Losses in an electrical transformer

In this post, we will discuss different losses in an electrical transformer.

Losses in an electrical transformer
Losses in an electrical transformer

Losses in an electrical transformer

Following are the losses in an electrical transformer

  • Iron Losses
    • Eddy Current Losses
    • Hysteresis Losses
  • Stray Losses
  • Ohmic Losses or Copper Losses
  • Dielectric Losses

Iron Losses

Iron losses are also known as core losses. Iron losses are caused by the alternating flux in the core of the transformer as these losses occur in the core of the transformer, these are also known as Core losses. Iron loss is further divided into two categories-

Hysteresis loss

And

Eddy current loss.

Hysteresis Losses

The hysteresis is caused by continuous magnetization & demagnetization of the core. This causes some losses. Whenever the core of the transformer is subjected to an alternating magnetic field, the domain present in the material will change their orientation after every half cycle. Power is dissipated in the form of heat known as hysteresis loss or the power consumed by the magnetic domains for changing the orientation after every half cycle is called Hysteresis loss. Therefore, the cores of the transformers are made of materials with narrow hysteresis loops so that the little energy will be wasted in the form of heat.

The Domains are like small permanent magnets situated randomly in the structure of the substance. The domains are arranged inside the material structure in such a random manner, that the net resultant magnetic field of the material is zero.

When an external magnetic field is applied to the substance, these randomly directed domains are arranged in parallel to the axis of the applied magnetic field. After removing this external magnetic field, maximum numbers of domains again arranged in the random positions, but some of the domains still remain in the changed position. Because of these unchanged positions of the domains, the substance becomes slightly magnetized permanently. This magnetism is called “Spontaneous Magnetism”. The magnetic field or MMF applied in the transformer core is alternating. For every cycle due to the domain reversal, some domains will remain in the unchanged position. For this reason, there will be a consumption of electrical energy which is known as Hysteresis loss of the transformer.

Eddy Current losses

In a transformer, the alternating current is supplied in the primary, this alternating current produces alternating magnetic flux in the core and as this flux links with the secondary winding, a voltage will induce in secondary, resulting in current to flow through the load connected with it. Some of the alternating fluxes of the transformer; may also link with other conducting parts like steel core or iron body of transformer etc. As the alternating flux links with these parts of the electrical transformer, an EMF will induce locally. Due to these EMFs, currents will circulate locally at that part of the transformer. These circulating currents will not contribute to the output of the transformer and dissipated as heat. This type of energy loss is called eddy current loss of transformer. These currents produce a loss (I2R loss) in the magnetic material known as an Eddy Current Loss.

Copper Losses Or Ohmic Losses

These losses occur due to the ohmic resistance of the transformer windings. If I1 is the primary current and I2  is the secondary current. R1 is the resistance of the primary winding and R2 is the resistance of the secondary winding. Then the copper losses in the primary and the secondary winding will be I12R1 and I22R2 respectively.

Total Copper Losses will be

Pc= I12R1 + I22R2

These losses varied according to the load and hence are also known as variable losses. Copper losses vary as the square of the load current.

Dielectric Losses

Dielectric losses occur in the insulating material of the transformer that is in the oil of the transformer, or in the solid insulations. When the oil gets deteriorated or the solid insulation gets damaged, or its quality decreases, and because of this, the efficiency of the transformer is affected.

Stray Losses

The percentages of the stray losses are very small as compared to the copper losses and iron losses so they can be neglected. The stray losses are due to the presence of the leakage field.

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