Transformer Name plate data Question

[Jnox]

I'm a little confused about the name plate data on a transformer.

I am trying to find the Nominal KVA and Full Load KVA for a tranformer.

Here is the name plate data:

Westinghouse 4160 - 480Y/277 60 Hz 3 phase
Type RSL Unit Substation Transformer
Class OA
Full Load KVA = 2000/2240
Deg C Rise = 55/65
263 Gal Liquid
Insturction Book = PC 1001
Full Wave Impulse Level HV 60KV LV 30KV
Impedance Level 5.56% at 2000 KVA
4160 to 480y Volts
Ser. No. PBT0297-0103
Mfg. Date 10/1979


My questions are:
The name plate lists Full Load KVA = 2000/2240. Why is there two settings? Which is the Nominal KVA and which is the Full KVA?

Impedance level is 5.56%. How do I calculate the X and R percentage for positive and negative.

There is another transformer with settings: 25/33/42/46MVA. Again, what does it mean and which numbers are Nominal KVA and Full Load KVA.

If the transformer is oil filled and has fans, is it called forced air transformer?

Thank you for your help!

 

[benta]

Seems to be a question of surrounding temperature.
If you can accept a temperature rise of 55 C, the full load rating is 2000 kVA. If the allowable temperature rise is 65 C, 2240 kVA is OK.

Benta.

 

[tonyjony]

The X/R should be in the Reception Test Documents. For that transformer size & type, X/R=7 is a typical value.

 

[jghrist]

There is another transformer with settings: 25/33/42/46MVA. Again, what does it mean and which numbers Nominal KVA and Full Load KVA.

These ratings are are rated full load kVA for ONAN/ONAF (first stage of fans)/ONAF (both stages of fans)/ONAF (both stages of fans with 65°C temperature). ONAN = Oil Natural, Air Natural. ONAF = Oil Natural, Air Forced.

 

[edison123]

Full Load KVA = 2000/2240
Deg C Rise = 55/65

The loading of a trafo (for that any electrical machine) is mainly determined by the insulation, whose life is affected by the temperature.

This name-plate specifies that the transformer can be loaded up to 2000 KVA with the allowed temperature rise of 55 deg C over an ambient of 40 deg C and loaded up to 2240 KVA with an allowed temperature rise of 65 deg C. The only difference is that the continuous operation at higher rating comes with a much reduced transformer life, in this case even up to 50% expected life.

 

[Jnox]

Thank you everyone! All clear now!