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  1. #1
    Join Date
    Aug 2005
    Posts
    52

    Electrical question

    I've recently moved my machine to a new location. The new location has "wild leg" 3 phase power. Are there any concerns about connecting my machine to it? My machine does not have a neutral (just three phases and ground) so I assume it's ok.

    In the electrical panel, if I measure the phases, I get 240v between any two phases, but if I go between neutral and the three phases, two are 120v and one is 208v (assumingly the wild leg..)

    One thing don't understand is this label that shows the center leg grounded. How could that be possible? Also it says 200/220/230v. But I'm measuring 240v..

    The three phases come into the machine, to the main 60A breaker, through a contactor, the filter you see on the right in the picture, and then to the bottom of this unit. You can see the red, white, and black wires at the bottom of the pic.

    I'm great with electronics, but delta and wye grid power stuff confuses the heck out of me..

  2. #2
    Join Date
    Aug 2005
    Posts
    52

    Re: Electrical question

    Also, figured I'd ask as well. The breaker on the machine is 60A. I'm going to have to run some 75 feet of conduit to get power to it. My previous install used 6AWG, but it was 10ft from the box. Using an online calculator, seems like 4awg would be needed for 75ft. Not that this machine will ever pull 60A with what I do with it, but want to do everything right. So does this sound right?

  3. #3
    Join Date
    Mar 2007
    Posts
    2083

    Re: Electrical question

    Hi

    to me the lable only makes sence if you had a delta connected supply transformer with one phase grounded
    or you connected it to a US single phase supply from a high sided delta supply
    this could be why there is ony 2 breakers and not 3 ( one for each phase)


    the only US supply I know is the high sided delta with the ground / neutral going to a centre tap on one winding
    this will give you the 120V , 120V , 208V you have measured

    in the UK the symetrical star {wye) connection is used
    the voltage between any phase and ground is 240V or 415V between any two phases
    ( a domestic single phase 240V supply being earth/neutral and one phase )


    Attachment 252268

    Attachment 252270

    Attachment 252272


    one for AL_THE_MAN
    I think


    John

  4. #4
    Join Date
    Aug 2005
    Posts
    52

    Re: Electrical question

    I called Yaskawa and they said the 240V I'm reading is too high. Looks like I'm going to need a buck/boost transformer.

  5. #5
    Join Date
    Aug 2005
    Posts
    52

    Re: Electrical question

    I called Yaskawa and they said the 240V I'm reading is too high. Looks like I'm going to need a buck/boost transformer. Really having a hard time understanding what size I need. Some places say I need 9kva and other s say 2kva. The breaker on the machine is 60a. I cannot find any electrical rating plate anywhere on the machine or in the manuals.

  6. #6
    Join Date
    Dec 2003
    Posts
    24216

    Re: Electrical question

    You can get some idea from the estimated VA of any power units, motor sizes, power supplies, physical size of transformers etc.
    If your transformer inputs are tapped for the 200/220/230 I would have thought 240 would not have been excessive on the 230v tap?
    If you have the schematics, look to see what maybe affected the most, if any, by the higher voltage, you could almost treat that individual unit to the reduction, if the rest are not critical.
    John is right, appears you have high side delta, I don't favour those set up's, myself.
    Al.
    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.

  7. #7
    Join Date
    Aug 2005
    Posts
    52

    Re: Electrical question

    There are no transformer taps in this machine. The sticker just says 200/220/230 (which I think is just for the DC power supply). There is a small transformer (fist size) elsewhere that has taps but they are 120/220/320/440 or something like that. Not to adjust for minor differences. Yaskawa rep said 220 +/-10%...which is 242V. So yes it might work, but it will be very high. Not sure I want to risk it as who knows if the 240V I'm reading today won't be closer to 250V at night.

    The 3 phases are fed right into the drives. Yaskawa Servopack CPCR-MR...also rated 200/220v +/- 10%. The MX1 control is rated 200/220V +10/-15%

    Think I'd rather play it safe and get a boost/buck transformer to bring the 240 down to 220. Unfortunately I'm looking at $350 minimum unless something pops up on craigslist.

    Thanks for the info everyone.

  8. #8
    Join Date
    Aug 2005
    Posts
    52

    Re: Electrical question

    Just for completeness, I just happened to find two Acme Transformer T-1-11684 on ebay for $180 shipped. These had the correct ratings for my machine. I purchased them immediately.

    I got them hooked up and tested them before I applied power to the machine. I measured the line voltage and one leg was as high as 247v. But on the output of the transformer it was 220-225v between phases. I haven't run any parts yet, but I warmed up the spindle a bit and everything seems to be working well. Thanks for the help.

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