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Power Factor Correction and Harmonics

Nick CaffasSenior Marketing Engineer

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Agenda

• What is Power Factor• What are Harmonics• Interaction of the two• Products available to mitigate their effects

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What is Power Factor

• Power Factor is the ratio Watts and Volt-Amps

• 𝑃𝑃𝑃𝑃 = 𝑘𝑘𝑘𝑘𝑘𝑘𝑘𝑘𝑘𝑘

• When kW=kVA PF is 1

• 𝑃𝑃𝑃𝑃 = 100100

= 1

• When kW≠ kVA, PF is less than 1

• 𝑃𝑃𝑃𝑃 = 100125

= 0.80

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The Power Factor Triangle

• Apparent Power (kVA) = Real Power (kW)

• Apparent Power (kVA) ≠ Real Power (kW)• kVAR make up the

additional current consumed

• The angle Θ is the Power Factor

kVA (Amps)

kW

kW

kvar

cap

Θ

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Power Quantity Analogy

Capacity(kVA)

Wasted Capacity(VAR’s)

Useful Work(Watts)

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Power Factor Triangle Continued

• A Loaded Motor will draw kW and kVAR.• We want to reduce the

kVAR draw

• 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

• Linear • Non-Linear

INDUCTIONMOTORS

INCANDESCENTLIGHTING

COMPUTERS

VARIABLEFREQUENCY

DRIVESFLUORESCENT &

HID LIGHTING

ELECTRONICBALLASTS

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Linear Loads Draw Power Linearly

• Electrical voltage and current “ebbs and flows” from plus to minus 60 times per second.

• 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

• Current is drawn in short “gulps” or pulses.

• Voltage and Currentwaveforms are irregular and don’t match – waveforms are said to be “DISTORTED”

• NON-LINEAR LOADS PRODUCE HARMONICS

• 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

Z∞

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Parallel Resonance – 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?• Make sure you perform calculation• Purchase Power Factor caps with detuned anti-resonance filter• Use capacitor-less solutions (HCU & others)

Z∞

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Parallel Harmonic Resonance

The “Self Correcting” Problem

- Blown Fuses

- Failed Capacitors

- Damaged Transformer

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What type of PFC solution?

• Capacitors (standard/heavy-duty)• Harmonic Filters (De-tuned) • Active Filters• LV or MV • Fixed or Switched (contactor or thyristor)• Active harmonic filter (PF and harmonic

mitigation)

CostCapacitors Detuned Filters Active FiltersHeavy Duty Capacitors

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QUESTIONS?