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  1. #1

    Unhappy Interesting Current behaviour

    Hi guys..i have came across a different Behaviour of Current measurement device im working on Single Screw Compressor Chiller.With starting method of soft starter so in that 3 Phase wire goes direct to 3 terinal and to co plete the circuit other goes via SCR and Contactor.

    NOw the problem im facing is when i measurement current before contactor im getting as normal at full load 130A but when i take after contactor its showing only 70A this is only of a single phase current.


    So anybody could help?

  2. #2
    Join Date
    Aug 2012
    Posts
    39
    You are seeing the measurement error of your meter. Use one with true RMS and the readings will make more sense.

  3. #3
    ok 1 more question why i cant use 2 or 3 wire in a clamp meter to measure current

  4. #4
    Join Date
    Aug 2009
    Location
    Ottawa ON
    Posts
    53
    Don't the magnetic fields cancel each other out as far as the meter can read

  5. #5
    Join Date
    Aug 2012
    Posts
    39
    Quote Originally Posted by mayank View Post
    ok 1 more question why i cant use 2 or 3 wire in a clamp meter to measure current
    The current would need to be in phase (or in sync) between each wire for the meter to read the combined current. Otherwise, as mentioned already, the interaction of the 'out of phase' magnetic fields would give you a false measurement.

  6. #6
    Join Date
    Aug 2009
    Location
    Prattville, Alabama
    Posts
    1,997
    The difference you are seeing could be because of where you are putting your meter clamp. If the chiller starter module is electrically located "inside the delta", you may be taking the first reading on 1 of 3 incoming leads, and the second reading on 1 of 6 motor leads. Let's see if we can get a site moderator to move this discussion to the "chillers pro" section. It will be more likely to be seen by more people with experience on this type equipment. Also, the model number and serial number will help people to give you better and more accurate information. And welcome, Mayank.

  7. #7
    Join Date
    Jul 2007
    Location
    Mount Airy, MD
    Posts
    7,281
    Thread relocated to the Chiller section of the site.

  8. #8
    c.JPGthank you for your reply Let me explain some detail im using HSA3221A Single Screw Compressor by J &E Hall,and yes motor is in delta connected have uploaded a pic to explain some more detail .Actualy what im measuring is The same phase wire like an example Red wire before contactor and after Contactor i am not getting sum of current.So any body could help me now?
    Attached Images Attached Images

  9. #9
    Join Date
    Aug 2009
    Location
    Prattville, Alabama
    Posts
    1,997
    Can you highlight, or indicate in some way, exactly where on this pic you are placing your meter clamp? And, where the pic shows "FUSE", is that actually where the starter module, or contactor, is?

  10. #10
    Join Date
    Aug 2009
    Location
    Prattville, Alabama
    Posts
    1,997
    It would be even more helpful if you could show pics of you, or whoever, actually measuring the current on the starter itself.

  11. #11
    Join Date
    Aug 2000
    Location
    Austell, Ga.
    Posts
    1,294
    Quote Originally Posted by Nuclrchiller View Post
    It would be even more helpful if you could show pics of you, or whoever, actually measuring the current on the starter itself.
    Now thats funny....LOL

    Reading "One" leg on a six-lead motor should give you a reading of 58% of the actual motor current. "NOT" 50%....I digress in stating the reasoning behind this.
    Ain't "None" of us as smart as "All" of us..

  12. #12
    Join Date
    Jan 2005
    Posts
    604
    Before you take picture, make sure you have a filter on the lens that will be good to take picture of ARC Welding.
    Just in case. At least if anything goes wrong, we might be able to tell you what you did wrong.

  13. #13
    Join Date
    Oct 2011
    Location
    South Georgia
    Posts
    64
    Don't use a electronic flash on the camera to take a picture of a solid state starter. Some drives will shut down due to the energy flash. I don't know why but i have seen it happen.

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