Question

Silicon steel used in lamination mainly reduces:
A) Hysteresis loss
B) Eddy current loss
C) Copper loss
D) All of the above

Answer 1

Hint: Steel is an alloy of iron and other elements. Silicon steel is a ferritic alloy of iron and silicon. It is used to make transformers and motors. Silicon content of this steel improves magnetic softness and increases the electric resistivity.

Complete solution:
First let us know what silicon steel is.
As the name suggests, silicon steel is the ferritic alloy of silicon and iron. Silicon is a semiconductor material which is used to make the alloy as it promotes electrical resistivity and desired crystal orientations. Silicon also improves the acid resistance and thus increases the magnetic permeability.
Now, that we know about silicon steel, we first understand all the terms mentioned in the options and then answer the question.
The silicon in the silicon steel is added so as to improve the magnetic softness and increase the electrical resistivity.

When the current through the core flows in forward and reverse directions it results in magnetization and demagnetization of the core causing hysteresis loss. Hysteresis loss depends on the core materials and is the characteristic of magnetic permeability. Higher the permeability and lower the hysteresis loss, higher is the efficiency of the transformer/motor.
And as we know that using silicon steel increases the magnetic permeability, we can also say that using silicon steel reduces the hysteresis loss.
Therefore, we know that option (A) is the correct option. Still we need to check the other options too.

The circulating currents which are induced whenever a time varying flux passes and flows against the internal resistance of the core produces the eddy current loss. The silicon added in the silicon steel increases the electrical resistivity i.e. reduces the conductivity and thus reduces the eddy currents loss. To reduce the eddy current loss more magnetic cores are laminated.
Therefore, we now know that option (B) is also correct.

The electric current in the electrical devices produces heat which is termed as the copper loss. These copper losses can be reduced by lowering the grain resistance. Silicon in the silicon steel reduces the grain resistance of the transformer/motor and thus we can say that silicon steel reduces copper loss.
Therefore, option (C) is also right.
Since all the three options are correct, thus we know that all the options for the given question are correct.

Therefore, option (D), all of the above is the correct answer.

Note: The content of silicon in silicon steel is $3.2$ mass $\% $ and is the most common alloying material used with steel. It is mainly used in motors and transformers. It is necessary that we know the meaning of all the terms mentioned in the options. Also, we need to check all of the options to ensure that all the options are correct are not.