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CHAPTER 4. SCREENING ANALYSIS

TABLE OF CONTENTS

4.1 INTRODUCTION .........................................................................................................4-1

4.2 DISCUSSION OF DESIGN OPTIONS ........................................................................4-2

4.3 DESIGN OPTIONS NOT SCREENED OUT OF THE ANALYSIS ...........................4-3

4.3.1 Improved Core Steel ......................................................................................4-3

4.3.2 Copper Wiring ...............................................................................................4-3

4.3.3 Increased Stack Height ..................................................................................4-3

4.3.4 Increased Conductor Cross-Section...............................................................4-4

4.3.5 Electronic Ballast...........................................................................................4-4

4.3.6 Improved Components...................................................................................4-5

4.3.7 Improved Circuit Design................................................................................4-5

4.4 DESIGN OPTIONS SCREENED OUT OF THE ANALYSIS ....................................4-5

LIST OF TABLES

Table 4.2.1 Metal Halide Lamp Fixtures Design Options............................................... 4-2
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CHAPTER 4. SCREENING ANALYSIS

4.1 INTRODUCTION

This chapter discusses the U.S. Department of Energy’s (DOE’s) screening 

analysis of the technology options identified for metal halide lamp fixtures. As discussed 

in chapter 3 of the preliminary technical support document (TSD), DOE consults with 

industry, technical experts, and other interested parties to develop a list of technology 

options for consideration. The purpose of the screening analysis is to determine which 

options to consider further and which to screen out. 

Section 325(o)(2) of the Energy Policy and Conservation Act (EPCA) provides 

that any new or revised standard must be designed to achieve the maximum improvement 

in energy efficiency that is determined to be technologically feasible and economically 

justified. (42 U.S.C. 6295(o)(2)) In view of the EPCA requirements appendix A to 

subpart C of title 10, Code of Federal Regulations (CFR), part 430 (10 CFR part 430), 

Procedures, Interpretations, and Policies for Consideration of New or Revised Energy 

Conservation Standards for Consumer Products (the Process Rule) sets forth procedures 

to guide DOE in its consideration and promulgation of new or revised energy 

conservation standards. These procedures elaborate on the statutory criteria provided in 

42 U.S.C. 6295(o) and, in part, eliminate problematic technologies early in the process of 

prescribing or amending an energy conservation standard. In particular, sections 4(b)(4) 

and 5(b) of the Process Rule provide guidance to DOE for determining which design 

options are unsuitable for further consideration: 

1. Technological feasibility. DOE will consider technologies incorporated in 

commercial products or in working prototypes to be technologically feasible.

2. Practicability to manufacture, install, and service. If mass production and 

reliable installation and servicing of a technology in commercial products could 

be achieved on the scale necessary to serve the relevant market at the time the 

standard comes into effect, then DOE will consider that technology practicable to 

manufacture, install, and service. 

3. Adverse impacts on product utility or product availability. If DOE determines 

a technology would have significant adverse impact on the utility of the product 

to significant subgroups of consumers, or would result in the unavailability of any 

covered product type with performance characteristics (including reliability), 

features, sizes, capacities, and volumes that are substantially the same as products 

generally available in the United States at the time, it will not consider this 

technology further.

4. Adverse impacts on health or safety. If DOE determines that a technology will 

have significant adverse impacts on health or safety, it will not consider this 

technology further.
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4.2 DISCUSSION OF DESIGN OPTIONS

Several well-established engineering practices and techniques exist for improving 

the efficiency of a metal halide lamp ballast. Improving the construction materials (e.g., 

core steel, conductor) and modifying the ballast’s geometry (i.e., the stack height and 

conductor gauge) can make a ballast more energy efficient. Increasing core cross-section, 

for instance, can reduce core losses but requires a greater length of conductor to encircle 

the larger core and thus increases resistive losses. In electronic ballasts, substituting for 

higher grade components (e.g., capacitor) or improving the circuit type can also increase 

efficiency by reducing conduction and switching losses. It takes a great degree of 

engineering skill to maximize the efficiency gains in the overall design, and there are 

multiple pathways to achieve a given efficiency level. Table 4.2.1 presents a general 

summary of the options a manufacturer may use to reduce losses in metal halide lamp 

ballasts.

Table 4.2.1 Metal Halide Lamp Fixtures Design Options

Relevant Ballast Type Technology Option Description

Magnetic

Improved Core Steel

Use a higher grade of electrical steel, 

including grain-oriented silicon or 

amorphous steel, for lower core losses.

Copper Wiring

Use copper wiring in place of 

aluminum wiring for lowered resistive 

losses.

Increased Stack Height To a point, adding steel laminations 

results in lowered core loss.

Increased Conductor Cross-Section To a point, increasing conductor cross 

section results in lowered winding loss.

Electronic Ballast Use an electronic ballast in place of a 

magnetic ballast.

Electronic

Improved 

Components

Magnetics

Use grain-oriented or amorphous 

electrical steel to reduce core losses.

Use optimized-gauge copper or litz wire 

to reduce winding losses.

To a point, adding steel laminations 

results in lowered core loss.

To a point, increasing conductor cross 

section results in lowered winding loss.

Diodes Use diodes with lower losses.

Capacitors Use capacitors with a lower effective 

series resistance and output capacitance.

Transistors Use transistors with lower drain-tosource resistance.

Improved Circuit 

Design

Integrated 

Circuits

Substitute discrete components with an 

integrated circuit.
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4.3 DESIGN OPTIONS NOT SCREENED OUT OF THE ANALYSIS

This section discusses the technology options that DOE considers viable means of 

improving the efficiency of metal halide lamp fixtures.

4.3.1 Improved Core Steel

Electrical steel, placed in a time-variant magnetic field, loses energy in two ways. 

Eddy currents are small, unproductive currents that dissipate energy resistively, whereas 

hysteresis is a nonlinearity in the magnetization of a material in response to the magnetic 

field applied. Electrical steels are made in different grades which correspond to different 

losses. Inexpensive magnetic ballasts typically use non-oriented steel whose magnetic 

properties are isotropic. Higher grades of steel can be grain-oriented, where the 

microscopic structure of the material is optimized for a particular field direction, or 

amorphous, which has no grain structure at all and the most desirable magnetic 

properties. Though amorphous steel has not yet been incorporated into commercially 

available metal halide ballasts, DOE did not screen this technology out because it has 

been used in similar products. These improved core steel types reduce eddy currents and 

hysteresis losses, and improves ballast efficiency.

Considering the four screening criteria for this technology option, DOE did not 

screen out improved steel as a core material. Because these materials are in commercial 

use today, DOE concluded that they are technologically feasible and practicable to 

manufacture, install, and service. DOE is not aware of any adverse impacts on consumer 

utility, reliability, health, or safety associated with higher grades of steel.

4.3.2 Copper Wiring

Most inexpensive magnetic ballasts use aluminum conductor, which is more 

resistive than copper conductor of the same gauge. Because conductor losses vary in 

proportion to the resistance of the conductor, lowered resistance yields lower losses and 

higher ballast efficiency.

Considering the four screening criteria for this technology option, DOE did not 

screen out copper wiring. Because this material is in commercial use today, DOE 

concluded that it is technologically feasible and practicable to manufacture, install, and 

service. DOE is not aware of any adverse impacts on consumer utility, reliability, health, 

or safety associated with copper wiring.

4.3.3 Increased Stack Height

Losses in electrical steel vary with magnetic flux density, with higher flux density 

yielding higher losses. For a given magnetic field, increasing core cross-section will 

lower flux density and, therefore, lower losses. Because steel laminations are said to be 

“stacked” to form a core, increasing core cross-section is ordinarily done by adding steel 

laminations, or increasing the stack height. However, adding steel also adds core losses in 
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the form of eddy currents and hysteresis, and also requires a greater length of conductor, 

eventually offsetting decreased core losses from increased core cross-section.

Considering the four screening criteria for this technology option, DOE did not 

screen out increased stack height. Because this practice is in commercial use today, DOE 

concluded that it is technologically feasible and practical to manufacturer, install, and 

service. Increasing stack height could affect the overall size and form factor of the ballast, 

but DOE believes there is sufficient flexibility in fixtures and the space in which they are 

installed to accommodate these changes. DOE is not aware of any adverse impacts on 

consumer utility, reliability, health, or safety associated with increased stack height.

4.3.4 Increased Conductor Cross-Section

The efficiency of a magnetic ballast could be increased with the use of increased 

conductor cross-sections in the windings of the magnetic choke and step-up transformer. 

This can be accomplished by both using larger wire gauges (i.e., lower numeric values), 

multiple strands of wire operating in parallel. Using greater cross-sectional area in the 

magnetic component windings decreases the winding resistance and associated losses. 

Increased cross-sectional area in the windings could necessitate a longer core or additional 

layers of wire if the core length cannot be changed to maintain the same electromagnetic 

properties. This design option typically corresponds to an increase in manufacturing cost.

Considering the four screening criteria for this technology option, DOE did not 

screen out increased conductor cross-section. Because increased conductor cross-section is 

available in commercially available products today, DOE concluded that this design is 

technologically feasible and practicable to manufacture, install, and service. Increasing 

conductor cross-section could affect the overall size and form factor of the ballast, but 

DOE believes there is sufficient flexibility in fixtures and the space in which they are 

installed to accommodate these changes. DOE is not aware of any adverse impacts on 

consumer utility, reliability, health, or safety associated with the use of increased 

conductor cross-section.

4.3.5 Electronic Ballast

The efficiency of a metal halide ballast can be increased through the use of an 

electronic ballast rather than a magnetic ballast, particularly at medium to low wattages. 

Electronic ballasts use modern, solid-state components and circuits to perform the same 

function as magnetic ballasts with lower electrical losses. Electronic ballasts are often 

more expensive than magnetic ballasts.

Considering the four screening criteria for this technology option, DOE did not 

screen out electronic ballasts. Because electronic ballasts are in commercial use today, 

DOE concluded that these ballasts are technologically feasible and practicable to 

manufacture, install, and service. DOE is not aware of any adverse impacts on consumer 

utility, reliability, health, or safety associated with the use of electronic ballasts.
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4.3.6 Improved Components

The efficiency of electronic metal halide ballasts can be increased through the use 

of improved components. Improved components can have reduced electrical losses, 

increasing overall ballast efficiency, though generally at higher cost than standard 

components. DOE has not screened out improved components not currently used in metal 

halide ballasts, as these components are used in related power electronics products.

Considering the four screening criteria for this technology option, DOE did not 

screen out improved components. Because high-grade components are in commercial use 

today, DOE concluded that these components are technologically feasible and practicable 

to manufacture, install, and service. DOE is not aware of any adverse impacts on 

consumer utility, reliability, health, or safety associated with the use of improved 

components.

4.3.7 Improved Circuit Design

The efficiency of electronic metal halide ballasts can be increased through the use 

of improved circuit designs through the use of integrated circuits. The use of integrated 

circuits provides for more advanced control of the operation of the ballast. The use of 

integrated circuits also allows for use of more advanced and higher grade components, 

such as improved transistors. More advanced control of the ballast makes efficiency gains 

possible in the overall ballast, though generally at higher cost than standard designs. 

Considering the four screening criteria for this technology option, DOE did not 

screen out improved circuit designs. Because improved circuit designs (such as the use of 

integrated circuits) are in commercial use today, DOE concluded that these designs are 

technologically feasible and practicable to manufacture, install, and service. DOE is not 

aware of any adverse impacts on consumer utility, reliability, health, or safety associated 

with the use of improved circuit designs.

4.4 DESIGN OPTIONS SCREENED OUT OF THE ANALYSIS

DOE did not screen out any technology options for metal halide lamp fixtures.