## 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 â€“ 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 Â·Â Volt)**LV Full load current**= VA / (1.732 Â·Â Volt)**HV Side I**= IÂ²R Â·Â 1.5^{2}R losses**LV Side IÂ²R losses**= IÂ²R Â·Â 0.5 Â·Â 3**Total IÂ² R lossses at Amb. temp**= Hv losses + Lv losses**Total Stray losses at Amb. temp**= Measured losses – IÂ²R losses**IÂ²R lossses at 75Â° C temp**= ((225 + 75) Â·Â losses) / (225 + Amb. temp) .**Stray losses at 75Â° C temp**=((225 + Amb. temp)(Stray losses at Amb. temp)) / 300**Total Full load losses at 75Â° C**= IÂ²R losses at 75Â° C + Stray losses at 75Â° C**Total Impedance at amb. temp**= (Imp. voltage Â·Â 1.732) / Full load current**Total Resistance at amb. temp**= IÂ²R losses / IÂ²**Total Reactance (X)**= SQRT (ImpedanceÂ² – ResistanceÂ²)**Resistance at 75Â° C**= (300 Â·Â resistance at amb ) / (225 + Amb. temp)**Impedance at 75Â° C**= SQRT (RÂ² at 75Â° C + XÂ²)**Percentage Impedance**= (Z at 75Â° C Â·Â I Â·Â 100)/V1**Percentage Resistance**= ( R 75Â° C Â·Â I Â·Â 100)/V1**Percentage Reactance**= (X Â·Â I Â·Â 100) / V**Regulation at Unity P.F.**= (%R cosÃ¸ + %XsinÃ¸)**Regulation at 0.8 P.F.**= (%R cosÃ¸ + %XsinÃ¸) + 1/200(%R sinÃ¸ – %XcosÃ¸)^{2}

#### Efficiency at Unity P.F

**At 125 % of Transformer Loading**= (kVAÂ Â·Â 1.25 Â·Â 100)/((kVAÂ Â·Â 1.25)+(IÂ²R losses Â·Â 1.25Â²)+(No Load Losses))

#### Efficiency at 0.8 P.F

**At 125 % of Transformer Loading**= (kVAÂ Â·Â 1.25 Â·Â P.F. Â·Â 100)/((kVA Â· P.F.Â Â·Â 1.25)+(IÂ²R losses Â·Â 1.25Â²)+(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 | Video Courses | Membership | Download Updates |

it is very useful for me

Dear Jignesh,

I don’t find Lv resistance nor Hv resistance (cells C16 and C17 in your Excel file) on my transformer user manual. I though at first that it was primary side resistance and secondary side resistance. But in that case, I don’t understand why you multiply by 0.5 in the IÂ²R losses formula (cells H7 and H8).

I thought it might be total resistance seen from primary and secondary, thus I computed IÂ²R losses / I1Â² and the same with I2Â², but figures are different.

Please, can you explain me how to find these values (Lv and Hv resistance) ?

With kind regards

Denis

Dear sir,

How to calculate 2500KVA (11kv/415V) Transformer no load loss and copper loss at 50% rated load.

Transformer details:

Make- Crompton

YOM- 2007

KVA- 2500

Impedance volts- 7.10%

HV Amp- 131

LV Amp- 3333

Volts HV- 11000

Volts LV- 433

Type of cooling- ONAN

Please reply me as soon as possible.

Regards,

Pankaj Patel

9879735195

Gujarat, India

Dear Mr. Pankaj patel,

This is very simple to measure no load losses.

First of all Switch off the transformer output breaker, which is installed on LT side called ACB. Then take Clamp meter and measure the Amps from transformer input (HT side) and put the amps in power formula, (P=HT Volt*HT Amps*pf*1.732/1000) P=11000*0.5*0.8*1.732/1000

Regards

Dear Sir,

Thank you for posting this calculator. I used it to check my own which was almost correct.

Sir, please note that we have old 400 kva tranformer,year of manufactured 2007 and MAKE: CROMPTON GREAVES. OIL COOLED TRANFORMER Hence kindly suggest us for replacement of the TRANSFORMER , since it is very old.we are assuming that lot of energy getting wasted due to the above conditions.

You can go with Esennar Transformers.. where you can save upto 50 thousands rupees per year..

Assuming the losses and impedance of the transformer is negligible, calculate the HV and LV currents if the transformer was loaded at 120%

What formula use ?

Sir, coul you explain temperature gradient calculation of HV and LV winding , if temperature rise 40/50

Please tell how to calculate no load losses of transformer.

Tell me how to get transformer copper loss

I have no load losses n total power loss

Total Power loss = No load loss + Copper loss + Stray loss

If assume Stray loss negligible then

Copper loss = Total power loss – No load loss

Dear sir,

Dry type and oil type transformer losses how to calculate.

specs of hi pot tester from 10 to 35kv?