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Power Factor Correction and Harmonics
Nick CaffasSenior Marketing Engineer
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Agenda
β’ What is Power Factorβ’ What are Harmonicsβ’ Interaction of the twoβ’ Products available to mitigate their effects
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What is Power Factor
β’ Power Factor is the ratio Watts and Volt-Amps
β’ ππππ = ππππππππππ
β’ When kW=kVA PF is 1
β’ ππππ = 100100
= 1
β’ When kWβ kVA, PF is less than 1
β’ ππππ = 100125
= 0.80
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The Power Factor Triangle
β’ Apparent Power (kVA) = Real Power (kW)
β’ Apparent Power (kVA) β Real Power (kW)β’ kVAR make up the
additional current consumed
β’ The angle Ξ is the Power Factor
kVA (Amps)
kW
kW
kvar
cap
Ξ
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Power Quantity Analogy
Capacity(kVA)
Wasted Capacity(VARβs)
Useful Work(Watts)
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Power Factor Triangle Continued
β’ A Loaded Motor will draw kW and kVAR.β’ We want to reduce the
kVAR draw
β’ An Unloaded motor draws the same amount of kVARs as a loaded motor.
kW
kvar
cap
kW kWkW
kvar
kvar
cap
kvar
Unloaded Motor
Loaded Motor
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Example: Improving PF
125 HP
no PFC
125 kVA100 kW150 A75 kvar
125 kVA 100 kW150 A
Power Factor = 0.80
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Example: Improving PF Cont.
125 HP 50 kvar
w/PFCno PFC103 kVA 100 kW124 A
25 kvar
kVA (and Amp) Reduction
Power Factor 0.80 ==> 0.97
125 kVA100 kW153 A75 kvar
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Two Types of Electrical Loads
β’ Linear β’ Non-Linear
INDUCTIONMOTORS
INCANDESCENTLIGHTING
COMPUTERS
VARIABLEFREQUENCY
DRIVESFLUORESCENT &
HID LIGHTING
ELECTRONICBALLASTS
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Linear Loads Draw Power Linearly
β’ Electrical voltage and current βebbs and flowsβ from plus to minus 60 times per second.
β’ Voltage and Currentfollow the same rhythm perfectly in a linear load
+
-
Voltage
Current
1/60T
H
SEC.
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Non-Linear Loads Draw Power Unevenly
β’ Current is drawn in short βgulpsβ or pulses.
β’ Voltage and Currentwaveforms are irregular and donβt match β waveforms are said to be βDISTORTEDβ
β’ NON-LINEAR LOADS PRODUCE HARMONICS
β’ Harmonics cause mis-operation of equipment and WASTE ENERGY.
+
-
Voltage
Current
1/60T
H
SEC.
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Parallel Resonance
PF Cap
100 HP
Utility
Transformer
VFDPF Cap Source
ImpedanceHarmonic Current Source
Parallel Resonance Equivalent Circuit
Xc XL
Zβ
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Parallel Resonance β the Problem
At 420Hz (the 7th harmonic) the Z (impedance) of the circuit increasesfrom around 80 ohms to 10,000 ohms
125 times increase!
Subsequently, harmonic voltageIncreases 125 times!
Solution?β’ Make sure you perform calculationβ’ Purchase Power Factor caps with detuned anti-resonance filterβ’ Use capacitor-less solutions (HCU & others)
Zβ
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Parallel Harmonic Resonance
The βSelf Correctingβ Problem
- Blown Fuses
- Failed Capacitors
- Damaged Transformer
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What type of PFC solution?
β’ Capacitors (standard/heavy-duty)β’ Harmonic Filters (De-tuned) β’ Active Filtersβ’ LV or MV β’ Fixed or Switched (contactor or thyristor)β’ Active harmonic filter (PF and harmonic
mitigation)
CostCapacitors Detuned Filters Active FiltersHeavy Duty Capacitors
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QUESTIONS?