IEC TR 61000-4-40:2020

IEC TR 61000-4-40 ®
Edition 1.0 2020-03
TECHNICAL
REPORT
colour
inside
Electromagnetic compatibility (EMC) –
Part 4-40: Testing and measurement techniques – Digital methods for the
measurement of power quantities of modulated or distorted signals
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IEC TR 61000-4-40 ®
Edition 1.0 2020-03
TECHNICAL
REPORT
colour
inside
Electromagnetic compatibility (EMC) –

Part 4-40: Testing and measurement techniques – Digital methods for the

measurement of power quantities of modulated or distorted signals

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 33.100.01 ISBN 978-2-8322-7907-6

– 2 – IEC TR 61000-4-40:2020 © IEC 2020
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 7
4 General . 7
5 Modulated sine waveforms used in this document to compare measurement
algorithms . 9
5.1 General . 9
5.2 Half-wave rectification . 10
5.3 Full-wave rectification . 10
5.4 Multi-cycle symmetrical control . 11
5.5 Random on-off control . 12
6 Measurement algorithms . 12
6.1 General . 12
6.2 Averaging algorithms . 12
6.2.1 General . 12
6.2.2 Performance of the averaging algorithm . 13
6.2.3 Instrumental errors of the averaging algorithm . 18
6.3 Smoothing filter algorithm . 19
6.3.1 Frequency and step response . 19
6.3.2 Verification of the smoothing filter algorithm . 21
6.3.3 Instrumental errors of the filtering algorithm . 25
7 Conclusions . 25
Annex A (informative) Smoothing filter studied in this document . 27
A.1 Algorithm . 27
A.2 General C++ class program code . 31
Bibliography . 34

Figure 1 – Typical resistive load current and supply voltage waveform of half-wave
rectification . 10
Figure 2 – Typical full-bridge rectifier current and supply voltage waveforms . 11
Figure 3 – Current and voltage patterns in an MCSC circuit, (left) 1/3 MCSC and
(right) 2/3 MCSC . 11
Figure 4 – Amplitude of 50 Hz current with on and off periods varying within a 1 min to
2 min range . 12
Figure 5 – Step response of an algorithm in Formula (6) with a half-cycle, 1-cycle and
10-cycle measurement interval . 14
Figure 6 – RMS current and active power for half-wave rectification . 15
Figure 7 – Sliding average RMS current and active power of a device controlled with a
1/3 MCSC circuit . 15
Figure 8 – Worst case 1/3 MCSC circuit active power calculation variation . 16
Figure 9 – Example of a 10 min sliding average power calculation for a load having a
92 s period . 17
Figure 10 – Active power of randomly fluctuating load averaged over a sliding 10 min
interval . 18

Figure 11 – Sensitivity of the full-bridge rectifier RMS current and active power
measurement to time interval error of single-cycle sliding average calculation . 19
th
Figure 12 – Comparison of the first and the 10 order filters used to estimate RMS

current of a step signal . 20
Figure 13 – Filter frequency responses . 20
Figure 14 – Filter step responses . 20
th
Figure 15 – Output of the 10 order smoothing filter used to calculate the active
power of a signal with a step change . 21
th
Figure 16 – Delay and response time of a 10 order filter used to assess the
sinusoidal current of a sinusoidal waveform . 22
Figure 17 – Measurement of the current and power of a half-wave rectified signal

using a smoothing filter with a 10 Hz cut-off frequency . 22
Figure 18 – Power quantities in full wave rectification assessed using a smoothing
filter with 16,667 Hz cut-off frequency . 23
Figure 19 – MCSC 1/3 pattern power quantities filtered with approximately 5,556 Hz
cut-off frequency . 23
Figure 20 – Active power of a load having a 92 s period measured with different

algorithms . 24
Figure 21 – Active power of randomly fluctuating load measured using different
algorithms . 25

Table 1 – Calculated power of 2/3 MCSC for different measurement windows . 16

– 4 – IEC TR 61000-4-40:2020 © IEC 2020
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ELECTROMAGNETIC COMPATIBILITY (EMC) –

Part 4-40: Testing and measurement techniques –
Digital methods for the measurement of power quantities
of modulated or distorted signals

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