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Power Quality Products and Applications
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Harmonic BasicsHarmonic Basics Harmonics is a term used to explain currents
and voltages that have multiplied in an AC electrical power network
Harmonic producing areas include ferromagnetics (transformers, motors), arcing equipment (welders, arc furnaces), and rectifiers (UPS, adjustable speed drives)
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Harmonic BasicsHarmonic Basics Power electronic devices
used in numerous equipment
Loads are non-linear, with an erratically shaped sine-wave
60hz fundamental becomes amplified when harmonics present
5th order harmonic represents 300hz
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Harmonic BasicsHarmonic Basics Harmonic spectrum may include various
harmonic orders, each with its own values for current and voltage
IEEE 519 Guide for Harmonics, references different types of harmonics and methods for mitigation
Industrial applications typically involve odd order harmonics, 5th, 7th, 11th, 13th
Zero sequence harmonics affect the neutral
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Harmonics BasicsHarmonics BasicsCommon Causes
Adjustable speed drives and systems, electric arc furnaces, welding equipment, transformers and generators, UPS and storage systems, medical/dental equipment, lighting controls/dimmers, computers, copiers, scanners
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Harmonic BasicsHarmonic BasicsEffects of Harmonics
Overheating of conductors, bus bar, switchgear, circuit breaker nuisance tripping/arcing, meters/instruments not accurate, AC motor reverse torque, transformers overheating/insulation breakdown, capacitors overload/blown fuse, reduced equipment life, early failure
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Harmonics BasicsHarmonics BasicsHarmonics and PFC
Capacitors do not create harmonics Concern for resonance – currents
amplified, voltage distortion, potential damage to capacitors
Reactors help to “de-tune” to below a certain order, balancing the capacitive requirement
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Harmonics Application ReviewHarmonics Application Review Facility walk-through – installed
equipment, systems and processes Review plant electrical documents Note plans for new equipment,
expansion Analyze 6-12 months of electric bills Review past electrical system studies,
may require a PQ survey, energy audit
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Harmonics Application ReviewHarmonics Application Review Note equipment most vulnerable to
harmonics Any critical loads and process requiring
“premium power”, outage concerns? Review downtime, scrap, maintenance,
equipment replacement costs, loss of production, profits
Isolated solution, long term PQ strategy
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Harmonic BasicsHarmonic BasicsWhere Harmonics Exist
Water treatment, glass making, steel processing, packaging, data centers, printing/publishing, paper processing, plastics, chemicals, automotive, to name few
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Harmonic BasicsHarmonic BasicsEconomic Considerations
Harmonics can create nuisance problems (rebooting a PC, restarting equipment) to serious concerns (product quality issues), through catastrophic events (production halted)…….monies lost
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Harmonic BasicsHarmonic Basics New and replacement
equipment/controls and devices typically are electronic, which may exacerbate a border-line harmonic condition, immediately creating a new set of problems, which ultimately affect business…….monies lost
Partial “fixes”, lack to review total PQ situation……..monies lost
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Harmonic BasicsHarmonic BasicsSuggestions
Keep a record of problems and associated costs
Actions taken to review and “fix” problem(s), associated costs
Potential need to monitor (collect data) on facility loads, to help with evaluation
Discuss problem with a “solutions driven” equipment manufacturer
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IEEE519-1992IEEE519-1992
SCR=IS/IL
Harmonic Percentage
H<11 11-16 17-22 23-24 34<h THD
<20 4.0 2.0 1.5 0.6 0.3 5.0
20-50 7.0 3.5 2.5 1.0 0.5 8.0
50-100 10.0 4.5 4.0 1.5 0.7 12.0100-1000 12.0 5.5 5.0 2.0 1.0 15.0
>1000 15.0 7.0 6.0 2.5 1.4 20.0
Current Distortion Limits for General Distribution Systems (120V through 69000V)
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EN61000-3-4EN61000-3-4Harmonic Number
n
Admissible Harmonic
Current In/Iact (%)
Harmonic Number
n
Admissible Harmonic
Current In/Iact (%)
3 19 21 <0.65 9.5 23 0.97 6.5 25 0.89 3.8 27 <0.611 3.1 29 0.713 2.0 31 0.715 0.7 <33 <0.6
17 1.219 1.1 Even <4/n or <0.6
Admissible Current for Entire Installation
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Conventional Methods to Conventional Methods to Solve HarmonicsSolve Harmonics
Poly-phase Rectifier and Phase-shift Transformer Adding transformers,
thyristors and controller… etc.
Regardless of Mains Power Impedance and Frequency
Must be built-in before equipment delivery
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Conventional Methods to Conventional Methods to Solve HarmonicsSolve Harmonics
Passive Power Filter Made of Capacitors
and Inductors Very Sensitive to
Mains Power Impedance and Frequency
Can be Built-In at Any Time
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Best Method to Solve Best Method to Solve HarmonicsHarmonics
Active Power Filter Uses Solid State
Power Converters Independent of
Mains Power Impedance and Frequency
Can be Built-In Any Time
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Operation Principle of Operation Principle of StacoSineStacoSine
Ih waveform
IeIh
IS
Phase 1: Measure the harmonic current from the load.
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Operation Principle of Operation Principle of StacoSineStacoSine
Ie waveform
IeIh
IS
Phase 2: Inject harmonic current in opposite phase to the load.