1、Designation: A 717/A 717M 06Standard Test Method forSurface Insulation Resistivity of Single-Strip Specimens1This standard is issued under the fixed designation A 717/A 717M; the number immediately following the designation indicates the yearof original adoption or, in the case of revision, the year
2、 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. Scope1.1 This test method covers a means of testing the surfaceinsulation resistivity of single strips or punchings of fla
3、t-rolledelectrical steel under predetermined conditions of voltage,pressure, and temperature.1.2 The values stated in either SI units or inch-pound unitsare to be regarded separately as standard. The values stated ineach system may not be exact equivalents; therefore, eachsystem shall be used indepe
4、ndently of the other. Combiningvalues from the two systems may result in non-conformancewith the standard.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety an
5、d health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2A 34/A 34M Practice for Sampling and Procurement Test-ing of Magnetic Materials3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 The term surface
6、 insulation resistivity used in thismethod refers to the effective resistivity of a single insulativelayer tested between applied bare metal contacts and the basemetal of the insulated test specimen. It is not the same as theterms interlaminar resistivity and stack resistivity, which referto the ave
7、rage resistivity of two adjacent insulative surfaces incontact with each other.3.2 The apparatus is popularly known as a Franklin tester.4. Summary of Test Method4.1 Ten metallic contacts of fixed area are applied to one ofthe surfaces of the specimen and electrical contact is made withthe base meta
8、l by two drills. The effectiveness of the surfaceinsulation is then indicated by a measurement of averageelectrical current flowing between the contacts and the basemetal under specified applied voltage. This measurement canbe used directly as an indicator of insulation quality or may beconverted to
9、 an apparent surface insulation resistivity value.5. Significance and Use5.1 This test method is particularly suitable for qualitycontrol in the application of insulating coatings.5.2 Surface insulation resistivity is evaluated from a dccurrent that can range from 0 (perfect insulator) to 1 A (perfe
10、ctconductor).5.3 Single readings should not be considered significantsince the nature of the test device and specimen are such thatsuccessive measurements of a specimen often yield differentvalues.6. Apparatus6.1 The apparatus, as shown in Fig. 1 and Fig. 2, shallconsist of a contact unit or test he
11、ad which is attached to thehead of a hydraulic press. Its associated measuring equipment,which may be remotely located, includes an ammeter, voltme-ter, and voltage regulated dc power supply. When measure-ments are to be made at elevated temperatures, the platenbeneath the specimen is heated and con
12、trolled. Detailed de-scriptions of the various components are given in Annex A1.7. Sampling7.1 Samples shall be representative of the steel and shall becut in a manner to assure representative sampling as describedin Practice A 34/A 34M.8. Test Specimen8.1 The width and length of a specimen strip sh
13、all be greaterthan the width and length respectively of the assembly ofcontacts. The suggested minimum specimen size is 2 by 5 in.50 by 130 mm.8.2 A minimum of five specimen strips is recommended.1This test method is under the jurisdiction of ASTM Committee A06 onMagnetic Properties, and is the dire
14、ct responsibility of Subcommittee A06.01 onTest Methods.Current edition approved May 1, 2006. Published May 2006. Originallyapproved in 1975. Last previous edition approved in 2001 as A 717/A 717M 01.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Servic
15、e at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.8.3 By mutual agreement between the producer a
16、nd theuser, tests may be run on Epstein test strips. The Epsteinspecimens may be less satisfactory than the minimum sizespecimen suggested in 8.1 because of the tilting effect due toburrs, shearing strains, and disturbances in the coating.9. Procedure9.1 To ensure correct contact button conditions,
17、make ashort circuit test occasionally by testing a bare metal surface.When the short circuit current is less than 0.99 A, clean thecontacts. The use of solvents for cleaning is preferred toabrasives because the latter can result in rounded tips withreduced contact areas.9.2 The recommended standard
18、pressure for purpose ofcomparative tests shall be 300 psi 2.1 MPa. Other pressures,depending upon the application, may be agreed upon by theproducer and the user. If more than one test pressure is to beused, apply the pressures in ascending order. During testing,apply the pressures only once, but an
19、 applied pressure may beincreased to a higher value.9.3 If both sides of the specimen are coated, do not use thesame area to test both sides.9.4 The recommended standard test temperatures are roomtemperature and 300F 150C. Other temperatures and thesequence of temperatures, depending upon the applic
20、ation,may be agreed upon by the producer and the user.9.5 When tests are made at elevated temperatures allowsufficient time (usually 30 s) to heat the specimen to thespecified temperature.9.6 When the insulation may be hygroscopic, a conditioningprocedure immediately prior to testing should be mutua
21、llyagreed upon by the producer and the user.9.7 Place the specimen on the platen beneath the test headand position it so that all contacts are within the test area whenthe test head is brought in contact with the specimen.Apply thespecified pressure. Check that the voltage is 0.50 V and readthe amme
22、ter.10. Calculations10.1 The average of electrical current measurements isusually acceptable for evaluating surface insulation. Averagethe current readings for each surface. The reported value for asample shall be the average of both surfaces.10.2 The surface insulation resistivity of the test sampl
23、e(two surfaces in series), Ri, may be calculated from I, theaverage ammeter reading in A, as follows:Ri5 6.451/I! 2 1! in Vcm2/lamination, (1)orRi5 6451/I! 2 1! in Vmm2/lamination.10.3 The equations in 10.2 may be derived as shown inAnnex A2.11. Precision and Bias11.1 Even with the best practices in
24、 design, instrumentation,maintenance, and operation, the repeatability and reproducibil-ity of the test method are greatly influenced by the nature of thesurfaces of the test specimens. Hence it is not consideredpossible to state meaningful values for repeatability andreproducibility that are univer
25、sally applicable.12. Keywords12.1 coating; electrical steel; Franklin tester; insulation;resistivity; single-strip specimens; surface insulation resistivityFIG. 1 Apparatus of Surface Insulation Resistivity MeasurementFIG. 2 Diagram of Connections for Contacts and ResistorsA 717/A 717M 062ANNEXES(Ma
26、ndatory Information)A1. APPARATUSA1.1 Test HeadThe test head shall consist of a mountingblock on which are assembled:A1.1.1 Two parallel longitudinal rows of five verticallymounted steel rods free to move axially against surroundingspiral springs or other means to apply equal pressure.A1.1.2 Brass,
27、stainless steel, or other suitable metalliccontact button on each rod, but insulated from it. Articulationof tips improves contact by compensating for minor misalign-ments. Avoid soft metals, poor conductors, or metals subject tooxidation or attack by solvents used in cleaning. Due tolow-voltage cir
28、cuitry (0.5 V) all contacting surfaces must bekept clean. Full area contact of tips to coreplate is needed toavoid decreases in Franklin amperage. Check with knownsamples or standard test blocks. The contact area of each of theten contact buttons shall be 0.645 cm264.5 mm2.A1.1.3 A 5-V (60.1 %) resi
29、stor connected to each contactbutton. Contacts with their individual resistors shall be con-nected in parallel as shown in Fig. 2.A1.1.4 Electrical contact with the base metal is madethrough two18 in. 3 mm diameter twist drills (preferablycarbide-tipped) or hardened and pointed rods. These arevertic
30、ally mounted and spring loaded in spiral slotted sleeves toimpart a twist while piercing the coating.A1.2 Hydraulic PressThe hydraulic press shall have acapacity of 2000 lb 10 000 N, with mountings to accommo-date the test head, test specimens or punchings, and a hot plate.The press or hot plate mus
31、t provide a smooth, flat, and rigidsupport for the test specimen.A1.3 Hot PlateThe hot plate, when used, shall besuitable for heating to the temperature of test with automaticcontrol to maintain the test temperature.A1.4 Test Head Power SupplyThe voltage regulated dcpower supply should be capable of
32、 voltage regulation of atleast 0.5 % at 0.5 V during load changes from zero to 1.0Aandline voltage variations of 610 %. This maintains the voltageadequately accurate during test and eliminates the necessity formanual voltage adjustment.A1.5 AmmeterThe dc ammeter should be a low imped-ance 0 to 1Adig
33、ital type rated for 0.1 % or better accuracy andhave resolution of 0.01 A.A1.6 VoltmeterThe dc voltmeter should be a high imped-ance 0 to 1 V digital type rated for 0.1 % or better accuracy andhave resolution of 0.01 V.A1.7 Hot Plate Power SupplyThe plate power supplyand temperature control equipmen
34、t should be capable ofautomatic temperature control and variable setting features. Itmay use thermocouples or other temperature sensing elements,but must be able to maintain temperature of the hot plate within10F 5C of the set temperature.A2. DERIVATIONA2.1 The equations in 10.2 may be derived as fo
35、llows:I 5 E(n 5 1101/Rs1 Rn!510E/Rs1Rj/Ab!Rj5 AbRs110E/I! (A2.1)Ri5 2 Rj5 2Ab10E/I!2Rs!where:I = ammeter reading in A,E = applied voltage in V,= 0.5V,Rs= resistance of resistor in series with each contactbutton in V,=5V,Rn= resistance of surface between single contact buttonand base metal of the tes
36、t specimen in V,Rj= surface insulation resistivity of one surface of testsample in Vcm2/surface or Vmm2/surface,Ab= area of each contact button in cm2or mm2= 0.645 cm2or 64.5 mm2,Ri= surface insulation resistivity of test sample (twosurfaces in series) in Vcm2/lamination or Vmm2/lamination.A 717/A 7
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40、Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).A 717/A 717M 064
