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Power Factor Correction V= Line Voltage I=Active Current I 1 I 2 I R(L) I R(C) Reactive Current (inductive) Reactive Current (capacitive)
Reduction in Transformer Rating Reduction in KVAR Demand Advantages of P.F Correction Reduction in KVA Demand Reduction in Line Current Reduction in Line loss Reduction in Cable / Bus-bar size Reduction in Switchgear Rating Avoid power factor penalties Reduction in KVA Demand
ESTIMATION OF kVAr REQUIRED for New Electrical Installations M 75 HP, (415V, 3ph, compressor pf. 0.7) 75 HP, (415V, 3ph, compressor) 20 HP, (415V, 3ph, Pump, PF =0.70 Lag) Other loads, (total of 25 Kw) 500kVA, 11kV/415V, %Impedance = 4.25% 50 kVA, (440V, 3ph, UPS) Lighting (Load 10kW) M 30 HP, (415V, 3ph, I M pf 0.7) Let us assume that the target Power Factor as desired by the Customer is 0.95. M M
• Suitable switching devices with coupled with inrush current limiting devices are provided for each step
• Power Factor sensed by CT in line side
• kVAr required to achieve target PF is computed by the Microprocessor based APFC relay
• APFC relay switches appropriate capacitor steps
• CT senses improved PF and gives feedback
• Thus target PF is achieved
How to Improve Power Factor Without Causing Harmonic Problem ?
Conventional capacitors should not be used.
Capacitors should be replaced by harmonic suppression filters (series combination of suitable series reactor & capacitors) so that,
It offers capacitive reactance at fundamental frequency for necessary power factor correction.
It offers inductive reactance at all higher order dominant harmonic frequencies to avoid resonance.
Its self series resonance frequency “f R ” do not coincide with predominant harmonics.
Network With Harmonic Filters No resonance at harmonic frequencies as filter is inductive at such frequencies Harmonic currents flow towards Grid , as it offers least impedance compared to filter Predominantly fundamental current flows through Capacitors Moderate THD(V) in the Bus No harmonic overloading of Capacitors Improvement in Power Factor without Harmonic overload Non Linear Load BUS M GRID Z T Equivalent Load Impedance “Z L ” Z N L C