ASTM D3145-03

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An American National Standard
Designation:D3145–03
Standard Test Method for
Thermal Endurance of Electrical Insulating Varnishes by the
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Helical Coil Method
This standard is issued under the fixed designation D 3145; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope D 5423 Specification for Forced-Convection Laboratory
Ovens for Evaluation of Electrical Insulation
1.1 Thistestmethodcoversthedeterminationofthethermal
D 6054 Practice for Conditioning Electrical Insulating Ma-
endurance of electrical insulating varnishes alone or in com-
terials for Testing
binations with magnet wire insulation. Changes in the helical
2.2 International Electrotechnical Commission Publica-
coil bond strength are used as the test criteria. The coils can be
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tions:
made from bare aluminum or copper wire, or from film- or
IEC 60216 Guide for the Determination of Thermal Endur-
fiber-insulated magnet wire.
ance Properties of Electrical Insulation Materials (Part 1)
1.2 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
3. Terminology
responsibility of the user of this standard to establish appro-
3.1 Definitions
priate safety and health practices and determine the applica-
3.1.1 For definitions of terms used in the test method, refer
bility of regulatory limitations prior to use. For a specific
to Terminology D 1711.
precautionary statement, see Section 7.
3.2 Definitions of Terms Specific to This Standard:
1.3 ThevaluesstatedinSIunitsarethestandard.Thevalues
3.2.1 bond strength, n—a measure of the force required to
given in parentheses are for information only.
separate surfaces which have been bonded together.
NOTE 1—There is no similar or equivalent IEC standard.
3.2.2 magnet wire, n—a metal electrical conductor, covered
with electrical insulation, for use in the assembly of electrical
2. Referenced Documents
inductive apparatus such as coils for motors, transformers,
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2.1 ASTM Standards:
generators, relays, magnets, etc.
D 1711 Terminology Relating to Electrical Insulation
3.2.2.1 Discussion—The electrical insulation is usually
D 1932 Test Method for Thermal Endurance of Flexible
composed of a film covering formed from a magnet wire
Electrical Insulating Varnishes
enamel applied over a bare conductor. In some specific
D 2307 Test Method for Thermal Endurance of Film-
applications, fibrous coverings, either taped or linear filament
Insulated Round Magnet Wire
served, are also used as electrical insulation.
D 2519 Test Method for Bond Strength of Electrical Insu-
3.2.3 varnish, electrical insulating, n— a liquid resin sys-
lating Varnishes by the Helical Coil Test
tem that is applied to and cured on electrical components
D 3251 Test Method forThermal Endurance Characteristics
providing electrical, mechanical and environmental protection.
of Electrical Insulating Varnishes Applied Over Film-
3.2.3.1 Discussion—There are two types of electrical insu-
Insulated Magnet Wire
lating varnishes—solvent-containing and solventless. Solvent-
D 3850 Test Method for Rapid Thermal Degradation of
containing types are solutions, dispersions or emulsions of a
Solid Electrical Insulating Materials by Thermogravimet-
polymer or a mixture of polymers in a volatile, nonreactable
ric Method (TGA)
liquid. Solventless types are liquid resin systems free of
volatile, nonreactable solvents.
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This test method is under the jurisdiction of ASTM Committee D09 on
4. Summary of Test Method
Electrical and Electronic Insulating Materials and is the direct responsibility of
Subcommittee D09.01 on Electrical Insulating Varnishes, Powders, and Encapsu-
4.1 Flexural strength of the helical coils is measured peri-
lating Compounds.
odically after exposure to several exposure temperatures. The
Current edition approved Dec. 1, 2003. Published January 2004. Originally
approved in 1973. Last previous edition approved in 2001 as D 3145 – 01.
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For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
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Standards volume information, refer to the standard’s Document Summary page on Available from American National Standards Institute, 25 W. 43rd St., 4th
the ASTM website. Floor, New York, NY 10036.
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D3145–03
time to reach an arbitrarily selected value of bond streng
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