ASTM A717/A717M-95
(Test Method)Standard Test Method for Surface Insulation Resistivity of Single-Strip Specimens
Standard Test Method for Surface Insulation Resistivity of Single-Strip Specimens
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 customary units (cgs-emu and inch-pound) or SI units are to be regarded separately as standard. Within the text, the SI units are shown in brackets. The values stated in each system are not exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in nonconformance with the specification.
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.
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Designation: A 717/A 717M – 95 An American National Standard
Standard Test Method for
Surface Insulation Resistivity of Single-Strip Specimens
This standard is issued under the fixed designation A 717/A 717M; 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 the base metal by two drills. The effectiveness of the surface
insulation is then indicated by a measurement of average
1.1 This test method covers a means of testing the surface
electrical current flowing between the contacts and the base
insulation resistivity of single strips or punchings of flat-rolled
metal under specified applied voltage. This measurement can
electrical steel under predetermined conditions of voltage,
be used directly as an indicator of insulation quality or may be
pressure, and temperature.
converted to an apparent surface insulation resistivity value.
1.2 The values stated in either customary units (cgs-emu
and inch-pound) or SI units are to be regarded separately as
5. Significance and Use
standard. Within the text, the SI units are shown in brackets.
5.1 This test method is particularly suitable for quality
The values stated in each system are not exact equivalents;
control in the application of insulating coatings.
therefore, each system shall be used independently of the other.
5.2 Surface insulation resistivity is evaluated from a dc
Combining values from the two systems may result in noncon-
current that can range from 0 (perfect insulator) to 1 A (perfect
formance with the specification.
conductor).
1.3 This standard does not purport to address all of the
5.3 Single readings should not be considered significant
safety concerns, if any, associated with its use. It is the
since the nature of the test device and specimen are such that
responsibility of the user of this standard to establish appro-
successive measurements of a specimen often yield different
priate safety and health practices and determine the applica-
values.
bility of regulatory limitations prior to use.
5.4 The surface insulation resistivity determined in accor-
2. Referenced Documents dance with this method is not the same quantity determined by
Test Method A 718.
2.1 ASTM Standards:
A 34 Practice for Procurement, Testing, and Sampling of
6. Apparatus
Magnetic Materials
6.1 The apparatus, as shown in Fig. 1 and Fig. 2, shall
A 718 Test Method for Surface Insulation Resistivity of
2 consist of a contact unit or test head which is attached to the
Multi-Strip Specimens
head of a hydraulic press. Its associated measuring equipment,
3. Terminology which may be remotely located, includes an ammeter, voltme-
ter, and voltage regulated dc power supply. When measure-
3.1 Definitions of Terms Specific to This Standard:
ments are to be made at elevated temperatures, the platen
3.1.1 The term surface insulation resistivity used in this
beneath the specimen is heated and controlled. Detailed de-
method refers to the effective resistivity of a single insulative
scriptions of the various components are given in Annex A1.
layer tested between applied bare metal contacts and the base
metal of the insulated test specimen. It is not the same as the
7. Sampling
terms interlaminar resistivity and stack resistivity, which refer
7.1 Samples shall be representative of the steel and shall be
to the average resistivity of two adjacent insulative surfaces in
cut in a manner to assure representative sampling as described
contact with each other.
in Practice A 34.
3.2 The apparatus is popularly known as a Franklin tester.
8. Test Specimen
4. Summary of Test Method
8.1 The width and length of a specimen strip shall be greater
4.1 Ten metallic contacts of fixed area are applied to one of
than the width and length respectively of the assembly of
the surfaces of the specimen and electrical contact is made with
contacts. The suggested minimum specimen size is 2 by 5 in.
[50 by 130 mm].
This test method is under the jurisdiction of ASTM Committee A-6 on
8.2 A minimum of five specimen strips is recommended.
Magnetic Properties, and is the direct responsibility of Subcommittee A06.01 on
Test Methods. 8.3 By mutual agreement, tests may be run on Epstein test
Current edition approved Aug. 15, 1995. Published October 1995. Originally
strips. The Epstein specimens may be less satisfactory than the
published as A 717 – 75. Last previous edition A 717 – 93.
minimum size specimen suggested in 8.1 because of the tilting
Annual Book of ASTM Standards, Vol 03.04.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
A 717/A 717M
FIG. 1 Apparatus of Surface Insulation Resistivity Measurement
9.6 When the insulation may be hygroscopic, a conditioning
procedure immediate prior to testing should be mutually agreed
by produce and user.
9.7 Place the specimen on the platen beneath the test head
and position it so that all contacts are within the test area when
the test head is brought in contact with the specimen. Apply the
specified pressure. Check that the voltage is 0.50 V and read
FIG. 2 Diagram of Connections for Contacts and Resistors
the ammeter.
10. Calculations
effect due to burrs, shearing strains, and disturbances in the
coating.
10.1 The average of electrical current measurements is
usually acceptable for evaluating surface insulation. Average
9. Procedure
the current readings for each surface. The reported value for a
9.1 To ensure correct contact button conditions, make a
sample shall be the average of both surfaces.
short circuit test occasionally by testing a bare metal surface.
10.2 R , the surface insulation resistivity of the test sample
i
When the short circuit current is less than 0.99 A, clean the
(two surfaces in series), may be calculated from I, the average
contacts. The use of solvents for cleaning is preferred to
ammeter reading in A, as follows:
abrasives because the latter can result in rounded tips with
R 5 6.45~~1/I! 2 1! in V·cm /lamination, (1)
i
reduced contact areas.
or
9.2 The recommended standard pressur
...
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