Download 1 Electromagnetic Interference Phenomena Two Aspects of

Electromagnetic Interference Phenomena
Picture or Drawing 20.7 x 8.6 cm
Frits J.K. Buesink, Senior Researcher EMC
[email protected]
Funded by the European Union on the basis of Decision No 912/2009/EC, and identified in the
European Metrology Research Program (EMRP) as Joint Research Project (JRP) IND60 EMC (2013-2016).
Additional funding was received from the EMRP participating countries.
UNIVERSITY OF TWENTE.
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TELECOMMUNICATION ENGINEERING.
Two Aspects of Achieving EMC
A. Engineering Compatible Equipment B. Qualifying Equipment for EMC
A
B
“White Box” approach
“Black Box” approach
Partner in the Design Team
Independent
Incorporate EMC in the Design
“GO” or “NO-GO”
Get information from the EM-Network
Standardized Approach
Formulate Design Rules
Find Problems and Fix them
Large Stationary Installations in Industry
EMRP IND60: Improved EMC methods (to qualify)
In Industrial Environments
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Interference mechanisms in installations
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The necessary elements for an interference situation
EMI, ElectroMagnetic Interference model: source – victim and coupling path
Source
coupling path
Victim
Susceptibility
(Immunity)
Emission
Coupling path: always electrical interconnections
this can
be demonstrated
Effects
appear using:
 a noise generator
at
any
scale
 a radio receiver
(relative
wavelength)

and sometocables
Very large….
to tiny.
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Interference mechanisms in installations
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Essential Requirements: No Emission, No Susceptibility
the question as to “how much” is answered by EMC Standards
Noise level
noisevoltage (LF)
noisefields (HF)
non-susceptibility
(immunity)
Generic standards
immunity industrial
EN-IEC 61000-6-2
immunity residential
EN-IEC 61000-6-1
industrial
EMC margin
emission industrial
EN-IEC 61000-6-4
emission residential
EN-IEC 61000-6-3
residential
emission
For Europe:
Source: C.J. Post Lambda Engineering B.V.
EMC on Tour 2011
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frequency
Interference mechanisms in installations
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2
EMC “standard violation”: EMI = EM Interference
if either emissions are too high or the immunity level is too low
Noise Level
noise voltages (LF)
noise fields (HF)
susceptibility
immunity level
(by standard)
emission limit
(by standard)
emission
Source: C.J. Post Lambda Engineering B.V.
EMC on Tour 2011
in cooperation with
frequency
Interference mechanisms in installations
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TELECOMMUNICATION ENGINEERING.
Common-mode currents dominate the EMC arena
currents, generated by cables from “desired currents” into CM or ground-loop
Source
Load
Idm “Differential-mode” current
Icm
“Common-mode” current
“Ground”
Icm(2)
“Common-mode” current (2)
System at the neighbours
Idm
Source
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Interference mechanisms in installations
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Load
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Induction in a Single Wire
current in a conductor is only possible when a magnetic field exists
1. Waveform for fast edge
A
B
50 
signal integrity =
no distortion on
the signal line
A
B
coax cable
single wire
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Interference mechanisms in installations
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Induction in a Single Wire
current in a conductor is only possible when magnetic field exists
1a. Waveform for fast edge
@ reduced loop area
B
50 
A
Reduce loop area:
less time and energy
needed to build H-field
A
B
coax cable
single wire
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Interference mechanisms in installations
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Induction in a Single Wire
current in a conductor is only possible when magnetic field exists
A
B
50 
2. Waveform for slow edge
A
B
coax cable
single wire
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Interference mechanisms in installations
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Cables are used to keep Signal and Return together
field of the return conductor is identical but opposite (if geometry is identical)
H = Magnetic Field [A/m]
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Interference mechanisms in installations
-H
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Current carrying conductor always exhibits H-field
minimize fields by locating the return conductor concentric
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Interference mechanisms in installations
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Properties of cables: Transfer Impedance ZT
cable may produce or pick up common mode currents
1. Coupling into external noise
ZT 
cable length D
Inoise
U noise
Inoise  D
[Ohm per meter]
external noise source
Unoise
Idesired
2. Generation of noise in other conductors
(e.g. “ground”)
?
return current flows where?
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Interference mechanisms in installations
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“Pig-tails” destroy good coax properties
effect of geometry changes: fields outside interconnections; CM currents
“Coax is better
when
than
compared…
twin wires”
Coax
Pig-tail destroys cable symmetry
Fields are
generated
Twin
wires
ZT goes UP
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Interference mechanisms in installations
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Whether Pacemakers are Indeed this Susceptible?
fields up to 30 kV/m and not just 50 Hz!
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Interference mechanisms in installations
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ElectroStatic Discharge
charges built on persons or equipment cause electric sparks (and currents)
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Interference mechanisms in installations
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Electric charging by induction
direct contact not necessary!
Wool
-------------------Teflon
1. Charging of an insulator
Printed Circuit Board
------------ ---------------------
++++++++++++++++
2. Insulated PCB on charged surface
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Interference mechanisms in installations
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Electric charging by induction
direct contact not necessary!
---------------------------------
++++++++++++++++
3.Touch or Ground PCB:
negative charge disappears (spark)
(PCB possibly damaged)
VPCB 
QPCB
CPCB
(CPCB decreases)
++++++++++++++++
-----------------
4. Lift PCB: voltage increases! Sparks fly!
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Interference mechanisms in installations
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Ground self-induction and a fast discharge edge
“Grounding” or “short-circuit” of an ESD source is difficult (better avoid!)
neon lamp flashes
on discharge over
“long” grounding path
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Interference mechanisms in installations
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Front Door / Back Door EMI
Front Door: Via Intended Coupling; Back Door: Via Unintended Coupling
100 [MHz] in-band
interference
9 [MHz] out-of-band
interference
Receiver
87 - 108 [MHz]
Front Door
Back Door
CM
Mains Cord
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Interference mechanisms in installations
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Experiment with Frequency Controlled Motor
PWM
Controller
crosstalk between cables due to transfer-impedance
Cable 1 (source)
DC Motor
(twin wires)
mode
Plastic support
50 
50 
AC supply
Cable 2 (passive)
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Interference mechanisms in installations
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Power Quality: influence of power-users
EMI related; Compatibility required
“Voltage Quality” or “Quality of Supply”
Various Power
disturbances
Conducted Susceptibility
Power Supply Mains Generator
Conducted Emissions
Power Line
Power User
User Load Fluctuations
Other users
“Current Quality” or “Quality of Consumption”
Reference: Bollen, Math H.J. “Understanding Power Quality Problems”, IEEE Press, 2000
ISBN 0-7803-4713-7, IEEE Order Number PC5764
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Interference mechanisms in installations
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Non-Sinusoidal Currents and Ohm’s Law
the root cause of most power-quality related problems
User Load Current
Original Mains Voltage
User Mains Voltage
V = I x RLINE
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Interference mechanisms in installations
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Mains Voltage and Current as Users Like to See It
clean sine wave voltage and resistive load
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Interference mechanisms in installations
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History: Reactive Loads
result: phase shift, cosine()
reactive power
im

re
true or real power
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Interference mechanisms in installations
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Today: Non-Linear Loads
most prominent: diodes charging bulk capacitors
Legend
Mains Voltage
Mains Current
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Interference mechanisms in installations
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Modern Compact Fluorescent Lamp (CFL)
electronic circuit with diode bridge and bulk capacitor
Diode Bridge
Bulk Capacitor
Current Waveform
on a “Decent” Sine-Shaped
Voltage Waveform
Source: Wikipedia
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Interference mechanisms in installations
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Problem with Diode Rectifiers: Synchronicity
all conduct simultaneously on mains voltage! distortion adds up
Same Fluorescent Lamp
in Large Office Building
with distorted Voltage
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Interference mechanisms in installations
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Small Users <75 W Have No PF Requirements
e.g. all LED’s , CFL’s and many laptops are exempt
Effect….
Heavily Distorted
Voltage Waveform
This effect is
called:
Harmonic
Distortion
Multiple Zero Crossings
in cooperation with
Wave-Shape in Large Office Building: Multiple Zero Crossings!
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Interference mechanisms in installations
TELECOMMUNICATION ENGINEERING.
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Monitor synchronous noise on the mains
special interface box that filters out frequencies below 2 kHz
The filter is intended for measurements from 2 – 150 kHz (high cutoff around 3 MHz)
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Interference mechanisms in installations
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Questionnaire
Please fill out the questionnaire (enquete) sent as a separate MSWord
file and mail it to the address shown there. In return we will send you
the schematic diagram of the noise monitoring box (CM & DM) shown
on the previous slide!
Thank you!
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Interference mechanisms in installations
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Mapping of EMC on Power Quality (User Aspects)
users on the grid are sources and victims, the grid is the coupling path!
User 1
User 2
SOURCE
Source
Emission
coupling path
Victim
VICTIM
Grid
Susceptibility
(Immunity)
Coupling path: always electrical interconnections
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Interference mechanisms in installations
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Problem 1: Synchronous Peaks Add Up
initial power budget new office building exceeded almost twofold
•
•
•
•
in cooperation with
Estimated required power:
3 MW
Initial installation:
4 MVA (4 x 1 MVA)
Installation upgraded to:
7.2 MVA (+ 2 x 1.6 MVA)
Question: are we or are we not saving cost and energy?
Interference mechanisms in installations
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Problem 2: Switcher Frequencies Pollute Environment
Source:
YouTube
low power fast switching requires short risetime IGBT’s and MOSFETs
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Interference mechanisms in installations
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CM currents can be produced elsewhere
if you connect your system to the outside world, currents will flow
Situation indetector:
practice
AM-radio
(Mains cord 1)
Unit 1
(Mains cord 2)
(I/O cable 1-2)
Unit 2
Icm (noise current)
“Ground 1”
“Ground 2”
loop closes through “ground”
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Interference mechanisms in installations
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CM currents can be produced elsewhere
fields in the environment are converted into CM currents
Situation indetector:
practice
AM-radio
(e.g. Mains cord 1)
Unit 1
(e.g. Mains cord 2)
(I/O cable 1-2)
Unit 2
Icm (noise current)
loop closes through “the air” (antenna-currents)
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Interference mechanisms in installations
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End of Part I
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Interference mechanisms in installations
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