This standard specifies methods of test for the determination of coating insulation resistance and coating adhesion of electrical strip and sheet.
This standard is applicable to the test for the determination of surface insulation resistance and interface resistance of non-oriented and oriented electrical strip and sheet, as well as the test for the determination of insulation coating adhesion of non-oriented and oriented electrical strip and sheet.
2 Test of Coating Insulation Resistance
2.1 Principle of measurement
The principle of the measurement is based on, and includes, the method originally described by Franklin which characterizes only one coated surface at a time.
The arrangement of the apparatus is shown in Figure 1. Ten metallic contacts of fixed area are applied to one coated surface of the sheet, under specified conditions of voltage and pressure. The effectiveness of the surface insulation is assessed by the measurement of the currents through the 10 contacts.
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Figure 1 Arrangement of Apparatus for the Measurement of Surface Insulation Resistance
Contacts are fed from a d.c. power supply, as shown in Figure 2, and the voltage between the 5×(1±1%)Ω resistor and the drill is stabilized at 500×(1±0.5%)mV over a current range of 0~1A. The two twist drills perform the function of current return contacts with the metallic substrate of test specimen.
