Question

THESE ARE QUESTION FROM THE TOPIC POWER FACTOR IMPROVEMENT FROM THE SUBJECT POWER SYSTEM FUNDAMENTALS PLEASE DO THE QUESTIONS STEP BY STEP AND IN NEAT HAND WRITTING THE ANSWERS ARE GIVEN WITH THE QUESTIONS

1) . A 3-phase, 400 V synchronous motor having a power consumption of 50 kW is connected in parallel with an induction motor which takes 200 kW at a power factor of 0·8 lagging.   

(i) Calculate the current drawn from the mains when the power factor of the synchronous motor is unity.

(ii) At what power factor should the synchronous motor operate so that the current drawn from the mains is minimum. ?

ANS [(i) 421 A (ii) 0·316 leading]

2) . A factory load consists of the following :

(i) an induction motor of 150 h.p. (111·9 kW) with 0·7 p.f. lagging and 80% efficiency ;

(ii) a synchronous motor of 100 h.p. (74·6 kW) with 0·85 p.f. leading at 90% efficiency

(iii) a lighting load of 50 kW.

Find the annual electric charges if the tariff is Rs 100 per annum per kVA maximum demand plus 7 paise per kWh ; assuming the load to be steady throughout the year.

ANS[Rs 1,96,070]

Answer 1