Question

4. Sarawak Energy Berhad provides real and reactive power to a shoe's factory in the form of apparent power. Initially the shoe's factory has an uncorrected 460 kVA/month demand, 480 V, three-phase at 0.87 power factor. The billing is RM 4.75/kVA demand. However, the shoe's factory plans to install capacitance bank to raise the power factor to 0.97 in order to reduce the amount of electric bill. Table 1 is multipliers to determine capacitor (kVar) required for power factor correction. Compute: a. the capacitive reactive power required to raise the power factor from 0.87 to 0.97 by using Table 1 (2 marks) b. the actual real power consumed by the factory after the power factor correction (2 marks) c. the apparent power consumed by the factory after the power factor correction (2 marks)

Answer 1

こ sino Solution : ceren data - Initial factores demand = 460 KVA ( moorth V = 480 V Initial Power factor (Cosoi) = 0.87 Desired power factor (cast2)=0.97 → Lets find real and reactive power before correction - Initial apparent power (S.) = P,+ ja, s, caso tę Cosd, - = 0.87 1 – 0.87 Send,= = 0.493 Real fower (P.)= Sçoson = 460 X 0.87 Po = 400.2 kW This is actual useful fower, so it will be same after correction. Benetical reactive fowes (81) = Sisend = 460 X 0.493 send, 2 - 1 - cosa, 2

226.8 kvar Bi= power factor raised to - When 0.97. Costz - 0.97 Sena2=√1-0.972 = 0.24 e Apparent power after correction (52)= P. 400.2 caso2 0.97 Sz= 412.5 KVA Reactive power after correction = S₂sinda 82= 412-5 5 X 0-24 B a 100.3 kvar

) Capacitive reactive power required to raise power factor, Difference between 8, &Qz = = 226.8 – loo:3 a 126.5 kvar (6) Actual real frower would not be changed after power factor correction So, p= 400.2 kW (5) Apparent fower consumed after correction is 82=100.3 kvar