1、Designation: A717/A717M 12Standard Test Method forSurface Insulation Resistivity of Single-Strip Specimens1This standard is issued under the fixed designation A717/A717M; the number immediately following the designation indicates the yearof original adoption or, in the case of revision, the year of
2、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. Scope1.1 This test method covers a means of testing the surfaceinsulation resistivity of single strips or punchings of flat-rol
3、ledelectrical 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 independent
4、ly 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 and hea
5、lth practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2A34/A34M Practice for Sampling and Procurement Testingof Magnetic Materials3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 surface insulation resist
6、ivityrefers to the effectiveresistivity of a single insulative layer tested between appliedbare metal contacts and the base metal of the insulated testspecimen. It is not the same as the terms interlaminar resistivityand stack resistivity, which refer to the average resistivity oftwo adjacent insula
7、tive surfaces in contact with each other.3.1.2 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 metal by two drills. The effectiveness o
8、f 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 an apparent surface insulation resi
9、stivity 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 (perfectconductor).5.3 Single readings sho
10、uld 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 head which is attached to thehead of a
11、 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 controlled. Detailed de-scriptions of t
12、he 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 A34/A34M.8. Test Specimen8.1 The width and length of a specimen strip shall be greaterthan the width and lengt
13、h 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 direct responsibility of Subcommittee A06.0
14、1 on TestMethods.Current edition approved May 1, 2012. Published July 2012. Originally approvedin 1975. Last previous edition approved in 2006 as A717/A717M 06. DOI:10.1520/A0717_A0717M-12.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at servic
15、eastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States18.3 By mutual agreement between the producer and theuser,
16、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, make ashort
17、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 pressure for
18、 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 applied pre
19、ssure 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 application,may be
20、 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 mutuallyagreed up
21、on 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 ammeter.10. Calc
22、ulations10.1 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 two surface insulation resistivity of the test sample(two su
23、rfaces in series), Ri, may be calculated from I, theaverage ammeter reading in A, as follows:Ri5 6.451/I! 2 1! inVcm2/lamination, (1)orRi5 6451/I! 2 1! inVmm2/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 design, i
24、nstrumentation,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 universally appl
25、icable.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 ResistorsA717/A717M 122ANNEXES(Mandatory Info
26、rmation)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, stainless st
27、eel, 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 circuitry (0.5
28、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 %) resistor connect
29、ed 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 arevertically mounted
30、 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 must provide a
31、smooth, flat, and rigidsupport for the test specimen.A1.3 Hot PlateThe hot plate, when used, shall be suitablefor heating to the temperature of test with automatic control tomaintain the test temperature.A1.4 Test Head Power SupplyThe voltage regulated dcpower supply should be capable of voltage reg
32、ulation 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 1Adigital type ra
33、ted 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 supply andtemperature control equipment should be
34、capable of automatictemperature control and variable setting features. It may usethermocouples or other temperature sensing elements, but mustbe able to maintain temperature of the hot plate within 10F5C of the set temperature.A2. DERIVATIONA2.1 The equations in 10.2 may be derived as follows:I 5 E(
35、n51101/Rs1 Rn!5 10E/Rs1Rj/Ab!Rj5 Ab(10E/I) 2 Rs! (A2.1)Ri5 2 Rj5 2Ab 10E/I! 2 Rs!where:I = ammeter reading in A,E = applied voltage in V,= 0.5V,Rs= resistance of resistor in series with each contact buttonin V,=5V,Rn= resistance of surface between single contact button andbase metal of the test spec
36、imen 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= two surface insulation resistivity of test sample (twosurfaces in series) in Vcm2/lamination orVmm2/lamination.A717/A717M 1
37、23ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, a
38、re entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional stand
39、ardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Commi
40、ttee 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). Permission rights to photocopy the standard may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).A717/A717M 124
