IEC 60404-10:2016

IEC 60404-10 ®
Edition 2.0 2016-10
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Magnetic materials –
Part 10: Methods of measurement of magnetic properties of magnetic electrical
steel strip and sheet at medium frequencies

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IEC 60404-10 ®
Edition 2.0 2016-10
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Magnetic materials –
Part 10: Methods of measurement of magnetic properties of magnetic electrical

steel strip and sheet at medium frequencies

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.030 ISBN 978-2-8322-3725-0

– 2 – IEC 60404-10:2016 RLV © IEC 2016

CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Field and scope of application .
2 Accuracy and reproducibility .
1 Scope . 7
4 Field of application .
2 Normative references . 7
3 Terms and definitions . 8
4 General principle of a.c. measurements . 8
4.1 General . 8
4.2 Principle of the 25 cm Epstein frame method . 8
4.3 Test specimen . 8
4.4 The 25 cm Epstein frame . 9
4.5 Air flux compensation . 11
4.6 Power supply . 12
10 Scope .
11 Field of application .
12 Principle of measurement .
13 Apparatus .
4.7 Voltage measurement . 13
4.7.1 General . 13
4.7.2 Average type voltmeter . 13
4.7.3 RMS voltmeter . 13
4.8 Current measurement . 13
4.9 Frequency measurement . 13
4.10 Power measurement . 13
5 Measuring Procedure for the determination of the specific total loss . 14
5.1 General . 14
5.2 Preparation for measurement . 14
5.3 Source setting Adjustment of power supply . 15
5.4 Measurements of power . 16
5.5 Determination of the specific total losses . 16
5.6 Reproducibility of the specific total loss measurement . 17
6 Procedure for the determination of the peak value of magnetic polarization, r.m.s.
value of magnetic field strength, peak value of magnetic field strength and specific
apparent power . 17
6.1 Scope General . 17
6.2 Test specimen . 17
6.3 Principle of measurement. 18
ˆ
6.3.1 Peak value of magnetic polarization J . 18
6.3.2 RMS value of the excitation magnetizing current (of the magnetic field
strength) . 18
6.3.3 Peak value of magnetic field strength . 18
6.4 Apparatus . 20
6.4.1 Average rectified voltage measurement . 20

6.4.2 Current measurement . 20
6.4.3 Peak current measurement . 20
6.4.4 Resistor R . 20
n
6.4.5 Mutual inductor M . 20
D
6.5 Measuring procedure . 20
21 Determination of characteristics .
ˆ
6.6 Determination of the peak value of magnetic polarization J . 21
~
6.7 Determination of the r.m.s. value of magnetic field strength H . 22

ˆ
6.8 Determination of the peak value of magnetic field strength H . 22
6.9 Determination of the specific apparent power S . 23
s
6.10 Reproducibility . 24
7 Test report . 24
Annex A (informative) Epstein frame for use at medium frequencies . 25
Annex B (informative) Digital sampling method for the determination of the magnetic
properties . 26
B.1 General . 26
B.2 Technical details and requirements . 26
B.3 Calibration aspects . 28
B.4 Numerical air flux compensation . 29
Bibliography . 30

Figure 1 – Double-lapped joints . 8
Figure 2 – The 25 cm Epstein frame . 10
Figure 3 – Circuit for the wattmeter method . 15
Figure 4 – Circuit for measuring r.m.s. value of the excitation magnetizing current . 18
Figure 5 – Circuit for measuring the peak value of magnetic field strength using a peak
voltmeter . 19
Figure 6 – Circuit for measuring the peak value of magnetic field strength using a
mutual inductor M . 19

– 4 – IEC 60404-10:2016 RLV © IEC 2016

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
MAGNETIC MATERIALS –
Part 10: Methods of measurement of magnetic properties
of magnetic electrical steel strip and sheet at medium frequencies

FOREWORD
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International Standard IEC 60404-10 has been prepared by IEC technical committee 68:
Magnetic alloys and steels.
This second edition cancels and replaces the first edition published in 1988. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) adaption to modern measurement and evaluation methods, in particular the introduction of
the widely spread digital sampling method for the acquisition and evaluation of the
measured data;
b) introduction of formal changes which adapt this standard to other standards of the 60404
series;
c) revision of the problem of the air flux compensation taking account of the condition of the
higher frequencies;
d) revision of the capacitive coupling of mutual inductor windings together with the
consideration of the alternative method of numerical air flux compensation.
The text of this standard is based on the following documents:
CDV Report of voting
68/523/CDV 68/556/RVC
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.
A list of all parts in the IEC 60404 series, published under the general title Magnetic materials,
can be found on the IEC website.
The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC website under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
The contents of the corrigendum of March 2018 have been included in this copy.
IMPORTANT – The “colour inside” logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct understanding
of its contents. Users should therefore print this publication using a colour printer.

– 6 – IEC 60404-10:2016 RLV © IEC 2016

INTRODUCTION
1 Field and scope of application
This standard is applicable to magnetic steel sheet and strip for the construction of magnetic
circuits for use in the frequency range 400 Hz to 10 000 Hz.
Its object is to define the terminology and to specify the methods for the measurement of
magnetic properties of magnetic steel sheet and strip.
2 Accuracy and reproducibility
The final accuracy of the test apparatus is a complex function dependent on the measuring
instruments and other features of the measuring environment and equipment components;
therefore it is not always possible to state the absolute accuracy which can be attained.
Moreover, experience in the use of a given method indicates the reproducibility which can be
expected. Whenever the drafting Technical Committee has agreed upon reproducibility values,
these have been given in this standard.
Besides the fact that the first edition of this part of IEC 60404 is more than 25 years old, the
main purpose of this revision is to adapt it to modern measurement and evaluation methods,
in particular to introduce the widely spread digital sampling method for the acquisition and
evaluation of the measured data.
In addition, the problem of the air flux compensation had to be re-considered under the
condition of the elevated frequencies. Capacitive coupling of mutual inductor windings require
observance of significant phase shift influence and suggest consideration of the alternative
method of numerical air flux compensation. An increase of the frequency range to 20 kHz was
discussed by TC 68 since some manufacturers of electrical steel include this range in their
catalogues. However, TC 68 decided to keep the frequency range to that defined in
IEC 60404-10:1988: 400 Hz to 10 kHz.

MAGNETIC MATERIALS –
Part 10: Methods of measurement of magnetic properties
of magnetic electrical steel strip and sheet at medium frequencies

CHAPTER I: GENERAL CONDITIONS FOR A.C. MEASUREMENTS
MADE WITH THE 25 CM EPSTEIN FRAME

1 Scope
This chapter specifies the general conditions for the determination of a.c. magnetic properties
of magnetic steel sheet and strip by means of the 25 cm Epstein frame.
This part of IEC 60404 is applicable to grain-oriented and non-oriented electrical steel strip
and sheet for measurements of a.c. magnetic properties in the frequency range 400 Hz to
10 000 Hz.
The object of this document is to define the general principles and the technical details of the
measurement of magnetic properties of electrical steel strip and sheet by means of an Epstein
frame.
4 Field of application
The use of the 25 cm Epstein frame is applicable to flat strip test specimens obtained from
magnetic electrical steel strips and sheets of any quality grade. The AC magnetic properties
characteristics are determined for a sinusoidal induced voltages, for specified peak values of
magnetic polarization and for a specified frequency.
The measurements are to be made at an ambient temperature of (23 ± 5)°C on test
specimens which have first been demagnetized.
NOTE Throughout this document the term "magnetic polarization" is used as defined in IEC 60050-221. In some
standards of the IEC 60404 series, the term "magnetic flux density" was used.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their
content constitutes requirements 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 60050-121, International Electrotechnical Vocabulary – Part 121: Electromagnetism
IEC 60050-221, International Electrotechnical Vocabulary – Chapter 221: Magnetic materials
and components
IEC 60404-8 (all parts), Magnetic materials – Part 8: Specifications for individual materials
IEC 60404-13, Magnetic materials – Part 13: Methods of measurement of density, resistivity
and stacking factor of electrical steel sheet and strip

– 8 – IEC 60404-10:2016 RLV © IEC 2016

3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60050-221 and
IEC 60050-121 apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
4 General principle of a.c. measurements
4.1 General
Clause 4 specifies the general conditions for the determination of a.c.magnetic properties of
electrical steel strip and sheet by means of the 25 cm Epstein frame.
4.2 Principle of the 25 cm Epstein frame method
The 25 cm Epstein frame, which comprises a primary winding, a secondary winding and the
specimen to be tested as a core, forms an unloaded transformer whose properties
characteristics are measured by the method described in the following subclauses 4.3 to 4.10.
At the higher end of the frequency range, a specially constructed Epstein frame (see Annex A)
may be required in which the interwinding capacitances are low, so that the capacitive part of
the impedance has a negligible impact on the loss results. The material of the winding formers
supporting the solenoids windings has a low dielectric loss.
A separate measuring system (for example a commercially available universal digital bridge
capable of measuring resistance, capacitance and inductance) is required to determine the
inter-winding capacitance of the Epstein frame.
4.3 Test specimen
The magnetic circuit shall be made up of a core constructed with the strips to be tested,
assembled in a square having double-lapped joints (see Figure 1) to form four branches The
strips to be tested are assembled in a square, having double-overlapped corner joints (see
Figure 1) thus forming four limbs of equal length and equal cross-sectional area.
IEC
Figure 1 – Double-lapped joints
The strips shall be sampled in accordance with the appropriate product standard in the
IEC 60404-8 series.
They shall be cut by a method which will produce clean substantially burr-free edges and, if
so specified, heat treated in accordance with the corresponding product standard. They shall
have the following dimensions:
– width b = 30 mm ± 0,2 mm;
– length 280 mm ≤ l ≤ 500 320 mm

The strips being of the same length of the strips shall be equal within a tolerance of
± 0,5 mm.
For strips of length greater than 305 mm, care shall be taken to avoid bending the strips
during the test.
When the strips are cut parallel or normal to the direction of rolling, the edge of the parent
sheet shall be taken as the reference direction.
The following tolerances shall be allowed apply for the angle between the specified and actual
direction of rolling and that of cutting:
– ± 1° for grain-oriented steel sheet;
– ± 5° for non-oriented steel sheet.
Only flat strips shall be used. Measurements shall be made without additional insulation.
The number of strips forming a comprising the test specimen shall be not less than twelve and
shall be a multiple of four. A force of (1 ± 0,1) N shall be applied to each corner, normal to the
plane of the overlapping strips.
4.4 The 25 cm Epstein frame
The 25 cm Epstein frame (hereinafter referred to as the Epstein frame) shall consist of four
solenoids into which the test specimen strips are introduced inserted in such a manner that a
closed magnetic circuit is formed (see Figure 2).

– 10 – IEC 60404-10:2016 RLV © IEC 2016

Dimensions in millimetres
+1
220  0
≥190
l = 940
IEC
Figure 2 – The 25 cm Epstein frame
If measurements are to be made under the conditions specified in 4.5, a mutual inductor for
air flux compensation shall may be provided.
The winding formers supporting the solenoids windings shall be made of hard insulating
material of low dielectric loss, such as polystyrene. They have a rectangular cross-section
with 32 mm inner width. A height of about approximately 5 mm will be sufficient and is
recommended.
The solenoids shall be mounted on a non-conducting fixed to an insulating and non-magnetic
base plate in a square arrangement in such a way to form a square (see Figure 2). Each side
of the inner square formed by the test specimen strip shall have a length of The length of the
sides of the square formed by the internal edges of the strips of the test specimen shall be
+
220 mm (see Figure 2).
In order to avoid undue wear of the winding formers and especially of their inner surfaces,
winding formers of larger cross-section can be used into which replaceable liners of
appropriate dimensions may be inserted.
Each of the four solenoids comprises shall have two windings:
– a primary winding, on the outside (magnetizing winding);
– a secondary winding, on the inside (voltage winding).
The windings on each solenoid shall be evenly distributed uniformly over a minimum length of
190 mm, each solenoid carrying one-fourth having one quarter of the total number of turns.
The individual primary windings of the four solenoids shall be connected in series, and the
individual secondary windings shall be connected in a similar fashion.
At high frequencies the higher end of the frequency range, the loss contribution due to the
capacitance between the primary and secondary windings and also the self-capacitance of the
secondary winding could be significant. The windings shall be spaced to minimize this loss.

The capacitance between the windings and the self-capacitance of the secondary winding
shall be measured. If necessary, a correction shall be applied for the loss introduced.
The number of turns of primary and secondary windings shall be chosen to suit the particular
conditions of the power supply, instrumentation and measuring equipment and frequency.
A total number of 200 turns for each of the primary and secondary windings is recommended
and is commonly used for tests in the frequency range 400 Hz to 10 000 Hz.
The impedance of the magnetizing windings shall be sufficiently small to avoid waveform
distortion and minimize internal voltage drops.
The effective magnetic path length, l , of the magnetic path circuit in this test equipment is
m
shall be conventionally taken as assumed to be equal to 0,94 m. This value shall be used.
Consequently, The effective active mass, m , i.e. the magnetically active mass of the test
a
specimen, is given by:
l
m
m = m (1)
a
4l
where:
m is the effective magnetically active mass of test specimen, in kilograms;
a
m is the mass of test specimen, in kilograms;
l is the conventional effective magnetic path length, in metres (l = 0,94 m);
m m
l is the length of a test specimen strip, in metres.
4.5 Air flux compensation
A correction compensation for air flux shall be made for magnetic field strengths greater than
or equal to 1 000 A/m. For low frequencies At the lower end of the frequency range (less than
or equal to 1 000 Hz) a mutual inductor may be used to compensate for the air flux.
The mutual inductance of the compensator shall be adjusted to be the same as that of the
windings of the empty Epstein frame. Thus when the windings are properly connected, the
voltage induced in the secondary winding of the mutual inductor by the primary current
compensates for the voltage induced in the secondary winding of the empty Epstein frame by
the flux attributed to the primary current.
The primary winding of the mutual inductor shall be connected in series with the primary
winding of the Epstein frame, and the secondary winding of the mutual inductor shall be
connected to the secondary winding of the Epstein frame in series opposition (see Figure 3).
An adjustment of the value of the mutual inductance shall be made so that, when passing an
alternating current through the combined primary windings in the absence of the specimen in
the apparatus, the voltage measured between the non-common terminals of the combined
secondary windings shall be no more than 0,1 % of the voltage appearing across the
secondary winding of the test apparatus alone.
Thus the average rectified value of the voltage induced in the combined secondary windings
is proportional to the peak value of the magnetic polarization in the test specimen.
At the higher end of the frequency range, coupling through interwinding capacitances of the
mutual inductor can lead to a significant phase shift of the secondary induced voltage
followed by a relevant error in the measurement of the magnetic loss value. It has to be
ensured that the mutual inductance does not lead to a significant phase shift of the secondary

– 12 – IEC 60404-10:2016 RLV © IEC 2016

induced voltage. Appropriate design of the secondary winding of the mutual inductor, i.e.
larger distances between the windings, can avoid the phase shift. If, at the higher end of the
frequency range, a relevant phase shift cannot be avoided in this way, the mutual inductor
shall be removed from the measurement circuit and numerical air flux compensation shall be
applied (see Clause B.4).
4.6 Power supply
The source power supply shall be of have a low internal impedance and shall be highly stable
a high stability of voltage and frequency. During the measurement, the voltage and frequency
variations shall not exceed ± 0,2 % of the specified required value.
For the determination of the specific total loss, the specific apparent power and r.m.s. value of
the magnetic field strength, the form factor of the secondary induced voltage shall be
maintained 1,111 within ± 1 % (this can be achieved by various means, e.g. electronic
feedback amplifiers).
NOTE This is possible in several ways; for example by using an electrically controlled power supply or a negative
feedback power amplifier.
The form factor of the secondary induced voltage is the quotient ratio of the its r.m.s. value
and the to its average rectified value. The former is measured by an r.m.s. voltmeter, such as
a moving iron instrument, and the latter by an average type voltmeter, such as a rectifier-type
instrument. Two voltmeters, one responsive to r.m.s. values and the other responsive to
average rectified values shall be used to determine the form factor.
NOTE When a negative feedback amplifier is used for the supply, it may be necessary to
observe the waveform of the secondary induced voltage on an oscilloscope to ensure that the
correct waveform of the fundamental frequency is being produced.

CHAPTER II: DETERMINATION OF SPECIFIC TOTAL LOSSES
BY THE WATTMETER METHOD
10 Scope
This chapter describes the wattmeter method for the determination of the specific total losses
of magnetic steel sheet and strip at frequencies in the range 400 Hz to 10 000 Hz.
11 Field of application
The specific total losses are determined, according to this method, for specified peak values
of magnetic polarization and for a specified frequency.
In order to obtain comparable results, test values shall be referred to magnetic polarization of
sinusoidal waveform.
NOTE Throughout this publication the term "magnetic polarization" is used as defined in Chapter 901 of the
International Electrotechnical Vocabulary (IEV) [IEC Publication 50(901)]. In some publications of the IEC 404
series, the term "magnetic flux density" has been used.
12 Principle of measurement
The 25 cm Epstein frame with the test specimen represents an unloaded transformer whose
total losses are measured by the wattmeter method in the circuit shown in Figure 3 which
illustrates the principle.
13 Apparatus
4.7 Voltage measurement
4.7.1 General
The secondary induced voltage shall be measured by means of appropriate voltmeters having
an input impedance greater than or equal to 1 000 Ω/V.
NOTE For the application of digital sampling methods, see Annex B.
4.7.2 Average type voltmeter
The average value of the secondary rectified voltage of the Epstein frame shall be measured
with an average type voltmeter of accuracy 0.5% or better, e.g. a rectifier type digital
voltmeter. A voltmeter responsive to average rectified values having an accuracy of ± 0,5 %
or better shall be used.
NOTE 1 Instruments of this type are usually graduated in average rectified value multiplied by 1,111.
The load on the secondary circuit of the network shall be as small as possible. Consequently,
the internal resistance of the average type voltmeter shall be at least 1 000 Ω/V.
NOTE 2 The preferred instrument is a digital voltmeter.
4.7.3 RMS voltmeter
A voltmeter responsive to r.m.s. values having an accuracy of ± 0,5 % or better shall be used.
NOTE e.g. a r.m.s. sensing The preferred instrument is a digital voltmeter.
4.8 Current measurement
The primary magnetizing current may shall be measured by either:
– an class 1 ammeter having an accuracy ± 0,5 % or better of low impedance;
or
– measuring the voltage drop across a non-inductive precision resistor connected in series
with the primary winding. The combined uncertainties of the resistor and the voltmeter shall
not exceed 1 %.
The ammeter and the precision resistor, respectively, current measuring device shall be short-
circuited when the secondary induced voltage is has been adjusted and the losses are is
being measured.
NOTE 1 The preferred instrument is a digital ammeter or a digital voltmeter.
NOTE 2 For the application of digital sampling methods, see Annex B.
4.9 Frequency measurement
A frequency meter having an accuracy 0.2 ± 0,1 % or better shall be used.
NOTE For the application of digital sampling methods, see Annex B.
4.10 Power measurement
The power shall be measured by a wattmeter having an accuracy of ± 0,5 % or better at the
frequency, power factor, and crest factor to be used. Readings in the first quarter of the scale
shall be avoided as far as possible.

– 14 – IEC 60404-10:2016 RLV © IEC 2016

NOTE For the application of digital sampling methods, see Annex B.
The resistance of the voltage circuit of the wattmeter shall be greater than or equal to at least
100 Ω/V for all ranges. If necessary the losses in the secondary circuit shall be subtracted
from the indicated loss value.
Moreover, the ohmic resistance of the voltage circuit of the wattmeter shall be at least 5 000
times the its reactance, unless the wattmeter is compensated for its reactance, to avoid
necessary corrections of phase angle.
5 Measuring Procedure for the determination of the specific total loss
5.1 General
Clause 5 describes the wattmeter method for the determination of the specific total loss of
electrical steel strip and sheet at frequencies in the range 400 Hz to 10 000 Hz.
The specific total loss is determined, according to this method, for specified peak values of
magnetic polarization and for a specified frequency.
In order to obtain comparable results, test values shall be referred to magnetic polarization of
sinusoidal waveform.
5.2 Preparation for measurement
The Epstein frame and measuring equipment shall be connected as shown in Figure 3.

A1
S1
V1 V2
E
F1
M
W1
IEC
Components
V1 mesures average rectified voltage type voltmeter
V2 mesures r.m.s. voltage voltmeter
A1 current measuring device
F1 frequency meter
W1 wattmeter
M mutual inductor
c
E Epstein frame
S1 switch
NOTE The circuit diagram of Figure 3 illustrates the principle of the wattmeter method. It also sets out the
fundamentals of the digital Wattmeter method where the instrumental functions are realized partly through the
evaluating software.
Figure 3 – Circuit for the wattmeter method
The test specimen shall be weighed and its mass determined within ± 0,1 %. After weighing,
the strips shall be loaded into the solenoids of the Epstein frame with forming double-
overlapping corner joints. In the case of strips which are cut half in the direction of rolling and
half normal to that direction, care shall be taken that all the strips cut in the direction of rolling
are placed in two opposite arms solenoids of the frame and that those cut normal to that
direction are placed in the two other opposite arms solenoids. The joints shall form a minimum
gap between the strips. The strips shall be positioned so as to conform with the requirements
of 4.4. The number of strips shall be the same in each solenoid.
Before measurement, the test specimen shall be demagnetized by a decreasing alternating
magnetic field of an initial level higher than used in previous measurements.
5.3 Source setting Adjustment of power supply
ˆ
In order to achieve the specified peak value of the polarisation, J , the source power supply
output shall be adjusted so that the average rectified value of the secondary induced voltage
is:
 R 
i ˆ
 
U = 4 fN AJ (2)
2 2
 
R +R
 i t 
where:
U is the average rectified value of the voltage induced in the combined secondary rectified
voltage windings, in volts;
– 16 – IEC 60404-10:2016 RLV © IEC 2016

f is the frequency, in hertz;
R is the combined equivalent resistance of instruments in the secondary circuit, in ohms;
i
R is the series resistance of the combined secondary windings of Epstein frame and
t
mutual inductor, in ohms;
N is the number of turns of the secondary winding of the Epstein frame;
A is the cross-sectional area of the test specimen, in square metres;
ˆ
J is the peak value of magnetic polarization, in teslas.
The cross-sectional area of the test specimen, A, is obtained by the formula:
m
A = (3)
4lρ
m
where:
m is the total mass of test specimen, in kilograms;
l is the length of a test specimen strip, in metres;
ρ is the conventional density, or the value determined in accordance with IEC 60404-13,
m
of the test material, in kilograms per cubic metre.
5.4 Measurements of power
The ammeter in the primary circuit shall be observed to ensure that the current circuit of the
wattmeter is not overloaded. Then the ammeter shall be short-circuited and the secondary
induced voltage readjusted. After checking the waveform of the secondary induced voltage in
compliance with 4.6, the wattmeter shall be read.
NOTE In order to avoid undue heating of the test specimen and to facilitate reproducibility,
measurements should be made as quickly as possible after energizing the Epstein frame. The
specimen should be allowed to cool between readings.
NOTE For the application of digital sampling methods, see Annex B.
5.5 Determination of the specific total losses
The power, P , measured by the wattmeter includes the power consumed by the instruments
m
in the secondary circuit, which to a first approximation is equal to (1,111⋅ U ) / R since the
2 i
secondary induced voltage is essentially sinusoidal.
NOTE For the application of digital sampling methods, see Annex B.
Thus, the total losses, P of the test specimen shall be calculated from the formula:
c
 
1,111⋅ U
 
N
 
P = ⋅ P – (4)
c m
N R
2 i
where:
P is the calculated total losses of test specimen, in watts;
c
P is the power measured by the wattmeter, in watts;
m
N is the number of turns of the primary winding;
N is the number of turns of the secondary winding;
R is the combined equivalent resistance of the instruments in the secondary circuit, in
i
ohms;
U is the average rectified value of the voltage induced in the combined secondary rectified
voltage winding, in volts.
The specific total losses, P shall be obtained by dividing P by the effective magnetically
s c
active mass of the test specimen (see 4.4).
P P ⋅ 4l
c c
P = = (5)
s
m m ⋅ l
a m
where:
P is the specific total losses of test specimen, in watts per kilogram (corrected if
s
necessary for flux waveform distortion according to 4.4);
m is the total mass of test specimen, in kilograms;
m is the effective magnetically active mass of test specimen, in kilograms;
a
l is the length of a test specimen, in metres;
l is the conventional effective magnetic path length, in metres (l = 0,94 m).
m m
5.6 Reproducibility of the specific total loss measurement
The reproducibility of the results obtained from this method is characterized by a relative
standard deviation in the range between 2% and 5%, the value of this standard deviation
depending on the frequency and the magnetic polarization which are used.

CHAPTER III: DETERMINATION OF MAGNETIC FIELD STRENGTH,
EXCITATION CURRENT AND SPECIFIC APPARENT POWER

6 Procedure for the determination of the peak value of magnetic polarization,
r.m.s. value of magnetic field strength, peak value of magnetic field strength
and specific apparent power
6.1 Scope General
Clause 6 describes measuring methods for the determination of the following quantities:

~
– r.m.s. value of the excitation current I ;
ˆ
– peak value of magnetic polarization J ;
~
– r.m.s. value of magnetic field strength H ;
ˆ
– peak value of magnetic field strength H ;
– specific apparent power S .
s
The quantities are determined, according to these methods, for specified peak values of
magnetic polarization and for a specified frequency.
6.2 Test specimen
The test specimen shall comply with 4.3.
...