ASTM D4881-05(2012)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: D4881 − 05 (Reapproved 2012)
Standard Test Method for
Thermal Endurance of Varnished Fibrous- or Film-Wrapped
Magnet Wire
This standard is issued under the fixed designation D4881; 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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope liquid. Solventless types are liquid resin systems free of
volatile, nonreactable solvents.
1.1 This test method covers the determination of thermal
endurance of rectangular and square fibrous- or film-wrapped 3.1.2 Refer to Terminology D1711 for definitions of other
magnet wire coated with an insulating varnish. terms.
1.2 The values given in SI units are the standard.The values
4. Significance and Use
given in parentheses are for information only.
4.1 Individual varnishes behave differently when applied to
1.3 This standard does not purport to address all of the
the same fibrous- or film-wrapped magnet wire when exposed
safety concerns, if any, associated with its use. It is the
to elevated temperatures. Likewise, a varnish does not always
responsibility of the user of this standard to establish appro-
behave the same when applied to different types of fibrous or
priate safety and health practices and determine the applica-
film-wrapped magnet wires and when exposed to elevated
bility of regulatory limitations prior to use. A specific precau-
temperatures.
tionary statement is given in Section 5.
5. Safety Precautions
NOTE 1—There is no similar or equivalent IEC Standard.
5.1 It is unsafe to use varnish at temperatures above the
2. Referenced Document
flash point without adequate ventilation, especially if the
possibility exists that flames or sparks are present. Store
2.1 ASTM Standards:
varnish in sealed containers.
D1711 Terminology Relating to Electrical Insulation
D2307 Test Method for Thermal Endurance of Film-
6. Test Specimens
Insulated Round Magnet Wire
6.1 Construction of Test Specimens:
D3353 Test Methods for Fibrous-Insulated Magnet Wire
6.1.1 Cut two 250-mm (10-in.) lengths of wire for each
3. Terminology specimen to be made.
6.1.2 Determine the thickness dimensions per Test Method
3.1 Definitions of Terms Specific to This Standard:
D3353.
3.1.1 varnish, electrical insulating, n—aliquidresinsystem
6.1.3 Form each length in a fixture as shown in Fig. 1.
that is applied to and cured on electrical components providing
6.1.4 Prepare a test specimen by placing the two formed
electrical, mechanical, and environmental protection.
wires together back to back and wrap tightly with a minimum
3.1.1.1 Discussion—There are two types of electrical insu-
of6turnsofglassyarnoverthemiddle6-in.(150-mm)section.
lating varnishes: solvent-containing and solventless. Solvent-
The glass yarn shall have a gap between turns and there must
containing types are solutions, dispersions, or emulsions of a
be intimate contact of the two wires.
polymer or a mixture of polymers in a volatile, nonreactable
6.1.5 Prepare ten specimens for each test temperature.
6.2 Varnishing the Test Specimens:
1 6.2.1 Adjust the consistency of a solvent-containing varnish
This test method is under the jurisdiction of ASTM Committee D09 on
Electrical and Electronic Insulating Materials and is the direct responsibility of
to give a 0.025 6 0.005-mm (0.0010 6 0.0002-in.) cured film
Subcommittee D09.01 on Electrical Insulating Varnishes, Powders and Encapsulat-
on each side of a 0.13-mm (0.005-in.) copper strip withdrawn
ing Compounds.
at a rate of 100 mm/min (4 in./min). Use solventless varnish as
Current edition approved Jan. 1, 2012. Published January 2012. Originally
received.
approved in 1988. Last previous edition approved in 2005 as D4881 – 05. DOI:
10.1520/D4881-05R12.
6.2.2 Submerge the test specimens vertically in the varnish
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
to be tested. Withdraw them at a rate of 100 mm/min (4
contact
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