CHAPTER 4. SCREENING ANALYSIS 

TABLE OF CONTENTS 

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

4.2 DISCUSSION OF DESIGN OPTIONS .......................................................................... 4-1
 

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

4.3.1 Copper Die-Cast Rotor Cage ............................................................................... 4-3
 

4.3.2 Reduce Skew on Conductor Cage........................................................................ 4-4
 

4.3.3 Increase Cross-Sectional Area of Rotor Conductor Bars .................................... 4-4
 

4.3.4 Increase End Ring Size ........................................................................................ 4-4
 

4.3.5 Change Gauges of Copper Wire in Stator............................................................ 4-5
 

4.3.6 Stator Slot Size Manipulation .............................................................................. 4-5
 

4.3.7 Air Gap Between Rotor and Stator ...................................................................... 4-6
 

4.3.8 Improved Grades of Electrical Steel.................................................................... 4-6
 

4.3.9 Thinner Steel Laminations................................................................................... 4-6
 

4.3.10 Anneal Steel Laminations.................................................................................... 4-7
 

4.3.11 Additional Stack Height....................................................................................... 4-7
 

4.3.12 High-Efficiency Lamination Materials................................................................ 4-8
 

4.3.13 Better Bearings and Lubricant ............................................................................. 4-8
 

4.3.14 More Efficient Cooling System ........................................................................... 4-8
 

4.3.15 Change Run-Capacitor Rating ............................................................................. 4-9
 

4.3.16 Summary of Technology Options Not Screened Out .......................................... 4-9
 

4.4 DESIGN OPTIONS SCREENED OUT OF THE ANALYSIS .................................... 4-10
 

4.4.1 Air Gap Between Rotor and Stator .................................................................... 4-10
 

4.4.2 Plastic Bonded Iron Powder............................................................................... 4-11
 

4.4.3 Summary of Technology Options Screened Out of the Analysis...................... 4-11
 

LIST OF TABLES 

Table 4.2.1 Summary List of Options from Technology Assessment.................................... 4-3
 

Table 4.3.1 Design Options Not Screened Out of the Analysis............................................ 4-10
 

Table 4.4.1 Design Options Screened Out of the Analysis................................................... 4-11
 

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CHAPTER 4. SCREENING ANALYSIS
 

4.1 INTRODUCTION 

The purpose of the screening analysis is to identify design options that improve small 

electric motor efficiency and determine which options the Department of Energy (DOE) will 

either evaluate or screen out. DOE consults with industry, technical experts, and other interested 

parties in developing a list of design options for consideration. Then DOE applies the following 

set of screening criteria to determine which design options are unsuitable for further 

consideration in the rulemaking (1 Title 10 of the Code of Federal Regulations, Part 430, Subpart 

C, Appendix A at 4(a)(4) and 5(b)): 

(1)	 Technological feasibility. Technologies incorporated in commercial products or in 

working prototypes will be considered technologically feasible. 

(2)	 Practicability to manufacture, install, and service. If mass production of a technology in 

commercial products and reliable installation and servicing of the technology could be 

achieved on the scale necessary to serve the relevant market at the time of the effective 

date of the standard, then DOE will consider that technology practicable to manufacture, 

install, and service. 

(3)	 Adverse impacts on product utility or product availability. If DOE determines that a 

technology will have significant adverse impact on the utility of the product to significant 

subgroups or consumers or 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, that technology will not be considered further. 

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

significant adverse impacts on health or safety, that technology will not be considered 

further. 

This chapter discusses the design options that DOE considered for improving the energy 

efficiency of small electric motors and describes how DOE applied the screening criteria. 

4.2	 DISCUSSION OF DESIGN OPTIONS 

Several well-established engineering practices and techniques exist for improving the 

efficiency of a small electric motor. Improving the construction materials (e.g., the core steel, 

winding material, cooling system) and modifying the motor’s geometric configuration (i.e., the 

core and winding assemblies, the rotor, and stator) can make an electric motor more energy 

efficient. 

As discussed in the market and technology assessment (chapter 3), there are four general 

areas of efficiency loss in small electric motors: I2

R, core, friction and windage, and stray load. 

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DOE presented an initial list of technology options used to reduce energy consumption and thus 

improve the efficiency of general purpose induction motors. Unfortunately, methods of reducing 

electrical losses in the equipment are not completely independent of one another. This means 

that some technology options that decrease one type of loss may cause an increase in a different 

type of loss in the motor. Thus, it takes a great degree of engineering skill to maximize the 

efficiency gains in a motor design overall, balancing out the loss mechanisms. In some 

instances, motor design engineers must make design tradeoffs when finding the appropriate 

combination of materials and costs. However, there are multiple design pathways to achieve a 

given efficiency level. 

 Although I2R and core losses account for the majority of the losses in an induction motor, 

friction and windage losses and stray load losses also contribute to the total loss. In an induction 

motor, friction and windage losses can manifest in the bearings, bearing lubricant, and cooling 

fan system. Stray load losses are electromagnetic losses that generally require process changes 

in manufacturing. These various technologies can constrain the design parameters of a motor 

and thus limit the improvement in efficiency. 

Table 4.2.1 presents a general summary of the methods that a manufacturer may use to 

reduce losses in small electric motors. The approaches presented in this table refer either to 

specific technologies (e.g., aluminum versus copper die-cast rotor cages, different grades of 

electrical steel) or physical changes to the motor geometries (e.g., cross-sectional area (CSA) of 

rotor conductor bars, additional stack height). 

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Table 4.2.1 Summary List of Options from Technology Assessment 

Type of Loss to Reduce Technology Option Applied 

I

2

R 

Use a copper die-cast rotor cage 

Reduce skew on conductor cage 

Increase cross-sectional area of rotor conductor bars 

Increase end ring size 

Change gauges of copper wire in stator 

Manipulate stator slot dimensions 

Decrease air gap between rotor and stator 

Change run-capacitor rating (CSCR motors only) 

Core 

Improve grades of electrical steel 

Use thinner steel laminations 

Anneal steel laminations 

Add stack height (i.e., more electrical steel) 

Use high-efficiency lamination materials 

Use plastic bonded iron powder 

Friction and Windage Install better bearings and lubricant 

Install a more efficient cooling system 

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 small electric motors. 

4.3.1 Copper Die-Cast Rotor Cage 

Aluminum is the most common material used today to create die-cast rotor bars in small 

motors. Some manufacturers that focus on producing high-efficiency designs have started to 

offer electric motors with die-cast rotor bars made of copper. Copper offers better performance 

than aluminum because, per unit area, copper has a higher electrical conductivity (i.e., a lower 

electrical resistance). However, copper has a higher melting point than aluminum, so the casting 

process becomes more difficult and is likely to increase both production time and cost for 

manufacturing a motor. 

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

copper as a die-cast rotor cage conductor material. Because this material is in commercial use 

today, DOE concluded that this material 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 the use of copper as a die-cast rotor cage material. 

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4.3.2 Reduce Skew on Conductor Cage 

In the rotor, the conductor bars are not straight from one end to the other, but skewed or 

twisted slightly around the axis of the rotor. Decreasing the degree of skew can improve a 

motor’s efficiency. The conductor bars are skewed to help eliminate harmonics that add cusps, 

losses, and noise to the motor’s speed-torque characteristics. Reducing the degree of skew can 

help reduce the rotor resistance and reactance, which helps improve efficiency. However, overly 

reducing the skew also may have adverse effects on starting, noise, and the speed-torque 

characteristics. 

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

adjusting rotor skew as a means of improving efficiency. Rotor skew is one of the variables that 

motor design engineers can manipulate to obtain certain performance and efficiency targets. The 

rotor skew is part of the overall motor design, which is input into automated production 

equipment that punches and stacks the steel to create a rotor with the desired skew. Because this 

design technique is in commercial use today, DOE considers this technology option both 

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 properly 

manipulating the rotor skew to obtain improved performance. 

4.3.3 Increase Cross-Sectional Area of Rotor Conductor Bars 

Increasing the cross-sectional area of the rotor conductor bars, either by making the 

diameter of the conductor bars larger or changing the cross-sectional geometry of the rotor, can 

improve motor efficiency. Either way, increasing the cross-sectional area of the rotor conductor 

bars will decrease the resistance, increase current flow, and lower losses. Note that the shape of 

the rotor may affect the size of the end rings. 

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

increasing the cross-sectional area of rotor conductor bars as a means of improving efficiency. 

Motor design engineers adjust this particular variable when manufacturing to obtain performance 

and efficiency targets. The rotor conductor bars are created by automated production equipment 

that have certain tolerances and allow variance in this parameter. Because this design technique 

is in commercial use today, DOE considers this technology option both 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 increasing the cross-sectional area 

of rotor conductor bars to obtain increased efficiency. 

4.3.4 Increase End Ring Size 

Creating an electrical connection between the rotor bars by increasing the size of the endrings can increase motor efficiency. Increasing the size of the end rings reduces the resistance 

and thus lowers the I2

R losses in the end rings. 

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

increasing end ring size as a means of improving efficiency. As with some of the previous 

technology options, motor design engineers adjust this variable when manufacturing an electric 

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motor to achieve performance and efficiency targets. Automated production and casting 

equipment, which allow some degree of variability, determine the end ring size. Because this 

design technique is in commercial use today, DOE considers this technology option both 

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 

increasing the size of the rotor end rings to obtain increased efficiency. 

4.3.5 Change Gauges of Copper Wire in Stator 

Increasing the slot fill by changing the gauge of wire used in the stator winding can also 

increase motor efficiency. Motor design engineers can achieve this by manipulating the wire 

gauges to allow a greater total cross-sectional area of wire to be incorporated into the stator slots. 

This could mean either an increase or decrease in wire gauge, depending on the dimensions of 

the stator slots and insulation thicknesses. As with the benefits associated with larger crosssectional area of rotor conductor bars, using more total cross-sectional area in the stator windings 

decreases the winding resistance and associated losses. However, this change could affect the 

packing factor of the wire in the stator slots. The stator slot openings must fit the wires so that 

machinery can pull (or push) the wire into the stator slots. DOE used 65 percent as a maximum 

peak slot fill percentage in all of the designs presented in chapter 5 of the Technical Support 

Document (TSD). 

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

changing gauges of copper wire in stator as a means of improving efficiency. Motor design 

engineers adjust this technology option in fractions of a half a gauge when manufacturing an 

electric motor to achieve desired performance and efficiency targets. Because this design 

technique is in commercial use today, DOE considers this technology option both 

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 changing 

the wire gauges in the stator to obtain increased efficiency. 

4.3.6 Stator Slot Size Manipulation 

Varying the stator slot size and geometry associated with a given motor design can 

improve motor efficiency. Similar to changing gauges of wires, manipulating the stator 

dimensions can allow the motor design engineer to incorporate more copper into the stator slots. 

This decreases the losses in the windings and can affect motor torque and performance 

(including efficiency). 

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

changing stator slot size as a means of improving efficiency. Motor design engineers modify this 

technology to achieve desired performance and efficiency targets. Because this design technique 

is in commercial use today, DOE considers this technology option both 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 changing stator slot sizes to obtain 

increased efficiency. 

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4.3.7 Air Gap Between Rotor and Stator 

Reducing the radial air gap between the rotor and stator can improve motor efficiency. 

For small electric motors, the air gap is commonly set at 15 thousandths of an inch. However, 

reducing the air gap to 12.5 thousandths of an inch per side is still practicable to manufacture. 

Although DOE is aware that some stepper motors have tighter tolerances, radial air gaps less 

than 10 thousandths of an inch are not achievable for continuous duty motors, such as small 

electric motors, as defined by the Energy Policy and Conservation Act, as amended, 42 U.S.C. 

6291–6317 (EPCA). 

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

decreasing the radial air gap to 12.5 thousandths of an inch as a means of improving efficiency. 

DOE recognizes that reducing the radial air gap is a means design engineers use to achieve 

desired performance and efficiency targets. Because this design technique is in commercial use 

today, DOE considers this technology option both 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 reducing the radial air gap to 12.5 thousandths of an 

inch. 

4.3.8 Improved Grades of Electrical Steel 

Losses generated in the electrical steel of an induction motor can be significant for an 

electric motor. Generally, these losses are classified as either hysteresis or eddy current. 

Hysteresis losses are caused by magnetic domains resisting reorientation to the alternating 

magnetic field (i.e., 60 times per second, or 60 hertz). Eddy currents are physical currents that 

are induced in the steel laminations by the magnetic flux produced by the current in the 

windings. Both of these losses generate heat in the electrical steel. 

One way to reduce hysteresis losses is to incorporate a higher grade of core steel into the 

electric motor design (e.g., switching from an M56 to an M19). Even for the same thickness 

(i.e., gauge) of core steel lamination, losses are reduced as the grain size increases, thus reducing 

magnetic resistance to reorientation by the alternating current. 

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

improved grades of electrical steel as a means of improving efficiency. Design engineers use 

this approach to achieve desired performance and efficiency targets. Because this design 

technique is in commercial use today, DOE considers this technology option both 

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 

improving the electrical steel. 

4.3.9 Thinner Steel Laminations 

DOE can use thinner laminations of core steel to reduce eddy currents. DOE can either 

change grades of electrical steel as described above, or use a thinner gauge of the same grade of 

electrical steel. The magnitude of the eddy currents induced by the magnetic field becomes 

smaller in thinner laminations, making the motor more energy efficient. 

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

thinner steel laminations as a means of improving efficiency. Design engineers use this 

approach to achieve desired improvements in performance and efficiency. Because this design 

technique is in commercial use today, DOE considers this technology option both 

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 using 

thinner steel laminations. 

4.3.10 Anneal Steel Laminations 

Annealing the laminations can also reduce the losses in the electrical steel. This process 

subjects the laminations to an extremely high temperature to alleviate the stresses from punching 

and assembly. There is reduced stress, but also grain growth, which alleviates hysteresis losses. 

In addition to these benefits, the steels are oxidized to create a resistive coating that helps reduce 

eddy current flow and thus core losses. 

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

annealing steel laminations as a means of improving efficiency. Design engineers use this 

approach to achieve desired improvements in performance and efficiency. Because this design 

technique is in commercial use today, DOE considers this technology option both 

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 

annealing steel laminations. 

4.3.11 Additional Stack Height 

Adding electrical steel to the rotor and stator to lengthen the motor can also reduce the 

efficiency losses in steel. Lengthening the motor by increasing stack length reduces the 

magnetic flux density, which lowers the core watts lost overall. However, increasing the stack 

length affects other performance attributes of the motor, such as starting torque. Issues can arise 

when installing a more efficient motor with additional stack height because the motor becomes 

longer and therefore may not fit into applications with dimensional constraints. 

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

additional stack height as a means of improving efficiency. Design engineers use this approach 

to achieve desired improvements in performance and efficiency. Because this design technique 

is in commercial use today, DOE considers this technology option technologically feasible. 

Regarding the second screening criterion–practicable to manufacture, install, and service–DOE is 

concerned that increasing motor length makes installation of these motors too problematic. 

However, DOE recognizes that many small motor applications are not constrained by motor 

length. Thus, DOE believes that this technology option meets the second screening criterion. 

DOE is not aware of any adverse impacts on consumer utility, reliability, health, or safety 

associated with increased stack height. 

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4.3.12 High-Efficiency Lamination Materials 

Another technology option to improve the efficiency of small electric motors is using 

nontraditional lamination materials. These materials are steel alloys that contain boron or cobalt 

(e.g., Hiperco 50TMa

, vanadium permendur, amorphous metals such as METGLASb), which are 

used instead of conventional and silicon steel when assembling a stator and rotor stack. 

These materials offer lower core losses because the laminations are extremely thin and 

the magnetic permeability is extremely high. These steels are not typically used in small electric 

motors, as defined by EPCA. However, DOE is not aware of any technical impediment 

preventing their use, because these are commercially available steels used in the manufacture of 

electric motors. DOE is aware of some small electric motor designs that were prepared for a 

manufacturer using one of these high-efficiency lamination materials. Thus, DOE believes that 

such steels are technologically feasible and practicable to manufacture, install, and service, 

because of their use in mass-produced electric motors. However, DOE is concerned that there 

may not be an adequate supply of these materials to meet the manufacturing requirements of all 

the small motors manufactured in the United States today. DOE is not aware of any adverse 

impacts on product utility, product availability, health, or safety for this technology option. 

4.3.13 Better Bearings and Lubricant 

Another technology option to improve the efficiency of small electric motors is using 

better ball bearings and a lower-friction lubricant. Using improved bearings and lubricants 

minimizes mechanical resistance to the rotation of the rotor, which also extends motor lifetime. 

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

better ball bearings and lubricants as a means of improving efficiency. Design engineers use this 

approach to achieve desired improvements in performance and efficiency. Because this design 

technique is in commercial use today, DOE considers this technology option both 

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 better 

ball bearings and lubricant. 

4.3.14 More Efficient Cooling System 

Using a more efficient cooling system that circulates air through the motor is another 

technology option to improve the efficiency of small electric motors. Improving the cooling 

system reduces air resistance and associated frictional losses and decreases the operating 

temperature (and associated electrical resistance) by cooling the motor during operation. 

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

a more efficient cooling system as a means of improving efficiency. Design engineers use this 

approach to achieve desired improvements in performance and efficiency. Because this design 

a

 Registered trademark of the Carpenter Technology Corporation.
 b

 Registered trademark of Metglas, Inc., a wholly-owned subsidiary of Hitachi Metals, Ltd., Tokyo, Japan.
 

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technique is in commercial use today, DOE considers this technology option both 

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 improved 

cooling systems for small electric motors. 

4.3.15 Change Run-Capacitor Rating 

Another technology option to improve the efficiency of CSCR small electric motors is 

changing the microfarad rating of the run-capacitor. A motor design engineer will usually 

modify the run-capacitor’s rating along with the auxiliary windings of a CSCR motor to simulate 

a balanced two phase motor at full load. The combination of these changes helps to minimize 

the required current to run the motor, thereby reducing the I2

R losses 

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

changing the rating of a run-capacitor in a CSCR motor as a means of improving efficiency. 

Design engineers use this approach to achieve desired improvements in performance and 

efficiency. Because this design technique is in commercial use today, DOE considers this 

technology option both 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 improved cooling systems for small electric motors. 

4.3.16 Summary of Technology Options Not Screened Out 

Table 4.3.1 summarizes the design options that DOE did not screen out of the analysis. 

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Table 4.3.1 Design Options Not Screened Out of the Analysis 

Type of Loss to Reduce Technology Option Applied 

I

2

R 

Use a copper die-cast rotor cage 

Reduce skew on conductor cage 

Increase cross-sectional area of rotor conductor bars 

Increase end ring size 

Change gauges of copper wire in stator 

Manipulate stator slot dimensions 

Decrease the air gap between rotor and stator (down to 10 

thousandths) 

Change run-capacitor rating (CSCR motors only) 

Core 

Use improved grades of electrical steel 

Use thinner steel laminations 

Anneal steel laminations 

Add stack height (i.e., more electrical steel) 

Use high-efficiency lamination materials 

Friction and Windage Install better bearings and lubricant 

Install a more efficient cooling system 

4.4 DESIGN OPTIONS SCREENED OUT OF THE ANALYSIS 

DOE screened out the following design options from further consideration because they 

do not meet the screening criteria. 

4.4.1 Air Gap Between Rotor and Stator 

Reducing the air gap between the rotor and stator can improve motor efficiency. For 

small electric motors, the air gap is commonly set at 15 thousandths of an inch. Although 

reducing this air gap can improve efficiency, there is some point at which the air gap is too tight 

and becomes impracticable to manufacture. DOE believes that air gaps below 12.5 thousandths 

of an inch would exceed the threshold for practicability to manufacture. 

Considering the four screening criteria for this technology option, DOE screened out 

decreasing the radial air gap below 12.5 thousandths of an inch as a means of improving 

efficiency. DOE considers this technology option technologically feasible, because smaller air 

gaps do not present any technological barrier. DOE also is not aware of any adverse impacts on 

health or safety associated with reducing the radial air gap below 12.5 thousandths of an inch. 

However, DOE believes that this technology option fails the screening criterion of being 

practicable to manufacture, install, and service. Such a tight air gap may cause problems in 

manufacturing and service, with the rotor potentially coming into contact with the stator. This 

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technology option fails the screening criterion of adverse impacts on consumer utility and 

reliability, because the motor may experience higher failure rates in service when the 

manufactured air gaps are less than 12.5 thousandths of an inch. 

4.4.2 Plastic Bonded Iron Powder 

Plastic bonded iron powder (PBIP) could cut production costs while increasing the output 

of electric motors. Although other researchers may be working on this technology option, DOE 

is aware of a research team at Lund University in Sweden that published a paper about PBIP. 

This technology option is based on an iron powder alloy that is suspended in plastic, and is used 

in certain motor applications such as fans, pumps, and household appliances.1 The compound is 

then shaped into motor components using a centrifugal mold, reducing the number of 

manufacturing steps. Researchers claim that this technology option could cut losses by as much 

as 50 percent. The Lund University team already produces inductors, transformers, and 

induction heating coils using PBIP, but has not yet produced a small electric motor. In addition, 

it appears that PBIP technology is aimed at torus, claw-pole, and transversal flux motors, none of 

which fit EPCA’s definition of small motors. 

Considering the four screening criteria for this technology option, DOE screened out 

PBIP as a means of improving efficiency. Although PBIP has the potential to improve efficiency 

while reducing manufacturing costs, DOE does not consider this technology option 

technologically feasible, because it has not been incorporated into a working prototype of a small 

electric motor. Also, DOE is uncertain whether the material has the structural integrity to form 

into the necessary shape of a small electric motor steel frame. Furthermore, DOE is uncertain 

whether PBIP is practicable to manufacture, install, and service, because a prototype PBIP small 

electric motor has not been made and little information is available on the ability to manufacture 

this technology to make a judgment. However, DOE is not aware of any adverse impacts on 

product utility, product availability, health, or safety that may arise from the use of PBIP in small 

electric motors. 

4.4.3 Summary of Technology Options Screened Out of the Analysis 

Table 4.4.1 shows the criteria DOE used to screen radial air gaps below 10 thousandths 

of an inch, PBIP, and permanent magnet electric motors out of the analysis. 

Table 4.4.1 Design Options Screened Out of the Analysis 

Design Option Screening Criteria 

Radial Air Gaps Below 10 Thousandths of 

an Inch 

Practicability to manufacture, install, and service; 

adverse impacts on product utility or product 

availability 

PBIP Technological feasibility 

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REFERENCES 

1

 Horrdin, H., and E. Olsson. Technology Shifts in Power Electronics and Electric Motors for 

Hybrid Electric Vehicles: A Study of Silicon Carbide and Iron Powder Materials. 2007. 

Chalmers University of Technology. Göteborg, Sweden. 

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