

I've been looking at this drawing all day(the normally closed Estop one), from what understand the estop and relay on the board engage the contactor which cuts power to the stepper motor psu.

But in our case how would we integrate a 220v 3phase contactor into this schematic?  Whats the safest way to do this?  Using another relay or could both contactors be run together?  Do we need two contactors?

I've been researching all day but I'm missing something, I would really appreciate any help or even a quick schematic to look at would be great!

thanks guys!


[ I won't respond to messages, use the forum please ]


I've worked with 3 phase 440vac contactors (sometimes called motor-starters). You can think of them as large 3 pole single throw relays. The relay coil (often called the M coil) wires to some signal phase AC control voltage, often 120vac but sometimes 24vac. That is about all I will say on the subject, as the common adage around here is "if you have to ask you probably shouldn't be messing with it". If that is the case you would be better of getting assistance from someone qualified in such equipment, as the voltage and power levels can be very dangerous.



Jul 08, 2011, 07:59 am Last Edit: Jul 08, 2011, 08:01 am by Yankee Reason: 1
What is shown in your schematic is a single phase contactor. A 3 phase contactor would have 3 wires in from the mains and 3 wires to your spindle motor. But as Retrolefty points out, it would be a good idea to play it safe and seek a qualified electrician to take care of the wiring. Also, I might point out that these sort of questions would be more appropriate to ask on the forums at cnczone.com where you will find a lot of people who are very experienced in this sort of thing.
Good luck with your project!


sorry for the cross post,

thanks for the replies guys, I will definitely want an electrician or controls specialist to check out my wiring later but for now I'd like to be as knowledgable as possible.

I was given the advice from two separate knowledgable sources to either run a 4 pole contactor and switch the 3 phases of the 220 and the hot leg of the AC, or to use  two contactors, a 2 pole (for 110 single phase) and 3 pole contactor (for 220v 3 phase) wired in parallel.  Both of these would be 110 coil voltage contactors.

Is one of these better than the other concerning safety?

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