PD IEC TR 62581 pdf download – Electrical steel — Methods of measurement of the magnetostriction characteristics by means of single sheet and Epstein test specimens

PD IEC TR 62581 pdf download – Electrical steel — Methods of measurement of the magnetostriction characteristics by means of single sheet and Epstein test specimens
1 Scope
This technical report describes the general principles and technical details of the measurementof the magnetostriction of single sheet specimens preferably 500 mm long and 100 mm wideand Epstein strip specimens,specified in lEC 60404-2, of electrical steel by means of opticalsensors and accelerometers.
These methods are applicable to test specimens obtained from electrical steel sheets and stripsof any grade.The characteristics of magnetostriction are determined for a sinusoidal inducedvoltage, 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 specimenswhich have first been demagnetized.
Normative references
The following referenced documents are indispensable for the application of this document. Fordated references, only the edition cited applies. For undated references, the latest edition of thereferenced document (including any amendments) applies.
IEC 60050-121, International Electrotechnical Vocabulary – Part 121:Electromagnetism
IEC 60050-221，International Electrotechnical Vocabulary – Chapter 221: Magnetic materialsand components
IEC 60404-2,Magnetic materials – Part 2: Methods of measurement of the magnetic propertiesof electrical steel sheet and strip by means of an Epstein frame
IEC 60404-3:1992,Magnetic materials – Part 3: Methods of measurement of the magneticproperties of electrical steel strip and sheet by means of a single sheet tester
Amendment 1 (2002)
Amendment 2 (20o9)
IEC 61672-1，Electroacoustics – Sound level meters – Part 1: Specifications
3 Terms and definitions
For the purpose of this document, the definitions of the principal terms relating to magneticproperties given in lEC 60050-121and IEC 60050-221 apply, as well as the following terms anddefinitions:
3.1
butterfly loop
hysteresis loop of the strain measured in the direction of applied field versus the magneticpolarization for a period of an alternating magnetization
3.2
zero-to-peak magnetostriction
p o−
λ
net strain measured in the direction of applied field from the zero magnetic polarization to a given magnetic polarization
3.3
peak-to-peak magnetostriction
p p−
λ
amplitude of the strain measured in the direction of the applied field under alternating magnetization
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
Measurement systems for magnetostriction are shown in Figure 1 and Figure 2. A block diagram of the measurement system is shown in Figure 3.
The test specimen comprises a sample of electrical steel sheet and is placed inside twowindings:
-an external primary winding;-an interior secondary winding.
The flux closure is made by a magnetic circuit consisting of a yoke, the cross-section of which islarge compared with that of the test specimen. There are narrow and homogeneous gapsbetween the test specimen and the pole faces of the yoke to weaken the electromagnetic forcebetween them. The test frame that consists of the yoke, the windings and a clamp should bepermanently fixed to a rigid base during the measurement.
The test specimen is fixed to the base at one end of the windings using the clamp shown inFigure 1.An optical target is pasted on the centerline of the surface of the test specimen at theother end of the windings. Changes in length between the clamping point and the optical targetare measured using an optical sensor.
ln order to reduce the effect of stray fields between the test specimen and the pole faces, theoptical sensor should be at a sufficient working distance from the test frame.
Two measurement types of optical sensor can be used: a single point measurement and adifferential measurement. The single point measurement uses a sensor head fixed on the baseand measures vibration or displacement between the optical target and the sensor head.Thedifferential measurement uses two sensor heads and measures vibration and displacementbetween the optical target and a reflector fixed on the base.The latter system has advantages of(a) cancellation of external noise and in (b) setting the sensors separately from the base.
Care shall be taken to minimize noise vibrations caused by resonances of the test frame andexternal vibrations. The test frame shall be placed on an anti-vibration table in order to isolatethe test frame from external vibration.
Care shall be taken to prevent out-of-plane deformations of the test specimen.The testspecimen shall be placed on a flat and smooth surface in the test frame and kept flat during themeasurement (see Annex A).
4.2Test specimen
The length of the test specimen should be not less than 500 mm. The part of the specimensituated outside the pole faces should not be longer than is necessary to facilitate insertion andremoval of the test specimen and to apply an external stress to the test specimen in thelongitudinal direction.