Understanding Transformer Capacity: 250 kva, 440 input, 220 output

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Discussion Overview

The discussion revolves around the capacity of a three-phase transformer rated at 250 kVA with a 440V input and a 220V output. Participants explore the current-carrying capacity on both the input and output sides, using various calculations and formulas.

Discussion Character

  • Technical explanation
  • Mathematical reasoning

Main Points Raised

  • One participant questions whether the transformer can handle 568.2 amps or 1136.3 amps.
  • Another participant clarifies that the transformer can provide 250 kVA to a load, suggesting a calculation of 250 kVA/220V for the output side.
  • Several participants assert that the transformer can bear 328 amps on the input side (440V) and 656 amps on the output side (220V), using the formula S = 1.73 * V * I.
  • There is a mention of the need to include the square root of 3 (approximately 1.73) in calculations for three-phase systems.

Areas of Agreement / Disagreement

Participants generally agree on the calculations for the input and output currents but do not reach a consensus on the initial question regarding the 568.2 amps or 1136.3 amps. The discussion remains somewhat unresolved as different interpretations of the transformer capacity are presented.

Contextual Notes

Some calculations depend on the understanding of three-phase power and the application of the square root of 3 in the formulas. There are also assumptions regarding the load and its connection to the transformer output.

neduet
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Hi friends

If I have three phase 250 kva Transformer, 440 input and 220 output then
Can I say that it can bear 568.2 amp current or 1136.3 amps?
 
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Your transformer can provide 250kva to a load. So you'd have 250kva/220v.

Assuming your "output" is where the load is attached.
 
It can bear 328 amp current in input side(440 V) and 656 amps in output(220V).

S=1.73*V*I
S input=S output
 
Last edited:
m.s.j said:
It can bear 328 amp current in input side(440 V) and 656 amps in output(220V).

S=1.73*V*I
S input=S output

Sir

how can you calculate. you use S=VI
 
neduet said:
Sir

how can you calculate. you use S=VI
I probably should wait for m.s.j to answer here. S = 3 phase VA (volt-amps) = V*I*sqrt(3). Sorry I didn't include the sqrt(3)=1.73 required in the equation since you were asking about 3 phase.
m.s.j said:
It can bear 328 amp current in input side(440 V) and 656 amps in output(220V).

S=1.73*V*I
S input=S output
I totally missed that the OP said "three phase". Thanks for the sqrt(3).
 

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