024

Fig. III.18 (a) Pictorial showing the inductive load of the example in this section. (b) The load with a capacitor added. With the exchange of the kVAR current between the capacitor and inductive load, very little kVAR current is supplied by the generator.

Comparing the original circuit to the circuit after adding capacity, we have:

Inductive Circuit Improved Circuit reinforced by Figure III.18. Adding capacitors to inductive loads can free generating capacity, reduce line loss, improve power factor, and in general be cost effective in controlling energy bills.

Line voltage 240 V 240 V

Line current 10 A 6.3 A

PF 62.5% 99% kVA 2.4 kVA 1.52 kVA kW 1.5 kW 1.5 kW kVAR 1.87 kVAR 0.19 kVAR

The big improvement noted is the reduction of line current by 37% with no decrease in real power, kW, used by the load. Also note the big change in kVA; less generating capacity is used to meet the same real power demand (generator input power is determined by KVA output).

III.5.4 Summary

Through an example it has been demonstrated how the addition of a capacitor across an inductive load can improve power factor, reduce line current, and reduce the amount of generating capacity required to supply the load. The way this comes about is by having the capacitor supply the inductive magnetizing current locally. Since inductive and capacitive elements store and release power at different times in each cycle, this reactive current simply flows back and forth between the capacitor and inductor of the load. This idea is

0 0

Post a comment