## 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.

**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 I**= I²R · 1.5^{2}R losses**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.

**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 |

Developer: | Jignesh Parmar |

Size: | 36 Kb |

Price: | Free |

Download: | Right here | Get Download Updates | Get Technical articles |

Carcky

On this formula: Total Stray losses at Amb. temp = Measured losses – I²R losses, if I measured V= 384, I= 20 and W= 1015, for a 24MVA, 231200V (on tap 1), how do I relate the measured power into the equivalent input power which I can use in the formula?

sam oketch

The spreadsheet for transformer losses calculations is a good work

mani

how do find out the value of resistance in hv and lv side

Genaro Lucas Jr

please review cell H33, i think efficiency should not be highest at 125%

Fernando Pereira Andrade

Dear all,

How can I get the value 1.5 in ” HV Side I2R losses = I²R · 1.5″ and 0.5*3 in

” LV Side I²R losses = I²R · 0.5 · 3″ .

Thank you in advanced.

Fernando Pereira Andrade

Dear all,

What are the values 1.5 in HV and 0.5*0.3 and LV ?

HV Side I2R losses = I²R · 1.5

LV Side I²R losses = I²R · 0.5 · 3

Thank you in advanced.

venjateswarlu

Dear sir,

For finding i^2R losses on hv side =I^2R.1.5

What does 1.5 means

Fernando Pereira Andrade

Dear Venjateswar,

Did you find any answer for this question ?

Best regards,

hafizah

Hello!

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

Thanks!

John Njuguna

The V1 is the voltage that, applied to the HV side of the Tx whose voltage rating is V, shall circulate the rated current on the LV side of the Tx with it’s terminal short circuited. This voltage is expressed as a %age.

Z%=(V1/V)*100.

hafizah

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

Wyn

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….

deepak

can you provide spreadsheet for transformer losses calculation of 1000kva

Edvard

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

Mario Tovar

How can we convert this losses to thermal losses?

Edvard

They are thermal origin. Find out more here:

https://electrical-engineering-portal.com/transformer-heat-copper-and-iron-losses

sagheer ahmad

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

Edvard

Thank you Ahmad!