IEC 60404-11-2021 pdf downlaod.Magnetic materials – Part 11: Methods of measurement of the surface insulation resistance of electrical steel strip and sheet.
This part of IEC 60404 is applicable to electrical steel strip and sheet insulated by coating on one or both sides.
The object of this document is to define the general principles and technical details of the measurement of the surface insulation resistance of electrical steel strip and sheet.
NOTE This test is suitable for manufacturing and quality control in the application of insulation coatings.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies.
For undated references, the latest edition of the referenced document (including any amendments) applies.
ISO/IEC Guide 98-3, Uncertainty of measurement – Part 3: Guide to the expression of uncertainty in measurement (GUM:1995)
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminological database for use in standardization at the following addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO: Online browsing platform: available at http://www.iso.org/obp
4 Principle of measurement
The principle of the measurement is based on, and includes, the method originally described by Franklin [1 ] 1 which characterizes one coated surface at a time.
The fundamental arrangement of the test apparatus is shown in Figure 1 . Ten metallic contact buttons of fixed area are applied to one coated surface of the test specimen, under specified conditions of voltage and pressure.
The effectiveness of the surface insulation is assessed by the measurement of currents flowing through the 1 0 contact buttons.
Ten contact buttons are applied to one coated surface of the test specimen. 5 Ω resistors of ±1 % precision are connected in series with each contact button as shown in Figure 2. Two conductive twist drills contact electrically with the metallic substrate under the insulation coating. The voltage between the supply side of the 5 Ω resistors and the twist drills is stabilized at DC 0,5 V with a relative tolerance of ±0,5 % over a current range from 0 A to 1 ,0 A. The two twist drills may be placed at each end of the contact buttons and applied to the same side of the test specimen. In Arrangement A, the two twist drills perform the function of current return contacts with the metallic substrate [see Figure 2 a)]. In Arrangement B, the two twist drills perform different functions [see Figure 2 b)]. One drill provides the current return contact with the metallic substrate. The other drill serves as a potential sensor for the voltage feedback control. This feedback control removes the influence of the contact resistance between the current return drill and the metallic substrate. NOTE The contribution of the contact resistance on the measurement is significant when measuring a relatively low surface insulation resistance. Arrangement B is recommended when measuring a relatively low surface insulation resistance. The total current flowing through the insulation coating between the 1 0 contact buttons and the metallic substrate in parallel connection is measured (see Figure 2). The value of the total current shall be determined by measuring the voltage drop across the current sensing resistor R s connected in series with the current circuit. The current sensing resistor shall not be included within the voltage stabilizing circuit. The individual contact button currents may be analysed by measuring the individual voltage drops across each 5 Ω resistor. Because the current path is between the contact buttons and the metallic substrate, this test is not a true measurement of interlaminar resistance, in which the current path is between two metallic substrates of adjacent sheets. However, this test provides a useful index of the quality of the surface insulation resistance.
5 Test specimen The test specimen shall be a length of strip or a sheet. The width and length of the test specimen shall be greater than the width and length of the contact assembly (see 6.1 ). The test specimen shall be representative for the material to be tested. The surfaces shall be clean and free from powder, dust and oil, etc. which may be the result of handling of the test specimen. Measurements shall be performed at room temperature of (23 ± 5) °C. This measurement is destructive, the surface of the test specimen where the contact assembly touched shall not be used again. NOTE To obtain a representative result, several test specimens can be taken evenly across the full width of the strip or sheet.IEC 60404-11 pdf download.