IEC 60404-11 pdf free download

IEC 60404-11 pdf free download.Magnetic materials – Part 11: Methods of measurement of the surface insulation resistance of electrical steel strip and sheet.
6 Test apparatus
6.1 Contact assembly
The contact assembly consists of 10 vertically mounted contact rods and two twist drills of approximately 3 mm in diameter. These 10 contact rods shall be able to move individually and axially against springs in a mounting block. The contact rods shall press on the surface of the test specimen with the same force. In order to achieve electrical contact with the metallic substrate, the two twist drills shall be rotated when pressed on the test specimen. The twist drills shall pierce the insulation coating but shall not pierce through the test specimen.
The 10 contact rods shall be arranged in one or two rows.
Each rod shall be provided with a contact button of bronze or other equivalent low resistive material with sufficient hardness (for example, stainless steel). The contact buttons shall be electrically insulated from the mounting block.
Each of the 10 contact buttons shall have a contact area of 64,5 mm2 with a relative tolerance of ±1 %, giving a total area for the 10 buttons of 645 mm2 with a relative tolerance of ±1 %. Each contact button shall press on the test specimen uniformly over the whole contact area and shall avoid concentrating the force at the edge of the contact button.
NOTE 1 A force concentration at the edge of the contact button can destroy the insulation coating and cause a direct contact between the contact button and the metallic substrate. Therefore, misalignments of the contact buttons can cause an erroneous large current through the contact buttons. Articulated joints which allow the contact buttons to follow the surface of the test specimen improve the contacts by compensating for minor misalignments.
NOTE 2 In case the purchaser and the manufacturer agree to use a different contact button size, e.g. 100 mm2, for each contact button (e.g. total area of 1 000 mm2), the measured values differ from the values measured with contact buttons of the standard size of 64,5 mm2 for each contact button (total area of 645 mm2).
The test specimen shall be pressed between a baseplate and the contact assembly. Alternatively, the test specimen may be pressed between pairs of contact assemblies (arrangement of the 10 contact buttons each) of the same dimensions in opposing positions provided that the comparability of the results can be demonstrated. This arrangement allows successive measurement of both sides of the test specimen without turning over the test specimen.
6.2 Power supply
The power supply shall be capable of maintaining a stabilized voltage of DC 0,5 V with a relative tolerance of ±0,5 % over a current range from 0 A to 1,0 A.
6.3 Current measurement
The total current flowing through the contact buttons shall be measured with an uncertainty of ±0,5 % or better.
The value of the total current shall be determined by measuring the voltage drop across the current sensing resistor R of a low resistance value (e.g. 0,2 0) by means of a suitable voltmeter (see Figure 2).
NOTE An ammeter with a low internal resistance value can be used Instead of the resistor R and the voltmeter.
6.4 Applied force
A pressure of 2 N/mm2 with a relative tolerance of ±5 % shall be applied to each of the 10 contact buttons pressing on the test specimen. This corresponds to a force of 1 290 N with a relative tolerance of ±5 % for the total contact area of 645 mm2.IEC 60404-11 pdf free download.