Federal Institute of Metrology METAS Introduction to emc Einführung in die EMV

Transcription

1 Federal Institute of Metrology METAS Einführung in die EMV EMV-Fachtagung, 21. Januar

2 1.1 How emc is important! A West GermanTornado fighter crashed after flying too close to a powerful transmitter. (1984) A foundry worker died when the radio-controlled overhead transporter thought out a few tons of liquid metal on him 2

3 1.2 Other situations 3

4 1.3 Outline 1. Introduction 2. Basics of electromagnetic fields 3. How may emc disturbances happen 4. Fundamentals of emc regulation 5. EMC Testing 6. Tips for preventing emc disturbances 4

5 2. The electromagnetic field Electromagnetic wave propagate likes waves 5

6 2.1 Wave propagation Motion up & down produces a wave

7 2.2 The wavelength

8 2.3 Overview of different waves Water Waves Sound Electromagnetic waves Observable Water height Pressure «Electric Field» Medium Water Air - Speed 2 m/s 25 m/s 300 m/s km/s 8

9 2.4 The electromagnetic spectrum 9

10 2.5 Maxwell s equations Equations James Clerk Maxwell ( ) r r H rot( E) = µ r t r E r rot( H ) = ε + j t ε div E r = div r ( ) ρ ( H ) = 0 Faraday s induction law Ampere-Maxwell law Electrostatic law Equation of Magnetismus Solution Retarded magnetic vector potential r µ j( r, t r r c) A = r r d τ 4π r r r r currents distances r H = r E = rot µ 1 ε t r ( A) r r ( rot( H ) j )dt 10

11 2.6 Interpretation i 1 E i 2 H Electric currents Electromagnetic Waves Electric currents 11

12 2.7 Examples 12

13 2.8 Our environment 13

14 3.1 Typical example of emc problem Shield «Abschirmung» currents 230 V control cable 14

15 3.2 Example: Ethernet (part 1) Rx Tx No Field 15

16 3.3 Example: Ethernet (part 2) Differential Mode Common Mode Current 16

17 3.4 Example: Ground loops 17

18 3.5 Example: capacitive coupling 3 GHz 18

19 4. Fundamentals of emc regulation 19

20 4.1 Principles: emission & immunity Reduce emissions Increase immunity 20

21 4.2 Immunity: is always limited 21

22 4.3 EMC Directive 2004/108 EC 22

23 5. EMC testing 23

24 5.1 Radiated & Conducted Measure Field Measure Currents 24

25 5.2 Overview of tests (emission) Norm EN.. CISPR Bezeichnung Feld Emission CISPR CISPR Conducted Emission auf Speisung CISPR 22 Conducted Emission auf Signal Leitungen 25

26 5.3 Overview of tests (immunity) Norm EN.. Bezeichnung Einfluss / typ. Phänomen ESD (pulse) Elektrostatische Entladung HF-Einstrahlung (sin. wave) Radiosender, Handy Burst (high ampl. pulses) Kontaktprellen Surge (high energy pulses) Blitzeinschlag in der Nähe HF-Einkopplung (sin. wave) Radiosender, Funksender /60 Hz Magnetfeld (sin. w.) Stromversorgungsleitung Spannungseinbrüche Netzspannungsausfall

27 5.4 Immunity levels Requirements according to the application: - Household - Industry - Medical Devices - Army - Aircrafts 27

28 5.5 Performance Criterion Performance criterion A: The apparatus shall continue to operate as intended Performance criterion B: The apparatus shall continue to operate as intended after the test. Performance criterion C: Temporary loss of function is allowed, provided the function is self-recoverable 28

29 5.6 Test must be realistic Device under test may have several states: -produce coffee -idle Important: Devices should be equiped with special test mode commands. 29

30 6. How to reduce distubance 30

31 6.1 Solution 1: shielding Shield «Abschirmung» Optical control cable 31

32 6.2 In case of galvanic coupling 32

33 6.3 Solution 2: cable shielding No earth connection «Double Shielding» 33

34 6.4 Solution 3: common mode reject. 34

35 6.5 Solution 4: correct shielding 35

36 6.6 Solution 5: printed boards Low frequency Higher frequency 36

37 6.7 Solution 6: separated masses 37

38 6.8 Solution 7: reduce common mode wrong correct 38

39 Thank you Literature Adolf J. Schwab, «Elektromagnetische Verträglichkeit», Springer Verlag, MC.pdf 39