IEC 60404-3:1992/AMD2:2009

IEC 60404-3 ®
Edition 2.0 2009-11
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
AMENDMENT 2
AMENDEMENT 2
Magnetic materials –
Part 3: Methods of measurement of the magnetic properties of electrical steel
strip and sheet by means of a single sheet tester

Matériaux magnétiques –
Partie 3: Méthodes de mesure des caractéristiques magnétiques des bandes et
tôles magnétiques en acier à l'aide de l'essai sur tôle unique

IEC 60404-3:1992/A2:2009
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IEC 60404-3 ®
Edition 2.0 2009-11
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
AMENDMENT 2
AMENDEMENT 2
Magnetic materials –
Part 3: Methods of measurement of the magnetic properties of electrical steel
strip and sheet by means of a single sheet tester

Matériaux magnétiques –
Partie 3: Méthodes de mesure des caractéristiques magnétiques des bandes et
tôles magnétiques en acier à l'aide de l'essai sur tôle unique

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
G
CODE PRIX
ICS 17.220.20; 29.030 ISBN 978-2-88910-185-6
– 2 – 60404-3 Amend. 2 © IEC:2009
FOREWORD
This amendment has been prepared by IEC technical committee 68: Magnetic alloys and steels.
The text of this amendment is based on the following documents:
CDV Report on voting
68/389/CDV 68/397/RVC
Full information on the voting for the approval of this amendment can be found in the report
on voting indicated in the above table.
The committee has decided that the contents of this amendment and the base publication will
remain unchanged until the maintenance result date indicated on the IEC web site 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• withdrawn,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 December 2009 have been included in this copy.
_____________
Title
Amend the title of this standard on the cover page, the title page, and before the Foreword
and Clause 1 as follows:
Replace “magnetic sheet and strip” by “electrical steel strip and sheet”.
2 Normative references
Replace the existing references by the following:
IEC 60050-221, International Electrotechnical Vocabulary – Part 221: Magnetic materials
and components
IEC 60404-2, Magnetic materials – Part 2: Methods of measurement of the magnetic
properties of electrical steel strip and sheet by means of an Epstein frame
4.2.1 Voltage measurement
Insert, after the subclause title and before 4.2.1.1 the following new note:
NOTE For the application of digital sampling methods, see Annex D.

60404-3 Amend. 2 © IEC:2009 – 3 –
4.2.2 Frequency measurement
Introduce the following note after the paragraph:
NOTE For the application of digital sampling methods, see Annex D.

4.2.3 Power measurement
Introduce the following note after the first paragraph:
NOTE For the application of digital sampling methods, see Annex D.

4.3 Measurement procedure
Replace the existing title by the following new title:
4.3 Measurement procedure of the specific total loss
Introduce the following note after the clause heading:
NOTE For the application of digital sampling methods, see Annex D.

Add the following new Annex D:

– 4 – 60404-3 Amend. 2 © IEC:2009
Annex D
(informative)
Digital sampling methods for the determination
of the magnetic properties
D.1 General
The digital sampling method is an advanced technique that is becoming almost exclusively
applied to the electrical part of the measurement procedure of this standard. It is
characterized by the digitalization of the secondary voltage, U (t), the voltage drop across the
non-inductive precision resistor in series with the primary winding (see Figures 4 and 6),
U (t), and the evaluation of the data for the determination of the magnetic properties of the

test specimen. For this purpose, instantaneous values of these voltages having index j, u
2j
and u respectively, are sampled and held simultaneously from the time-dependent voltage

1j
functions during a narrow and equidistant time period each by sample-and-hold circuits. They
are then immediately converted to digital values by analog-to-digital converters (ADC). The
data pairs sampled over one or more periods together with the specimen and the set-up
parameters, provide the complete information for one measurement. This data set enables
computer processing for the determination of all magnetic properties required in this standard.
The digital sampling method may be applied to the measurement procedures which are
described in the main part of this standard. The block diagram in Figure 4 applies equally to
the analogue methods and the digital sampling method; the digital sampling method allows all
functions of the measurement equipments in Figure 4 to 6 to be realized by a combined
system of a data acquisition equipment and software. The control of the sinusoidal waveform
of the secondary voltage can also be realized by a digital method. However, the purpose and
procedure of this technique are different from those of this annex and are not treated here.

More information can be found in [3] and [4].
This annex is helpful in understanding the impact of the digital sampling method on the
precision achievable by the methods of this standard. This is particularly important because
ADC circuits, transient recorders and supporting software are easily available thus
encouraging one to build one’s own wattmeter. The digital sampling method can offer low
uncertainty, but it leads to large errors if improperly used.
D.2 Technical details and requirements
The principle of the digital sampling method is the discretization of voltage and time, i.e. the
replacement of the infinitesimal time interval dt by the finite time interval Δt:
T 1 1
(D.1)
Δt = = =
n f ⋅ n f
s
where
Δt is the time interval between the sampled points, in seconds;
T is the length of the period of the magnetization, in seconds;
n is the number of instantaneous values sampled over one period;
f is the frequency of the magnetization, in hertz;
f is the sampling frequency, in points per seconds.

s
60404-3 Amend. 2 © IEC:2009 – 5 –
In order to achieve lower uncertainties, the length of the period of the magnetization divided
by the time interval between the sampled points, i.e. the ratio f /f, should be an integer
s
(Nyquist condition [7]) and the sampling frequency, f , should be greater than twice the input
s
signal bandwidth.
According to an average-sensing voltmeter, the peak value of the flux density can be
calculated by the sum of the u values sampled over one period as follows:
2j
T
n −1
1 1 1
ˆ
(D.2)
J = U (t )dt ≅ u
2 ∑ 2 j
∫
4fN A T 4f N A
2 s 2
j =0
t =0
The calculation of the specific total loss is carried out by point-by-point multiplication of the u
2j
and u values and summation over one period as follows :

1j
T
n −1
N 1 N 1
1 1
(D.3)
P = U ()t U (t)dt ≅ u u
s 1 2 1j 2 j
∑
∫
l RN Aρ T l RN Aρ n
m 2 m m 2 m
j =0
t =0
where
ˆ
J is the peak value of the magnetic polarization, in teslas;
P is the specific total loss of the specimen, in watts per kilogram;
s
T is the length of the period of the magnetization, in seconds;
f is the frequency of the magnetization, in hertz;
f is the sampling frequency, in points per second;

s
N is the number of turns of the primary winding;
N is the number of turns of the secondary winding;
A is the cross-sectional area of the test specimen, in square metres;
R is the resistance of the non-inductive precision resistor R in series with the primary
winding (see Figure 6), in ohms;
U is the voltage drop across the non-inductive precision resistor R, in volts;
U is the secondary voltage, in volts;
n is the number of instantaneous values sampled over one period;
j is the index of instantaneous values;
l is the conventional effective magnetic path length, in metres (l = 0,45 m; for
m m
measurements in connection with a calibration by means of Epstein measurements, see
Annex B);
ρ is the conventional density of the test material, in kilograms per cubic metre.
m
—————————
The peak value of the magnetic field strength and the apparent power can be calculated correspondingly by
using
n n
N
N 1 1
ˆ ˆ
1 1 2 2
and
H = U
S ≅ u u
s ∑ 1j ∑ 2 j
Rl
l RN Aρ n n
m
m 2 m
j = 0 j = 0
– 6 – 60404-3 Amend. 2 © IEC:2009
The pairs of values, u and u , can then be processed by a computer or, for real time
2j 1j
processing, by a digital signal processor (DSP) using a sufficiently fast digital multiplier and
adder without intermediate storage being required. Keeping the Nyquist condition is possible
only where the sampling frequency f and the frequency f of the magnetization are derived
s
from a common high frequency clock and thus, have an integer ratio f /f. In that case, U (t)
s
and U (t) may be scanned using 128 samples per period with sufficient accuracy. This figure
is, according to the Shannon theorem, determined by the highest relevant frequency in the
st
H(t) signal, which is normally not higher than that of the 41 harmonic [5]. However, some
commercial data acquisition equipment cannot be synchronized with the frequency of the
magnetization and, as a consequence, the ratio f /f is not an integer, i.e. the Nyquist condition
s
is not met. In that case, the sampling frequency must be considerably higher (500 samples
per period or more) in order to keep the deviation of the true period length from the nearest
time of sampled point small. Keeping the Nyquist condition becomes a decisive advantage in
the case of higher frequency applications (for instance at 400 Hz which is within the scope of
this standard). The use of a low-pass anti-aliasing filter [7] is recommended in order to
eliminate irrelevant higher frequency components which would otherwise interact with the
digital sampling process producing aliasing noise.
Regarding the amplitude resolution, studies [5, 6] have shown that below a 12 bit resolution,
the digitalization error can be considerable, particularly for non-oriented material with high
silicon content. Thus, at least a 12 bit resolution of the given amplitude is recommended.
Moreover, the two voltage channels should transfer the signals without a significant phase
shift. The phase shift should be small enough so that the power measurement uncertainty
specified in this standard, namely 0,5 %, is not exceeded. The consideration of the phase
shift is more relevant the lower the power factor cos(φ) becomes (φ being the phase shift
between the fundamental components of the two voltage signals). For this reason the concept
of a single channel with multiplexer leading to different sampling times for the instantaneous
values of the two voltages is not to be recommended.
Signal conditioning amplifiers are preferably d.c. coupled to avoid any low frequency phase
shift. However, d.c. offsets in the signal conditioning amplifiers can lead to significant errors
in the numerically calculated values. Numerical correction cancelling can be applied to
remove such d.c. offsets.
D.3 Calibration aspects
The verification of the repeatability and reproducibility requirements of this standard make
careful calibration of the measurement equipment necessary. The two voltage channels
including preamplifiers and ADC can be calibrated using a calibrated reference a.c. voltage
source [8]. In addition, the phase performance of the two channels and its dependence on the
frequency should be verified and possibly be taken into account with the evaluation
processing in the computer. In any case, it would not be sufficient to calibrate the set-up using
reference
...