(A) 5, 7 (X)

(B) 4, 6 (X)

**(C) 7, 5 ()**

(D) 6, 4 (X)

Answers: **A thyristor string is made of a no. of SCR connected in series and parallel. The string have volume and current of 11 KV and 4 KA. The voltage and current rating of available SCRs are 1800 V and 1000 A. For a string efficiency of 90 % let the number of SCRs in series and parallel are a and b respectively. Then the value of a and b will be ****7, 5.**