ASTM D4881-01
(Test Method)Standard Test Method for Thermal Endurance of Varnished Fibrous- or Film-Wrapped Magnet Wire
Standard Test Method for Thermal Endurance of Varnished Fibrous- or Film-Wrapped Magnet Wire
SCOPE
1.1 This test method covers the determination of thermal endurance of rectangular and square fibrous- or film-wrapped magnet wire coated with an insulating varnish.
1.2 The values given in SI units are the standard. The values given in parentheses are for information only.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. A specific precautionary statement is given in Section 5.
Note 1—There is no similar or equivalent IEC Standard.
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An American National Standard
Designation:D4881–01
Standard Test Method for
Thermal Endurance of Varnished Fibrous- or Film-Wrapped
1
Magnet Wire
This standard is issued under the fixed designation D 4881; 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.
1. Scope 4. Significance and Use
1.1 This test method covers the determination of thermal 4.1 Individual varnishes may behave differently when ap-
endurance of rectangular and square fibrous- or film-wrapped plied to the same fibrous- or film-wrapped magnet wire and
magnet wire coated with an insulating varnish. aged at elevated temperatures. Likewise, a varnish may not
1.2 The values given in SI units are the standard.The values behave the same when applied to different types of fibrous or
given in parentheses are for information only. film-wrapped magnet wires and aged at elevated temperatures.
1.3 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use. A specific precau-
tionary statement is given in Section 5.
NOTE 1—There is no similar or equivalent IEC Standard.
2. Referenced Document
2.1 ASTM Standards:
2
D 1711 Terminology Relating to Electrical Insulation
D 2307 Test Method for Relative Thermal Endurance of
2
Film-Insulated Round Magnet Wire
3. Terminology
3.1 Definitions of Terms Specific to This Standard:
3.1.1 varnish, electrical insulating, n— a liquid resin sys-
tem that is applied to and cured on electrical components
providing electrical, mechanical, and environmental protec-
tion.
FIG. 1 Jig for Forming Wire
3.1.1.1 Discussion—There are two types of electrical insu-
lating varnishes—solvent-containing and solventless. Solvent-
containing types are solutions, dispersions, or emulsions of a
5. Safety Precautions
polymer or a mixture of polymers in a volatile, nonreactable
5.1 It is unsafe to use varnish at temperatures above the
liquid. Solventless types are liquid resin systems free of
flash point without adequate ventilation, especially if the
volatile, nonreactable solvents.
possibility exists that flames or sparks are present. Store
3.1.2 Refer to Terminology D 1711 for definitions of other
varnish in sealed containers.
terms.
6. Test Specimens
6.1 Construction of Test Specimens:
1
This test method is under the jurisdiction of ASTM Committee D09 on
6.1.1 Cut two 250-mm (10-in.) lengths of wire for each
Electrical and Electronic Insulating Materials and is the direct responsibility of
Subcommittee D09.01 on Electrical Insulating Varnishes, Powders, and Encapsu-
specimen to be made.
lating Compounds.
6.1.2 Form each length in a fixture as shown in Fig. 1.
Current edition approved Sept. 10, 2001. Published November 2001. Originally
6.1.3 Prepare a test specimen by placing the two formed
published as D 4881 – 88. Last previous edition D 4881 – 97.
2
Annual Book of ASTM Standards, Vol 10.01. wires together back to back and wrap tightly with glass yarn
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1
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D4881
over the middle 6-in. (150-mm) section. The glass yarn shall procedure in Test Method D 2307.
have a gap between turns and there must be intimate contact of
8. Calculation
the two wires.
8.1 After all specimens have failed, calculate the average
6.1.4 Prepare ten specimens for each test temperature.
life at each test temperature in accordance with Test Method
6.2 Varnishing the Test Specimens:
D 2307.
6.2.1 Adjust the consistency of a solvent-containing varnish
8.2 Plot the results using the average life calculated for each
to give a 0.025 6 0.005-mm (0.0010 6 0.0002-in.) cured film
temperature as the ordinate on a logarithmic time scale and the
on each side of a 0.13-mm (0.005-in.) copper strip withdrawn
reciprocal of the absolute temperature as the abscissa.
at a rate of 100 mm/min (4 in./min). Use solventless varnish as
8.3 Calculate the temperature index using the procedure
received.
givenintheAppendixofTestMethodD 2307.Thetemperature
6.2.2 Submerge the test specimens vertically in the varnish
index is calculated at 20 000 h.
to be tested. Withdraw them at a rate of 100 mm/min (4
in./min). Drain the test specimens for 10 to 12 min. Cure
9. Report
according to the manufacturer’s recommendations. If a
9.1 Report the following information:
solvent-containing varnish is being tested, the test speci
...
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