ASTM A717/A717M-12(2022)

Standard Test Method for Surface Insulation Resistivity of Single-Strip Specimens

SIGNIFICANCE AND USE
5.1 This test method is particularly suitable for quality control in the application of insulating coatings.  
5.2 Surface insulation resistivity is evaluated from a dc current that can range from 0 (perfect insulator) to 1 A (perfect conductor).  
5.3 Single readings should not be considered significant since the nature of the test device and specimen are such that successive measurements of a specimen often yield different values.
SCOPE
1.1 This test method covers a means of testing the surface insulation resistivity of single strips or punchings of flat-rolled electrical steel under predetermined conditions of voltage, pressure, and temperature.  
1.2 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system are not necessarily exact equivalents; therefore, to ensure conformance with the standard, each system shall be used independently of the other, and values from the two systems shall not be combined.  
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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.4 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

• Status: Published
• Publication Date: 30-Sep-2022
• ICS: 29.035.20 - Plastics and rubber insulating materials
• Technical Committee: A06 - Magnetic Properties
• Drafting Committee: A06.01 - Test Methods

Relations

• Refers: ASTM A34/A34M-06(2012) - Standard Practice for Sampling and Procurement Testing of Magnetic Materials
• Effective Date: 01-Nov-2012
• Refers: ASTM A34/A34M-06 - Standard Practice for Sampling and Procurement Testing of Magnetic Materials
• Effective Date: 01-Nov-2006
• Refers: ASTM A34/A34M-01 - Standard Practice for Sampling and Procurement Testing of Magnetic Materials
• Effective Date: 10-Oct-2001
• Refers: ASTM A34/A34M-96 - Standard Practice for Sampling and Procurement Testing of Magnetic Materials
• Effective Date: 10-Oct-2001

Overview

ASTM A717/A717M-12(2022) specifies the standard test method for measuring the surface insulation resistivity of single-strip specimens, notably flat-rolled electrical steel. This internationally recognized ASTM standard provides a reliable means for assessing the effectiveness of insulating coatings via controlled testing variables, including voltage, pressure, and temperature. Primarily, this test method supports quality control and process monitoring in the manufacture and application of insulating coatings for electrical steels. Both SI and inch-pound units are permitted, but measurements in each system must remain separate for compliance.

Surface insulation resistivity testing is essential for understanding the electrical insulation characteristics of coatings applied to electrical steel, which plays a crucial role in applications such as transformers, motors, and other electrical devices where insulating properties affect energy efficiency and safety.

Key Topics

• Surface Insulation Resistivity: Measures how well an insulating coating resists current flow across the surface of a single strip specimen. The result reflects the effectiveness of the coating under predefined test conditions.
• Test Method Procedure:
  • Utilizes a specialized device (commonly a Franklin tester) with ten metallic contacts applied to the specimen.
  • DC current is measured between the contacts and the base metal at a specified voltage (commonly 0.5V) and pressure (commonly 300 psi/2.1 MPa).
  • The test can be performed at room temperature or elevated temperatures (up to 150 °C / 300 °F), as applicable.
  • Multiple readings are recommended due to the possible variation in results from a single specimen.
• Sampling and Preparation:
  • Specimen size should typically be at least 2 x 5 inches (50 x 130 mm).
  • A minimum of five specimen strips is recommended for representative results.
  • Sampling and preparation should comply with referenced practices for accuracy.
• Data Interpretation:
  • Average current readings are used to report insulation performance.
  • Surface insulation resistivity is calculated from the average ammeter readings.
  • Single measurements are not considered definitive due to the inherent variability of the test process.

Applications

• Quality Control: The test method is vital in quality control during the application of insulating coatings on electrical steel strips, ensuring coatings meet required insulation performance for use in electrical equipment.
• Manufacturing Verification: Enables material producers and users to verify that insulating coatings conform to industry and client specifications.
• Material Development: Supports research and development of new insulation materials by providing a standardized method for performance evaluation.
• Performance Assessment: Used to evaluate the aging or degradation of insulation during routine maintenance or investigation of underperforming components in transformers, electric motors, and generators.

Related Standards

• ASTM A34/A34M - Practice for Sampling and Procurement Testing of Magnetic Materials: Referenced for proper sampling procedures associated with the electrical steel specimen preparation.
• ASTM A717/A717M-12(2022) is developed in accordance with international standardization principles, aligning with requirements set by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

For further guidance or updated methods, consult the latest edition via the official ASTM website or other referenced ASTM International documents related to electrical steel testing and insulation measurements.

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: A717/A717M − 12 (Reapproved 2022)
Standard Test Method for
Surface Insulation Resistivity of Single-Strip Specimens
This standard is issued under the fixed designationA717/A717M; 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 specimen.Itisnotthesameasthetermsinterlaminarresistivity
and stack resistivity, which refer to the average resistivity of
1.1 This test method covers a means of testing the surface
two adjacent insulative surfaces in contact with each other.
insulation resistivity of single strips or punchings of flat-rolled
electrical steel under predetermined conditions of voltage,
3.1.2 The apparatus is popularly known as a Franklin tester.
pressure, and temperature.
1.2 The values stated in either SI units or inch-pound units 4. Summary of Test Method
are to be regarded separately as standard. The values stated in
4.1 Ten metallic contacts of fixed area are applied to one of
each system are not necessarily exact equivalents; therefore, to
thesurfacesofthespecimenandelectricalcontactismadewith
ensure conformance with the standard, each system shall be
the base metal by two drills. The effectiveness of the surface
used independently of the other, and values from the two
insulation is then indicated by a measurement of average
systems shall not be combined.
electrical current flowing between the contacts and the base
1.3 This standard does not purport to address all of the
metal under specified applied voltage. This measurement can
safety concerns, if any, associated with its use. It is the
be used directly as an indicator of insulation quality or may be
responsibility of the user of this standard to establish appro-
converted to an apparent surface insulation resistivity value.
priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use.
5. Significance and Use
1.4 This international standard was developed in accor-
5.1 This test method is particularly suitable for quality
dance with internationally recognized principles on standard-
control in the application of insulating coatings.
ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom-
5.2 Surface insulation resistivity is evaluated from a dc
mendations issued by the World Trade Organization Technical
current that can range from 0 (perfect insulator) to 1A(perfect
Barriers to Trade (TBT) Committee.
conductor).
2. Referenced Documents
5.3 Single readings should not be considered significant
since the nature of the test device and specimen are such that
2.1 ASTM Standards:
successive measurements of a specimen often yield different
A34/A34M Practice for Sampling and Procurement Testing
values.
of Magnetic Materials
3. Terminology
6. Apparatus
3.1 Definitions of Terms Specific to This Standard:
6.1 The apparatus, as shown in Fig. 1 and Fig. 2, shall
3.1.1 surface insulation resistivity—refers to the effective
consist of a contact unit or test head which is attached to the
resistivity of a single insulative layer tested between applied
head of a hydraulic press. Its associated measuring equipment,
bare metal contacts and the base metal of the insulated test
which may be remotely located, includes an ammeter,
voltmeter, and voltage regulated dc power supply. When
measurements are to be made at elevated temperatures, the
This test method is under the jurisdiction of ASTM Committee A06 on
platen beneath the specimen is heated and controlled. Detailed
MagneticPropertiesandisthedirectresponsibilityofSubcommitteeA06.01onTest
descriptions of the various components are given in AnnexA1.
Methods.
Current edition approved Oct. 1, 2022. Published October 2022. Originally
approved in 1975. Last previous edition approved in 2018 as A717/A717M – 12
7. Sampling
(2018). DOI: 10.1520/A0717_A0717M-12R22.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
7.1 Samples shall be representative of the steel and shall be
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
cut in a manner to assure representative sampling as described
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. in Practice A34/A34M.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
A717/A717M − 12 (2022)
FIG. 1 Apparatus of Surface Insulation Resistivity Measurement
9.4 The recommended standard test temperatures are room
temperature and 300 °F [150 °C]. Other temperatures and the
sequence of temperatures, depending upon the application,
may be agreed upon by the producer and the user.
9.5 When tests are made at elevated temperatures allow
sufficient time (usually 30 s) to heat the specimen to the
FIG. 2 Diagram of Connections for Contacts and Resistors
specified temperature.
9.6 When the insulation may be hygroscopic, a conditioning
procedure immediately prior to testing should be mutually
8. Test Specimen
agreed upon by the producer and the user.
8.1 Thewidthandlengthofaspecimenstripshallbegreater
9.7 Place the specimen on the platen beneath the test head
than the width and length respectively of the assembly of
and position it so that all contacts are within the test area when
contacts. The suggested minimum specimen size is 2 by 5 in.
the test head is brought in contact with the specimen.Apply the
[50 by 130 mm].
specified pressure. Check that the voltage is 0.50 V and read
8.2 A minimum of five specimen strips is recommended.
the ammeter.
8.3 By mutual agreement between the producer and the
10. Calculations
user, tests may be run on Epstein test strips. The Epstein
specimens may be less satisfactory than the minimum size
10.1 The average of electrical current measurements is
specimen suggested in 8.1 because of the tilting effect due to
usually acceptable for evaluating surface insulation. Average
burrs, shearing strains, and disturbances in the coating.
the current readings for each surface. The reported value for a
sample shall be the average of both surfaces.
9. Procedure
10.2 The two surface insulation resistivity of the t
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