Tap setting

[kikay0115]

If I want to increase by 2.5% the secondary voltage of a transformer, what tap should put it in? It is now at tap 3(nominal). The transformer is a 3MVA, 6900-480V, delta-wye. Tap 1 voltage = 7245; tap2 = 7073; tap3 = 6900; tap4 = 6728 and tap5 = 6555.Thanks in advance gentlemen

 

[jusme123]

tap 2

tap3 = 6900 X 2.5%(.025)= 172.5

6900 + 172.5= 7072.2 (tap #2)

 

[kikay0115]

It's the output of the secondary transformer I want to step-up and not the primary:?are you sure that it is tap 2?

 

[Smart $]

It's the output of the secondary transformer I want to step-up and not the primary:?are you sure that it is tap 2?

If you want to step up the secondary voltage you connect to the next lower primary voltage tap... in your case Tap 4.

 

[jimdavis]

Use tap 4. This will lower the transformer's primary-to-secondary turns ratio which will raise the secondary voltage.

 

[kingpb]

Taps change the voltage by the percent indicated by changing the turns ratio. So, if you have a 480-208Y/120V (nominal) rating and the taps are on the HV side of the transformer you want to lower the turns ratio to increase voltage on LV side.

480/208 = 2.308 ratio (nominal tap)

468.3/208 = 2.25 ratio (-2.5% tap)

Which means that with 480V in the HV side, 480/2.25 = 213V on LV side.

Typically, the taps will be on side of the transformer with the lower rated current, i.e. HV side, but it would be prudent to always verify.

If the taps happen to be on the LV side, then you would increase the tap (+) to raise the LV side voltage which seems more intuitive.

example 480/213.2 = 2.25 ratio (+2.5%), and 480V in would give you 213V out.

 

[xformer]

If I want to increase by 2.5% the secondary voltage of a transformer, what tap should put it in? It is now at tap 3(nominal). The transformer is a 3MVA, 6900-480V, delta-wye. Tap 1 voltage = 7245; tap2 = 7073; tap3 = 6900; tap4 = 6728 and tap5 = 6555.Thanks in advance gentlemen

Are these taps located on Primary side or the Secondary side...?

 

[Smart $]

Since he gave high voltage numbers for the taps, I'm assuming from the nameplate, the taps are on the high voltage side... :blink: