User Tag List

Page 3 of 3 FirstFirst 1 2 3
Results 21 to 26 of 26

Thread: Transformer tap

  1. #21
    Join Date
    Feb 2003
    Location
    Wisconsin
    Posts
    10,184
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by hhsting View Post
    What is the purpose of primary breaker? In theory would not the primary breaker if sized 125% protect the transformer from overloads?
    Yes, that would be the case.

    But remember if a transformer was intended to be overloaded, the primary side breaker would be sized based on the larger primary current.

    According to Hammond Power Solutions, https://www.hammondpowersolutions.co...g-transformer/
    "The most common way to increase the available kVA rating of an existing transformer is to add additional fan cooling."
    Just because you can, doesn't mean you should.

  2. #22
    Join Date
    Jul 2012
    Location
    Houston
    Posts
    31
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    Transformer Tap

    I know this is an old thread, but, forgive my ignorance on this matter.

    2017 NEC - Doesn't 240.3 (F) specifically say that the secondary conductors of a delta-wye transformer is not allowed to be protected by the primary side over current device or am I just reading that wrong?

    You would then go by the tap rules?

  3. #23
    Join Date
    Nov 2007
    Posts
    923
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by Muneepit View Post
    I know this is an old thread, but, forgive my ignorance on this matter.

    2017 NEC - Doesn't 240.3 (F) specifically say that the secondary conductors of a delta-wye transformer is not allowed to be protected by the primary side over current device or am I just reading that wrong?

    You would then go by the tap rules?
    Suggest you go to Table 450.3(A) for better understanding of transformer protection.

  4. #24
    Join Date
    Dec 2007
    Location
    NE Nebraska
    Posts
    39,120
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by Muneepit View Post
    I know this is an old thread, but, forgive my ignorance on this matter.

    2017 NEC - Doesn't 240.3 (F) specifically say that the secondary conductors of a delta-wye transformer is not allowed to be protected by the primary side over current device or am I just reading that wrong?

    You would then go by the tap rules?
    Assume you meant 240.4(F)? 240.3 has no sub parts, and yes the way I read it delta-wye secondary conductors is not considered protected by the primary overcurrent protection, there are unbalance conditions where you can overload a portion of the secondary yet not see overcurrent on primary conductors.
    I live for today, I'm just a day behind.

  5. #25
    Join Date
    Dec 2012
    Location
    Placerville, CA, USA
    Posts
    19,953
    Mentioned
    3 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by kwired View Post
    Assume you meant 240.4(F)? 240.3 has no sub parts, and yes the way I read it delta-wye secondary conductors is not considered protected by the primary overcurrent protection, there are unbalance conditions where you can overload a portion of the secondary yet not see overcurrent on primary conductors.
    Yes, that.
    Just as you can overload a single phase transformer secondary without overloading the primary if the secondary has a center tap and the load is imbalanced.

  6. #26
    Join Date
    May 2018
    Location
    Ohio
    Posts
    259
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Deleted

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •