© K.U.Leuven - ESAT/ELECTA Controlling HID lamps by intelligent power electronics Geert Deconinck,...

© 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

2© K.U.Leuven - ESAT/ELECTA

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


kathode anode

Discharge lampsDischarge lamps

• breakdown and arc between electrodes in tube

• collisions ionising / elastic / inelastic collisions

• Planck’s law

• discrete spectrum12. WWfh


Discharge voltage vs. discharge currentDischarge voltage vs. discharge current


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


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


HID lampHID lamp


OutlineOutline

• discharge lamps





• conclusions


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


Starter and ballast for TL-lampStarter and ballast for TL-lamp

elektrode

starter

ballast

condensator


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


Ballast typesBallast types

• ‘passive’ magnetic ballasts core & coil at net frequency

• ‘active’ electronic ballasts at higher frequency often integrated starter


Electronic ballastElectronic ballast


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


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


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


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)


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


OutlineOutline

• discharge lamps





• conclusions


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,…


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


Test setupTest setup



asymmetrical H-bridgeLC resonance circuit comprising T, L and Chigh sinusoidal voltage across C



lamp connected in parallel with C

high-bandwidth, high-voltage 1:1000 probe

Rogowski coil current sensor



switching rate controlled by pulse generatoradjust to resonance frequency of LC circuit



DC bus voltage output voltage amplitudeprogrammable waveform generator



optional resistor Rlim limits breakdown current(omitted when LC tank energy is small)



DSO: records voltage, current and timestamp at each breakdown



Res. Res.Diss.

ENABLE

Res. Diss. Off

detect the first breakdown event, and inhibit further control pulses



lamp ballast in series with the igniter circuit


OutlineOutline

• discharge lamps





• conclusions


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


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



• 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



762 V/s

1550 V/s


OutlineOutline

• discharge lamps





• conclusions


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


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)



• 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



• 39W MHD lamp

• fRES = 100 kHz, ramp rate = 348 V/ms (high)


OutlineOutline

• discharge lamps





• conclusions


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


Questions?Questions?

© K.U.Leuven - ESAT/ELECTA Controlling HID lamps by intelligent power electronics Geert Deconinck,...

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