Question

Calculate the De-rating factor if the string efficiency is 90 %.

(a) .4

(b) .1

(c) .7

(d) .8

I have been asked this question during an interview.

This key question is from Solid-State Devices in section Introduction to Solid-State Devices of Electric Drives

Answer 1

The correct option is (a) .4

The best I can explain: De-rating factor is used to measure the reliability of a string. The value of the De-rating factor is 1-(string efficiency)=1-.9=.1.