GOST 12119.8-98

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  ГОСТ 12119.8-98

GOST 12119.8−98 electrotechnical Steel. Methods for determining magnetic and electrical properties. Method of measurement of resistance ratio of insulating coating

GOST 12119.8−98

Group B39

INTERSTATE STANDARD

Electrotechnical steel

METHODS FOR DETERMINING MAGNETIC AND ELECTRICAL PROPERTIES

Method of measurement of resistance ratio of insulating coating

Electrical steel. Methods of test for magnetic and electrical properties.
Method for measurement of resistance ratio of insulating coating

ISS 77.040.20
AXTU 0909

Date of introduction 1999−07−01

Preface

1 DEVELOPED by the Russian Federation, the Interstate technical Committee for standardization MTK 120 «steel Products from ferrous metals and alloys"

INTRODUCED by Gosstandart of Russia

2 ADOPTED by the Interstate Council for standardization, Metrology and certification (minutes N 13 dated 28 may 1998)

The adoption voted:

3 Resolution of the State Committee of the Russian Federation for standardization and Metrology dated December 8, 1998 N 437 inter-state standard GOST 12119.8−98 introduced directly as state standard of the Russian Federation from July 1, 1999

4 REPLACE GOST 12119−80 in section 7

5 REISSUE

1 Scope

This standard specifies a method of measuring the coefficient of resistance of insulating coatings on electrical steel.

2 Normative references

The present standard features references to the following standards:

GOST 8711−93 Devices showing analog electrical measuring direct action and auxiliary parts to them. Part 2. Special requirements for ammeters and voltmeters

GOST 12119.0−98 electrotechnical Steel. Methods for determining magnetic and electrical properties. General requirements

3 General requirements

General requirements for methods of measurements GOST 12119.0.

Terms used in this standard — GOST 12119.0.

4 Preparation of samples for testing

Samples made from ribbon or strips of length from 250 to 1000 mm, a width of not less than 30 mm.

The surface of the samples shall conform to the requirements of the normative documents materials.

5 Used equipment

5.1 Install. Installation diagram is shown in figure 1.

Figure 1 — Scheme for measuring the resistance of insulating coatings

Figure 1 — Scheme for measuring the resistance of insulating coatings

5.1.1 Ammeter to measure DC current should have a limit of measurement from 10 mA to 1 A, accuracy classes of not less than 0.2 according to GOST 8711 in the measurement of resistance ratio of insulating coating of less than 10 Ω·cm and not less than 0,5 at higher value of the coefficient.

5.1.2 Voltmeter to measure voltage must have a measurement limit of 1.0 or 1.5 V, input resistance of at least 1000 Ohm/V, class of accuracy not less than 0.5 according to GOST 8711.

5.1.3 the DC Source must ensure that the output voltage is 0.5 V with an accuracy of ±0.5% for load current up to 1.0 A.

5.1.4 Device for continuous adjustment of the pressure up to 2 MPa, and applying a voltage to the sample must be ten identical electrodes isof a cylindrical shape with a diameter of from 10 to 40 mm, measured with the error not more than ±0.05 mm, and ten resistors -resistance (5±0.05) Ohm, a capacity of at least 0.5 watts. The electrodes must have negative potential, the material coated is positive. Allowed any means of measuring pressure, if their error is not beyond ±5%.

6 Preparation of samples for measurement

The sample clean from dust and powdery substances and lay between the electrodes.

7 procedures for measuring

7.1 the Electrodes pressed against the sample surface, creating a pressure of 2 N/mm, set the voltage of 0.5 V and measure the current , .

7.2 position the electrodes on the portions of the sample not undergoing testing, and repeat operations 7.1. The total number of measurements on the same side of the specimen shall be equal to ten.

7.3 Sample two-way isolation turn over and repeat the operation in 7.1, 7.2.

8 Rules for processing results of measurements

8.1 Coefficient of resistance of a unilateral coating , Ohm/cm, is calculated by the formula

, (1)

where is the arithmetic mean of the results of measurements of current strength, determined as specified in 7.1, And;

 — resistance of each of resistors  — Ohms;

 — the total area of the contact surfaces of the electrodes, cm, calculated from the diameter of the electrodes;

 — the voltage measured by the voltmeter,

.

8.2 For the samples with double-sided insulation resistance coefficient , Ohms/cm, is calculated by the formula

. (2)

8.3 permitted to take into account the current flowing in the input circuit of the voltmeter. In the formulas (1) and (2) substitute the value for , where is the input resistance of the voltmeter in Ohms.



The text of the document is verified by:
the official publication of the
Electrotechnical steel.
Specifications. Methods of analysis:
SB. Standards. -

M.: IPK Publishing house of standards, 2003