BS EN 61788-8:2010
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Superconductivity – AC loss measurements. Total AC loss measurement of round superconducting wires exposed to a transverse alternating magnetic field at liquid helium temperature by a pickup coil method
| Published By | Publication Date | Number of Pages |
| BSI | 2010 | 38 |
IEC 61788-8:2010 specifies the measurement method of total AC losses by the pickup coil method in composite superconducting wires exposed to a transverse alternating magnetic field. The losses may contain hysteresis, coupling and eddy current losses. The standard method to measure only the hysteresis loss in DC or low-sweep-rate magnetic field is specified in IEC 61788-13. In metallic and oxide round superconducting wires expected to be mainly used for pulsed coil and AC coil applications, AC loss is generated by the application of time-varying magnetic field and/or current. The contribution of the magnetic field to the AC loss is predominant in usual electromagnetic configurations of the coil applications. For the superconducting wires exposed to a transverse alternating magnetic field, the present method can be generally used in measurements of the total AC loss in a wide range of frequency up to the commercial level, 50/60 Hz, at liquid helium temperature. For the superconducting wires with fine filaments, the AC loss measured with the present method can be divided into the hysteresis loss in the individual filaments, the coupling loss among the filaments and the eddy current loss in the normal conducting parts. In cases where the wires do not have a thick outer normal conducting sheath, the main components are the hysteresis loss and the coupling loss by estimating the former part as an extrapolated level of the AC loss per cycle to zero frequency in the region of lower frequency, where the coupling loss per cycle is proportional to the frequency. This second edition cancels and replaces the first edition published in 2003. This edition constitutes a technical revision. The main changes with respect to the previous edition are listed below: – extending the applications of the pickup coil method to the a.c. loss measurements in metallic and oxide superconducting wires with a round cross section at liquid helium temperature, – using the word “uncertainty” for all quantitative (associated with a number) statistical expressions and eliminating the quantitative use of “precision” and “accuracy”. Key words: superconductivity, TC90
PDF Catalog
| PDF Pages | PDF Title |
|---|---|
| 6 | CONTENTS |
| 8 | INTRODUCTION |
| 9 | 1 Scope 2 Normative references 3 Terms and definitions |
| 11 | 4 Principle |
| 12 | 5 Apparatus 5.1 Testing apparatus 5.2 Pickup coils 5.3 Compensation circuit |
| 13 | 6 Specimen preparation 6.1 Coiled specimen 6.2 Specimen coil form 7 Testing conditions 7.1 External applied magnetic field |
| 14 | 7.2 Setting of the specimen 7.3 Measurement temperature 7.4 Test procedure |
| 15 | 8 Calculation of results 8.1 Amplitude of applied magnetic field 8.2 Magnetization |
| 16 | 8.3 Magnetization curve 8.4 AC loss 8.5 Hysteresis loss 8.6 Coupling loss and coupling time constant [5,6] 9 Uncertainty 9.1 General |
| 17 | 9.2 Uncertainty of measurement apparatus 9.3 Uncertainty of applied field 9.4 Uncertainty of measurement temperature 10 Test report 10.1 Identification of specimen 10.2 Configuration of coiled specimen |
| 18 | 10.3 Testing conditions 10.4 Results 10.5 Measurement apparatus |
| 19 | Figures Figure 1 – Standard arrangement of the specimen and pickup coils |
| 20 | Figure 2 – A typical electrical circuit for AC loss measurement by pickup coils |
| 21 | Annex A (informative) Additional information relating to Clauses 1 to 10 |
| 23 | Annex B (informative) Explanation of AC loss measurement with Poynting’s vector [10] |
| 24 | Annex C (informative) Estimation of geometrical error in the pickup coil method Figure C.1 – Examples of calculated contour line map of the coefficient G |
| 25 | Annex D (informative) Recommended method for calibration of magnetization and AC loss |
| 26 | Figure D.1 – Evaluation of critical field from magnetization curves |
| 27 | Annex E (informative) Coupling loss for various types of applied magnetic field Figure E.1 – Waveforms of applied magnetic field with a period T = 1/f |
| 28 | Annex F (informative) Uncertainty considerations |
| 29 | Tables Table F.1 – Output signals from two nominally identical extensometers Table F.2 – Mean values of two output signals Table F.3 – Experimental standard deviations of two output signals |
| 30 | Table F.4 – Standard uncertainties of two output signals Table F.5 – Coefficient of variations of two output signals |
| 33 | Annex G (informative) Evaluation of uncertainty in AC loss measurement by pickup coil method [13] |
| 35 | Table G.1 – Propagation of relative uncertainty in the pickup coil method (α = 0,5) |
| 36 | Bibliography |
