Tutorial on Electromagnetic Interference (EMI) in Hybrid...
Transcript of Tutorial on Electromagnetic Interference (EMI) in Hybrid...
Dr. James Gover, IEEE Fellow
Professor of Electrical Engineering, Kettering University
Retired, Sandia National Laboratories – 35 Years
Ph.D. Nuclear Engineering
MS & BS Electrical Engineering
Tutorial on
Electromagnetic Interference (EMI) in
Hybrid Vehicles
Introduction to EMC Phenomena
EMI Generated by Rapid Changes in Electric Currents and Voltages
These Features Are Inherent in Power Electronics
The US Automotive Sector Traditionally Treats EMC as a Testing Discipline
EMI Big Picture
ELECTROMAGNETIC INTERFERENCE or CROSS TALK IN VICTIM
RADIATED CAPACITIVE OR ELECTRIC FIELD
COUPLING
RADIATED INDUCTIVE OR MAGNETIC FIELD
COUPLING
COMMON IMPEDANCE
USUALLY GROUND
SHIELDED SOURCE
GROUNDED SHIELD
SHIELDING, FIELD CANCELLATION &
ATTENUATION
ISOLATE
FILTER NOISE FROM VICTIM
UNSHIELDED SOURCE
TIME CHANGING CURRENT, I1 AND/OR VOLTAGE, V1 SOURCES
ELECTROMAGNETIC FIELDS
+dt
dILM
1
dt
dVCM
1
Electric Power Sources of EMI in Vehicles
– Ignition system
– Relays and Solenoids
– Modulated dc for interior lighting
– Voltage sag from engine starting
– Inductive load kicks
– Alternator load dump
– Power electronics
• Radiated Power Due to PWM Switching
• Conducted Output Ripple into Power System
– Cables Connecting these Power Sources to Loads Act as Antennas
– Gap Antennas Can Exist Between the Chassis and the Metal Cover of Products.
Radiated High Frequency EMI Classifications
• Near Field
– “Close to Source”: Wave impedance (ratio of
electric and magnetic field) depends on
characteristics of the source, e.g., a source with low
current and high voltage tends to generate an
electric field.
• Far Field
– “Away from Source”: Wave impedance (ratio of
electric and magnetic field) is constant and equal to
377 ohms.
Two Approaches to Dealing with High Frequency Noise
• Suppress it at source
• Prevent it from entering the victims’
environment by using filters, shields
and grounding methods
Impact of Ground Impedance on
Circuits with Common Grounds:common impedance coupling
0V
1 2I I
1GZ 2GZ
Circuit
I
Circuit
II
1V
2V
1I 2I
Common
Ground
Return
1 0 1 1G 2 2G 1 2
2 0 2 2G 1G 1 1G 2 1
V V I Z I Z V depends on I
V V I Z Z I Z V depends on I
GGG
G
ZIZZIVV
ZIIVV
1121202
12101
][
][
Analysis of Effect of Common Ground Impedance
50 Ohms
L1 L2
Voltage Source = 10Sin wtf = 100 MHz
V1 V2 L1/L2 V1 V210nH/10nH 9.55v 9.48v50nH/50nH 5.92v 4.98v10nH/50nH 9.26v 8.11v50nH/10nH 6.01v 5.94v
Avoidance of Common Return Path
Bosch, p66
Consider Signal Return Current for Time Dependent Source
R1
Ground
I
1
Vs Is
I1-IS
Low Frequency Return Current Zero Impedance Ground
KVL Gives
I R j L I j M
But M L Therefore
I Ij L
R j L
I
j
R
LShield Cut off
For I
For I I
S S S
S
S
S
S S SCO
SCO
S
S
SCO S
SCO S
:
( )
, ; ,
, ;
,
0
1
0
1
1
1
1
R1
Ground
I
1
I1-IS
IS
R1RSLS
IS
I1-IS
M
I
1
Vs
Vs
KVL Loop
Plot of Analysis
1ˆ
ˆ
I
IS
S
SSCO
L
R
1
SCO
S
jI
I
1
1
ˆ
ˆ
1
Shield Cut-Off Frequencies
Cable Impedance
(Ohms)
Shield Cut-Off
Frequency (kHz)
5XShield Cut-Off
Frequency (kHz)
RG-6A Coax 75 0.6 3.0
RG-213 Coax 50 0.7 3.5
RG-214 Coax 50 0.7 3.5
RG-62A Coax 93 1.5 7.5
RG-59C Coax 75 1.6 8.0
RG-58C Coax 50 2.0 10.0
754E ShTWP 125 0.8 4.0
24G ShTWP 2.2 11.0
22G ShTWP 7.0 35.0
24G ShSingle 4.0 20.0
Henry W. Ott, Noise Reduction Techniques in Electrical Systems, Wiley, 1988, p. 47
Shield Current for Resistive Ground
R1
Ground Resistance RG
I1-IS IS
IS
I1
R1
LS
M=LS
RS
S
GS
S
G
SG
GS
GSSSSS
L
RR
L
R
j
j
RR
R
I
I
RIILjIRLjIKVL
21
2
1
1
11
,,
)1(
)1(
~
~
0)~~
(~
)(~
:
~
I1
RG I1-IS
Plot for Resistive Ground
1ˆ
ˆ
I
IS
S
S
L
R1
1
S
GS
L
RR 2
GS
G
RR
R
At High Frequency (50 MHz-1GHz) the Ground Return Impedance Is
Dominated by Inductance
-35.4x 10 / inch -365.9 x 10 /inch
-48.44 x 10 /inch -325.9 x 10 /inch
9.43 / inch
# 28 Gauge copper wire (Radius = 6.3 mils)
DC Resistance
AC Resistance @ 100 MHz
# 20 Gauge copper wire (Radius = 16 mils)
DC Resistance
AC Resistance @ 100 MHz
Z inductance @ 100 MHz
Minimizing Ground Impedance at High Frequency
Means Minimizing Inductance of the Return Path
How to Connect Low Frequency Signals and Avoid Electromagnetic
Field Radiation
R1
Ground
I
Vs I1
H dl IENCLOSED
0
How to Connect Low Frequency Signals and Avoid Electromagnetic
Field Radiation
R1
Ground
I1
Vs I1
H dl IENCLOSED
0
EMC Hardening of Prius
Shielded High Voltage
Battery Tray
High Voltage Circuits with Noise Filters
Shielded Motor and Power Control Unit
Power Lines Shielded by
Coaxial Cable
Power Line Connectors Shieldedby Aluminum Diecast
Electromagnetic Field Countermeasures in Prius
During development strong EM fields noticed inside and outside of Prius
Several countermeasures were taken Use shielded coaxial DC power transmission
Shield cases for storing high voltage parts in Engine compartment
High voltage battery in trunk
Countermeasures resulted in EM fields inside and outside of Prius at same level of gasoline engine vehicles
The EM field from the Prius is less than approximately 1/300 in 50-60Hz range of ICNIRP criteria. International Commission on Non-Ionizing Radiation Protection.
What Are TEM Electromagnetic Waves?
• A TEM electromagnetic wave has an electric field wave and a magnetic field wave
• Both waves are traveling in the same direction
• The waves are perpendicular to each other
• The electric field wave is related to the magnetic field wave through Maxwell’s Equations
What Is Their Relationship?
• The ratio of the electric field intensity, E,
to the magnetic field intensity, H, is the
impedance, , of the medium through
which the wave is traveling. For free
space,
= 377 ohms.
Differential Equations for TEMWave Propagation- Phasor Domain
Sinusoid Sources
0~
~)(
))((
0~
~
2
2
2
2
2
2
2
y
y
x
x
Hdy
Hd
andofdefinitionj
jj
Edy
Ed
Solution to ODE: TEM Wave in Lossy Medium
jzjzmjzjzmy
zjzm
zjzmx
zmzmy
z
m
z
mx
eeeE
eeeE
H
eeEeeEE
zteE
zteE
tzH
zteEzteEtzE
)cos()cos(),(
)cos()cos(),(Forward traveling wave +z direction
Forward traveling wave +z direction
Backward traveling wave -z direction
Backward traveling wave -z direction
TIME DOMAIN
PHASOR DOMAINForward traveling wave +z direction
Forward traveling wave +z direction
Backward traveling wave -z direction
Backward traveling wave -z direction
The Electric Dipole-Phasor Domain
I
Z
X
YL
H
Er
E
{ }
{ }
{ }
H H E
HIL
Sinj
r re
EIL
Cosr
j
re
EIL
Sinj
r r
j
re
r
j r
r
j r
j r
0
4
1
24
1
4
1
0
2
0 0
2 2
0 0
2
0
2 2
0
3 3
0 0
2
0 0
2 2
0
3 3
0
0
0
0
0
0
0
0
0
02 1
, ,v
f T
r
Clayton Paul, Introduction to Electromagnetic Compatibility, Wiley, 1992, p. 178
Near Field of Electric Dipole
I
Z
X
YL
H
Er
E
{ }
{ }
{ }
HIL
Sinj
r re
EIL
Cosr
j
re
EIL
Sinj
r r
j
re
j r
r
j r
j r
4
1
24
1
4
1
0
2
0 0
2 2
0 0
2
0
2 2
0
3 3
0 0
2
0 0
2 2
0
3 3
0
0
0
r
Clayton Paul, Introduction to Electromagnetic Compatibility, Wiley, 1992, p. 178
( ) ( )
( )
( )
ZE
H
j
r r
j
r
j
r r
Wave Impedance
Z Far Field
Zj
r rNear Field r
W
W
W
0
0 0
2
0
3
0 0
2
0
0
0
0
0
0
0
1
1
90 1
Electric Dipole Far Field(retaining only 1/r terms)
I
Z
X
YL
H
Er
E
( )
( ) ( )
( )
( , ) [ ( ) ]
( , ) [ { }]
( , ) [ { }]
H farj IL
Sine
ra
E far E far
E farj IL
Sine
ra
E r t e E far e a
E r tE
rSin t
r
va
H r tE
rSin t
r
va
E
j r
r
j r
far
j t
far
M
far
M
M
0
0 0
0
0 0
4
4
0
0
0 0
4
ILSin
0
0
0
0
0
0
02
, ,v
f
r
Clayton Paul, Introduction to Electromagnetic Compatibility, Wiley, 1992, p. 178
Ratio of Far Fields from Electric Dipole
E r tE
rSin t
r
va
H r tE
rSin t
r
va
E r t
H r t
far
M
far
M
far
far
( , ) [ { }]
( , ) [ { }]
( , )
( , )
0
0 0
0
Field of Electric Dipole
E
H
r
0
1
2
Near Field Far Field
3
High
Impedance
Field
0
H~1/r2
E~1/r3
The Magnetic Dipole: Phasor Domain
{ }
{ }
{ }
E H E
Ej m
Sinj
r re
H jm
Cosr
j
re
H jm
Sinj
r r
j
re
m I b
r
j r
r
j r
j r
0
4
1
24
1
4
1
0
0
2
0 0
2 2
0
0
0
2
0
2 2
0
3 3
0
0
0
2
0 0
2 2
0
3 3
2
0
0
0
I
Z
X
Y
H
Hr
E
r
Clayton Paul, Introduction to Electromagnetic Compatibility, Wiley, 1992, p. 182
b
0
0
0
0
0
0
01202
, ,v
f
Far Fields from Magnetic Dipole: retaining only 1/r terms
( )
( )
( )
( )
E far fieldm
rSin e a
H far fieldm
rSin e a
m I b
j r
j r
0 0
0 0
0
2
4
4
0
0
I
Z
X
Y
H
Hr
E
r
Clayton Paul, Introduction to Electromagnetic Compatibility, Wiley, 1992, p. 182
b
0
0
0
0
0
0
01202
, ,v
f
Field of Magnetic Dipole
E
H
r
0
1
2
Near Field Far Field
3
Low
Impedance
Field
0
H~1/r3
E~1/r2
What Is The Relationship Between E and H for Far Field
Case?• The ratio of the electric field intensity, E,
to the magnetic field intensity, H, is the
impedance, , of the medium through
which the wave is traveling. For free
space,
= 377 ohms.
What Are Physical Mechanisms of Magnetic
Field Cross-Talk?
Source of
Magnetic
Field
Transmission
Medium
Induced
EMF
Inductive Coupling Between Two Circuits
Bosch, p66
Equivalent Circuit
1z 2z
Source
Loop - 1
Victim
Loop - 212M12M
Mutual Inductance Describes
Induction Phenomena
Lumped Circuit Model of Magnetic Field Induced Cross-
Talk Voltage Divider Cross-Talk voltage generated in series
with victim conductor
Victim equivalent circuit (lumped model)
1R2R1
CT 12
dV L
dt
voltage
divider
Henry W. Ott, Noise Reduction Techniques in Electronic
Systems, John Wiley & Sons
Polarity of induced voltage will be such that the direction of the magnetic field associated with the current flow will oppose any change in the direction of the magnetic field that induces the voltage.
What Are Physical Mechanisms of Electric Field Cross-Talk?
Source of
Electric
Field
Transmission
Medium
Induced
Current
Capacitive Coupling Between Two Circuits
Bosch, p66
Lumped Circuit Model of Electric Field Induced Cross-
Talk (Current Divider)
Cross-Talk current generated between victim
conductor and ground
Victim equivalent circuit (lumped model)
1R2R1
12
dC
dt
current
divider
Henry W. Ott, Noise Reduction Techniques in Electronic
Systems, John Wiley & Sons
C12 dV1
dt
+
dt
dVC G
M
dt
dIL G
M
Identification of Type of Crosstalk Between Circuits
If current source (capacitive or electric field coupling) is dominant and R1 is decreased, V is reduced.
If voltage source (inductive or magnetic field coupling) is dominant and R1 is decreased, more current flows through R2
and V is increased.
R2R1 V
Prius Three Phase Cable Between Inverter and Motor
DC Power Cable Used in Prius and Ford Escape Hybrid
Positive Voltage to
Power Electronics
Negative Voltage to
Power Electronics
Rear of Prius
Engine Compartment
of Prius
Two Separate Cables, Each Shielded with
External Insulation Over Shields
Shields tied together.
Power Electronics Are Large Source of EMI
• Ripple in on Power Supply Voltage Line
• Radiated Noise from Fast Switching of
High Voltage and High Currents
– Rectifiers
– DC-DC Converters
– Inverters
– Motor Drives
– DC Motors
EMC Paths in Auto Electric Drives
• Power Converters/Inverters: dv/dt and di/dt Sources– Main Source of EMI
– IGBT Switches Must Be Modeled at High Frequency (One source of high frequency noise)
– Time domain modeling requires knowledge of mutual inductances and capacitances and high frequency models of all components up to 30MHz for conducted EMI and 1 GHz for radiated EMI.
• Electric Motor– Need to know impedance at high frequency
– Common mode capacitance path through bearings
• Cable Between Battery and Inverters– Model as transmission line
• Traction Battery– Need to know impedance at high frequency
Guttowski, Weber, Hoene, John & Reichl, EMC Issues in Cars with Electric Drives, IEEE Symposium on EMC, Aug. 2003.
Plane Wave Reflection and Transmission Through Shields
Hi
Eiz
x
uy
Et
Ht
Er
Hr
Electronics Inside Box
yo
Reflection and Transmission at Shield Boundary
jzjz
shield
mt
x
yjyi
x
t
z
air
i
xr
x
i
z
r
z
eeeE
TH
eeETE
ytE
tzH
ytEtyE
)cos(),(
)cos(),(
Shields of Finite Thickness
E E e az
x1 1
H
Ee a
r
r j z
y
0
0
E E e az
x2 2
b
E E e a
i i
j z
x 0
H
Ee a
i
i j z
y
0
0
E E e a
r r
j z
x 0
HE
e ai z
y1
HE
e azy2
2
E E e a
t t
j z
x 0
H
Ee a
t
t j z
y
0
0
z
x
y
0 0 0
0
0
0
j
j
j j j( )
Boundary Conditions
E z E z E z E z
E z b E z b E z b
H z H z H z H z
H z b H z b H z b
E E E E
E e E e
i r
t
i r
t
i r
b
( ) ( ) ( ) ( )
( ) ( ) ( )
( ) ( ) ( ) ( )
( ) ( ) ( )
.
.
0 0 0 0
0 0 0 0
1
2
1 2
1 2
1 2
1 2
1 2
1 2
b
t
j b
i r
i b r b t j b
E e
E E E E
Ee
Ee
Ee
.
.
0
0
3
4
0 0
1 2
0
Solution of 1., 2., 3., and 4.
Have 4 equations and 5 variables; therefore, may solve for ratio of
incident E field to transmitted E field.
( )
[ (
) ]
,
,
( )
/ /
/ /
E
Ee e e e e
For bE
Ee e
i
t
b j b b j b j b
i
t
b b
0
2
0
0
0
2 2 2
0
0
0
0
2
0
0
41
1
4 4
0
Approximate Solutions for Good Conductor Shield
Several Skin Depths Thick
( )
( )
E
E
E
E
E
E
H
H
H
H
H
H
i
t t
i
i
t t
i
1
0 1
0
0
0
0
2
1 0
0 1 0
0
0
2
2 2 4
2 2 4
Most of E field reflected at front surface whereas H field is not only
transmitted, it doubles at front surface. E field that arrives at back surface
is doubled when it propagates into free space; almost none of the H field
that is not attenuated and makes it to the back surface is reflected back into
the shield. For frequencies above 3MHz for a 20 mil copper shield,
attenuation of the shield dominates the effect of reflection from the front
and rear surface.
Far Field or TEM Wave Shielding Conclusions
• Electric field shields can be “thin”because most of the E field is reflected at the front surface. But must be grounded.
• Magnetic shields must be “thick”so that the field can be attenuated as it propagates through the shield.
Prius Motor Housing/Shield
Staunton, Ayers, Marlino, Chiasson,& Burress, Evaluation of 2004 Toyota Prius Hybrid Electric Drive System, ORNL/TM-2006/423, May, 2006.
Packaging of Power Electronics in
Prius
Staunton, Ayers, Marlino, Chiasson,& Burress, Evaluation of 2004 Toyota Prius Hybrid Electric Drive System, ORNL/TM-2006/423, May, 2006.
Prius Inverter/Converter with
Capacitor Module Removed
Staunton, Ayers, Marlino, Chiasson,& Burress, Evaluation of 2004 Toyota Prius Hybrid Electric Drive System, ORNL/TM-2006/423, May, 2006.
Empty Inverter/Converter Housing
Showing Cold Plate Surfaces
Staunton, Ayers, Marlino, Chiasson,& Burress, Evaluation of 2004 Toyota Prius Hybrid Electric Drive System, ORNL/TM-2006/423, May, 2006.
Inverter Power Module 18 Pack Array
Staunton, Ayers, Marlino, Chiasson,& Burress, Evaluation of 2004 Toyota Prius Hybrid Electric Drive System, ORNL/TM-2006/423, May, 2006.
IGBT-Diode Pair
Staunton, Ayers, Marlino, Chiasson,& Burress, Evaluation of 2004 Toyota Prius Hybrid Electric Drive System, ORNL/TM-2006/423, May, 2006.
Toyota Camry Hybrid Integrated
Power Module
Camry HEV Inverters with Top Circuit
Board and Side Housing Removed
EMI Observations from Motor Drive Inverters
• For 10kHz<f<150kHz, DM Noise Dominant with
peaks at multiples of 20kHz Switching Frequency.
Predictable by Simulation.
• For 150kHz<f<30MHz, CM Noise Dominant.
Predictable by Simulation up to 10MHz.
– Path of CM noise is through stray capacitance of motor
windings back to source.
– Another CM path is through stray capacitance between
IGBT collector and heat sink.
Zui, Lai, Tang, Hefnew and Chen, Analysis of Conducted EMI Emissions from PWM Inverter Based on Empirical
Models and Comparative Experiments, 1999 IEEE Symposium on EMC.
Effects of Inverter Generated Common Mode
Noise on Motors
• Leakage Currents or Bearing Current Going to
Ground Through Stray Capacitance Between
Stator and Rotor Can Create Skin Currents on
Auto Body. (Very low impedance at high
frequency.)
– Want CM return currents to flow on cable shield so no
external electromagnetic field generated.
• Shortened Insulation Lifetime of Stator Windings.
Noise Spectrum Due to IGBT or MOSFET Switching in Power
Electronics
''
T
A
]
2
'2
'
][
2
)2
(
[2
T
nT
nSin
T
nT
nSin
T
ACn
Mathematics of SincX
f
fSin
f
fSin
T
AC
XelforXX
Xsmallfor
XelforX
XsmallforX
SinXSincX
r
rn
10101010
1010
1010
log20log202
log20log20
arglog201
log20
01log20log20
arg1
1
Frequency Spectrum of an Ideal Trapezoid Signal
Trapezoid signal amplitude = 1, Frequency = 20kHz, Rise time = Fall time = 400ns =
tau, full width at half max of current = 25 microseconds = t0.
F. Costa and D. Magnon, Graphical Analysis of the Spectra of EMI Sources in Power Electronics, IEEE Transactions
on Power Electronics, Vol. 20, No. 6, Nov. 2005.
Firuz Zare, EMC and Modern Power Electronics, Tutorial, 2007 IEEE International Symposium on EMC
Three Phase Inverter
Firuz Zare, EMC and Modern Power Electronics, Tutorial, 2007 IEEE International Symposium on EMC
Firuz Zare, EMC and Modern Power Electronics, Tutorial, 2007 IEEE International Symposium on EMC
HEPWM and SHRPWM
HEPWM: Harmonic Elimination PWM
Eliminate low ranked harmonics to simplify the remaining harmonics
filtering process. The main drawback is that the first significant
harmonics display high amplitude. A high number of switching actions
is required to shift upward the first significant harmonics rank.
SHRPWM: Switching and Harmonics Reduction PWM
Optimize the Total Harmonic Distortion (THD) by reducing the
amplitude of all the harmonics present within the inverter output
voltage spectrum and by reducing the number of switching angles.
Mansouri, Allah, Meghriche , Cherifi,& Hoet, Proceedings of 2007 IEEE VPPC, Sept. 11 & 12, 2007 Arlington, Texas
Comparison of SHRPWM and
HEPWM Phase-to-Phase Inverter
Output Voltage Frequency Spectrum
HEPWM
SHRPWM
THD=50.26%
THD=39.42%
Even-ranked
and multiple of
3 odd-ranked
harmonics are
automatically
eliminated
Low-Ranked Harmonics Eliminated
Mansouri, Allah, Meghriche , Cherifi,& Hoet, Proceedings of 2007 IEEE VPPC, Sept. 11 & 12, 2007 Arlington, Texas
Dependence of THD on The Number of
Precalculated Switching Angles
Mansouri, Allah, Meghriche , Cherifi,& Hoet, Proceedings of 2007 IEEE VPPC, Sept. 11 & 12, 2007 Arlington, Texas
Inverter Common Mode Noise
Firuz Zare, EMC and Modern Power Electronics, Tutorial, 2007 IEEE International Symposium on EMC
Common-Mode Voltage Generation in a PWM Inverter
N. Hanigovszki, J. Landkildehus, G. Spiazzzi, and F. Blaabjerg, An EMC Evaluation of the Use of Unshielded Motor
Cables in AC Adjustable Speed Drive Applications, IEEE Transactions on Power Electronics, January, 2005.
3
cbacm
VVVV
Firuz Zare, EMC and Modern Power Electronics, Tutorial, 2007 IEEE International Symposium on EMC
Phase Voltages and Common Mode
Voltage in Six Step 3 Phase Inverter
Firuz Zare, EMC and Modern Power Electronics, Tutorial, 2007 IEEE International Symposium on EMC
Major Motor Elements
Firuz Zare, EMC and Modern Power Electronics, Tutorial, 2007 IEEE International Symposium on EMC
Stator Turn-to-Turn Winding
Capacitance
Firuz Zare, EMC and Modern Power Electronics, Tutorial, 2007 IEEE International Symposium on EMC
Relevant Motor Capacitances
Firuz Zare, EMC and Modern Power Electronics, Tutorial, 2007 IEEE International Symposium on EMC
Equivalent Circuit of Motor
Firuz Zare, EMC and Modern Power Electronics, Tutorial, 2007 IEEE International Symposium on EMC
Electrical Behavior of Ball Bearings
Firuz Zare, EMC and Modern Power Electronics, Tutorial, 2007 IEEE International Symposium on EMC
Motor with Capacitive Couplings
Firuz Zare, EMC and Modern Power Electronics, Tutorial, 2007 IEEE International Symposium on EMC
High Frequency Electrical Model
of Motor
Firuz Zare, EMC and Modern Power Electronics, Tutorial, 2007 IEEE International Symposium on EMC
Response of Motor to Common
Mode Voltage
Firuz Zare, EMC and Modern Power Electronics, Tutorial, 2007 IEEE International Symposium on EMC
Estimates of Common Mode
Current
Firuz Zare, EMC and Modern Power Electronics, Tutorial, 2007 IEEE International Symposium on EMC
Capacitive Coupling Between Stator
Windings and Stator Is Most
Important Source of Noise
Firuz Zare, EMC and Modern Power Electronics, Tutorial, 2007 IEEE International Symposium on EMC
EMI Modeling of Motor
Firuz Zare, EMC and Modern Power Electronics, Tutorial, 2007 IEEE International Symposium on EMC
Measurement of Cstray, Ls and Rloss
Firuz Zare, EMC and Modern Power Electronics, Tutorial, 2007 IEEE International Symposium on EMC
Unfolding Measurements
Firuz Zare, EMC and Modern Power Electronics, Tutorial, 2007 IEEE International Symposium on EMC
Interpretation of Measurements
Firuz Zare, EMC and Modern Power Electronics, Tutorial, 2007 IEEE International Symposium on EMC
Alternative Approach to Modeling
Motor
• Use Three-dimensional Maxwell Equation Solver to Determine all Electrical Losses, Capacitances, Inductances, Speed, etc. as Function of Three Phase Drive Voltages and Currents.
• Store Data in Look-Up Table.
• Run Circuit Analysis Code and Use Data From Look-Up Table.
Reduction of Common Mode Inverter Noise
• Passive filters are large, expensive and do not
work well at high frequencies.
• Active common mode canceller circuits can be
effective.
• Use dual bridge inverter topology – adds another
bridge to output circuit.
• Add a fourth phase to inverter to balance the
inverter network and realize active filtering of the
common mode noise.
• Advanced PWM techniques can be implemented
in software.
PWM Techniques
• Sinusoidal PWM (SPWM)
• Selected Harmonic Elimination (HEPWM)
• Minimum Ripple Current
• Space-Vector PWM
• Random PWM
• Hysteresis Band Current Control
• Sinusoidal PWM with Instantaneous Current Control
• Delta Modulation
• Sigma-Delta Modulation
Bimal K. Bose, Modern Power Electronics and AC Drives, Prentice Hall, 2002, p. 211.
Reduction of EMI in Converters
• Passive filters take large space, are expensive and do not solve the problem perfectly.
• Active ripple filters include– Current and voltage active filters
– Feedforward active filter measures ripple and injects its inverse to obtain net cancellation of ripple.
– Feedback active filters suppress ripple via high-gain feedback control.
• PWM switching frequency modulation may be used to spread the noise concentrated at discrete frequencies over a continuous frequency range.
• ZVT soft switching (reduces dv/dt and di/dt) has minimal effect on conducted EMI at low frequency but out performs hard switching by few dB at high frequency.
Shielded or Unshielded Cables for Three Phase Motor Drives? Most AC adjustable speed motor drives for induction
motors are PWM voltage-source inverters.
To achieve high efficiency (up to 98%), high frequency switching IGBTs are used with dv/dt values of 6 kV/microsecond or higher
Asymmetry in output pulses in three leg inverters results in common mode voltage on the three phase lines.
The common mode voltage causes EMC that is avoided by using shielded cables to connect the inverter to the motor.
Can an unshielded cable and common-mode filters give acceptable EMC performance at lower cost than shielded cables?
N. Hanigovszki, J. Landkildehus, G. Spiazzzi, and F. Blaabjerg, An EMC Evaluation of the Use of Unshielded Motor
Cables in AC Adjustable Speed Drive Applications, IEEE Transactions on Power Electronics, January, 2005.
Price Comparison Between Shielded and Unshielded Cable
N. Hanigovszki, J. Landkildehus, G. Spiazzzi, and F. Blaabjerg, An EMC Evaluation of the Use of Unshielded Motor
Cables in AC Adjustable Speed Drive Applications, IEEE Transactions on Power Electronics, January, 2005.
Inverter-Motor Connections Without Filter
N. Hanigovszki, J. Landkildehus, G. Spiazzzi, and F. Blaabjerg, An EMC Evaluation of the Use of Unshielded Motor
Cables in AC Adjustable Speed Drive Applications, IEEE Transactions on Power Electronics, January, 2005.
Inverter-Motor Connections With LC Filter
N. Hanigovszki, J. Landkildehus, G. Spiazzzi, and F. Blaabjerg, An EMC Evaluation of the Use of Unshielded Motor
Cables in AC Adjustable Speed Drive Applications, IEEE Transactions on Power Electronics, January, 2005.
Output Filter Topology with DC Link Feedback
N. Hanigovszki, J. Landkildehus, G. Spiazzzi, and F. Blaabjerg, An EMC evaluation of the Use of Unshielded Motor
Cables in AC Adjustable Speed Drive Applications, IEEE Transactions on Power Electronics, January, 2005.
Conclusions
• In an adjustable speed drive application using a PWM voltage source inverter without any filtering at the output of the inverter or cable shielding very high EMI signals were observed.
• A classical LC filter does not significantly reduce the noise.
• An output filter with dc link feedback which works in both common mode and differential mode reduces the conducted EMI to acceptable levels even when long motor cables are used.
• Shielded cables are unnecessary with this filtering method.
N. Hanigovszki, J. Landkildehus, G. Spiazzzi, and F. Blaabjerg, An EMC Evaluation of the Use of Unshielded Motor
Cables in AC Adjustable Speed Drive Applications, IEEE Transactions on Power Electronics, January, 2005.
Active Filtering of Common Mode
Signals
Firuz Zare, EMC and Modern Power Electronics, Tutorial, 2007 IEEE International Symposium on EMC
Active Filter Connection
Firuz Zare, EMC and Modern Power Electronics, Tutorial, 2007 IEEE International Symposium on EMC
Current Sensor Design
Firuz Zare, EMC and Modern Power Electronics, Tutorial, 2007 IEEE International Symposium on EMC
Long Cable Effects
Firuz Zare, EMC and Modern Power Electronics, Tutorial, 2007 IEEE International Symposium on EMC
Voltage Waveforms Due to Long Cables
Firuz Zare, EMC and Modern Power Electronics, Tutorial, 2007 IEEE International Symposium on EMC
Effect of Passive LC Filter on
Voltage
Firuz Zare, EMC and Modern Power Electronics, Tutorial, 2007 IEEE International Symposium on EMC
Active Filtering Summary
Firuz Zare, EMC and Modern Power Electronics, Tutorial, 2007 IEEE International Symposium on EMC
Summary• System designers have dealt with EMI problems
by shielding, grounding and filtering.
• Power switches (IGBTs and MOSFETs) in
Inverters and Converters are major source of EMI
in power electronics.
• Noise is common mode and differential mode.
• Frequency domain models are straight forward;
time domain models require extensive knowledge
of mutual inductances and capacitances.
• The physical phenomena can be modeled with
lumped circuit models unless “long” cables are
between the inverter and motor.