Losses in Transformer

In this lecture, we will learn about the Losses in transformers in every detail with the equation where and when needed. So start by knowing the types of Losses in transformed and then we will discuss each in detail.

Losses in Transformer

An ideal transformer is loss-free. But in practice, there are some losses taking place in the transformer that we are going to discuss today.

Losses in a transformer refer to the energy dissipated as heat while transforming electrical energy from one voltage level to another. These losses can occur in various components of the transformer due to different factors.

Losses in Transformer

As shown in the above figure, the losses in transformed is divided into two types:

Types of Losses in Transformer
1.Copper Losses (Pcu)
2.Iron Losses (Pi)

The Iron losses are further classified into two types:

  1. Hysteresis loss in transformer
  2. Eddy current loss in transformer

Now we will discuss losses in transformers one by one in detail.

Copper Loss In Transformer (Pcu)

The total power loss taking place in the winding resistances of a transformer is known as the copper loss.

\therefore Copper Loss = Power loss in the primary resistance + Power loss in the secondary resistance

The Copper loss is denoted by Pcu,

\therefore \;\boxed{\mathbf{P_{cu}= I_1^2 R_1 + I_2^2 R_2}}

Where, I_1^2 R_1 = Power loss taking place in the primary resistance R1

and I_2^2 R_2 = Power loss taking place in the primary resistance R2

The copper loss in the transformer should be kept as low as possible to increase the efficiency of the transformer. To reduce the copper loss, it is essential to reduce the resistance R1 and R2 of the primary and secondary windings.

Copper losses are also called variable losses as they are dependent on the square of load current. The relation between copper loss at full load and that of half load is as follows:

\mathbf{P_{cu(HL)} = \left(\frac{1}{2}\right)^2 P_{cu(FL)}}

\therefore \mathbf{P_{cu(HL)} = \frac{P_{cu(FL)}}{4}}

where P_{cu(HL)} = copper loss at half load and P_{cu(FL)} = copper loss at full load.

Iron Loss in Transformer (Pi)

Iron loss Pi is the power loss taking place in the iron core of the transformer.

There are two types of Iron loss in transformers:

Types of Iron Loss in Transformer
1.Hysteresis Loss in Transformer
2.Eddy current loss in Transformer

Iton loss is equal to the sum of two components called hysteresis loss and Eddy current loss.

Pi = Hysteresis Loss + Eddy current loss

Now we will study each component of Iron loss in detail.

Hysteresis Loss in Transformer

  • The area enclosed by the hysteresis loop of a material represents the hysteresis loss.
  • Hence special magnetic materials should be used in order to reduce the hysteresis loss.
  • Material such as silicon steel has hysteresis loops with very small areas.
  • Hence such materials are preferred for the construction of the core. Commercially such steel is called Logy, which means low hysteresis materials.
  • The hysteresis loss is frequency-dependent. As we increase the frequency of operation, the hysteresis loss will increase proportionally.

Eddy current loss in Transformer

  • Due to the time-varying flux, there is some induced EMF in the transformer core.
  • This induced EMF causes some currents to flow through the core body. These currents are known as eddy current loss in transformers.
  • The core is made of steel and has some finite resistance. hence due to the flow of eddy currents. heat will be produced. The power loss due to the eddy current is given by:

Eddy current loss = (Eddy Current)2 x r

Where r = resistance of the core

  • The core is manufactured as a stack of laminations rather than a solid iron core.
  • These laminations are insulated from each other by means of a varnish coating on all the laminations.
  • Hence each lamination acts as a separate core with a small cross-sectional area, providing a large resistance to the flow of eddy currents.
  • The eddy current loss is also frequency-dependent. It is directly proportional to the square of the operating frequency.
  • Hence the iron loss Pi of the total loss is dependent on the frequency but the copper loss Pcu is constant irrespective of the frequency.

The iron loss is denoted by Pi, It is the sum of hysteresis and eddy current loss. Iron loss is a constant loss that does not depend on the level of load.

FAQs on Losses in Transformer

What are the types of losses in transformers?

Copper Losses (Pcu), Iron Losses (Pi), hysteresis loss, eddy current loss

What is the cause of losses in transformer?

Heat loss due to copper

What are the 4 losses in transformers?

The four main types of loss are resistive loss, eddy currents, hysteresis, and flux loss.

What is eddy losses in transformer?

Eddy current loss in the transformer is basically I2R loss present in the core due to the production of eddy current in the core.

Which loss is zero in transformer?

The friction losses are zero in the transformer because the transformer is a static device.

What is dielectric loss in transformer?

The power loss that occurs in insulating materials like oil, solid insulation of the transformer, etc. is known as dielectric loss.

What is transformer efficiency?

The ratio of the output power to the input power in a transformer is known as the efficiency of the transformer. The transformer efficiency is represented by the Greek letter Eta (η).

Also Read: Power Triangle: Understanding the Relationship Between Voltage, Current, and Power

Hello friends, my name is Trupal Bhavsar, I am the Writer and Founder of this blog. I am Electronics Engineer(2014 pass out), Currently working as Junior Telecom Officer(B.S.N.L.) also I do Project Development, PCB designing and Teaching of Electronics Subjects.

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