Electrical engineering Interview questions and answers

6.What are the different type of transformer earthing ? What is the function of transformer earthing?

The two types of earthing are familiar as equipment earthing and system earthing. In equipment earthing body of the equipment should be earthed to safeguard the human beings.

System earthing : In this neutral of the supply source should be grounded. With this, in case of unbalanced loading neutral will not be shifted.

So that unbalanced voltages will not arise.We can protect the equipment also. With size of the equipment and selection of relying system earthing will be further classified into directly earthed,Impedance earthing,resistive.

7.What is SF6 Circuit breaker?

SF6 is sulpher hexa flouride gas.If the gas is used as arc quenching medium in a circuit breaker SF6 CB.

8.What is frantic effect?

Output voltage is greater than the input voltage or receiving end voltage is greater than the sending end voltage.

9.What is the difference between MCB and MCCB where it can be used?

MCB is miniature circuit breaker which is thermal operated and use for short circuit protection in small current rating circuit.

MCCB molded case circuit breaker and is thermal operated for over loaded and magnetic operation for instant trip in short circuit condition.

Under voltage and under frequency may be in inbuilt. Normally it is used where normal current is more than 100A.