a method of driving microwave-driven lamps for … · radtech2018 (chicago, il), 9 may 2018, d....

A METHOD OF DRIVING MICROWAVE-DRIVEN LAMPS FOR IMPROVED PERFORMANCERadTech 2018 (Chicago, IL), 9 May 2018, D. Leonhardt

DC-driven lamps have be adopted for UV curing lamps for many years› Improved equipment (higher efficiency, lighter weight, and more)› More stable UV output for high-speed processes› Slot arcing less of a problem› Doesn’t need multiple versions for 50Hz and 60Hz› More precise power controlContinuous “DC” power causes ‘color separation’ when metal halides are present with vertical bulb› Constant convection creates hot core and cooler surroundings (chimney effect) › Metal halides recombine/dissociate in localized portion of bulb – making two different discharges in bulb› Aka axial segregation, cataphoresis

Color separation leads to increased envelope temperatures and poor optical homogeneity

“DC-like” operation of the additive bulb that still maintains the benefits of the DC power supply and alleviates the inhomogeneity of the color separation

MOTIVATION

Method for Driving Microwave-Driven Additive Lamps for Improved Performance | D. Leonhardt PhD | HNA-Innovation5/9/20182

Ferroresonant designs› Tried and true design; simple; moderately robust› Heavy step-up transformers for HV› HV is modulated at line frequency

FERRORESONANT AND DC POWER SUPPLIES


Mag

netro

n C

urre

nt

Time

Legacy System 2

A Mag B Mag

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n C

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nt

Time

Legacy System 1

A Mag B Mag

120° out-of phase, rectified by phase180° out-of phase, phase-split

DC designs› Power factor correction built in – extremely high efficiency› No heavy step-up transformers! Weight ~ 25% of ferroresonant design› Can distribute load evenly to bulb

DC POWER SUPPLIES


Constant current…

Magne

tron

Current

Time

DC

A Mag B Mag

Temperature distribution of additive bulbs in horizontal orientation

FERRORESONANT AND DC POWER BULB OPERATION


DC (Tmax = 925 °C)Legacy 2 (Tmax = 920 °C)

Temperature distribution of additive bulbs in vertical orientation



DC (Tmax = 1156 °C)

Legacy 2 (Tmax = 925 °C)

Temperature distribution and optical appearance of additive bulbs in vertical orientation



DC Legacy 2

Data from iron halide bulb operated by DC power, horizontal compared to vertical orientation

DC OPERATION OF ADDITIVE BULB – BULB PERFORMANCE


75%

67%

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40%

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60%

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Horizontal Vertical

Rel

ativ

e U

VA

Total UV (201-400nm) Key Band (351-400nm)

> 25% loss of optical output

Iron additive material position>1000 °C, and red in appearance

Mercury discharge primarily, no iron emissions

Briefly reduce power delivery to bulb to ‘mix’ additive but maintain DC operation character › Optimize duration, depth, waveform character and phase relationship

› ~ 80% of modulation required› Magnetron currents ~ 40° out-of-phase

› Keep peak power low, to maximize component life› Other critical parameters to optical output

› Rise and fall of driving current waveform› Duty cycle› Phase angle› Frequency› Peak Current › Magnetron delay (A delayed or B delayed)

› DC-like waveform is Patent Pending

DC-LIKE OPERATION OF ADDITIVE BULB – MAGNETRON WAVEFORM


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DC-Like Modulated

A Mag B Mag

Temperature distribution of additive bulbs in vertical orientation

DC-LIKE OPERATION OF ADDITIVE BULB – BULB OPERATION


DC (as shown previously)0

1: bottom magnetron delayedTmax = 929 °C

2: top magnetron delayed

DC-like waveform 1 2

Orientation

DC-LIKE OPERATION OF ADDITIVE BULB – LAMP PERFORMANCE


0

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0 200 400 600 800 1000 1200

Irradiance (m

W/cm

2 )

UV Irradiance (%

of m

ax)

Time (s)

Surveying with Broadband Radiometer

UVA UVC uvasecondary

Horizontal60Hz

B Delay 40°

Vertical60HzB Delay 40°

Vertical60HzA Delay 40°

Vertical120HzA Delay 35°

Vertical120HzB Delay 35°

100% 94% 99% 97% 93% <80%

VerticalDC

Achieved improved performance for DC-like operation over legacy designs

DC-LIKE OPERATION OF ADDITIVE BULB – OPTICAL OUTPUT PERFORMANCE


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201-260 261-300 301-350 351-400 401-450 451-500 501-550 551-600

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Horizontal Bulb Spectral Comparison

DC Legacy System 1 Legacy System 2 DC-Like Modulated

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201-260 261-300 301-350 351-400 401-450 451-500 501-550 551-600

Rad

iate

d Po

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Vertical Bulb Spectral Comparison

60Hz, A Up DC, A Up Legacy System 1 Legacy System 2

Achieved improved performance for DC-like operation over legacy designs› Magnetron-driving waveform mostly “DC”

› Minor fluctuations added to power delivered to bulb› Rise/Fall of waveform important for plasma stability› Also depends on additive composition (plasma reactions complex)

› Comparable or better bulb temperatures than when operated horizontally› No life time compromises

› Comparable or better bulb radiances› Horizontal: 4-6% higher than legacy power supplies, comparable to DC› Vertical: 6% higher than legacy power supplies, 15-25% higher than DC

› Comparable curing performance (still under study)

SUMMARY


ACKNOWLEDGMENTS: BRETT SKINNER, MIKE GHARAGOZLOO, CHUCK WOOD, PK SWAIN

THANK YOU FOR YOUR ATTENTION


a method of driving microwave-driven lamps for … · radtech2018 (chicago, il), 9 may 2018, d....

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