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Ballasts and the Generation of Light
Publication of this Design Guide has been approved by the IESNA. Suggestions for revisions should be directed to the IESNA.
Prepared by: The IESNA Ballast Task Force
Copyright 1996 by the Illuminating Engineering Society of North America.
Approved by the IESNA Board of Directors, August 4, 1996, as a Transaction of the Illuminating Engineering Society of North America.
All rights reserved. No part of this publication may be reproduced in any form, in any electronic retrieval system or otherwise, without prior written permission of the IESNA.
Published by the Illuminating Engineering Society of North America, 120 Wall Street, New York, New York 10005.
IESNA Standards and Guides are developed through committee consensus and produced by the IESNA Office in New York. Careful attention is given to style and accuracy. If any errors are noted in this document, please forward them to Rita Harrold, Director Educational and Technical Development, at the above address for verification and correction. The IESNA welcomes and urges feed- back and comments.
Printed in the United States of America.
This Design Guide explains the basics of ballast technology, and de- scribes the many ballast-lamp options available to today's lighting designer This Guide covers ballast designs applicable to a wide cross-section of fluorescent and high intensity discharge (HID) lamp products However, it does not discuss the ballasting or operation of low pressure sodium lamps
This document represents the combined efforts of a specially selected group from within the IESNA membership and the lighting industry. This "Ballast Task Force" is not a formally organized committee within the Society, but rather a hand-picked team of lighting professionals, selected because of their experience and expertise with electromagnetic and electronic ballasts.
Ballast Task Force:
K.W. Booty G. Forrler B. Hitchcock N.C. Grimshaw W.D. Kirkland N. Maiale R.D. Sierleja M.A. Stein J. Sulcs H. Wolfman
2.0 HOW FLUORESCENT LAMPS OPERATE . . . . . . . . . . . . . . . . . 2.1 Fluorescent Lamp Families .......................
2.1.1 T12 Fluorescent Lamps .. . . . . . . . . . . . . . . . . 2.1.2 T8 Fluorescent Lamps ............................... 2.1.3 Compact Fluorescent Lamps .................... 2.1.4 T5 Linear Fluorescent Lamps . . . . . . . . .
2.2 Basic Fluorescent Ballast Types ..........................
3.0 HOW HID LAMPS OPERATE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3.1 Mercury Lamps ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3.2 Metal Halide Lamps ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3.3 3.4
High-pressure Sodium Lamps ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 HID Lamp Operating Position ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4.0 FLUORESCENT BALLAST DESIGN ALTERNATIVES. . . . . . . . . 4.1 Ballasts for Preheat Lamps .................................. 4.2 Ballasts for Instant-Start Lamps ........................... 4.3 Ballasts for Rapid-Start Lamps ........................................ 4.4 Cathode-Disconnect Ballasts,. ........................................ 4.5 Ballasts for Low Temperature Lamp Operation ... 4.6 Reduced-Wattage Ballasts. ............................................. 4.7 Energy-Saving Ballasts ................................................... 4.8 Dimming Ballasts ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
5.0 FLUORESCENT BALLAST SYSTEM CONSIDERATIONS,, . . . . . 5.1 Inrush Current ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 5.2 Heat Dissipation ............................ 5.3 Ballast Factor ................................. 5.4 Ballast Power Factor ................................. 5.5 Harmonic Distortion . ......................................................................... 14 5.6 Crest Factor . . . . . . . . . . . . . ......................................................................... 14 5.7 Lamp-Ballast System Efficacy .................... .............................. 15 5.8 Lamp-Ballast System Flicker ...................... ..................................... 15 5.9 Lamp-Ballast System Compatibility ............................. 15
6.2
6.3
6.1.3 Constant-Wattage Autotransform
6.2.4 Regulated Lag Ballast . . . . . . . . . ..................................................... 19
High-Pressure Sodium Lam sts.. ..................... ........................ .20
6.3.2 Magnetic Regulatl ...................... 21
Ignitors and Starters ............................................. HID D'mming . . . . . . . . . . . . . . . . . ........................................................ HID Ballast Factor and E
6.2.3 High Reactance Autotransformer ...............................
6.3.1 Lag (Reactor) Baba
....................................... .23
7.0 FLUORESCENT BALLAST CERTIFICATION AND LISTING .............................. 23
8.0 PERFORMANCE MANDATES FOR LIGHTING SYSTEMS.. .............................. .24 8.1 Fluorescent Ballast Efficacy Factor ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.2 Pending Energy Policies ................................................. 8.3 Fluorescent Ballasts and RFI Regulations ............................................
8.5 Grant and Rebate Program Requirements ........................................... 8.4 Transient Sensitivity ..............................................
9.0 FLUORESCENT BALLAST TESTS ............................... ............................ .26 9.1 Troubleshooting Preheat ........... ...................................................... .26 9.2 Troubleshooting Rapid-Start .................................. 9.3 Troubleshooting Instant-Start . . . . . . . . . . . . . . . . . .
10.0 HID BALLAST TESTS ...................................... ........................................ .29 ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
.................................... 31 10.1 Visual Checks . . . . . . . . . . . . . 10.2 Executing the Quick Fix ...................................
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References .32
Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
1 .O INTRODUCTION
Ballasts are needed by all fluorescent and high- intensity discharge lamps primarily to start the lamps and limit lamp current flow after ignition. Often these lamps also need special external starting circuits. None of these lamps use 120 V (or 277 V) power directly because ai. turn-on they exhibit a "negative impedance." (As the lamp draws more current, the voltage drop across the lamp becomes lower.) If connected to the power mains without current-limiting circuitry, such lamps would draw enormous currents and quickly self- destruct. However, a simple series inductor con- sisting of a coil and an iron core can effectively limit the lamp's input current, while additional transformer windirigs and starter switches will heat lamp electrodes and/or provide starting voltage (when required).
Ballasts though, are often called upon to do much more The starting characteristics of the lamp, the amount of power the lamp/ballast system con- sumes, and the lamp's operating temperature range are all strongly influenced by ballast design Often lamps and ballasts must be regarded as complementary teammates, not generic components A particular lamp configuration must be matched with the correct ballast if i t is to give top performance and maximum service life This match must be maintained for the life of the system despite relamping and random repairs
The most recent development in ballast technology is the high frequency electronic (as opposed to 60 Hz electromagnetic) ballast for fluorescent lamps. The electronic ballast uses solid-state power processing components to convert the frequency of 60 Hz line input power to 20 kHz (and higher) before delivering starting and operating current to the lamps. While initially more expensive than electromagnetic ballasts, electronic ballasts offer many advantages that make them prime can- didates for new lighting installations and major retrofit projects.
Lighting design philosophy has undergone a major change over the past 20 years Once, when energy was less costly, It was standard practice to pur-
posely overlight an area in anticipation of equip- ment aging and erratic maintenance. However, today's lighting users demand efficient. energy- saving, environmentally-friendly systems, and lighting designers must work within small calcula- tion margins.
A common lighting project today involves retrofitting existing lighting systems to substantially reduce monthly electric bills. Recent bailasting innovations have made achievable the goals of saving energy, increasing lighting efficiency, improving lighting quality, and preserving the envi- ronment. However, retrofitting with ballasts is only one part of the energy savings opportLnity. A retrofit program is not simply a case of maintaining horizontal illuminance while installing a few pieces of new lighting hardware. Any such project should be based on multiple quantitative objectives which underlie all properly executed lighting designs. The designer should review guidelines in consulta- tion with the client and consider those which meet the needs of the client and the building's occu- pants.
A list of recommendations for developing an erier- gy management program for lighting new con- struction or existing spaces can be found in the lESNA Lighting Handbook, 8th Edition, Chapter 30, Figure 30-4. This Design Guide does rlot con- tain a comprehensive treatment of retrofitting.
2.0 HOW FLUORESCENT LAMPS OPERATE
Fluorescent lamp technology was made commer- cially available in 1938. A typical fluorescent lamp consists of a cylindrical glass tube filled with an inert gas such as argon, krypton, neon, helium (or a mixture of such gases), and a small droplet of mercury. Operating pressure is low, typically 2 to 3 Torr [2.6 x 10-3 to 3.9 x 10-3 atmospheres]. The lamp tube's inner surface is coated with fluorescent phosphors. Two electrodes are hermetically sealed into the tube, one at each end.
These electrodes can take the form of simple solid metal cylinders, posts, or filaments coated with an emissive material. Hot cathode electrodes are heated with voltage applied by two exterrlal con- nections through pins at each end of the lamp. When only one external connection is made to
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