Electrical insulation for electric/hybrid electric vehicles

In the exciting new field of alternatively fueled vehicles, only DuPont has the necessary combination of design expertise, evaluation technology and superior electrical insulation material—DuPont™ Nomex®—to help meet original equipment manufacturers’ (OEMs’) needs.

Exceptional thermal stabilityDuPont™ Nomex® has an Underwriters Laboratories (UL) thermal rating

of 220°C and a long history of proven endurance under high thermal

stress. This high-temperature durability helps to allow miniaturization

and/or higher power density of electrical drive motors and enables

long-term electrical dependability.

This also helps OEMs to reduce the size and weight of components

such as traction motors, which in turn can increase fuel efficiency.

The effects of long-term exposure to high temperature on important

electrical and mechanical properties of DuPont™ Nomex® are shown

in Figures 1 and 2.

Superior mechanical strengthThe superior mechanical strength and resilience of DuPont™ Nomex®

insulation (refer to Table I) help extend the service life of rotating

equipment, such as traction motors, which are subjected to harsh

operating conditions that include severe shock and vibration, as well

as abrasion caused by thermal expansion and centrifugal forces.

An added benefit of the superior mechanical strength of

DuPont™ Nomex® is the manufacturing efficiencies that can

be gained from automatic insertion of slot liners.

DuPont™ Nomex® has a long history as an electrical insulation material of choice for traction motors, automotive motors and automotive generators due to its proven performance and reliability. Based on its track record of helping OEMs around the world to improve performance and prevent premature failures in these applications, OEMs are now choosing DuPont™ Nomex® to help them meet the increased power density requirements and harsh operating conditions of motors and generators used in (H)EVs.

100 140 180 220 300 340 380 100 140 180 220 300 340 380

Temperature, ˚C Temperature, ˚C

Figure 2. Effect of prolonged exposure to high temperature on the initial strength of DuPont™ Nomex®. (Tested per UL-746)

Figure 1. Effect of prolonged exposure to high temperature on the dielectric strength of DuPont™ Nomex®. (ASTM D-1830, curved electrodes)

106

105

104

103

102

106

105

104

103

102

Agi

ng ti

me,

hou

rs to

12

kV/m

m (3

00 V

/mil)

diel

ectr

ic s

tren

gth

Agi

ng ti

me,

hou

rs to

50%

of i

nitia

l st

reng

th in

mac

hine

dir

ectio

n

Log time =8262

˚C + 273– 11,44 Log time =

7461

˚C + 273– 10,40

Excellent dielectric strengthDuPont™ Nomex® features excellent electrical properties and endures electrical stresses that are

commonly encountered in (H)EVs due to the use of inverters. As shown in Table II, DuPont™ Nomex®

has excellent dielectric strength. It is important to note that these values differ from long-term

strength potential. DuPont recommends that continuous stresses in transformers not exceed

1.6 kV/mm (40 V/mil) in order to minimize the risk of partial discharges (corona). DuPont has

materials designed for applications where corona is present, should this be necessary.

Excellent chemical stabilityDecades of experience in similar types of automotive motors and generators have proven that

DuPont™ Nomex® is compatible with a wide range of chemicals, including virtually all classes

of electrical varnishes and adhesives, as well as the oils and automatic transmission fluids often

used in (H)EVs.

Design and testing expertiseAs a leader in electrical insulation systems for more than 40 years, DuPont has earned a strong

reputation for evaluating the performance of insulation used in equipment. Our experts are drawing

on this experience to help global OEMs translate their performance needs into measurable criteria,

even designing new test protocols and testing equipment when necessary.

DuPont experts in motor design are also working with top OEMs around the world to help them

develop specific solutions that will optimize their motor designs and help advance this evolving industry.

Table I. Typical mechanical properties of DuPont™ Nomex®

Nominal thickness mil (mm)

2(0.05)

3(0.08)

5(0.13)

7(0.18)

10(0.25)

12(0.30)

15(0.38)

20(0.51)

24(0.61)

25.5(0.65)

29(0.73)

30(0.76)

Test method

Tensile strength, N/cm MD XD

3918

6532

13766

219111

285152

378196

459252

606354

741497

758524

860630

841595

ASTM D-828

Elongation, % MD XD

96

118

1512

1814

1915

2217

1914

2016

1814

1916

1612

1713

ASTM D-828

Elmendorf Tear, N MD XD

0.81.6

1.22.3

3.45.2

3.97.4

6.010.8

7.414.2

9.517.2

14.223.7

N/AN/A

N/AN/A

N/AN/A

N/AN/A

TAPPI-414

Initial Tear Strength,1 N MD XD

116

168

3317

5027

7142

9355

11674

163113

201157

209159

252199

251200

ASTM D-1004

MD = machine direction of paper XD = cross direction of paper 1Data presented for Initial Tear Strength is listed in the direction of the sample per ASTM D-1004. The tear is 90 degrees to sample direction; hence, for papers with a higher reported MD ITR, the paper will be tougher to tear in the cross direction.

Table II. Typical Electrical Properties of DuPont™ Nomex®

Nominal thickness mil (mm)

2(0.05)

3(0.08)

5(0.13)

7(0.18)

10(0.25)

12(0.30)

15(0.38)

20(0.51)

24(0.61)

25.5(0.65)

29(0.73)

30(0.76)

Dielectric strength, AC rapid rise1

V/mil kV/mm

43017

55022

68027

84033

81532

82032

83033

81032

80031

73029

75030

68027

Dielectric constant2 at 60 Hz 1.6 1.6 2.4 2.7 2.7 2.9 3.2 3.4 3.7 N/A 3.7 3.7

Dissipation factor2 at 60 Hz (x10-3) 4 5 6 6 6 7 7 7 7 N/A 7 7

1ASTM D-149 using 50 mm (2 in.) electrodes, rapid rise; corresponds with IEC 60243-1 sub-clause 9.1, except for electrode set-up of 50 mm (2 in.). These rapid rise values represent 10 to 20 seconds of withstand strength.

2ASTM D-150

Product safety information is available upon requestThis information corresponds to our current knowledge on the subject. It is offered solely to provide possible suggestions for your own experimentations. It is not intended, however, to substitute for any testing you may need to conduct to determine for yourself the suitability of our products for your particular purposes. This information may be subject to revision as new knowledge and experience become available. Since we cannot anticipate all variations in actual end-use conditions, DUPONT MAKES NO WARRANTIES AND ASSUMES NO LIABILITY IN CONNECTION WITH ANY USE OF THIS INFORMATION. Nothing in this publication is to be considered as a license to operate under or a recommendation to infringe any trademark or patent right.

Please note: The properties in this sell sheet are typical or average values and should not be used as specification limits. Unless otherwise noted, all properties were measured in air under “standard” conditions (in equilibrium at 23°C, 50% relative humidity). Note that, like other products of papermaking technology, DuPont™ Nomex® papers have somewhat different properties in the papermaking machine direction (MD) compared to the cross direction (XD). In some applications (for example, motor slot liners), it is necessary to orient the paper in the optimum direction to obtain its maximum potential performance.

Copyright © 2011 DuPont. The DuPont Oval Logo, DuPont™, The miracles of science™, and Nomex® are trademarks or registered trademarks of E.I. du Pont de Nemours and Company or its affiliates. All rights reserved. K-24364 4/11

To learn more about how DuPont™ Nomex® electrical insulation can help you improve the performance and reliability of motors and generators for (H)EVs, call 1.800.931.3456 or visit www.nomex.dupont.com