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Thread: 240/480 volt question

  1. #16
    Quote Originally Posted by Greg Funk View Post
    Where are you getting your 3-phase power from? That combination shouldn't be available from any line to line or line to neutral combination. Locally, we have either 480/277 or 208/110 available from our utility. If you have similar you should see 208V between any combination of L1,L2 and L3
    Greg,
    the power is coming from a rotary phase converter. The readings were from the lines to ground. When i go l1 to l2, l1 to l3, l2 to l3 is get 230. I think that is all normal for a phase converter.
    I did get a little further i think. I verified that the wires were connected in the correct places on the start/stop switch and on the coil, contactor. I also tried to isolate it by disconnecting both motors from the contactor and the contactor and switch work correctly with no motors. That leads me to believe that something in the first motor is incorrect, maybe a wire was connected at the motor incorrectly when switching to low voltage, but I did verify the connections on the motor plate. The line numbers were very hard to read on the motor wires, but I thought they were correct and relabeled them. I will triple check them again.
    I do still get power at the blue wire on the start/stop which per Northfield should not be the case, but again without a motor the contactor and on/off switch work correctly.
    thanks,
    Stevo

  2. #17
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    With a rotary phase converter, make sure that the the 2 lines that provide control power do not come from the manufactured phase, and one of the single phase inputs, make sure both single phase inputs are used for the control circuit.

    Regards,, Rod

  3. #18
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    Quote Originally Posted by Malcolm McLeod View Post
    Sorry to disagree, but I just can't tell for sure.


    Malcom is correct we can not tell. The one I was checking out is a screen shot of some coil somewhere in the world. Probably not the one being discussed.
    Bill D.
    Last edited by Jim Becker; 07-07-2022 at 8:53 PM. Reason: fixed quote tagging

  4. #19
    Quote Originally Posted by Rod Sheridan View Post
    With a rotary phase converter, make sure that the the 2 lines that provide control power do not come from the manufactured phase, and one of the single phase inputs, make sure both single phase inputs are used for the control circuit.

    Regards,, Rod
    Rod, how do i tell which are not the manufactured phases?
    thanks,
    Stevo

  5. #20
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    Quote Originally Posted by stevo wis View Post
    Rod, how do i tell which are not the manufactured phases?
    thanks,
    Stevo
    I'm curious what difference it makes, but the manufactured phase should be the one that you measured at 250V. The other two phases should be ~120V from a neutral.
    edit: It appears the high leg voltage isn't as stable and will vary with load and could cause problems with control equipment.
    deltawye_figure3.jpg
    Last edited by Greg Funk; 07-07-2022 at 7:39 PM.

  6. #21
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    Quote Originally Posted by stevo wis View Post
    Rod, how do i tell which are not the manufactured phases?
    thanks,
    Stevo
    Measure the incoming voltage, for example it’s 238 volts and 119 volts to ground on each line.

    Now measure the input to your machine, find the same voltages, those are the phases you want to use for control.

    For sake of argument assume you have to interchange 2 phases to accomplish this, the motor will now run backwards, interchange 2 of the motor leads to solve that….Rod.

  7. #22
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    Quote Originally Posted by Greg Funk View Post
    I'm curious what difference it makes, but the manufactured phase should be the one that you measured at 250V. The other two phases should be ~120V from a neutral.
    edit: It appears the high leg voltage isn't as stable and will vary with load and could cause problems with control equipment.
    deltawye_figure3.jpg

    That is correct, during motor starting that phase voltage may dip low enough to prevent the contactor armature from pulling in….Rod

  8. #23

    Solved it

    Quote Originally Posted by Rod Sheridan View Post
    That is correct, during motor starting that phase voltage may dip low enough to prevent the contactor armature from pulling in….Rod
    Hey everyone, I took Rod's and Greg's advice, and by switching the inputs at the contactor, my problem went away.

    It now runs fine. I still have to rewire the drive motor to use the lower voltage and some of the wire numbers are hard to read. If anyone has any hints on how to identify them, that should do it. I am heading out for a two week vacation, so I wont be able to work on it for a while. I am also going to paint it and when its all done, i will post some pictures.


    Thanks to everyone who contributed!!
    Stevo

  9. #24
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    3 Phase off the line in 'our' shop in Calif is 120/120/220. Any combination results in 240 or a bit more.

    Run that into a transformer and get 3 legs of 120, for 208 (Japanese machine). Or 3 220's for 380 (Swiss machine). Took me awhile to figure out how that worked.

  10. #25
    Quote Originally Posted by Greg Funk View Post
    Where are you getting your 3-phase power from? That combination shouldn't be available from any line to line or line to neutral combination. Locally, we have either 480/277 or 208/110 available from our utility. If you have similar you should see 208V between any combination of L1,L2 and L3
    No such thing as "208/110", to have a line to neutral voltage of 110V, the line to line voltage would be around 190V.

  11. #26
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    Quote Originally Posted by Rollie Meyers View Post
    No such thing as "208/110", to have a line to neutral voltage of 110V, the line to line voltage would be around 190V.
    You're correct. For whatever reason I often refer to line voltage as 110V even though we have 120 here. should have been 208/120

  12. #27
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    Quote Originally Posted by stevo wis View Post
    Hey everyone, I took Rod's and Greg's advice, and by switching the inputs at the contactor, my problem went away.
    That was all Rod. Thanks for starting this thread - I learned a lot in case I ever switch to 3-phase.

  13. #28
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    Quote Originally Posted by Greg Funk View Post
    You're correct. For whatever reason I often refer to line voltage as 110V even though we have 120 here. should have been 208/120
    Yeah, I always have to correct myself with '120/240' these days. It was 'always' 110/220.

  14. #29
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    Quote Originally Posted by Wes Grass View Post
    Yeah, I always have to correct myself with '120/240' these days. It was 'always' 110/220.
    I once checked the plates on all the songle phase motors in the shop. They were either 115v or 230v.

  15. #30
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    Quote Originally Posted by Wes Grass View Post
    Yeah, I always have to correct myself with '120/240' these days. It was 'always' 110/220.

    Not in your lifetime it wasn't.
    Bill D

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