Superconductivity - Part 8: AC loss measurements - Total AC loss measurement of Cu/Nb-Ti composite superconducting wires exposed to a transverse alternating magnetic field by a pickup coil method

Specifies the measurement method of total AC losses by the pickup coil method in Cu/Nb-Ti composite superconducting wires exposed to a transverse alternating magnetic field. The losses may contain both hysteresis and coupling losses. The standard method to measure only the hysteresis loss in DC or low-sweep-rate magnetic field is specified in EN 61788-13.

Supraleitfähigkeit - Teil 8: Messung der Wechselstromverluste - Messung der gesamten Wechselstromverluste von Cu/NbTi-Verbundsupraleiterdrähten in transversalen magnetischen Wechselfeldern mit Hilfe eines Pickupspulen-Verfahrens

Supraconductivité - Partie 8: Mesure des pertes en courant alternatif - Méthode de mesure par bobines de détection des pertes totales en courant alternatif des fils composites supraconducteurs de Cu/Nb-Ti exposés à un champ magnétique alternatif transverse

Spécifie la méthode de mesure par bobines de détection des pertes totales en courant alternatif des fils supraconducteurs de Cu/Nb-Ti exposés à un champ magnétique alternatif transverse. Les pertes peuvent être à la fois des pertes par hystérésis et des pertes par couplage. La méthode normalisée permettant de mesurer uniquement les pertes par hystérésis en courant continu ou en champ magnétique à faible vitesse de balayage est spécifiée dans la EN 61788-13.

Superconductivity - Part 8: AC loss measurements - Total AC loss measurement of Cu/Nb-Ti composite superconducting wires exposed to a transverse alternating magnetic field by a pickup coil method

General Information

Status
Withdrawn
Publication Date
08-May-2003
Technical Committee
Drafting Committee
Parallel Committee
Current Stage
6060 - Document made available
Start Date
09-May-2003
Completion Date
09-May-2003

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SLOVENSKI SIST EN 61788-8:2003
STANDARD
oktober 2003
Superconductivity - Part 8: AC loss measurements - Total AC loss measurement of
Cu/Nb-Ti composite superconducting wires exposed to a transverse alternating
magnetic field by a pickup coil method
ICS 17.220.20; 29.050 Referenčna številka
SIST EN 61788-8:2003(en)

© Standard je založil in izdal Slovenski inštitut za standardizacijo. Razmnoževanje ali kopiranje celote ali delov tega dokumenta ni dovoljeno

---------------------- Page: 1 ----------------------
EUROPEAN STANDARD EN 61788-8
NORME EUROPÉENNE
EUROPÄISCHE NORM May 2003
ICS 17.220; 29.050
English version
Superconductivity
Part 8: AC loss measurements -
Total AC loss measurement of Cu/Nb-Ti composite superconducting wires
exposed to a transverse alternating magnetic field
by a pickup coil method
(IEC 61788-8:2003)
Supraconductivité Supraleitfähigkeit
Partie 8: Mesure des pertes Teil 8: Messung der
en courant alternatif - Wechselstromverluste -
Méthode de mesure par bobines Messung der gesamten
de détection des pertes totales Wechselstromverluste von
en courant alternatif des fils composites Cu/NbTi-Verbundsupraleiterdrähten
supraconducteurs de Cu/Nb-Ti in transversalen magnetischen
exposés à un champ magnétique Wechselfeldern mit Hilfe eines
alternatif transverse Pickupspulen-Verfahrens
(CEI 61788-8:2003) (IEC 61788-8:2003)

This European Standard was approved by CENELEC on 2003-05-01. CENELEC members are bound to

comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European

Standard the status of a national standard without any alteration.

Up-to-date lists and bibliographical references concerning such national standards may be obtained on

application to the Central Secretariat or to any CENELEC member.

This European Standard exists in three official versions (English, French, German). A version in any other

language made by translation under the responsibility of a CENELEC member into its own language and

notified to the Central Secretariat has the same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Czech Republic,

Denmark, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Luxembourg, Malta,

Netherlands, Norway, Portugal, Slovakia, Spain, Sweden, Switzerland and United Kingdom.

CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
Central Secretariat: rue de Stassart 35, B - 1050 Brussels

© 2003 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.

Ref. No. EN 61788-8:2003 E
---------------------- Page: 2 ----------------------
EN 61788-8:2003 - 2 -
Foreword

The text of document 90/135A/FDIS, future edition 1 of IEC 61788-8, prepared by IEC TC 90,

Superconductivity, was submitted to the IEC-CENELEC parallel vote and was approved by CENELEC

as EN 61788-8 on 2003-05-01.
The following dates were fixed:
– latest date by which the EN has to be implemented
at national level by publication of an identical
national standard or by endorsement dop) 2004-02-01
– latest date by which the national standards conflicting
with the EN have to be withdrawn dow) 2006-05-01
Annexes designated "normative" are part of the body of the standard.
Annexes designated "informative" are given for information only.
In this standard, annex ZA is normative and annexes A to E are informative.
Annex ZA has been added by CENELEC.
__________
Endorsement notice

The text of the International Standard IEC 61788-8:2003 was approved by CENELEC as a European

Standard without any modification.
__________
---------------------- Page: 3 ----------------------
- 3 - «Field32»
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications

This European Standard incorporates by dated or undated reference, provisions from other

publications. These normative references are cited at the appropriate places in the text and the

publications are listed hereafter. For dated references, subsequent amendments to or revisions of any

of these publications apply to this European Standard only when incorporated in it by amendment or

revision. For undated references the latest edition of the publication referred to applies (including

amendments).

NOTE When an international publication has been modified by common modifications, indicated by (mod), the relevant

EN/HD applies.
Publication Year Title EN/HD Year
IEC 60050-815 - International Electrotechnical - -
Vocabulary (IEV)
Chapter 815: Superconductivity
Undated reference.
---------------------- Page: 4 ----------------------
NORME CEI
INTERNATIONALE IEC
61788-8
INTERNATIONAL
Première édition
STANDARD
First edition
2003-04
Supraconductivité –
Partie 8:
Mesure des pertes en courant alternatif –
Méthode de mesure par bobines de détection
des pertes totales en courant alternatif des fils
composites supraconducteurs de Cu/Nb-Ti
exposés à un champ magnétique alternatif
transverse
Superconductivity –
Part 8:
AC loss measurements –
Total AC loss measurement of Cu/Nb-Ti composite
superconducting wires exposed to a transverse
alternating magnetic field by a pickup coil method
© IEC 2003 Droits de reproduction réservés ⎯ Copyright - all rights reserved

Aucune partie de cette publication ne peut être reproduite ni No part of this publication may be reproduced or utilized in any

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électronique ou mécanique, y compris la photocopie et les photocopying and microfilm, without permission in writing from

microfilms, sans l'accord écrit de l'éditeur. the publisher.

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Telephone: +41 22 919 02 11 Telefax: +41 22 919 03 00 E-mail: inmail@iec.ch Web: www.iec.ch

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Pour prix, voir catalogue en vigueur
For price, see current catalogue
---------------------- Page: 5 ----------------------
61788-8 © IEC:2003 – 3 –
CONTENTS

FOREWORD .......................................................................................................................... 5

INTRODUCTION ....................................................................................................................7

1 Scope .............................................................................................................................. 9

2 Normative references....................................................................................................... 9

3 Terms and definitions ...................................................................................................... 9

4 Principle .........................................................................................................................13

5 Apparatus .......................................................................................................................15

6 Specimen preparation.....................................................................................................17

7 Testing conditions...........................................................................................................17

8 Calculation of results ......................................................................................................21

9 Precision and accuracy...................................................................................................25

10 Test report......................................................................................................................25

Annex A (informative) Explanation of AC loss measurement with Poynting’s vector .............31

Annex B (informative) Estimation of geometrical error in the pickup coil method ..................33

Annex C (informative) Recommended method for calibration of magnetization and

AC loss .................................................................................................................................35

Annex D (informative) Coupling loss for various types of applied magnetic field ..................39

Annex E (informative) Extension to three-component superconducting wires.......................41

Bibliography..........................................................................................................................43

Figure 1 – Standard arrangement of the specimen and pickup coils ......................................29

Figure 2 – A typical electrical circuit for AC loss measurement by pickup coils ......................29

Figure B.1 − Examples of calculated contour line map of the coefficient G for a

radius R of the coiled specimen and a difference a between radii of the specimen and

each pickup coil ....................................................................................................................33

Figure C.1 − Evaluation of critical field from magnetization curves ........................................37

Figure D.1 – Waveforms of applied magnetic field with a period T.........................................39

---------------------- Page: 6 ----------------------
61788-8 © IEC:2003 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
__________
SUPERCONDUCTIVITY –
Part 8: AC loss measurements –
Total AC loss measurement of Cu/Nb-Ti composite
superconducting wires exposed to a transverse alternating
magnetic field by a pickup coil method
FOREWORD

1) The IEC (International Electrotechnical Commission) is a worldwide organization for standardization comprising

all national electrotechnical committees (IEC National Committees). The object of the IEC is to promote

international co-operation on all questions concerning standardization in the electrical and electronic fields. To

this end and in addition to other activities, the IEC publishes International Standards. Their preparation is

entrusted to technical committees; any IEC National Committee interested in the subject dealt with may

participate in this preparatory work. International, governmental and non-governmental organizations liaising

with the IEC also participate in this preparation. The IEC collaborates closely with the International

Organization for Standardization (ISO) in accordance with conditions determined by agreement between the

two organizations.

2) The formal decisions or agreements of the IEC on technical matters express, as nearly as possible, an

international consensus of opinion on the relevant subjects since each technical committee has representation

from all interested National Committees.

3) The documents produced have the form of recommendations for international use and are published in the form

of standards, technical specifications, technical reports or guides and they are accepted by the National

Committees in that sense.

4) In order to promote international unification, IEC National Committees undertake to apply IEC International

Standards transparently to the maximum extent possible in their national and regional standards. Any

divergence between the IEC Standard and the corresponding national or regional standard shall be clearly

indicated in the latter.

5) The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any

equipment declared to be in conformity with one of its standards.

6) Attention is drawn to the possibility that some of the elements of this International Standard may be the subject

of patent rights. The IEC shall not be held responsible for identifying any or all such patent rights.

International Standard IEC 61788-8 has been prepared by IEC technical committee 90:

Superconductivity.
The text of this standard is based on the following documents:
FDIS Report on voting
90/135A/FDIS 90/140/RVD

Full information on the voting for the approval of this standard can be found in the report on

voting indicated in the above table.

This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.

The committee has decided that the contents of this publication will remain unchanged

until 2008. At this date, the publication will be
• reconfirmed;
• withdrawn;
• replaced by a revised edition, or
• amended.
---------------------- Page: 7 ----------------------
61788-8 © IEC:2003 – 7 –
INTRODUCTION

Magnetometer and pickup coil methods are proposed for measuring the AC losses of Cu/Nb-

Ti composite superconducting wires in transverse time-varying magnetic fields. These

represent initial steps in standardization of methods for measuring the various contributions to

AC loss in transverse fields, the most frequently encountered configuration.

It was decided to split the initial proposal mentioned above, into two documents covering two

standard methods. One of them describes the magnetometer method for hysteresis loss and

low frequency (or sweep rate) total AC loss measurement in a slowly varying magnetic field,

and the other describes the pickup coil method for total AC loss measurement in higher

frequency (or sweep rate) magnetic fields. The frequency range is 0 Hz to 0,06 Hz for the

magnetometer method and 0,005 Hz to 1 Hz for the pickup coil method. The overlap between

0,005 Hz and 0,06 Hz is a complementary frequency range for the two methods.

This standard covers the pickup coil method. The test method for standardization of AC loss

covered in this standard is partly based on the Versailles Project on Advanced Materials and

Standards (VAMAS) pre-standardization work on the AC loss of NbTi composite super-

conductors [1] .
___________
Figures in square brackets refer to the Bibliography.
---------------------- Page: 8 ----------------------
61788-8 © IEC:2003 – 9 –
SUPERCONDUCTIVITY –
Part 8: AC loss measurements –
Total AC loss measurement of Cu/Nb-Ti composite
superconducting wires exposed to a transverse alternating
magnetic field by a pickup coil method
1 Scope

This part of IEC 61788-8 specifies the measurement method of total AC losses by the pickup

coil method in Cu/Nb-Ti composite superconducting wires exposed to a transverse alternating

magnetic field. The losses may contain both hysteresis and coupling losses. The standard

method to measure only the hysteresis loss in DC or low-sweep-rate magnetic field is

specified in IEC 61788-13 [2].

The specimen shall be a multifilamentary round or rectangular wire, expected to be mainly

used for pulsed coil applications with relatively higher frequencies or sweep rates up to 1 Hz

or 4 T/s, with diameter or average size from 0,2 mm to 1,0 mm, filament diameter from 1 µm

to around 50 µm, and a coupling time constant less than about 40 ms.

The present method can be also extended to the AC loss measurement in a higher range of

frequency and sweep rate up to more than 10 Hz or 40 T/s for three-component

superconducting wires (IEV 815-04-33) with a shorter coupling time constant down to about

0,1 ms (see Annex E).
2 Normative references

The following referenced documents are indispensable for the application of this document.

For dated references, only the edition cited applies. For undated references, the latest edition

of the referenced document (including any amendments) applies.

IEC 60050-815, International Electrotechnical Vocabulary (IEV) – Part 815: Superconductivity

3 Terms and definitions

For the purposes of this part of IEC 61788, the definitions of IEC 60050-815 and the following

apply.
3.1
AC loss

power dissipated in a composite superconductor due to application of time-varying magnetic

field or current
[IEV 815-04-54]
---------------------- Page: 9 ----------------------
61788-8 © IEC:2003 – 11 –
3.2
hysteresis loss

loss of the type whose value per cycle is independent of frequency arising in a super-

conductor under a varying magnetic field

NOTE This loss is caused by the irreversible magnetic properties of the superconducting material due to pinning

of flux lines.
[IEV 815-04-55]
3.3
eddy current loss

loss arising in the normal matrix of a composite superconductor or the structural material

when exposed to a varying magnetic field, either from an applied field or from a self-field

[IEV 815-04-56, modified]
3.4
(filament) coupling (current) loss

loss arising in multi-filamentary superconducting wires with a normal matrix due to coupling

current
[IEV 815-04-59]
3.5
coupling time constant
ττττ

characteristic time constant of coupling current directed perpendicularly to filaments within

a strand for low frequencies
[IEV 815-04-60]
3.6
shielding current

current induced by a change of external magnetic field applied to a superconductor and which

includes coupling current and eddy current in composite superconductors
3.7
critical field strength

magnetic field strength corresponding to the superconducting condensation energy at zero

magnetic field strength
[IEV 815-01-21]
3.8
magnetization of a superconductor
magnetic moment divided by the volume of the superconductor

NOTE The macroscopic magnetic moment is also equal to the product of the shielding current and the area of

the closed path in a composite superconductor together with the magnetic moment of any penetrated trapped flux.

---------------------- Page: 10 ----------------------
61788-8 © IEC:2003 – 13 –
3.9
magnetization method for AC loss

method to determine the AC loss of materials from the area of the loop of the magnetization

curve

NOTE When pickup coils are used to measure the change in flux, which is then integrated to get the

magnetization of stationary coiled specimens, the method is called the pickup coil method.

[IEV 815-08-15, modified]
3.10
pickup coil method

method to determine the AC loss of materials by evaluating electromagnetic power flow into

the materials by pickup coils

NOTE The pickup coil arrangement consists essentially of a primary winding (a superconducting magnet supplied

with a time varying current) and a pair of secondary windings (pickup coils), one of which (the main pickup coil)

contains the specimen to be measured and the other (the compensation coil) plays two roles: 1) it compensates the

signal from the main pickup coil when empty; 2) it supplies the field sweep information.

Here the coaxial and concentric arrangement of the pickup coils as shown in Figure 1 is used as the standard one

for the AC loss measurement. In order to obtain sufficient volume of the wire specimen to be measured and at the

same time to expose it to a transverse magnetic field, it must be wound into a coil. The specimen so prepared is

also referred to as the “coiled specimen”.
3.11
background loss

apparent loss obtained by the pickup coil method in the case where no specimen is located

inside the pickup coils

NOTE The background loss gives the experimental error in the system of the AC loss measurement by the pickup

coil method. It results from phase shift of electrical signal in the compensation process, an additional magnetic

moment induced in many components of experimental hardware, and imbalance in the pickup coils.

3.12
effective cross-sectional area of the coiled specimen

total specimen volume divided by the larger of the specimen coil height or the pickup coil

height
3.13
bending strain
εεεε

strain in percent arising from pure bending defined as ε = 100 r / R, where r is a half of

the specimen thickness and R is the bending radius
[IEV 815-08-03]
4 Principle

The test consists of applying an alternating transverse magnetic field to a specimen and

detecting the magnetic moment of shielding currents induced in the specimen by means of

pickup coils for the purpose of estimating the AC losses defined in Clause 3.
---------------------- Page: 11 ----------------------
61788-8 © IEC:2003 – 15 –
5 Apparatus
5.1 Testing apparatus

The testing apparatus shall be constructed such that the pickup coils and a coiled specimen

are arranged in a uniform alternating magnetic field applied by a superconducting magnet.

The coils of the testing apparatus are arranged as described below. Typically, the main pickup

and compensation coils are coaxially positioned on the outside and inside of the coiled

specimen, respectively.

The applied alternating magnetic field shall have a high uniformity as shown in 7.1.5.

The testing apparatus has a sub-system that calculates the magnetization and the AC loss of

the specimen by integrating the signal of the pickup coils. A typical electrical circuit for the AC

loss measurement is given in Figure 2.
5.2 Pickup coils

Pickup coils shall be made of very fine insulated wire, such as insulated copper wire with

a diameter of 0,1 mm, to avoid eddy currents at low temperatures.

The pickup coil forms shall be made of non-metallic and non-magnetic material such as glass

fiber reinforced plastic, phenol resin, etc.

The main pickup coil shall be arranged coaxially and adjusted concentrically outside the

compensation coil. The standard arrangement is shown schematically in Figure 1, where the

height of the compensation coil is the same as that of the main pickup coil. The number of

turns in the compensation coil shall be usually adjusted to be a little larger than the balance

level in which the total interlinkage flux of the applied magnetic field into the compensation

coil is equal to that into the main pickup coil.

The pickup coil system shall be constructed so that the coiled specimen can be taken in and

out easily from the system.

The pickup coil method has geometrical error in relation with the arrangement of the coiled

specimen and the pickup coils. The geometrical error is mentioned briefly in Annex B. For a

reduced geometrical error of less than 1 %, the following arrangement for the coiled specimen

and the two pickup coils shall be the standard one; a height of 30 mm for the coiled specimen,

a height of 10 mm for the pickup coils, a coil radius of 18 mm for the specimen, and a

difference 2 mm between the radii of the specimen and each pickup coil. In the case where

the arrangement of the specimen and pickup coils are a little different from the above

standard one, the geometrical error in the arrangement shall be estimated, as shown in

Annex B. If the geometrical error cannot be estimated quantitatively, the calibration

indicated in Annex C may need to be performed.
5.3 Compensation circuit

The total interlinkage flux of the applied field in the compensation coil is usually a little larger

than that in the main pickup coil by adjusting the number of turns. The signal from the main

pickup coil is counterbalanced against a reduced signal of the compensation coil by means of

the compensation circuit. For delicate adjustment of the reduction ratio, called the

–4 –5

compensation coefficient, the compensation circuit has an accuracy of 10 to 10 to modify

the signal without a phase shift. For the conditions mentioned above, the compensation circuit

usually has the structure of a resistive potential divider.
---------------------- Page: 12 ----------------------
61788-8 © IEC:2003 – 17 –
6 Specimen preparation
6.1 Coiled specimen
6.1.1 Winding of specimen

A coil form shall be used to wind the specimen into a single-layer solenoidal coil. When the

specimen has an insulation layer, the turns of the coil shall be tightly wound right next to

adjacent turns. When the specimen surface is not coated with an insulating material, the

specimen shall be wound with an equal space between turns by inserting a non-metallic and

non-magnetic spacer such as a fishing line to achieve turn-to-turn insulation of the specimen.

The diameter of the spacer shall be approximately half the specimen diameter.
6.1.2 Configuration of coiled specimen

The coil height of the specimen shall be more than three times as high as that of the pickup

coil in order to reduce geometrical error coming from the end effects of the coiled specimen.

6.1.3 Maximum bending strain

The maximum bending strain induced in the winding of the specimen shall not exceed 5 %

and shall be preferably 3 %.
6.1.4 Treatment of terminal cross section of specimen

Both ends of a specimen shall be opened and filaments prevented from contacting each other.

Both ends of the specimen shall be ground by emery paper of 12 µm (800 mesh) to 7 µm

(1 000 mesh).
6.2 Specimen coil form

The form upon which the specimen is wound shall be made of non-metallic and non-magnetic

material such as glass fiber reinforced plastic and phenol resin. An adhesive, such as

cyanoacrylate or epoxy resin, shall be used as a bonding material to bond the specimen to

the coil form to keep the cylindrical coil shape.
7 Testing conditions
7.1 External applied magnetic field
7.1.1 Amplitude of applied field

The standard condition for the amplitude of applied field shall be 1 T. It is also recommended

that the amplitude of applied field be ranged from around 0,3 T to 1 T.
7.1.2 Direction of applied field
In a coiled specimen, the external field shall be applied along the coil axis.
7.1.3 Waveform of applied field

The standard waveform of the applied field shall be a sine waveform or a triangular waveform.

---------------------- Page: 13 ----------------------
61788-8 © IEC:2003 – 19 –
7.1.4 Frequency or sweep rate of applied field

When the waveform of the applied field is a sine waveform, the range of measurement

frequency shall be from 0,005 Hz to 1 Hz. When the waveform of the applied field is a

triangular waveform, the range of sweep rate shall be from 0,02 T/s to 4 T/s. The number of

measurement points shall be more than five in the fixed range of frequency or sweep rate so

as to calculate the coupling time constant for the coupling loss. In the measurement of

frequency dependence of AC losses, the amplitude of the applied field shall be fixed.

7.1.5 Uniformity of applied field

The applied field shall have uniformity within 5 % over the coil length of the specimen and

within 1 % over the length of the pickup coils.
7.2 Setting of the specimen

The coiled specimen shall be arranged coaxially and concentrically between a main pickup

coil and a compensation coil.
7.3 Measurement temperature

The specimen and the pickup coils shall be immersed in liquid helium. The measurement

temperature shall be determined using a calibrated thermometer or an atmospheric pressure

measurement.
7.4 Test procedure
7.4.1 Compensation

The first step of the compensation is to measure a hysteresis loop of magnetization of the

specimen for a fixed amplitude of applied field by subtracting the signal of the compensation

coil from that of the main pickup coil as they are. Since the total interlinkage flux of the

applied field into the compensation coil is a little larger than that into the main pickup coil,

the obtained magnetization loop is usually tilted against the horizontal axis of applied

magnetic field.

In the second step of the compensation, the signal from the compensation coil is loosely

modified by multiplying by a compensation coefficient slightly less than unity through the

compensation circuit to reduce the tilt of magnetization loop.

In the final step, the compensation coefficient is delicately adjusted to get the condition that

both branches of the magnetization curve in increasing and decreasing processes are

symmetric with respect to the horizontal axis in the regions around the extreme values of

applied field.
7.4.2 Measurement of background loss

In order to estimate background loss in the pickup coil system including pickup coils,

compensation circuit, amplifiers, etc., apparent loss shall be measured when no specimen is

located inside the pickup coils. The measurement procedure is the same as that for usual

specimens mentioned in 7.4.3.
---------------------- Page: 14 ----------------------
61788-8 © IEC:2003 – 21 –
7.4.3 Loss measurement

In the pickup coil method, the AC loss shall be calculated by integrating the product between

the compensated signal from the main pickup coil (moment related) and the signal from the

compensation coil (field related), following Equation (3). If the apparent background loss

cannot be neglected in the system of loss measurement, the AC loss for the specimen shall

be obtained by subtracting the background loss from the apparent, measured one. In the

correction by the background loss, attention shall be paid to the sign of the background loss.

The AC loss can be also estimated by integrating the magnetization for the applied field

through a period, as shown in Annex A.
7.4.4 Calibration

In general, calibration is a basic procedure in the AC loss measurement with imperfect

detection of signals. A recommended method of the calibration is given in Annex C. On the

other hand, if the conditions for the configuration of the pickup coils and the coiled specimen,

indicated in Clauses 5 and 6 and Annex B, are satisfied, the AC loss and magnetization

measurements with an error less than a few percent can be performed without calibration.

However, when the configuration of the pickup coil system is outside the given conditions, the

calibration indicated in Annex C may need to be performed.
8 Calculation of results
8.1 Amplitude of applied magnetic field

The applied field H (t) shall be calculated by substituting the measured voltage U (t) from the

e c
compensation coil into Equation (1):
(1)
H ()t = U ()t' dt'
e c
µ N S
0 c c
where N and S are the number of turns and the interlinkage area per turn of the
c c

compensation coil, respectively. The initial time of integration is a zero-crossing point of U

...

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