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EMC dag voor Installateurs
Picture or Drawing 20.7 x 8.6 cm
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Frits J.K. Buesink, Senior Researcher EMC
[email protected]
in cooperation with
UNIVERSITY OF TWENTE.
TELECOMMUNICATION ENGINEERING.
The Current Boundary
a provision to split loops (and shut out noise sources)
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”
check
Short
circuit(s)
“Ground 1”
reduce loop
area
Create one or more “inner-loops”
Icm
“Ground 2”
loop closes through “ground”
in cooperation with
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TELECOMMUNICATION ENGINEERING.
1
Install current boundaries at natural interfaces
edge of PCB, cabinet wall, basement of a building; one boundary per unit!
Right
Wrong
Drawbacks:
Current follows long
path over equipment
Loop area cannot easily
be minimized
Icm
in cooperation with
Icm
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TELECOMMUNICATION ENGINEERING.
Examples of current boundaries on equipment
wide conductors and low-resistance transitions (be careful with paint) !
Wide
Short
No
Paint!
protect all units with a current boundary!
(and check any conductor that passes it)
check DC resistance with
a milli-Ω meter: < 1 mΩ!
in cooperation with
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TELECOMMUNICATION ENGINEERING.
2
Use Current Boundary to protect existing “pig-tail”
pig-tails can be acceptable as long as CM currents are kept away from it
H-field
lines
Wide metal plate
(Current Boundary)
Icm
EMC glands
in cooperation with
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TELECOMMUNICATION ENGINEERING.
What goes wrong on current boundaries…
mix of plastic and metal EMC glands signals errors
Metal gland on
plastic cable sheath
No cable shield…
no connection
either ??
Paint….?
in cooperation with
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TELECOMMUNICATION ENGINEERING.
3
Separating cables with current boundaries
classify cables into categories
Category
1. Noisy (E)
2. Sensitive (I)
3. Indifferent (N)
red = “source” =“Emission”
green =
“sensitive” =
“Immunity”
E
blue =
“indifferent” =
“Neutral”
I
ICM
N
Model
in cooperation with
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TELECOMMUNICATION ENGINEERING.
Separating cables with current boundaries
use Neutral conductor to reduce loop area; then insert current boundary
E
N
Steps:
I
1. herken
recognize
kring
loop
N
2. reduce looparea
3. add boundary
in cooperation with
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TELECOMMUNICATION ENGINEERING.
4
Separating cables with current boundaries
neutral conductor in practical cases: never a “wire”, always a structure part
Ιcm
Emission
Neutral
(CM-) Transfer impedance of combination
of two relatively thin conductors
is too high (radiates fields)
(does not work for high frequencies)
cross section:
twin wires!
in cooperation with
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TELECOMMUNICATION ENGINEERING.
Separating cables with current boundaries
wide metal reduces fields i.e. the transfer-impedance of the cm-current loop
Ιcm
Emission
Neutral
advantage:
proximity & skin
effects
in cooperation with
Wide sheet metal (“cable guide”) is far superior
to the previous situation. The common-mode
transfer impedance is much lower. Skin effect helps.
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TELECOMMUNICATION ENGINEERING.
5
Special form of current boundary: a cable guide
Neutral conductor, usually structural part of existing installation
50 Ω
E-Cable (source)
Noisegenerator
ICM (=noise)
ICM (=noise)
50 Ω
I-Cable (passive)
scope
Icm “squeezes”
under cable
(proximity effect)
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TELECOMMUNICATION ENGINEERING.
Mutual induction in practice
noise greatly reduced with wide return conductor (ground plane)
source (50Ω)
Wide ground plane is preferred
return path for current!
E-cable (source)
A
Ground Plane
50 Ω
50 Ω
scope
B
in cooperation with
I-cable(passive)
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TELECOMMUNICATION ENGINEERING.
6
Mutual induction in practice
proximity effect: return current concentrates under “red” wire
source (50Ω)
E-cable (source)
A
Ground Plane
50 Ω
50 Ω
scope
I-cable (passive)
B
(proximity
effect)
Icm “squeezes”
under cable
in cooperation with
UNIVERSITY OF TWENTE.
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TELECOMMUNICATION ENGINEERING.
Wide metal also features: the Skin Effect
Lenz’ Law and the basis for shielding effects
Eddy currents
current density
J0
Current
Source
δ=
0
Jd = J0 ⋅ e
d
−
d
δ
d
0 δ
Ι
in cooperation with
J0
e
1
π ⋅ f ⋅σ ⋅ µ
f = frequency [Hz]
σ = conductivity [S/m]
µ = permeability [H/m]
Induced Eddy currents oppose
direction of external current
(Lenz’ Law)
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TELECOMMUNICATION ENGINEERING.
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Proximity effect
current concentrates under conductor, minimizing loop inductance
Ι
R=50Ω
J(x)
x
Current concentrates under
conductor (proximity effect)
Field distribution can be
measured with small
sniffer probe
in cooperation with
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TELECOMMUNICATION ENGINEERING.
Separating cables with current boundaries
use (Ground-) Plane to reduce loop area; then insert current boundaries
E
“Plane” could be metal mesh
I
N
Steps:
1. recognize loop
2. cover loop with metal (ground-)plane
3. connect current boundaries to plane
in cooperation with
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TELECOMMUNICATION ENGINEERING.
8
Cables without Cable-Tray
crosstalk through transfer-impedance
in cooperation with
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TELECOMMUNICATION ENGINEERING.
Cables over Cable-Tray, Large Separation
in cooperation with
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TELECOMMUNICATION ENGINEERING.
9
Cable Against Cable-Tray, Pig-Tail Ignored….
in cooperation with
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TELECOMMUNICATION ENGINEERING.
Cable Against Cable-Tray, Pig-Tail Treated Properly
in cooperation with
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TELECOMMUNICATION ENGINEERING.
10
Use available metal to “short-out” CM-currents
ship’s deck and walls can be used as groundplane(s)
UNPROTECTED
Good
contact
PROTECTED
Good contact
(< 1 mΩ)
! ?
in cooperation with
Important: keep cables near metal over their full length!
(unless cables have sufficient shielding to go “unprotected”)
UNIVERSITY OF TWENTE.
21
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TELECOMMUNICATION ENGINEERING.
“Grounded Cabinet on Shock-Absorbers” (Litz Wire)
in cooperation with
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TELECOMMUNICATION ENGINEERING.
11
Cabinet on Wide Grounding Bracket, Cables Float
in cooperation with
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TELECOMMUNICATION ENGINEERING.
Cabinet on Wide Grounding Bracket, Cables Improved
in cooperation with
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TELECOMMUNICATION ENGINEERING.
12
Either filter or shield entire cable
when passing through shielding wall
O.K.
C
L
C
EMC Filter
EMC Gland
O.K.
E, H fields
E, H fields
reradiate
Ιcm
(3 - 5 µA = RE limit)
10 mA
Not O.K.
1 V/m
in cooperation with
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TELECOMMUNICATION ENGINEERING.
Shielding Experiment
Shielding a noisy interconnection using a metal tube (wave guide)
Ιcm
Generator
Wire carrying
modulated RF signal
Radio tuned to RF
harmonic frequency
in cooperation with
Battery
DC cable
Modulation
Detected
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TELECOMMUNICATION ENGINEERING.
13
Shielding Experiment
Entering a conductor into tube couples out the noise again
Generator
Wire carrying
modulated RF signal
Radio tuned to RF
harmonic frequency
in cooperation with
Battery
DC cable
Modulation
Detected
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TELECOMMUNICATION ENGINEERING.
Shielding Experiment
Insulating generator case: battery cable now reradiates noise (antenna)
Ιcm
Generator
Wire carrying
modulated RF signal
Radio tuned to RF
harmonic frequency
in cooperation with
Battery
DC cable
Modulation
Detected
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TELECOMMUNICATION ENGINEERING.
14
Shielding Experiment
Entering a shielded conductor into tube also couples out the noise again
Generator
Wire carrying
modulated RF signal
Battery
DC cable
grounding wire
Radio tuned to RF
harmonic frequency
in cooperation with
Modulation
Detected
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TELECOMMUNICATION ENGINEERING.
Shielding Experiment
Grounding the shield with the wire does not solve the interference problem!
Generator
Wire carrying
modulated RF signal
Radio tuned to RF
harmonic frequency
in cooperation with
Battery
DC cable
Modulation
Detected
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TELECOMMUNICATION ENGINEERING.
15
Shielding Experiment
Cable shield must be grounded directly to the metal shield to stop the noise
Generator
Wire carrying
modulated RF signal
Radio tuned to RF
harmonic frequency
in cooperation with
Battery
DC cable
Modulation
Detected
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TELECOMMUNICATION ENGINEERING.
Bad “Grounding” habits
it is Inductance, not the milliOhms that count!
in cooperation with
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TELECOMMUNICATION ENGINEERING.
16
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]
Back Door
Front Door
ΙCM
Mains Cord
in cooperation with
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TELECOMMUNICATION ENGINEERING.
Shielding Experiment
A filter in the inserted wire does not help if only grounded with a wire
Generator
Wire carrying
modulated RF signal
Radio tuned to RF
harmonic frequency
in cooperation with
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Battery
DC cable
Modulation
Detected
UNIVERSITY OF TWENTE.
34
TELECOMMUNICATION ENGINEERING.
17
Shielding Experiment
only when the wide metal filter plate touches, the shielding works
Generator
Wire carrying
modulated RF signal
Battery
DC cable
Radio tuned to RF
harmonic frequency
in cooperation with
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35
TELECOMMUNICATION ENGINEERING.
Filter Installation
installation at least as important as the correct filter choice
C. Filter mounted “Plumbers Delight” fashion
(input and output completely separated by shielding)
B. Filter mounted on wide metal strip
A. Filter grounded with long wire
in cooperation with
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TELECOMMUNICATION ENGINEERING.
18
Filter Grounded with Long Wire
some effect in the low frequency range; hardly any in higher frequencies
in cooperation with
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TELECOMMUNICATION ENGINEERING.
Filter Mounted on Wide Metal Strip
better than the long wire; sensitive to cable routing (crosstalk)
Wires pressed against ground plane
Wires far from ground plane
in cooperation with
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TELECOMMUNICATION ENGINEERING.
19
Filter In and Output Separated by Shielding
construction often called “Plumbers Delight” by radio amateurs
Filter performance as specified by manufacturer
(noise floor on analyser)
in cooperation with
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TELECOMMUNICATION ENGINEERING.
“Systems Designers Heaven”
independent building blocks with “abstract” behaviour
Object Oriented
realise complex from simpler behaviour
System
make assemblies independent
EMC Principal Laws
No high frequencies
Do not transport them
Use adequate boundaries
solve “undesired” as low as possible
Software
Modules
Hardware
Components
in cooperation with
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TELECOMMUNICATION ENGINEERING.
20
Good EMC behavior insensitive to standard used
systems EMC requirements are set by the environment it is intended for
Industry
Ground Based
Airborne
At Sea
Domestic
[Tests to cover]
Small
Medium
Large
in cooperation with
UNIVERSITY OF TWENTE.
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TELECOMMUNICATION ENGINEERING.
EMC is achieved during the design process
when problems appear during testing, we are too late!
many
M$$
Available Mitigation Options
Measures
Cost of Modification
Bankruptcy
Requirements
Repair/redesign
Check bonding
0
0
Concept
Design
Manufacture
Test
Operational
phase in the lifecycle
in cooperation with
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TELECOMMUNICATION ENGINEERING.
21
Product Development/Program Support
perform engineering & qualification tests
http://www.thales-ecc.nl/onze-expertise/emc/
in cooperation with
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43
TELECOMMUNICATION ENGINEERING.
EMC approach through the Knowledge Cycle
insert electro magnetic behavior up front
Problem definition:
“desired behavior”
“Test”
Validation/Verification
Development
Support
in cooperation with
Validated
models
Research/Analyses
Knowledge
Transfer &
Education
Behavioral Model
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22
EMC Rules and Guidelines
a lot of information on EMC engineering can be found on the internet
in cooperation with
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TELECOMMUNICATION ENGINEERING.
EMC Rules and Guidelines
or: buy a book!
ISBN 978-0-470-18930-6
in cooperation with
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TELECOMMUNICATION ENGINEERING.
23
The End
http://literature.rockwellautomation.com/idc/groups/literature/documents/rm/gmc-rm001_-en-p.pdf
http://www.engineering.schneider-electric.dk/Attachments/ia/instal/electromagnetic_compatibility_install_guide.pdf
in cooperation with
UNIVERSITY OF TWENTE.
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TELECOMMUNICATION ENGINEERING.
Relation of MIL-STD-461E tests to Phenomena
survey of test identifiers
CE102
Conducted Emissions, Power Leads, 10 kHz to 10 MHz
RE101
Radiated Emissions, Magnetic Field, 30 Hz to 100 kHz
RE102
Radiated Emissions, Electric Field, 10 kHz to 18 GHz
RE103
Radiated Emissions, Antenna Spurious and Harmonic Outputs, 10 kHz – 40 GHz
CS101
Conducted Susceptibility, Power Leads, 30 Hz to 150 kHz
CS114
Conducted Susceptibility, Bulk Cable Injection, 10 kHz to 200 MHz
CS116
Conducted Susceptibility, Damped Sinusoidal Transients, 10 kHz to 100 MHz
RS101
Radiated Susceptibility, Magnetic Field 30 Hz to 100 kHz
RS103
Radiated Susceptibility, Electric Field, 2 MHz to 40 GHz
RS105
Radiated Susceptibility, Transient Electromagnetic Field (NEMP)
in cooperation with
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TELECOMMUNICATION ENGINEERING.
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