Electrical steel. Methods of measurement of the magnetostriction characteristics by means of single sheet and Epstein test specimens

PD IEC/TR 62581:2010 Electrical steel. Methods of measurement of the magnetostriction characteristics by means of single sheet and Epstein test specimens

PD IEC/TR 62581 is a technical report which describes the general principles and technical details of the measurement of the magnetostriction of single sheet specimens preferably 500 mm long and 100 mm wide and Epstein strip specimens, specified in IEC 60404-2, of electrical steel by means of optical sensors and accelerometers.

These methods are applicable to test specimens obtained from electrical steel sheets and strips of any grade. The characteristics of magnetostriction are determined for a sinusoidal induced voltage, for specified peak values of magnetic polarization and for a specified frequency.

The measurements are made at an ambient temperature of 23 °C ± 5 °C on test specimens which have first been demagnetized.

Contents of PD IEC/TR 62581:

Foreword

Introduction

1 Scope

2 Normative references

3 Terms and definitions

4 Method of measurement of the magnetostriction characteristics of electrical steel sheets under applied stress by means of a single sheet tester

4.1 Principle of the method

4.2 Test specimen

4.3 Yokes

4.4 Windings

4.5 Air flux compensation

4.6 Power supply

4.7 Optical sensor

4.8 Stressing device

4.9 Data acquisitions

4.10 Data processing

4.11 Preparation for measurement

4.12 Adjustment of power supply

4.13 Measurement

4.14 Determination of the butterfly loop

4.15 Determinations of the zero-to-peak and peak-to-peak values

4.16 Reproducibility

5 Examples of the measurement systems

5.1 Single sheet tester

5.2 Epstein strip tester

6 Examples of measurement

6.1 Magnetostriction without external stress

6.2 Magnetostriction under applied stress

6.3 Variation of magnetostriction with coating tension

6.4 Factors affecting precision and reproducibility

6.4.1 General

6.4.2 Overlap length between test specimen and yoke

6.4.3 The averaging effect on environmental noise

6.4.4 Gap between test specimen and yoke

6.4.5 Resetting the test specimen

7 Methods of evaluation of the magnetostriction behaviour

7.1 Relationship between magnetostriction and magnetic domain structure

7.2 A simple model of magnetostriction behaviour