© k.u.leuven - esat/electa controlling hid lamps by intelligent power electronics geert deconinck,...
TRANSCRIPT
© K.U.Leuven - ESAT/ELECTA
Controlling HID lamps by Controlling HID lamps by intelligent power electronicsintelligent power electronics
Geert Deconinck, Peter TantGeert Deconinck, Peter Tant
K.U.Leuven-ESATK.U.Leuven-ESAT
8 November 20078 November 2007
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OutlineOutline
• discharge lamps
• role of ballasts for discharge lamps
• variable frequency high-voltage power supply for hot-restrike modelling of HID lamps
• cold breakdown experiments
• hot restrike experiments
• conclusions
3© K.U.Leuven - ESAT/ELECTA
kathode anode
Discharge lampsDischarge lamps
• breakdown and arc between electrodes in tube
• collisions ionising / elastic / inelastic collisions
• Planck’s law
• discrete spectrum12. WWfh
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Discharge voltage vs. discharge currentDischarge voltage vs. discharge current
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Low pressure discharge lampsLow pressure discharge lamps
Ultraviolette straling
Straling in het zichtbare gebied
Elektrode (gloeidraad)
Elektronen Kwikatoom
Fluorescerend poeder
• fluorescent lamps (TL) mercury, sodium, … 50-100 lm/W, 8000 hr
• compact fluorescent lamps energy saving 35-70 lm/W, 10000 hr
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Molydeen bandje Elektrode + emitter Kwarts ontladingsbuis Vulling (77mm kwik & 20 torr argon) Weerstand 10k + hulpelektrode
High pressure discharge lamps High pressure discharge lamps
• higher luminance compact discharge tube
high intensity discharge (HID) lamps
• typical 80-200 lm/W, up to 25000 hr
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HID lampHID lamp
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OutlineOutline
• discharge lamps
• role of ballasts for discharge lamps
• variable frequency high-voltage power supply for hot-restrike modelling of HID lamps
• cold breakdown experiments
• hot restrike experiments
• conclusions
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Role of control gearRole of control gear
• ballasts provide power supply correct starting and operating voltage and current
o initiate & sustain arc discharge between lamp electrodes
• ignition: high voltage required (kV)
• limit current to correct levels discharge lamps have negative resistance
• ‘ballasts’, auxiliaries
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Starter and ballast for TL-lampStarter and ballast for TL-lamp
elektrode
starter
ballast
condensator
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Ballast characteristicsBallast characteristics
• ballast factor
• power factor
• lamp current crest factor
• total harmonic distortion
commercial ballast light outputBF
laboratory referenceballast light output
total powerPF
input voltage input current
peak currentCF
RMScurrent
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Ballast typesBallast types
• ‘passive’ magnetic ballasts core & coil at net frequency
• ‘active’ electronic ballasts at higher frequency often integrated starter
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Electronic ballastElectronic ballast
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Electronic ballastsElectronic ballasts
• operate at higher frequencies 40-60 kHz for low-pressure discharge lamps 100-400 Hz for low wattage HID lamps 100-130 kHz for high wattage HID lamps
• higher frequency allows smaller size of coils avoid interference and resonance in arc no stroboscopic effects
• smaller, lighter, more efficient more ionised gas
o flux +8..12 % above 10 kHz
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Electronic ballastsElectronic ballasts
• compensate lamp characteristics at start-up: ignition (breakdown) + warm-up in steady-state
• sometimes separate start-up device higher voltage is less statistical lag time often many consequent start-up pulses
• typical HID – ballast PFC (power factor correction) + H-bridge typically 400 Hz (no resonance) blockwave
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Electronic ballast advantages:Electronic ballast advantages:lamp protectionlamp protection
• can allow protection of lamp e.g. at end of life, to ensure that if inner tube
breaks, no external arc is established based on measuring low or erratic voltages
• output short-circuit protection
• thermal protection within ballast
• internal fusing
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Electronic ballast advantages (ctd.)Electronic ballast advantages (ctd.)
• better colour output colour output depends on operating point (power)
o (e.g. ceramic HID) maintaining current for optimal operating point
o e.g. 200K over lamp lifeo also when lamp is ageingo also for incoming voltage changes (surges / sags)
• allows dimming continuous dimming for 50%-100% of lamp power
o automatically after 15’ warm-up period
• allows integration with domotics (IED)
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Electronic ballasts disadvantagesElectronic ballasts disadvantages
• higher capital cost
• sometimes lower power quality (depends on components, e.g. PFC) harmonics filters required
o but also for magnetic ballasts
• interferenceo filters required
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OutlineOutline
• discharge lamps
• role of ballasts for discharge lamps
• variable frequency high-voltage power supply for hot-restrike modelling of HID lamps
• cold breakdown experiments
• hot restrike experiments
• conclusions
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Power supply for HID lampsPower supply for HID lamps
• HID lamps require a high ignition voltage 1 to 4 kV in cold condition up to several tens of kV in hot condition, hot-restrike trend mercury-free HID lamps: higher ignition voltages
• characterization of (cold lamp) ignition properties = statistical analysis
• characterization of hot-restrike properties ballast design
o output voltage, output voltage for a given restrike time…
given ballast: estimation of restrike time,…
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ApproachApproach
• power electronics power supply
• continuous sine-wave output voltage adjustable frequency (<300 kHz) variable amplitude ( <15 kV) low harmonic contents, no switching noise
research purposes
• control and protection mechanisms
• automated measurements of hot-restrike characteristics
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Test setupTest setup
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Test setupTest setup
asymmetrical H-bridgeLC resonance circuit comprising T, L and Chigh sinusoidal voltage across C
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Test setupTest setup
lamp connected in parallel with C
high-bandwidth, high-voltage 1:1000 probe
Rogowski coil current sensor
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Test setupTest setup
switching rate controlled by pulse generatoradjust to resonance frequency of LC circuit
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Test setupTest setup
DC bus voltage output voltage amplitudeprogrammable waveform generator
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Test setupTest setup
optional resistor Rlim limits breakdown current(omitted when LC tank energy is small)
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Test setupTest setup
DSO: records voltage, current and timestamp at each breakdown
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Test setupTest setup
Res. Res.Diss.
ENABLE
Res. Diss. Off
detect the first breakdown event, and inhibit further control pulses
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Test setupTest setup
lamp ballast in series with the igniter circuit
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OutlineOutline
• discharge lamps
• role of ballasts for discharge lamps
• variable frequency high-voltage power supply for hot-restrike modelling of HID lamps
• cold breakdown experiments
• hot restrike experiments
• conclusions
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Test procedureTest procedurecold breakdown experimentscold breakdown experiments
• amplitude waveform generator produces repeating linear ramps ramp rate (kV/s)
• when breakdown occurs: a scope image is recorded further pulses are blocked
• after given sample time (5s), voltage ramp restarts
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Measurement resultsMeasurement resultscold breakdown experimentscold breakdown experiments
• context 39 W metal halide lamp room temperature, fRES = 50 kHz
ramp rate = 762 V/s (slow) 300 measurement samples
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Measurement resultsMeasurement resultscold breakdown experimentscold breakdown experiments
• discussion distribution of breakdown voltage:
long right tail (not a normal distribution). a free electron must be available statistical time lag between exceeding
min. VBD and actual breakdown
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Measurement resultsMeasurement resultscold breakdown experimentscold breakdown experiments
762 V/s
1550 V/s
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OutlineOutline
• discharge lamps
• role of ballasts for discharge lamps
• variable frequency high-voltage power supply for hot-restrike modelling of HID lamps
• cold breakdown experiments
• hot restrike experiments
• conclusions
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Test procedureTest procedurehot restrike experimentshot restrike experiments
• lamp burns at nominal power for 15 min.• at t = 0, the lamp is switched off• output voltage rises until lamp ignites• when breakdown occurs:
a scope image is recorded further pulses are blocked
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Measurement resultsMeasurement resultshot restrike experimentshot restrike experiments
- High initial VBD
- High statistical spread
< Steady state VBD Steady state VBD
• 39W metal halide arc tube only
• fRES = 50 kHz, ramp rate = 4.4 kV/s (slow)
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Measurement resultsMeasurement resultshot restrike experimentshot restrike experiments
• 39W MHD lamp arc tube + jacket, single-ended
• fRES = 50 kHz, ramp rate = 4.4 kV/s (slow)
External breakdown
< Steady state VBDSteady state VBD
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Measurement resultsMeasurement resultshot restrike experimentshot restrike experiments
• 39W MHD lamp
• fRES = 100 kHz, ramp rate = 348 V/ms (high)
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OutlineOutline
• discharge lamps
• role of ballasts for discharge lamps
• variable frequency high-voltage power supply for hot-restrike modelling of HID lamps
• cold breakdown experiments
• hot restrike experiments
• conclusions
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ConclusionsConclusions
• versatile & simple power supply for testing purposes
• output: high voltage & continuous wave avoid saturation of output inductors avoid excessive power dissipation in output capacitor
• multiple, subsequent lamp breakdowns avoided lamp temperature and electrodes are affected detection of breakdown
• voltage ramp rate is an important parameter lower ramp rate =
o lower mean breakdown voltage o less statistical spread
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Questions?Questions?