Key Things To Consider While Calculating Transformer Load

energy-efficient transformers February 21, 2023

In the electrifying world, power plays a vital role in operating everything from a wide range of household products to vehicles, and thus, the unavoidable function of transformers comes in. A transformer is a device that transfers, converts, and supplies electric current from one circuit to another by stepping up and stepping down the voltage. Different industries and residential places have unique requirements for transformers like Three-Phase transformers, Distribution Transformers, or Energy-Efficient Transformers. The application of transformers depends on the electricity usage at that particular place and the number of electric appliances. Hence, determining the transformer load for selecting the transformer is crucial. So, let's understand the transformer load and how to calculate it.

Transformer Load - A Brief :

A transformer load is the quantity of current that moves through the transformer or a regulator that modifies the output power. To calculate the transformer load, we determine the current transmitted by transformers by considering the full load and safe load capacity. The full load is known to be the maximum amount of the current, and the safe load is 75-80% of the current.

In simple words, it is the quantity of power that moves through the transformers.

Significance Of Power Ratings In Transformer Load Calculation?

To understand the calculation, first, we need to understand the power ratings and significance:

The calculation of the transformer load depends on the output voltage and the current of the electrical load of equipment. The result will reflect the power of transformers in the unit of kilovolt ampere. (1 Unit can handle 100 Volts and 10 Amps of Current)

The Calculation of the Apparent Power Ratings of Equipment:

The calculation of the apparent power (kVA) or power (kW) of the equipment depends on voltage and current (V - Voltage mentioned on the equipment, A - Ampere, mentioned along with the equipment specification).

Note - If ampere or current ratings are absent, the value stating resistance (R) can be used. Ohm’s law can be used by the formula to calculate the apparent power ratings.

V = IR

(V refers to voltage, I stands for current, and R refers to Resistance)

How to Calculate Transformer Load - Formula

We will use below formula

P = VI/1000

The result will be in kVA, which needs to be divided by 0.8. For calculating the power rating, if the result comes in decimal should be rounded off.

Single-phase and Three-phase Transformers:

The above-derived formula is for single-phase transformers but varies for three-phase transformers. Three-phase transformers are transformers that have power with a phase difference of 120 degrees, representing the formula -

P = VI√3/1000

The formula will remain the same other than multiplication with √3.


The application of transformer load is-

  1. The calculation of transformer load can also be performed as current ratings.
  2. The apparent power will be divided by the supply voltage, multiplied by 1000.
  3. In the end, considering the extra current on the start-up of the device, we will multiply by 25.
  4. To find the voltage requirement of the equipment, we refer to the formula (kVA * 1000) / Current Ratings.
  5. We can also have the safe voltage amount from the transformer load calculation formula.


Transformer load is the easiest way to calculate the efficiency of the transformers. You can use the transformer load to select the transformer for a particular place. However, the calculation method differs for single-phase transformers and three-phase transformers. So, you must consider the correct formula according to the type of transformers.

Along with the transformer load, one should select transformers depending on Voltage taps, Voltage ratio, Method of connection, Harmonic content of Load, Impedance values, Transformer failure predictability, Insulation temperatures, Paralleling transformers, Insulation classes, and Sound levels.

You can ensure high-quality transformers by buying from the best transformer manufacturer in India. You can find various Industrial transformers in India providing their products and services ensuring high quality. One trustable name to mention is Electro-tech Transformers.

Electro-tech Transformers is one of the leading transformer manufacturing companies and is recognized for being the best Industrial transformer in Madhya Pradesh. To explore the wide range of transformers, you can visit

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