A.100 KVA
B. 150KVA
C. 200KVA
D. 250KVA
Ans: A. 100KVA
Explanation:
For Three phase Transformer formula
Power P = √3 * Voltage * Current
Here we take
Voltage V = 440V
Current I = 140 A
Here √3 = 1.73
than power P = 1.73 * 440 * 140
= 106568 VA
= 107KVA is equal to 100 KVA
Transformer ratting is 100KVA
Now we Note Transformer related points which is useful for exams
1. Transformer is static device which has no any rotating parts
2. Transformer never run on Dc supply If we give Dc supply to transformer Transformer Primary will be burn
3. Transformer convert only Voltage and current only and frequency remain constant for all load.
4. Transformer having breather and silica gel filled inside the breather which is used for taking air during breathing work.
5. Silica gel having Blue color when not absorb moisture And become pink when fully absorb moisture.
6. Pressure relief valve used for protection of transformer internal fault.
7. Bucholz relay used for protection of transformer internal fault. this relay give alarm during fault generated if fault is not cleared and become high than transformer tripped.
8. Isolation transformer is used for isolation purpose only and primary to secondary turn ratio is 1:1.
9.Isolation transformer is used in sensitive equipment's for protection for electrical shocks and used in medical equipment's.
10. Transformer step down or step up AC voltage & Current.
11. In an Autotransformer primary and secondary winding are connected magnetically As well electrically.
12. impedance ratio of transformer is equal to square of turn ratio.