Power Transformer Voltage

Power Transformer Voltage & Voltage Measurement

The power transformer is an electrical device used to amplify, abate or control the voltage in the electrical power generation station or any other where needed. The primary and secondary windings are the central working part of a transformer. A difference is maintained between the two windings. A power transformer voltage range is 5v to 34.5   kV, BILL rating is 60v 150 kV, and the thermal rating is 0.5v to 150 kVA. A transformer is built with metal of iron and other components.

What is Power Transformer Voltage?

The transformers are always associated with the operational voltage. Power transformer voltage means that the output voltage of a transformer. There has always been a difference between the two windings of the power transformer for the turns ratio. The maximum voltage increasing power of a power transformer is 34.5 kV.

A step-up power transformer is a transformer that’s secondary windings turn number is greater than the primary windings number. It uses to increase the voltage from the AC.

A step-down power transformer is a transformer that’s primary windings turn number is greater than the secondary windings number. It uses to decrease the voltage from the AC.

Power Transformer Voltage Control

It is essential to control the voltage during the flow of electricity. If left unmanaged, it can be left astray and lose the right path. The voltage control means the change of percentage in an output voltage from no-load to full-load. The controlling of the voltage can reduce the transfer losses and protect the other electric equipment.

Power Transformer Voltage Range

Many types of power transformers are constructed for different purposes. All of them are not the same efficiency. But standard criteria are followed when it makes. Voltage range, BIIL ratings, thermal rating, etc., are a follows when constructing it. The range of them are given below:

  • Voltage range: 5v to 34.5   kV
  • BILL rating: 60v 150 kV
  • Thermal rating: 0.5v to 150 kVA

Power Transformer Voltage Ratio

A transformer ratio depends on the turns number and voltage of the primary and secondary coil. The primary voltage is Vp, and the secondary voltage is Vs. The primary winding is Np, and the secondary winding is Ns. Here the power transformer voltage ratio is Np/Ns= Vp/Vs.

If it is necessary to calculate the primary voltage, the value of Vp has to be found, or if essential secondary voltage then calculates the value of Vs.

The voltage ratio(VR) is equal to the turns ratio (TR). Simply it is, VR= TR.

If a transformer voltage ratio is 1: 6, how does it mean? The answer is each of the volts in the primary winding is amplified six folds in the secondary windings. A step-up power transformer does it.

If the ratio is 6: 1, each volt of the primary winding will be six times less than the secondary winding.

An example is given below for the purposes:(single phage transformer)

If the primary turning number of a power transformer is 650 and the voltage is 280. The secondary turn number is 70, and the voltage is 35. What is the ratio of voltage to turn?



  • Vp= 280
  • Vs= 35
  • Np= 650
  • Ns= 70
  • VR and TR=?

The power transformer voltage ratio is TR= Np/Ns⇒ 560/70⇒ 56:7 and VR= Vp/Vs⇒ 280/35⇒ 56:7

The transformer ratio is 56:7

Another example is given below for the purposes: (three phage transformer)

If a transformer ratio is 6:1. The secondary coil has 300 turns, and the secondary voltage is 120V. Calculate the voltage ratio Vp and Np.

We know, VR= TR

VR= Vp/Vs

6:1= Vp/Vs

6/1= Vp/Vs

Vp= Vs/6= 120/6= 20

TR= Np/Ns

Np= TR/Ns= 300/6= 50

The answer is Vp= 20, Np= 50

Power Transformer Voltage Ratings

Engineers can know the transformers working efficiency and transformers’ losses by testing the Voltage rating. So, it is important for the transformer.

The calculation formula both the single and three phages transformers are given below:

  • Full load current (single phage)= VA/ Voltage⇒ (kVA*1000)/ Voltage
  • Full load current (three phages)= VA/ Voltage⇒ (kVA*1000)/ (1.73*Voltage)

Power Transformer Voltage Drop Calculation

Sometimes need to calculate the voltage drop in the power transformer to know the working efficiency. An example is given below how to calculate the transformer voltage drop:


  • Single phage: Vd = I*(R cosθ + X sinθ)
  • Three phages: Vd = sqrt(3) x I (R cosθ + Xθ)


  • R= Resistance
  • X= Resistance
  • Vd= Voltage drop
  • θ= Power factor angle

The power transformer spreadly uses in the electrical sector. There have many things to know about the power transformer. This blog describes the voltage information of the power transformer. This will be helpful for you. Keep the learning continuously and share your experience with others. If you want to read more about the power transformer, then visit our website. Thank you.


About the Author: Mehedi Hasan

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