Glen Wallis. Senior Field Application Engineer / Wurth Electronics (UK) Ltd.

1. Wurth Electronics (UK) Ltd
1
EMC Seminar 2015
Speaker
Glen Wallis
Senior Field Application Engineer

2. Agenda
- What is EMC?
- Magnetic and Material Basics
- Transmission Modes & Filter Topologies
- Component Solutions
- Design Guides
2

3. What is EMC?

4. EMC Standards and tests are seen by customers as
HUGE PROBLEMS

5. Economical point of view:
Cost
Pre-design Prototype Production Time
EMC Effect
• dependent on when EMC conformity is considered in a design phase

6. EMC, what frequency range does it cover?
6

7. Magnetic and Material Basics

8. EMC – Electromagnetic Wave

9. Mai 10 AR 9
Electromagnetic Wave

10. EMC – Electromagnetic Wave
1 cycle = 0o to 360o
360o
Frequency (F) = 1 / Period
= 1 / 20uS
= 50 kHz
Wavelength (λ) = Speed of Light (m/s) / Frequency
= 3x108 / 50x103
= 6000 metres
20us
0S
Period (S) = 0 seconds to 20uS
0o
Electric field
Magnetic field

11. The magnetic field
Each electric powered wire generates
an electro magnetic field
Field model
current I
Magnetic field H

12. 12
Right Hand Rule

13. 13
The magnetic field - Field model

14. Magnetic Fields – The magnetic field

15. N
O
R
T
H
S
O
U
T
H
Magnetic field H
Current I
15
The magnetic field – Field Model

16. R
I
mAH


2
)/(
R
IN
mAH



2
)/(
l
IN
mAH

)/(
Straight wire
Toroidal
l
R
R
solenoid
I = Current
N = Number of turns
R = Radius
L= Length
H (A/m) = Field strength (A/m)
16
The magnetic field

17. R
I
mAH


2
)/(
R
IN
mAH



2
)/(
Straight wire
Toroidal
R
R
The magnetic field strength is depending from:
• Geometries
• No. of turns
• Current
17
But NOT MATERIAL
e.g I = 5A, R = 0.2, N =10
=5 / 2 x 3.14 x 0.2
=3.978 A/m
=10 x 5 / 2 x 3.14 x 0.2
=39.78 A/m
The magnetic field

18. averageR
I
HHH


2
21 1B 2B?


Current I
averageR
1H
2H
averageR
The magnetic field

19. What is permeability?
• un ordered (random position)
• soft magnetic
• ordered
• hard magnetic
Ferrite material Permanent magnet
Relative permeability
• describe the capacity of concentration of the
magnetic flux in the material.
• it is a energy factor to magnetize the material
Typical permeability µr : • Iron power :
• Nickel Zinc :
• Manganese Zinc :
50 ~ 150
40 ~ 1500
300 ~ 20000
19

20. -50 50 150 250
1000
T / °C
500
540
670
770
+15 %
-20 %
- The magnetization depends from the temperature
T therm. movement Alignment
Alignment of
elementary magnets
Ferromagnetic change
to Paramagnetic
Point reached at
µr = ?1
-40°C 23°C 85°C
Curie-temperature
Temperature influnce
µr
Permeability – Core material parameter
20

21. Permeability – complex permeability
=1 turn
Core material-Parameter
XL(NiZn)
R(NiZn)
Z
X L__
22
Z R
R
X L
Z
Replacement circuit
21

22. 0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0,01 0,1 1 10 100 1000
Core material – Inductors (Storage)
f/MHz
XL(NiZn)XL(MnZn)XL(Fe)
Impedance
22

23. 0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0,01 0,1 1 10 100 1000
Core material – Choke (Filter)
f/MHz
R (NiZn)R (MnZn)R (Fe)
Impedance
23

24. Core Losses
Electro Magnetic energy cannot disappear, it will be just transformed into
other energy form energy conservation law
e.g. electrical energy transformed into  thermal energy
the core losses from ferrite transform the noise energy into heat

25. Transmission Modes
&
Filter Topologies

26. Transmission modes
Live (Positive)
Earth (Ground)
 Recognize the transmission mode:
Differential Mode
signals on a
line(s) with a return path
Common Mode
noise on all lines
propagating in the
same direction with
respect to earth
Neutral (Return)
Cs

27. EMC - Coupling
 Primary procedure
…to aim at source a low noise
 Secondary procedure
… eliminate the noise thru interrupting the coupling way
 Tertiary procedure
… increase the noise immunity at load
Noise source Load
Coupling way

28. Capacitive coupling
• Effects are dominant when the dimensions are 10% below the wave length (l < /10)
-> Why 1/10 ?
-> Reduction ? - Increase the distance
- harmonics
Field model Network model
EMC - Coupling

29. Inductive coupling
 Reduction? - Increase the distance
• Antenna principle –> each piece of wire is a antenna
fc  
• Effects are dominant when the PCB traces are ca. 25% from the noise wave length (l < /4)
Field model Network model
EMC - Coupling

30. Coupling - Wavelengths
Frequency
(MHz)
Wavelength
(m)
H field
1/4 wavelength
(m)
E field
1/10 wavelength
(m)
30 10 2.5 1
100 3 0.75 0.3
500 0.6 0.15 0.06
1000 0.3 0.075 0.03
2500 0.12 0.03 0.012
3000 0.1 0.025 0.01
6000 0.05 0.0125 0.005

31. Recognizing the coupling mode
 common mode noise ?
 differential mode noise ?

32. Common mode or differential mode?
Take a Snap Ferrite and fix it on the cable
(both lines e.g. VCC and GND)
if noise is reduced or
noise immunity increase
you have Common Mode Interference
If not
you have Differential Mode Interference
e.g. Common mode
choke
e.g. chip bead ferrite

33. • Impedance
BA
BFA
ZZ
ZZZ
A


 log20
• System attenuation
   BABA
A
F
ZZZZZ 





 20
10
)(dBin
)(in
Insertion loss – Mathematical Definition
LoadSource
ZA ZF
ZBU1U0 U2
Coupling way
33

34. Insertion loss – recommended filter topology
Pay attention to:
SRF of used
components
 small C = higher SRF
Choose ferrite bead or
inductors L which
= build no resonance with C
= broadband filter
Source Impedance Load Impedance
low
low low
high
high
high
high or
unknow
n
low or
unknow
n
low or
unknow
n
C
L CC
L
L
C
L
high or
unknow
n

35. Filter design
How to?:
 defined filter using 2 components
 at least 1 component must be frequency dependant
 Matching the working frequency for the signal
 Matching the cut of frequency for the noise
Filter input Z1
Z2
UE U A
Filter output
Conclusion: Filter are frequency dependant voltage divider
35

36. Low pass filter
…are most popular used filter for EMI
UE U A
L
C
1UE U A
LPF 1. rank
LPF 2. rank
C
1
R
f ZC
f ZL
f ZC
36

37. -40
-35
-30
-25
-20
-15
-10
-5
0
1 10 100 1000
Frequenz [MHz]
Filter topologies – L-Filter
• L-Filter
Zmax= 3000 Ω @ 80 MHz
• WE-CBF 742 792 093
AF = -29 dB @ 80 MHz
Simulated Measured
• instead of inductor use
SMD-Ferrite

38. -90
-81
-72
-63
-54
-45
-36
-27
-18
-9
0
1 10 100 1000
Frequenz [MHz]
Filter topologies – Parallel-C-Filter
• Parallel-C-Filter
• Resonant freq.

39. Filter topologies – LC-Filter
• LC-Filter
WE-CBF 742 792 093
C=100nF
-90
-81
-72
-63
-54
-45
-36
-27
-18
-9
0
1 10 100 1000
Frequenz [MHz]
Simulated Measured
• Compare simulated vs. measured

40. Design-Tip: avoid over current (load dump)
Uin
e.g. 12V DC
SMD/Ferrite
+
Umax
U(t)
Imax
I(t)
 2 3 4 5
 2 3 4 5
Filter topologies – LC-Filter

41. Filter topologies – LC-Filter
Uin
e.g. 12V DC
SMD/Ferrite
+
Design-Tip: avoid over load of bead ferrite!
• Safety for SMD-Ferrite against low dump current
• Not an PI-Filter
 Capacity C1 is just for stabilizing

42. Filter topologies – PI-Filter
• Compare simulated vs. measured
• π-Filter
WE-CBF 742 792 093
C1=1nF
C2=100nF
-90
-81
-72
-63
-54
-45
-36
-27
-18
-9
0
1 10 100 1000
Frequenz [MHz]
Simulated Measured

43. Filter topologies – T-Filter
• T-Filter
C=100nF
L1=742 792 040
L2=742 792 093
-90
-81
-72
-63
-54
-45
-36
-27
-18
-9
0
1 10 100 1000
Frequenz [MHz]
Simulated Measured
• Compare simulated vs. measured

44. Common Mode Filter – Signal theories
Transmitter/
Source
Receiver/
Load
differential
common
Data lines
Noise mode:
• Common mode noise
• Differential mode noise
D-
D+
e.g.: USB
44

45. It is a Bi-directional filter
• From device to outside environment
• From outside environment to inside
device
Conclusion:
Common Mode Filter – How it works
Intended Signal - Differential mode
Interference Signal (noise) – Common Mode
• “almost” no affect the signal - Differential mode
• high attenuation to the interference signal (noise) – Common Mode

46. Source LoadSignal path
Common mode
VCC
GND
D-
D+
e.g.: USB
Filtering
WE-CNSW Type 0805
Common Mode Filter – Signal theories

47. Filter with two inductors
Filter input Filter output
Filter with CMC
Filter input Filter output
• Signal not affected
• Noise attenuated even close to the signal frequency
Common mode choke - advantages

48. USB1.0
IC
USB1.0
IC
Spektrum
-80
-70
-60
-50
-40
-30
-20
-10
0
0 500 1000 1500 2000 2500 3000
Frequenz in MHz
LeistungindBm
D+
D-
D+
D-
 filtered  un filtered  Tx signal
RF-Generator
Common Mode Choke Common Mode Choke
 Data source
Common mode choke – application USB

49. 32 Ohm
0.7 Ohm
Increase ZFail rate: 3.4% Fail rate: 2.55%
Fail rate: 0% Fail rate: 2.05%
@ 12 MHz
CM 
DM 
41 Ohm
0.7 Ohm @ 12 MHz
CM 
DM 
363 Ohm
1 Ohm @ 12 MHz
CM 
DM 
77 Ohm
1 Ohm @ 12 MHz
CM 
DM 
Common Mode Choke
D+
D-
D+
D-
Increase Z
Common mode choke - construction

50. SMD-Ferrite – application USB
Fail rate: 0‰
Fail rate: 4.4% Fail rate: 7.5%
35 Ohm @ 12 MHzDM 
110 Ohm @ 12 MHzDM 
Using an WE-CBF instead of CMC
2 x SMD-Ferrit
D+
D-
D+
D-
Increase Z

51. Component Solutions

52. How to resolve EMI using EMC counter measures
52

53. PCB mounted EMC ferrites
 Ideal time is to design these series of components in at the product
design stage
 Why?
The benefits are as follows:
1. Small package size, thus footprint.
2. Saving valuable PCB space
3. Allows for positioning close to the EMI source or point of filtering

54. PCB mounted EMC ferrites- Key points
 Applications
- DC power line filtering
- Low voltage AC power line filtering
- Data/Signal line filtering
 EMC Phenomena
– Radiated Emission
– Radiated Immunity
– Conducted Emissions
– Conducted Immunity
– Electro Static Discharge (ESD)
– Electric Fast Transients (EFT)

55. PCB mounted EMC ferrites
 Majority are Differential mode filters
– WE-CBF
– WE-CBF HF
– WE-MPSB
– WE-PBF
– WE-PF
– WE-SUKW
– WE-UKW
– WE-WAFB
 Maximum operating voltage
- 80Vdc
- 42Vac

56. PCB mounted EMC ferrites
WE-CBF (Chip Bead Ferrites)
Three types in the series
High Speed Wide Band High Current

57. WE-CBF vs WE-CBF HF
Both are 0603 package size, Z = 1k Ω @ 100MHz
WE-CBF WE-CBF HF
WE-CBF HF has greater than 3 times the impedance at 1GHz

58. CBF DETAILS/READING DATASHEETS
WE-CBF WE-CBF HF

59. Retro fit EMC ferrites - Key points
 Applications
- AC power line filtering
- DC power line filtering
- Data/Signal line filtering
 EMC Phenomena
– Radiated Emission
– Radiated Immunity
– Conducted Emissions
– Conducted Immunity
– Electric Fast Transients (EFT)

60. Retro fit EMC ferrites
 These components are design to be fitted to cables or cable harnesses
 These are all Split ferrites. Design for quick application to the cable
 * Use a unique ‘key’ system that reduced
unauthorised removal of the ferrite
Snap ferrite sleeve
Snap ferrite ring
WE-NCF
Split EMI ferrite ring
Split EMI flat ferrite
STAR-BUENO *
STAR-FIX *
STAR-LFS *
STAR-TEC *
STAR-GAP *
STAR-RING *
STAR-FLAT *
Only manufacturer to offer this key system

61. Retro fit EMC ferrites
Mai 10 AR 61
STAR – xxx series
FIX - LFS TEC / RING /FIX GAP

62. 12 1
10
23 100
0
200
400
600
800
1000
1200
1400
1600
1800
2000
1 10 100 1000
f/MHz
Retro fit EMC ferrites – Number of turns
MnZn NiZn
 2 turns

63. Retro fit EMC ferrites
 These ferrites are defined as solid core
WE-SFA
WE-FLAT
WE-FAP
WE-FLAT (Flexible PCB)
WE-TOF
WE-AFB
WE-AFB LFS
WE-SAFB
Mutli-Aperture ferrite
 Used largely to replace the split ferrites used during
EMC testing
 Have to be applied to the cable/cable harness prior to
any connectors are crimped to the ends of the cables
 These components are design to be fitted to cables and cable harnesses

64. Where do we place the ferrite ?
Design:
 As close as possible to the
source of the noise
Ideally 20mm to 50mm from the
point of cable connectivity

65. Recognizing the coupling mode
 common mode noise ?
 differential mode noise ?

66. How can we find out what interference we have?
Common mode or differential mode?
Take a Snap Ferrite and fix it on the cable
(both lines e.g. VCC and GND)
if noise is reduced or
noise immunity increase
you have Common Mode Interference
If not
you have Differential Mode Interference
e.g. Common mode
choke
e.g. chip bead ferrite

67. • Impedance
BA
BFA
ZZ
ZZZ
A


 log20• System attenuation
   BABA
A
F
ZZZZZ 





 20
10
)(dBin
)(in
Insertion loss - Definition
LoadSource
ZA ZF
ZBU1U0 U2
Coupling way

68. >90 
1 
10 
System Impedances

69. 1 
50 - 90 
10 
System Impedances

70. The problem
 Example, Radiated Emission plot

71. Mai 10 AR 71
Quick Solution
Impedance of ferrite (Ω)
Attenuation(dB)
1. 1.Require 20dB of
attenuation at 125 MHz
2. Know that it is a power
cable
3. Power port has 10 Ω
impedance
180
• Result is a minimum
impedance of 180Ω

72. The result
 Example with Ferrite fitted Example, Radiated Emission plot

73. Filter Chokes
WE-CPU Plate

74. Current compensated common mode chokes -
Key points
 Applications – Power line
- AC power line (110 to 250Vac rms) filtering
- DC power (<250V) line filtering
 Applications – Signal/Data line
- Low voltage (<42V) AC power line filtering
- DC power (<80V) line filtering
- Data/Signal line filtering
 EMC Phenomena
– Radiated Emission
– Radiated Immunity
– Conducted Emissions
– Discontinuous Conducted Emissions
– Conducted Immunity

75. Common mode choke - construction
bifilar sectional

76. Data/Signal lines Common mode chokes
 Rated at 80Vdc or 42Vac (except WE-CNSW 50Vdc)
WE-CNSW – 0603, 0805 & 1206 sizes. Bifilar wound
WE-SLM - Bifilar wound
WE-SL1 – Sectional wound
WE-SL2 - Bifilar wound & Sectional wound (denoted with a S)
WE-SL3 - Either 2 or 3 wire. Bifilar or Trifilar wound
WE-SL5 - Maximum current 2.5A Bifilar wound & Sectional wound
(denoted with a S)
WE-SL5HC - Maximum current 5A Sectional wound
WE-SL – Either 2 or 4 wire. Bifilar or Quadfilar wound

77. P/N:
EP-CBF-0805  SMD Ferrite 0805
EP-CBF-1206  SMD Ferrite 1206
EP-STROKO  WE-SLxy… Series SMD common mode chokes
VPE 12 pcs.  Price £20 inclusive P&P
Application demo boards

78. Common mode chokes – Power lines
 Rated at 250Vac rms @ 50/60Hz, maximum current is 35A
 Also possible to pass high current DC through them
 WE-CMB
 WE-CMB HC
 WE-CMB NiZn*
 WE-LF
 WE-LF SMD
 WE-FC Mini
 WE-FC
 WE-TFC
 Used for low frequency suppression in the frequency range of 150KHz to 30MHz.
 * 30MHz to 300MHz due to NiZn core

79. Common mode chokes – line card
Insertion loss (common mode) WE-CMB XS: MnZn <=> NiZn
0
10
20
30
40
50
60
70
0,1 1 10 100 1000
frequency [MHz]
attenuation[dB]
14 µH
30 µH
47 µH
100 µH
1 mH
5 mH
10 mH
20 mH
39 mH
CMB NiZnCMB MnZn

80. Nano Crystalline – WE-CMBNC
80

81. Internal structure
81

82. WE-CMB Impedance vs Temperature
82
1
10
100
1000
10000
100 1000 10000 100000
Impedance(Ohm)
f (kHz)
CMB @ -40
CMB @ 80
CMB @ 120
CMB @ 150
CMB @ 180
2014-02-24 / IMA

83. WE-CMBNC Impedance vs Temperature
83
1
10
100
1000
10000
100 1000 10000 100000
Impedance(Ohm)
f (kHz)
CMBNC @ -40
CMBNC @ 80
CMBNC @ 120
CMBNC @ 150
CMBNC @ 180
2014-02-24 / IMA

84. Cost saving?
Insertion loss (common mode) WE-CMB XS: MnZn <=> NiZn
0
10
20
30
40
50
60
70
0,1 1 10 100 1000
frequency [MHz]
attenuation[dB]
14 µH
30 µH
47 µH
100 µH
1 mH
5 mH
10 mH
20 mH
39 mH
CMB NiZnCMB MnZn
CMB NC

85. Circuit Protection – Key points
 Applications
- AC power line (14 to 1000Vac rms) protection
- DC power line (18 to 1465Vdc) protection
- Signal/Data line protection
 EMC Phenomena
– Electro Static Discharge (ESD)
– Electrical Fast Transients (EFT)
– High Energy Surges (HES)
The EMC phenomena can be defined as a
transient event, a phenomena that's presence is
not constant
 These products are for protection against over
voltages

86. Why do we need circuit protection?
Mai 10 AR 86

87. Circuit Protection
 What is an over voltage?
Typically 500V to 15kV
AC voltage 230V ± 10%
Over voltage > 260V

88. Circuit Protection
 The following components are
WE-TVS Standard Series
WE-TVS High Speed Series
WE-TVS Super speed Series
WE-VE
WE-VE ULC
WE-VEA
WE-VEA ULC
WE-VS
WE-VD

89. Circuit Protection – ESD/EFT
 TVS Diodes – Transient Voltage Suppressors
 WE-TVS Standard Series
Application = USB 1.1 (12Mbps)
 WE-TVS High Speed Series
Application = USB 2.0 (480Mbps)
 WE-TVS Super speed Series
Application = USB 3.0 (4.8Gbps)
These devices can be used to protect the DC power and also the signal lines
in one package

90. Waveshape - ESD
 ESD
 Maximum rise time = 1ns
 Duration = approx 40ns
 Maximum pk I (8kV) = 30A
Mai 10 AR 90

91. Waveshape - EFT
 FTB/EFT
 Rise time 5nS
 Duration 50ns
Mai 10 AR 91

92. Circuit Protection - TVS
 What do I need to know to be able to select one?

93. USB – 2 Port solution (ESD/EFT solution)
Mai 10 AR 93

94. USB – 2 Port solution (ESD/EFT-EMI solution)
Mai 10 AR 94

95. LAN ESD/EFT-solution
Mai 10 AR 95

96. Circuit Protection - ESD
 The WE-VE series of components are suited for the ultra fast voltage pulses
caused by Electro Static Discharge
 The following components are
WE-VE
WE-VE ULC (Ultra Low capacitance)
WE-VEA
WE-VEA ULC (Ultra Low capacitance)
 These devices are applied to the DC power and also signal/data lines

97. Circuit Protection - ESD
 What do I need to know to be able to select one?

98. Layout design
Mai 10 AR 98

99. Mai 10 AR 99
USB 2.0 filter dongle
P/N 829999 BAG

100. Mai 10 AR 100
WE-USBH Connector with Integrated EMI & ESD function
Full Speed – 480MHz
P/N 8492121

101. Mai 10 AR 101
WE-USBH Connector with Integrated EMI & ESD function

102. Circuit Protection - HES
 Surge protection devices
 WE-VS
Application
- AC power line (4 to 40Vac rms) protection
- DC power line (5.5 to 56Vdc) protection
 WE-VD
Application
- AC power line (14 to 1000Vac rms) protection
- DC power line (18 to 1465Vdc) protection

103. What size of varistor to select?
 Vrms or Vdc
 Peak I (A)
 Wmax (J)
 Pdiss (W)
It is necessary to calculate (estimate) the maximum
surge current that could flow through the varistor
Parameters to consider:
Operating Voltage
Maximum withstand surge current
Maximum energy absorption
Maximum Power dissipation

104. Surge Test - Waveforms
Mai 10 AR 104
Test waveforms as specifed by the test method EN 61000-4-5:2006:
Open Circuit
Rise Time : 1.2 µs
Duration : 50 µs
Short Circuit
Rise Time : 8 µs
Duration : 20 µs

105. Varistor Characteristics – V I Curve
+U
+I
VVar VCVM
IL
IVar
Ic
IMax
Max. Operating Voltage
Clamping Voltage
Leakage Current
0,1mA or 1mA
Current @ Clamping Voltage
U-I Graph for SMD-Varistor 825 42 350
0
1
2
3
4
5
6
7
30 40 50 60 70
Voltage [V]
Current[mA]
max. Current
Varistor Breakdown Voltage

106. EUT
 Common Mode Z = 12Ω
E
Power lines
L1
L2
L3
Signal lines
 Differential Mode Z = 2Ω
 Signal lines Z = 42Ω
Surge Test - Application

107. Calculation of the current: Ic
 According to Ohms Law
Surge Voltage (kV)
Z (Ohms)
Supply Voltage (Vpk)
Surge
Clamping
Ic
Impedance of the generator according to
the type of port (Power or Signal) I load
I load is negligible =>

108. Method 2
 Second Method ( estimation)
 Vclamp ~ 2*V breakdown
7mm Disk Varistor
VRMS 275 V
V breakdown : 430V
14mm Disk Varistor
VRMS 275 V
V breakdown : 430V

109. Method 2

110. Calculation of the Energy Absorption
• The energy in Joules (Watt per second) is
given by the following formula:
W (J) = K * V (V) * I (A) * t (s) Surge
Clamping
I Max
• It can be difficult to make an exact
calculation of the energy.
• We can make an approximation, in
considering rectangular wave.
• V = Vclamp (just calculated before)
• I = Ic ( just calculated)
• T = 20µS ( time duration of the surge current)
W (J) = Vclamp(V) • Ic (A) • 20µ(s)
50µs
20µs
T(s)
Surge Voltage
Surge Current

111. Calculation of the Power dissipation


112. Method 2
FAE Dez. 2011

113. Circuit Protection - MOV
 What do I need to know to be able to select one?

114. Derating curve according to the number of applied pulses
Numberofsurges
Example: Surge spaced 30 seconds.
Time (s)
Temperature(C)

115. Layout of varistor for surge protection
 Safety standards disapprove for varistors to Earth
 Also the product likely to fail the Hi-pot, earth leakage test
 If using fuses they must
be suitable rated against
surges.
i.e Anti-Surge (T)
FAE Dez. 2011

116. UL 1449 3rd Edition
 The WE-VD are typically designed into a product to protect against an
overvoltage situation that could potential damage the product
 It therefore makes the WE-VD are “safety critical component”
 Underwriters Laboratory Inc. (UL) is a US based testing and Certification
organisation
 UL 1449 3rd Edition is a safety standard for circuit protection devices
 Has four classes listed
Type 1 – Protection of the mains distribution network
Type 2 – Protection of permanent connected devices the mains
distribution network
Type 3 - Protection of non permanent connected devices the mains
distribution network
Type 4 – Discrete components
 WE-VD are approved for Type 2, 3 & 4

117. EMI Shielding material
 The products can be constructed of two classes of
material when it comes to RF:
1. Metallic – Aluminium, Steel, Brass, Copper
Natural shielding material
2. Non Metallic – Plastic, Nylon, Polystyrene, PVC.
RF transparent materials

118. EMI Shielding material – Key points
 Applications
Shielding of non metallic enclosures
Bonding of metallic enclosures
Absorbing (Attenuating)
 EMC Phenomena
– Radiated Emissions
– Radiated Immunity
 Effective frequency range
– 30MHz to 18GHz

119. EMI Shielding material
 WE-LT- RF gasket
 WE-LTS – Stamped gasket
 WE-LS – Conductive foam
 WE-ST – Conductive weave
 WE-CF – Copper tape.
Largest user of copper tape are the
EMC Labs
 WE-TS – Textile tape

120. EMI Shielding material
 Earthing cable connectors
 Earthing nylon clips
 Earthing belts
 WE-FAS EMI
 WE-FAS RFID
 WE-FSFS
 WE-SECF
 WE-SHC

121. EMI Shielding material
RF Gasket, WE-LT and WE-GS can
be used in the following
configurations to establish a good
bond
To enable good electrical
conductivity, gasket must make
direct metal work to metal work
contact
Any painted surface will act as an
insulator (high resistance to RF)

122. EMI Shielding material
 Surface resistance

123. EMI Shielding material
WE-FAS EMI
WE-LS

124. Ethernet EMI solution

125. Ethernet EMI solution: WE-RJ45 HPLE

126. Leakage inductance shielded vs. unshielded

127. Radiation by inductor
WE - PD2 unshielded
10µH, 2MHz clock, 1A

128. Radiation by inductor
WE – PD shielded
10µH, 2MHz clock, 1A
19dBm
improvement

129. • consider start of winding
Inductors are two poles only
 but start of winding is important
 use effect of self shielding of the winding
connection switch node
“EMI hot side”
Self sheilding

130. Design Guides

131. Catalogue
EMC Components
Power Magnetics
Signal & Communications
Additional technical drawing data supplied (inc. tolerances)
Also addition of QR codes

132. Trilogy of Magnetics
Now published as 4th edition
Three sections:-
Magnetic basics
Components
Application notes
Filtering
DC/DC PSU design

133. Design Tools
LT Spice Simulator
WE Component Selector
Inductor Selector
WE-Flex transformer designer
RF inductor Selector
Chip Bead Ferrite Selector

134. Lab rack/design kits

135. THANK YOU
&
Any Questions