User Tag List

Page 2 of 2 FirstFirst 1 2
Results 11 to 17 of 17

Thread: Transformer Taps

  1. #11
    Join Date
    Nov 2007
    Posts
    984
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by steve66 View Post
    Standard dry type 300KVA 480V delta to 208V wye transformer.

    Shop drawings say "Taps 6 - 2.5% 2+4- Taps"

    I would assume these are secondary taps, and that means there are six taps at -2.5%? So I could set the secondary at -2.5% nominal, or at -5% .... clear down to -15% nominal voltage (177Y/102 volts)?

    And there are two taps at +4%? That would allow +4% or +8% voltage on the secondary?

    Do those both sound correct?

    I'm also wondering why anyone would even need to drop the output voltage by 15%? It would be better to have more positive + taps to help make up for voltage drop.
    I guess tap 4 is your nominal voltage tap (480/208V). Your unit's taps 5, 6 as your + taps while tap nos. 3, 2, and 1 is used as the unit's -taps! All taps are in the primary. There will be more -taps to boost the secondary voltage.

  2. #12
    Join Date
    Jan 2019
    Location
    UK
    Posts
    537
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by steve66 View Post
    Standard dry type 300KVA 480V delta to 208V wye transformer.

    Shop drawings say "Taps 6 - 2.5% 2+4- Taps"

    I would assume these are secondary taps, and that means there are six taps at -2.5%? So I could set the secondary at -2.5% nominal, or at -5% .... clear down to -15% nominal voltage (177Y/102 volts)?

    And there are two taps at +4%? That would allow +4% or +8% voltage on the secondary?

    Do those both sound correct?

    I'm also wondering why anyone would even need to drop the output voltage by 15%? It would be better to have more positive + taps to help make up for voltage drop.
    Apart from special applications I've only come across taps on the HV side, usually 11kV in our case.

  3. #13
    Join Date
    Feb 2003
    Location
    Connecticut
    Posts
    3,587
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by topgone View Post
    I guess tap 4 is your nominal voltage tap (480/208V). Your unit's taps 5, 6 as your + taps while tap nos. 3, 2, and 1 is used as the unit's -taps! All taps are in the primary. There will be more -taps to boost the secondary voltage.
    Tap "5" would be the nominal voltage.

    1,2,3 & 4 would be the "-" taps and 6 & 7 would be the "+" taps

    There are 4 below nominal and 2 above nominal.

  4. #14
    Join Date
    Jun 2003
    Posts
    7,079
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by topgone View Post
    I guess tap 4 is your nominal voltage tap (480/208V). Your unit's taps 5, 6 as your + taps while tap nos. 3, 2, and 1 is used as the unit's -taps! All taps are in the primary. There will be more -taps to boost the secondary voltage.
    I'm not sure, but I think the transformer nameplate will explain that in detail. Here is the nameplate from a different xformer that has 7 taps;

    Name:  IMG_0030.jpg
Views: 24
Size:  44.1 KB

    Looking at a couple of different nameplates, the #1 tap seems to usually be the most windings on the primary side (lowest output voltage).


    Quote Originally Posted by Besoeker3 View Post
    Apart from special applications I've only come across taps on the HV side, usually 11kV in our case.
    Yes, from the few nameplates I've looked at, it looks like taps are usually (or maybe always) on the primary side.

  5. #15
    Join Date
    Jun 2004
    Location
    Cherry Valley NY, Seattle, WA
    Posts
    5,921
    Mentioned
    2 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by steve66 View Post
    I'm not sure, but I think the transformer nameplate will explain that in detail. Here is the nameplate from a different xformer that has 7 taps;

    Name:  IMG_0030.jpg
Views: 24
Size:  44.1 KB

    Looking at a couple of different nameplates, the #1 tap seems to usually be the most windings on the primary side (lowest output voltage).
    Looks to me like #1 is highest secondary voltage, lower overall turns ratio, yes?
    Ethan Brush - East West Electric. NY, WA. MA

    "You can't generalize"

  6. #16
    Join Date
    Feb 2003
    Location
    Connecticut
    Posts
    3,587
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by electrofelon View Post
    Looks to me like #1 is highest secondary voltage, lower overall turns ratio, yes?
    The opposite is true.

    #1 has the highest turns ratio 2.42:1.

    #7 has the lowest turns ratio 2.08:1.

  7. #17
    Join Date
    Jun 2004
    Location
    Cherry Valley NY, Seattle, WA
    Posts
    5,921
    Mentioned
    2 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by david luchini View Post
    The opposite is true.

    #1 has the highest turns ratio 2.42:1.

    #7 has the lowest turns ratio 2.08:1.
    Oh, was thinking of another thread where 480 was the secondary side
    Ethan Brush - East West Electric. NY, WA. MA

    "You can't generalize"

Posting Permissions

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