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Directions (Q. No. 11 to 15):

Read the following text and answer the following questions on the basis of the same:

Losses of transformer

There are 4 types of losses in a transformer:

Core loss, Ohmic loss.  Stray load loss and dielectric loss.

(1) Core loss

Core loss has two components - hysteresis loss and eddy current loss. These together are called no-load losses of a transformer and are calculated by open circuit test.

Hysteresis loss: This loss mainly depends on the core material used in the transformer. To reduce this loss, the high-grade core material can be used. CRGO- Cold rolled grain oriented Si steel is commonly used for this purpose.

Eddy current loss: This loss can be reduced by designing the core using slight laminations.

These losses are present even when no load is connected. So, these are also known as no-load loss.

(2) Copper Loss

Copper losses occur because of the Ohmic resistance in the windings of the transformer. If the currents in primary and secondary windings of the transformer are \[{{\operatorname{I}}_{1}}\] and \[{{\operatorname{I}}_{2}}\], and if the resistances of these windings are \[{{\operatorname{R}}_{1}}\] & \[{{\operatorname{R}}_{2}}\] then the copper losses that occurred in the windings are \[{{I}_{1}}^{2}{{\operatorname{R}}_{1}}\] & \[{{I}_{2}}^{2}{{\operatorname{R}}_{2}}\] respectively. So, the entire copper loss will be

\[{{I}_{1}}^{2}{{\operatorname{R}}_{1}}+{{I}_{2}}^{2}{{\operatorname{R}}_{2}}\].

This loss is also called variable or ohmic losses because this loss changes based on the load.

(3) Stray Loss

These types of losses in a transformer occur because of the occurrence of the leakage flux. As compared with copper and iron losses, the percentage of stray losses are less, so these losses can be neglected.

(4) Dielectric Loss

This loss mainly occurs within the oil of the transformer. Oil is an insulating material. Once the oil quality in the transformer deteriorates then the transformer's efficiency is affected.

Efficiency of Transformer

It is the ratio of output power and input power.

Efficiency = Output Power / Input Power.

The transformer is a highly efficient device which ranges between 95% - 98.5%.

What is the relationship among core loss, hysteresis loss and eddy current loss?

A) Eddy current loss = Core loss + Hysteresis loss

B) Core loss = Hysteresis loss + eddy current loss

C) Hysteresis loss = Core loss + eddy current loss

D) Core loss = Hysteresis loss X eddy current loss