ASTM A937/A937M-12(2019)
(Test Method)Standard Test Method for Determining Interlaminar Resistance of Insulating Coatings Using Two Adjacent Test Surfaces
Standard Test Method for Determining Interlaminar Resistance of Insulating Coatings Using Two Adjacent Test Surfaces
SIGNIFICANCE AND USE
5.1 This test method is particularly suitable for quality control in the application of insulating coatings. This test method measures the interlaminar resistance of insulating coatings, as defined in 3.1.4. Interlaminar resistance is the measure of the insulating quality of the coating. Interlaminar resistance is reported in units of kΩ.
5.2 The interlaminar resistance determined in accordance with this test method is not the same quantity determined by Test Method A717/A717M.
5.3 This test method is particularly useful for electrical steels coated with inorganic insulating coatings having surface insulation resistivities in excess of 0.3 kΩ·cm2 [30 kΩ·mm2] when tested using Test Method A717/A717M (a Franklin current less than 0.02 A). This test method can readily be extended to any range of insulation resistivity that the equipment comprising the two-surface tester allows. For the equipment specified herein, the maximum measurable resistance is 1200 kΩ for the 10-μA current setting and 12 000 kΩ for the 1-μA current setting; the maximum voltage for the test system is 12 V.
5.4 Repeat readings on the same set of two electrical steel laminations using different contact positions, as well as the testing of multiple laminations from the same lot of electrical steel, are recommended. Several readings are suggested because the coating thickness may vary across the surface of a given electrical steel lamination. Additionally, the coating thickness may vary across several laminations taken from the same lot of electrical steel. Such variations in coating thickness are likely to yield variations in the measured interlaminar resistance. The required number of readings depends on the nature of the coating and the accuracy required.
SCOPE
1.1 This test method covers a means of testing the interlaminar resistance of electrically insulating coatings as applied to adjacent laminations of flat-rolled electrical steel, under predetermined conditions of voltage, pressure and temperature. It indicates the effectiveness of surface coatings on electrical sheet steels for limiting interlaminar losses in electrical machinery. The interlaminar resistance is measured directly in units of resistance (kΩ).
1.2 This test method is particularly useful for, but not limited to, electrical steels coated with inorganic insulating coatings.
1.3 The values and equations stated in customary (cgs-emu and inch-pound) or SI units are to be regarded separately as standard. Within this standard, SI units are shown in brackets. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in nonconformance with this standard.
1.4 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
General Information
Relations
Standards Content (Sample)
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: A937/A937M −12 (Reapproved 2019)
Standard Test Method for
Determining Interlaminar Resistance of Insulating Coatings
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Using Two Adjacent Test Surfaces
This standard is issued under the fixed designationA937/A937M; the number immediately following the designation indicates the year
of original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.
A superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2. Referenced Documents
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1.1 This test method covers a means of testing the inter- 2.1 ASTM Standards:
laminar resistance of electrically insulating coatings as applied A34/A34MPractice for Sampling and Procurement Testing
to adjacent laminations of flat-rolled electrical steel, under of Magnetic Materials
predeterminedconditionsofvoltage,pressureandtemperature. A717/A717MTestMethodforSurfaceInsulationResistivity
It indicates the effectiveness of surface coatings on electrical of Single-Strip Specimens
sheet steels for limiting interlaminar losses in electrical ma-
3. Terminology
chinery. The interlaminar resistance is measured directly in
units of resistance (kΩ). 3.1 Definitions of Terms Specific to This Standard:
3.1.1 bad contact—acontactwhichresultsinavoltagedrop
1.2 This test method is particularly useful for, but not
in excess of 0.6 V as described in 6.1.3.
limited to, electrical steels coated with inorganic insulating
coatings. 3.1.2 exposed test surface—the insulating top surface of the
top lamination or the insulating bottom surface of the bottom
1.3 The values and equations stated in customary (cgs-emu
lamination of the test specimen.
and inch-pound) or SI units are to be regarded separately as
3.1.3 four-terminal measuring technique, often referred to
standard. Within this standard, SI units are shown in brackets.
as four-probe measuring technique—a common method to
Thevaluesstatedineachsystemmaynotbeexactequivalents;
measure resistance when a high degree of accuracy is re-
therefore,eachsystemshallbeusedindependentlyoftheother.
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quired. In this standard, the circuit configuration for this
Combining values from the two systems may result in noncon-
technique is referred to as a four-probe configuration.Inthe
formance with this standard.
two-surface tester, this configuration features two probes con-
1.4 This standard does not purport to address all of the
nected to the top lamination test surface and two probes
safety concerns, if any, associated with its use. It is the
connected to the bottom lamination test surface. One of the
responsibility of the user of this standard to establish appro-
probesineachpaircarriesthemeasuringcurrent,andtheother
priate safety, health, and environmental practices and deter-
providesacontactforthevoltagemeasurement.Becauseofthe
mine the applicability of regulatory limitations prior to use.
extremely high impedance of the measuring circuit, very little
1.5 This international standard was developed in accor-
current flows through the voltage contacts, and thus very little
dance with internationally recognized principles on standard-
voltage is produced across the contacts to influence the true
ization established in the Decision on Principles for the
reading,thatis,anyeffectfromcontactresistanceisavoidedor
Development of International Standards, Guides and Recom-
reduced to a negligible amount. The two-surface tester has
mendations issued by the World Trade Organization Technical
provision to check the integrity of the contacts made between
Barriers to Trade (TBT) Committee.
the probes and the test surfaces.
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This test method is under the jurisdiction of ASTM Committee A06 on For referenced ASTM standards, visit the ASTM website, www.astm.org, or
MagneticPropertiesandisthedirectresponsibilityofSubcommitteeA06.01onTest contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Methods. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved April 1, 2019. Published April 2019. Originally the ASTM website.
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approved in 1995. Last previous edition approved in 2012 as A937/A937M–12. Harris,F.K., Electrical Measurements,RobertE.KriegerPublishingCompany,
DOI: 10.1520/A0937_A0937M-12R19. Huntington, New York, 1975, pp. 220–224.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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A937/A937M − 12 (2019)
3.1.4 interlaminar resistance—theaverageresistanceoftwo current source using metallic contacts (drill bits). The tester
adjacent insulating surfaces i
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