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Spreadsheet for Transformer Losses Calculation
Spreadsheet for Transformer Losses Calculation

Transformer Losses

Transformers have two major components that drive losses: the core and the coils. The typical core is an assembly of laminated steel, and core losses are mostly related to magnetizing (energizing) the core.

These losses, also known as no-load losses, are present all the time the transformer is powered on – regardless of whether there is any load or not.

Core losses are roughly constant from no-load to full-load when feeding linear loads. They represent a continuous cost, 24 hours/day, for the 25-year or more life of the transformer.


Formulas in spreadsheet

  • HV Full load current = VA / (1.732 · Volt)
  • LV Full load current = VA / (1.732 · Volt)
  • HV Side I2R losses = I²R · 1.5
  • LV Side I²R losses = I²R · 0.5 · 3
  • Total I² R lossses at Amb. temp = Hv losses + Lv losses
  • Total Stray losses at Amb. temp = Measured losses – I²R losses
  • I²R lossses at 75° C temp = ((225 + 75) · losses) / (225 + Amb. temp) .
  • Stray losses at 75° C temp=((225 + Amb. temp)(Stray losses at Amb. temp)) / 300
  • Total Full load losses at 75° C = I²R losses at 75° C + Stray losses at 75° C
  • Total Impedance at amb. temp = (Imp. voltage · 1.732) / Full load current
  • Total Resistance at amb. temp = I²R losses / I²
  • Total Reactance (X) = SQRT (Impedance² – Resistance²)
  • Resistance at 75° C = (300 · resistance at amb ) / (225 + Amb. temp)
  • Impedance at 75° C = SQRT (R² at 75° C + X²)
  • Percentage Impedance = (Z at 75° C · I · 100)/V1
  • Percentage Resistance = ( R 75° C · I · 100)/V1
  • Percentage Reactance = (X · I · 100) / V
  • Regulation at Unity P.F. = (%R cosø + %Xsinø)
  • Regulation at 0.8 P.F. = (%R cosø + %Xsinø) + 1/200(%R sinø – %Xcosø)2

Efficiency at Unity P.F

  • At 125 % of Transformer Loading = (kVA · 1.25 · 100)/((kVA · 1.25)+(I²R losses · 1.25²)+(No Load Losses))

Efficiency at 0.8 P.F

  • At 125 % of Transformer Loading = (kVA · 1.25 · P.F. · 100)/((kVA · P.F. · 1.25)+(I²R losses · 1.25²)+(No Load Losses))

Contribution to transformer losses

Load level varies widely, with some installations running very heavily loaded and others more lightly loaded.

This difference substantially impacts actual losses incurred. Unfortunately, there is a small body of field data available, driven by the factors such as a lack of awareness of the cost of the losses, and the cost of gathering detailed data from a reasonable number of individual transformers.

Several variables contribute to transformer losses, the most important of which include load level, load profile, and core and coil construction.

Since there are a wide variety of transformers on the market serving different purposes, and available from different manufacturers, actual losses incurred in the field will vary substantially from installation to installation.

Software:Spreadsheet for Transformer Losses Calculation
Version:10.06.2013 New
Developer:Jignesh Parmar
Size:36 Kb
Price:Free
Download:Right here | Get Download Updates | Get Technical articles
Spreadsheet for Transformer Losses Calculation
Spreadsheet for Transformer Losses Calculation

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Page edited by E.C. (Google).

10 Comments


  1. venjateswarlu
    Jul 30, 2015

    Dear sir,
    For finding i^2R losses on hv side =I^2R.1.5
    What does 1.5 means


  2. hafizah
    Jun 09, 2015

    Hello!

    what is V1 and V for the percentage impedance and reactance?

    Thanks!


  3. hafizah
    Jun 09, 2015

    Is the measured loss a physically measured value? Is there a way of estimating this number based on the transformer size?


  4. Wyn
    Feb 12, 2015

    Edvard / Jignesh
    well done gents this is practical and useful I like it!.
    Here is a suggestion for you ready reckoner spread sheets for estimating:
    overhead power lines e.g. 415V AC distance covered number of bends and calculate the number of posts, cross arms, insulators, conductor sizes, tension, weight of the conductors….
    same for 22kV or 33kv or underground with approximate schedules of rates so I can enter local steel costs ideal pole spacing typical sag heights….


  5. deepak
    Jan 03, 2015

    can you provide spreadsheet for transformer losses calculation of 1000kva

    • Edvard
      Edvard
      Jan 03, 2015

      Can’t you use this spreadsheet? Just edit field rated power in kVA.


  6. Mario Tovar
    Oct 13, 2014

    How can we convert this losses to thermal losses?


  7. sagheer ahmad
    Oct 12, 2014

    EEP provides much more information about any given electrical article which is guide line for technical people.

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