Generation,
Control
and Regulation
G. Skibinski,
Rockwell
J. Pankau,
Automation
of EMI
R. Sladky,
Mequon,
(414) 242-7151
Adjustable
Abstract:
manufacturer’s
Transistor
Bipolar
recently
(BJT)
(IGBTs)
resulting
drive
to
package.
(ASD)
Insulated
is 5-
Gate
Fax
the noise impressed.
covered
in detail,
Each aspect of the noise problem
starting
with
is that
device
faster
output
dv/dt
Experience
suggests all PWM drives with steep fronted
output
voltage waveforms
have these problems.
This
paper provides a basic understanding
of EMI generated
drives solutions
to control
EMI,
as well as
standards on allowable conducted and radiated
susceptible circuits.
B. Susceptible Equipment,
Circuits&
Systems
Fig. 1 shows potential
CM noise problems
increase with
susceptible equipment present, system input voltage, system
drive quantity, and, length of motor leads. Other factors are
type of ground system and cabinet layout practice.
Susceptible
equipment
may be computer
systems,
communication
links, ultrasonic
sensors, weighing
and
temperature sensors, bar code/vision systems, and capacitive
proximity or photoelectric sensors. Control interfaces include
encoder feedback, O-10 Vdc, and 4-20 mA signals.
Higher
system
ac line
voltages
voltages ( V~US).The higher output
emissions to insure a successful drive system installation.
have higher
switching
dc bus
dv/dt increases
peak CM ground current (i = C~traY dv/dzj. Increasing
I. INTRODUCTION
TO EMI
NOISE
Electromagnetic
Interference (EMI) noise is defined as
an unwanted electrical
signal that produces undesirable
effects in a control system, such as communication
errors,
number
degraded
ground capacitance
performance
and malfimction
operation.
References on the general principles
available
[1-3],
as well
as methodologies
or non-
of EMI
drive carrier Iiequency
of switch
current.
Motor
transitions
cable lengths
are
WC), increases the
and sum total
<20
ft exhibit
of CM
~edium
R&
on calculating
SCR DC drives in 1982 [5]. All ac PWM
drives have the potential to cause EMI with adjacent sensitive
equipment, when large quantities of drives are assembled in a
concentrated area [6- 10]. However, faster switching speeds
of new converterlinverter
topologies require an updated study
of new system EMI problems created.
A. What is Common Mode Noise?
Common
Mode (CM) noise is a type of electrical
induced on signals with respect to a reference
noise
problems
imply
noise by conduction
a source
of
or radiation
susceptible to the magnitude,
noise,
a
means
and circuits
noise
ground.
of
CM
coupling
/ equipment
frequency and repetition
rate of
Figure 1. Applications with potential problems
07803-4070-1/97/$10.00 (c) 1997 IEEE
noise
low cable line to
and low CM noise risk ffom
radiated emissions [4]. IEEE Std. 518 applied these principles
to slow switching
drive
quantity increases the sum total of transient CM noise current
to ground. Higher
equipment
is
the effect of CM noise on
10 times faster,
transitions
and higher drive carrier frequencies
increase
the magnitude
of Common Mode (CM) electrical
noise
and
Electromagnetic
Interference
(EMI)
problems.
by these
regulation
53092
output
losses, a more efficient
However,
Company
Drive
(414) 242-8300
Junction
preferred
of IGBTs
capability
in lower device switching
and smaller
Bipolar
as the
device. The advantage
rise / fall time switching
Drive
from
semiconductors
Transistors
switching
AC
Speed
migrated
WI
AC Drives
J. Campbell
- Allen-Bradley
6400 W. Enterprise
from
capacitive
dv/dt
ground
capacitance
currents.
As
cable
increases and CM
lengths,
cable
to ground
high
frequency
increases.
At
of reflected wave voltage transients (-2 V& ) also
on motor
cable
increase,
current
oscillations
appear
long
lengths
charging
terminals,
to create
current through the stator winding
EMI
mitigation
must
the
CM
ground
noise
and cable capacitance [7].
involve
a discussion
equipment
ground, signal grounding
grounding system type on CM noise.
and
of
the
safety
effect
of
Drive Power Equipment
current
(PE) terminal
in Fig. 2 serves as
metal accumulates electrical charge thru leakage
that may exceed 50 Vdc
(a safe touch
potential).
Cable conduits, armor or cable trays should be bonded to the
cabinet, since it is shown later that these carry high frequency
noise currents. Drive PE, mounting panels and cabinet are
then bonded to system PE copper bus and connected (ground
conductor sized per NEC code) to True Earth (TE) zero
voltage ground such as building
structure steel to insure safe
Drive logic common may go to PE or a separate isolated
connected
to TE
ground along with the PE wire. This TE installation
effects of PE noise between multiple
drive logic and susceptible interface
close to TE potential.
reduces
drives and maintains
equipment commons
zero voltage
or TE potential
may be
obtained at structure steel, since steel girder grid connections
provide
affected
multiple
by soil
paths to
resistivity
ground. Ground
and dependent
content. TE may be low impedance
ground water tables dry up. Multiple
resistivity
safety
current.
resistance is
on moisture
until summer when
ground rods in low
soil may be an adequate low impedance
and signal
ground
However.
for
high
frequency
instances of ground
for 60 Hz
EMI
rods driven
noise
in plant
Q
between
rod
(lao)
Potential
#1 ( Vl) to TE structure steel Potential
will
passing
through
have a high noise voltage
system impedance
a
relative
Drive
and susceptible
equipment
interface
have a CM noise voltage
VIZ is set up
logic common
common
(tied to V])
(tied to V2),
is difficult.
point,
system is essential for safety and noise free signal grounds.
E. EMI & Ground Philosophy:
Ungrounded
High, Solid
grounding
philosophy
System
for
multi-drive
applications is specified by users and based on concerns other
than EMI. An advantage of grounded wye systems in Fig. 3
is typical 20 dB attenuation of primary line to ground voltage
transients. However,
it is shown that a wye secondary with a
completes a transient CM
noise current return path from the drive output to the ground
grid and back to drive by the ac input leads. CM current is
highest with grounded
systems, but the noise loop is
contained at the transformer neutral (Xo) and noise does not
progress into the primary PE grid.
and significantly
differences
resistance ground system adds 150Xo to ground circuit. Attenuation of
voltage transients is acceptable. This
with the CM noise current return path
reduces peak CM current, so CM potential
across the ground grid become smaller.
A disadvantage of ungrounded systems is that primary
line to ground voltage transients are passed directly to the
secondary without attenuation. Safety concerns must also be
addressed with this system. However, the return path of CM
noise current path back to the drive input is broken, so CM
%
=z$)--z
PE
/////////////////////////////
CO,”mm
G.m,d
P*C”,!4
#l
,1=.!.
C.rrc.l
l.O
(hnmd
Ptien,i81
#2
Figure 2. CM current and CM voltage in safety
PE & signal TE grounds
with
A good ground
—
!’,.
VI
to TE, if the ground
the best ground
across a plant,
Ill
Mode Vdtw
from
#2 (VJ.
( V12) to degrade the signal
In real sites, finding
located
system
is high. A CM noise voltage
between the two grounds.
drives
ground
Ungrounded System
IOIIIm,m
and
As shown in Fig. 2, often there are hidden CM ground
In Fig. 3, the high
300 Q in the secondary
primary line to ground
resistor is now in series
D. EMI & System Signal TE Ground
Inside buildings,
1,000-5,000
solid ground neutral detrimentally
touch potential exist under ground fault conditions.
TE bus in the cabinet that is single point
exhibited
steel, due to dry rocky soil under the building.
interface.
safety ground. Drive metal is bonded to PE, since
ungrounded
have
currents
will
C. EMI & System Safety PE Ground
equipment
floors
building
1
PE
Figure 3. Grounding philosophy affects system EMI
07803-4070-1/97/$10.00 (c) 1997 IEEE
Unshielded Phase Conductor of Drive
-m
I
Iao I
t_T
%g
Critical Distance
send
I
~
. ..--+
I
t
‘p--
+:,
‘1?
k’-
I
l=
I .
.
noise current,
known
so an instantaneous
NOISE
time and which
GENERATOR
equivalent
risetimes
(tri~e) are 0.05 -0.2
to fn
of
ps, while
Send end is referenced
motors
transitions
ground
interact
positive
high
frequency
to generate
noise currents
(Iao,
Ibo,
and higher
bus voltage.
tic) increases EMI,
BJTs are 1 -2
ps,
320-160
or
negative
transient
kHz,
dv/dt
phase to
to as common
increases with
Increasing
is
drive carrier
drive quantity
site.
(CMRR)
VI ground.
Thus, CM noise
frequency
rate is
increases CM ground
back through
ground.
III.
A. Critical
SYSTEM
NOISE
Operational
If both
COUPLING
may
noise
Ratio
PATHS
Distance vs. Ckl Current Risetime
VI and V2 of Fig. 5 were maintained
then V1 =V2 = O and V12 = O, eliminating
potential,
Susceptible
circuits
may fimction
with
at TE
the signal
lao ground
noise present, if both V] and V2 have the same magnitude
phase waveshape. In this case both VI and V2 are not=
V12 -O, so the minimal
CMRR.
Thus,
high
and
O, but
noise present is rejected by the circuit
peak l.O ground
risetime noise may still have V12 -0,
CM Voltage in Ground
The signal
threshold tested at noise fiequencyfm
separation.
B. Conducted CM Current Inducing
structure steel) at V., while the
to noisy
ability to tlmction in the presence of high ffequency
depends on it’s Common
Mode noise Rejection
noise.
faster tri~e
since the CM current repetition
faster. Higher localized
current at an application
with
to TE zero
lines and circulate
an
and may reach 20 Apk.
CM noise current magnitude
circuit,
develop a noise voltage due to ii-z. The interface equipment’s
mode (CM), or zero sequence currents. Peak lao magnitude
approx. (Cl.g ) times ( V1.g/ tJ
interface
time determines
referred
ICO)
susceptible
sources of radiated
6.4- 1.6 MHz and
during
( P’Z2 -
voltage impressed on both HI and LO signal lines, allows a
CM noise current ii-2 to appear in the same direction on both
respectively. Output dv/dt is now 20 to 40 times higher.
Most drive related EMI is due to conducted noise
currents in Fig. 4. Line to ground capacitance Cl.g of cables
and
Receive)
voltage ground (via building
IGBT
fkequency fn = 0.318 / tri~e.
noise coupling
corresponding
transition
difference
exists across the
source and return signal current is, is referenced
Common Mode Current
are inherent
noise. Voltage
voltage
mode noise voltage)
ground grid.
A PWM output voltage has abrupt transitions to and
the de bus, essentially controlled by semiconductor
and conducted
Ground Potential #2
as common
A (Send/
switching
2 *
Iao
Figure 5. CM current inducing CM voltage
noise current does not exist in the ground grid.
from
Common Mode Currmt
%
Ground Potential #1
Figure 4. Noise source: Drive induced CM current & voltage
A. Drive CM Voltage Inducing
, ‘E
L----.-k-=+
--------------
k
AS AN EMI
**
i5
. . . . . . . . . ...4...
=.. . .. . . .
k-----a
4-2
I
Common Mode Vottage V
m
~
I
‘+—---’
●
. . . 4.
-.--~
*
v 1-2
Receive
is
I
II. AC DRIVE
~J
,-------● ++*+* ***m ● *+ m+m ● *T * ● *I
1
I
I ao
f-2
currents
depending
with
slow
on distance
Low peak ZaOwith fast 50 ns risetimes may have
large instantaneous
voltage differences
at either end, even for
short ground distance separation.
A transient high frequency
CM current path exists in Fig.
5 from each drive output phase during
switching,
thru stray
cable and motor CZ.g capacitance, into ground Potential
(Vl)
and thru the ground
Ground
grids are high
grid to ground
impedance
Potential
to CM
high
#l
#2 (Vz).
frequency
The term (U8)
where magnitude
VZ2 -0
defines a maximum
and phase relationships
critical
distance lC
are equal, such that
between two separated single ended interface
grounds. Wavelength
(1) in meters is calculated ash=
circuit
c /fn,
where c = 3.108 m/s and fn is in Hz. Fig. 6 shows the lC chart
07803-4070-1/97/$10.00 (c) 1997 IEEE
Unshielded Phase Conductor
700
600
500
““”l
Critical
Region Suseqttible
toCMNoise
/
of IMve
Distance
E’!
I H!
--“0.01
1
0.1
Drive Output
Voltage
Risetiu
120 VAC
U
Interface
Power Lads
10“
CM Noise
q -.-,
(uS)
Figure 6. Interface distance vs. CM voltage risetime
‘u.
:.,.
(. -....4
ommon Mode Voltage V
%.
:*”=
,-’
for various PWM voltage risetimes.
Consider
an IGBT
drive
tri~e
= 100 ns, logic
with
WO wire interface
circuit
a possibility
for CM noise voltage
interference
with
these
of 2
after 40 ft. In contrast, a BJT drive with tri~e
conditions
p
TE ground. Fig. 6 shows there is
has VIZ -0
and minimal
CM
noise up to 900 tl of
interface length.
This chart applies to single ended systems and does not
imply equipment will not operate properly
above lC if
systems containing
or differential
CM filters, galvonic
or optically
coupling
C1~ to each signal
in open air, conduit
cables.
(2)
Shield
C. CA4 Current Capacitively
isolation
In Fig. 8, unshielded
Voltage
High dv/dts from drive unshielded output leads in Fig. 7
will capacitively couple lao thru stray capacitance Cl~ onto
both signal lines in close proximity
and produce an error
voltage depending on load impedance balance. Worst case
z~0 - (Cls ) (Vi-g I A %.,), where CI, is proportional
to the
of parallel
and signal
power
problems
Standard
9
signal
solutions available are: (1)
to provide balanced capacitive
noise reduction
leads together
Unshielded Phase Conductor of Drive
-99--I
ao
[~
l~c
%s[
120 Vac power leads in a conduit
drive power leads cause EMI
when dv/dts of 10,000 V/Vs or greater are present.
. . .
i
;
Lo
.... .<.. ... J%-.=.=
Signal shields reduce external
may introduce
ground
. . ..-
potential.
power
supply
on W and LO signal
electrostatic
if the shield
As discussed,
coupling
is connected
drive
but
to a noisy
dv/dt at “noisy”
CM ZaOpath to “quiet”
Unshielded Phase Conductor
.R
‘Cpg
-m
■. . .
. .
Critical
send
1
I
VI
V2 and induces a
of Drive
Distance
~
Receive
1
4
&-_
b-y
. ....
D-
“-
-
II
n!’
,Own;i,
~ro””d
#l
EMI,
creates a transient
r
I
Ground Potential
to impress noise voltage
couple to 120 Vac
load
D. Noisy Shield Ground
ao
A’
susceptible
Ton
. .*
J.
capacitance,
lines at TE.
1-s
L 4. ~.
. . . . .
leads and through
—
I
. . . . .
power
leads and separation
distance.
Twist
so
Coupled to Interface Power
High dv/dt from drive leads capacitively
length
signals
or cable trays, (4) Use shielded power
or cable tray with unshielded
Coupled to Signal
lead,
electrostatic coupled noise currents flow on shield to ground
instead of signal leads, (3) Separate control ffom power wires
circuits are used.
B. CM Current Capacitively
Ground Potential #2
Figure 8. CM current capacitively coupled to interface power
of 200 ft length, and with receive
end referenced to a different
‘
Ground Potential #1
common to noisy PE, connected to a O-10 Vdc single ended
I
I
I
I
I
k
[ ~,~
J
-------/m//////////////////////////////N/
.-
7!7
Ground
9
Potentiat
..---------
Common Mode Currwst ~
#l
/79
b
-----------
r!hmd
TE
Figure 7. CM current capacitively coupled to signals
Figure 9. Noise coupling:
07803-4070-1/97/$10.00 (c) 1997 IEEE
Noisy shield ground
P#entkd
#2
VIZ CM noise voltage.
Unshielded
Shield connections to noisy VI potential
CM current i12 path thru shield capacitance
creating
susceptible
load noise. Current
zero voltage ground
shield
induced
Phase Conductor
of IWW
in Fig. 9 cause a
C~.H1 & C~-Lo
i12 continues
thru
V2 and back to VI. Load noise due to
noise
is verified
by
removing
the shield
ground.
Solutions include: (1) Galvonic
modules,
(2)
Inductance
on
or optical signal isolation
power
leads
to
reduce
IaO
risetime to ground, so noisy VI is closer to quiet V2 potential
and V12 -0,
SEND
end. CM
choke
inductance
in the i12 ground
reduces the effect of V12 dv/dt reducing
C~-H1 & C.-LO , reducing
susceptible
i12 coupling
load noise. CM cores
do not affect line to line signal quality.
E. Noisy Source Ground
h
Ground
Potential
#1
Signal shields reduce external electrostatic
coupling
but
Potential
K!
up and down with identical noise voltage, so coupled noise
into differential signal leads is minimal.
Disadvantages of multipoint
ground schemes are VI to
V2 ground loops may produce high shield current limited
by
shield
V2
resistance
and
becomes polluted with
still may introduce
Ground
Figure 11. Conducted CM current creating radiated emissions
path
through
h
‘ao
(3) CM choke on both signals and shield at
“quiet”
“noisy”
other sensitive equipment
zero
voltage
ground
VI ground voltage and affects
tied to V2.
EM1, if the shield is connected to a noisy
ground potential to TE ground potential,
while interface
equipment source is referenced to Fig. 10 noisy ground. The
fast di/dt edges of CM l.O current set up a high dv/dt V12
voltage as demonstrated before. The ilz paths due to non-zero
V12 are shown in Fig. 10. Noisy
VI end in Section III-D
had
a metallic shield path to couple noise in the entire length of
signal cable, while now noisy VI end must first get through
the Send end power supply ground impedance,
so that noise
F. Conducted
CM Current and Radiated Emissions
Unshielded drive wires act as antennas for the electric
fields set by the steep dvldt of the PWM output voltage.
Radiated emissions occur at llntri~e and its higher harmonics.
Unshielded
drive input / output cables carrying
CM ZaOmay
act as loop antennas for radiated emissions, due to the current
path in these wires returning via the ground grid in Fig. 11.
levels will be lower with this configuration.
Drive CM output cores and conduit,
Previous solutions also apply in this case. Signal quality
may be improved by grounding the shield at both ends in
solutions
substantially
reduce radiated
noise, but full
compliance to FCC / European CE regulations may require
cases of CM noise with fast rising edges or high frequency
ringing. Shield low impedance co-axial braid, parallels the
high ground impedance between V12, but forces VI - V., so
EMI filters.
CM noise voltage
VZ2 -0.
However,
interface
grounds ride
G. Noise Coupling
Fig.
when
Unshielded Phase Conductor of Drive
wiring
practice
output wires, randomly
~
i
I
I
c
l-g
_S&oL!!~
or shielded cable
Paths in a Drive System
12 shows system CM
poor
armor
noise
using
current
three
paths taken
unshielded
Frame
Critical
Distance
~~
1
1
I
1
I
bm9---m---------
A7
Common Mode Crrrnmt
Ground Potential #1
110
A“
Build
Ground Potential #Z
Figure 10. Noise coupling: Noisy source ground
Figure 12. Noise paths due to poor wiring practice
07803-4070-1/97/$10.00 (c) 1997 IEEE
phase
laid in cable tray, and a local motor
A. Noisy Source Ground
ground wire to the ground grid is used. Transient CM current
IaO is sourced
transition,
current
tiom
the drive
ground
cable capacitance
to the grounded
couples through
load. Load Common
stator winding
grid
voltage
#2 and capacitively
couples through
the motor
an output
In Fig. 13, the ASD Analog Out lCommon is connected
with a 200 ft, twisted, shielded pair to a 2 kQ single ended
e.g., phase “A” IGBT
cable tray at Potential
during
turns on to (+) dc bus. ZaO
capacitance
via the motor
ground
into Potential
wire.
#3 PE
Conducted
“quiet”
drive
CM
is bonded to remote building
TE potential.
logic
A Noisy Source Ground
common
was created with
structure
potential
for
a 600 tl drive
PE
current continues through the ground grid bypassing drive PE
Ground
until returning at the feed transformer secondary grounded
neutral XO, where a low impedance path back to the drive
source can occur on phase A, B or C. Inside the drive, the CM
current selects the bridge rectifier diode that is conducting
frequency
Fig. 6 (Critical Interface Distance for IGBT risetimes) so CM
voltage V12 is impressed on single ended signal V~ = 10 Vdc.
back
TE zero voltage
to the
provides
(+)
dc bus source.
Building
a True Earth (TE) ground for the solidly
transformer
voltage
grounded
#l is noisy, while receive ground is
Potential
on signal
VS for
#2. Table’ I shows pk-pk
various
shield
noise
terminations
and
configurations.
to high frequency
noise current IaO , so that an instantaneous
Table I. Noise Voltage
voltage
difference, known as CM noise voltage, is created across the
ground grid Potential #1 through Potential #4. CM voltage is
impressed on susceptible interface equipment between drive
logic ground Potential
#I (which is noisy compared to
structure steel) and interface ground Potential #4 (referenced
at zero voltage TE potential). Common mode voltage is also
impressed between the encoder case at Potential #3 and drive
PE logic ground Potential
is capacitively
from the noisy encoder case into encoder circuitry.
of Fig. 6 may help determine
probability
Additional
referencing
equipment
Shield
Connection
I
Noisy Source
Ground
WPP)
30
Drive
Open
on Signal Voltage
Drive
CM Core
Noisy Shield
Ground
(Vpp)
26
I
16
WPP)
8
14
6
0.2
0
Both
5
4
Load
8
4
#1. Successful encoder operation
depends on how much CM voltage
potentials
ground to high
CM transient current. Signal cable length exceeds
Source ground Potential
steel
neutral.
The ground grid is a high impedance
ground
structure
wire. This creates a high inductance
users
coupled
The chart
of CM problems.
to
VI, V2 and V3 may also experience
ground
Shield connection options as demonstrated in TABLE I,
are not effective if interface distance is long and drive logic
PE source ground
grid
impedance
CM voltage
is noisy due to high
PE ground.
Receive commons
Bonding
through
inductance
or high
shield ends to both Send /
the low impedance
shield brings
problems. Ability of interface equipment to fi.mction in the
presence of noise is ultimately
determined by it’s CMRR
threshold tested at noise ~n. Poor wiring practice (shown in
these potentials closer in instantaneous magnitude and phase.
CM voltage on V. is reduced ( VZTO), even though both
Fig. 12) also exemplifies
currents may flow and TE ground
the radiated emissions problem.
system loop antenna is formed
between both drive output
input wires and return ground grid. Thus, a better
practice is desired prior to drive installation.
IV.
solid
NOISE
COUPLING
A
/
are not at absolute zero potential.
However,
is now polluted
shield
for other
users.
wiring
B. Noisy Shield Ground
Section IV-A conditions were repeated with a 50 fl PE
ground to plant grid as in Fig. 14. Shield connection to noisy
DEMONSTRATION
This section shows the advantageous
PE panel grounds, using proper
grounds
effect of insuring
shield grounding
No Shield
techniques on signal interfaces, and using drive CM cores.
o
Shield on
drive side
only
o
Wield
connecied
to both
sides
2k
o
o
(m)
TE
Figure 13. Single ended interface circuit tested
Potential
10 V/Div.
2
Shield
connected
to load side
.Only
500 P @iv.
Figure 14. Noise demonstration: Noisy shield ground
07803-4070-1/97/$10.00 (c) 1997 IEEE
Ov
Shield
Ov
connected
to drive
Open
Shield
Ov
Shield connected
to both sides.
Shield
Ov
10 V/Div.
500ps/Div.
Figure 15. Noise demonstration:
drive
connected
to load side.
PE ground
impresses
CM
Figure 16, Drive cabinet grounding
CM core solution
voltage
on V. as before.
to the cabinet frame, Programmable
Logic Controllers
(PLC)
reduces CM noise.
or other susceptible equipment.
ground
bus for fault
safety.
C. Equalizing
buses may be tied together at one point in the control cabinet
Shield
connection
to “quiet”
load
side TE ground
vastly
instrumentation
Grounds with CM Core Solution
and drives
All metal is bonded to PE
Two choices exists for
with
TE commons.
TE & PE
ZaOrisetime to 2 ps. Using Fig. 6,2 MSrisetimes indicate CM
or brought back separately to the PE ground point. Motor
cable fourth
green wire meets NEC requirements
for
grounding motors. Some high hp motors with very long leads
sometimes are additionally
bonded to nearest low inductance
noise is not an issue up to 600 ft of interface cable. CM Noise
ground,
since ground wire “inductance”
is now significantly
winding
capacitance may allow voltage buildup
Section IV-B conditions were repeated with a CM core
added on the drive output leads in Fig. 15. This reduces CM
shield connections.
reduced for open shields or drive end
CM cores allow
instantaneous
PE & TE
and high motor Csg
under PWM
operation.
potentials to track each other ( VIZ-O). CM noise is eliminated
with load side shield connections,
multipoint
without
disadvantages
of
shield bonding.
V. SOLUTIONS
TO CONTROL
conduit/armor
and motor ground wire, are important factors
for reducing PLC backplane noise and preventing CM noise
EMI
There are four basic steps to the philosophy
mitigation
(3) Drive Panel Layout & Susceptible Equ@ment:
A PLC
chassis fi-ame is also it’s logic common. PE panel layouts that
route high fi-equency CM noise current, returning on both
of noise
interface
potentials.
and abatement that are discussed.
problems
with external equipment
Grouping
side of the cabinet
(1)
(2)
(3)
(4)
The importance
of ground
and separating
Common
Current
system
and drive / equipment
selection,
panel layout
single
PLC
Mode
on Armor
point
grounds
as
related to CM noise are discussed.
Fig. 12 shows system CM noise fi-om
(1) Ground System:
the drive output returning through the solid ground neutral of
the drive feed transformer. Thus, use of a floating secondary
will reduce the metallic conduction
path and CM noise
magnitude. High resistance grounding
leaves a conducting
noise path but greatly attenuates CM noise.
(2) Single Point Grounding
/Panel
Layout:
‘yop;:dlu:
Fig. 16 shows a
Steel if
system single point ground scheme with drives in a cabinet,
recommended
input / output conduit
to one
and susceptible
equipment to the opposite side will eliminate CM noise going
through the PLC fiarne as in Fig. 17. CM noise returning on
output conduit or armor will flow into the cabinet bond and
exit through the adjacent input conduitJarmor bond near the
cabinet to find the transformer Xo neutral. Thus, proper panel
Proper grounding
Attenuate the noise source
Shield noise aw~fiom
sensitive equipment
Capture and return noise to the source ( drive)
A. Proper Grounding
grounding,
at other ground
input and output conduitiarmor
or armor cable bonded
Required
Figure 17. Cabinet layout with drives & controls
07803-4070-1/97/$10.00 (c) 1997 IEEE
Inverter
output
voltage
D
nd
-20
Apk
Mode
Current
+
VW
6 MHz
1
1 PEAK
Current ~ - 1.st. 5us +
With
I
i
/
Common
Y-1
///////////
m
A’
Chokas
n
~
Ground Potentiat W
GroundPotentiaI#l
W SPECTSUM
I
~7
‘
Mode
1/3
Figure 18. CMcoresolution
I ~mK
forpower /signal leads
Figure 19. Effect of CM core of system Iao noise
layout insures noise isawayfiom
sensitive equipment. CM
current on the return ground wire tlom the motor will flow to
the copper PE bus and backup the input PE ground wire, also
away from sensitive equipment. If a cabinet PE ground wire
to the closest building structure steel is necessary, then a right
ide wire under the conduits and drives will shunt CM noise
CMC
away from the upper left PLC backplane of Fig. 17.
now occurs at 5 ps at a di/dt rate of 1 Alps versus 100 ns at a
B. Attenuate the Noise Source
di/dt rate of 200 Alps without a CMC. The ground grid is a
high impedance to the 100 ns high peak current creating large
available
motor
Typical
output
CM
high
torque.
fkequency
line
inductance.
system noise is to attenuate it
at the drive source before it enters a system grid and takes
multiple high frequency “sneak” paths, which are difficult to
find in installations. CM chokes on drive output and CM
cores on interface equipment in Fig. 18 are highly effective in
reducing
CM noise and ensuring
filly
operational
tripless
systems in the medium to high risk installations
of Fig. 1.
(1) CM Chokes on the Drive Output: Common
Mode Chokes
ground
Fig. 19 shows CMC peak ground
instantaneous CM voltage differences.
The best way to eliminate
to
current
magnitude in Fig. 19 is substantially reduced from 20 Apk to
<5 Apk, as well as the rate of rise (di/dt) which is limited by
reduced
ground
current magnitude
However,
and
current
with a CMC
low
di/dt
rate
maintain ground potential difference
fluctuations
close to
zero voltage or TE ground. As a result, common mode
voltages are reduced and error free operation of an ASD,
interface,
and sensitive equipment
is possible. A CMC
inserted in Fig. 12, would reduce voltage differences
drive Potential
#1 and interface Potential
between
#4 several hundred
feet away and thus reduce CM noise.
(CMC) are inductors with phase A, B and C conductors
wound in the same direction with one or more turns through a
ferrite or common magnetic core. Typically,
one or more
toroid shape cores in a stack. Drive PWM output voltage
transitions of 50-100 ns do not change when a CMC is added
to the output. However, the CMC provides a high inductance
(high impedance)
to the line to ground noise current
generated
during
Magnitude
reduced
waveform
PWM
and risetime
high
dv/dt voltage
below
equipment
quality
of line to line output is unaffected,
ground
based noise is “choked”
smaller
than
three
phase
line
thresholds.
drive output leads is not possible.
C. Shield Noise Away from Sensitive Equipment
Voltage
while
After high frequency CM noise is attenuated with CMCS,
off. CMCS are physically
the third mitigation
step is to control the noise path taken,
the noise away from sensitive
equipment
done by diwting
reactors.
Line
reactors
reduce
line to ground and line to line capacitive coupled noise,
but phase inductance reduces fimdamental motor voltage and
both
A CMC
transitions.
of CM noise current is substantially
noise
(2) CMC on 120 Vac and Drive Signal Interjace:
around drive HI-LO signal interface lead and shield in Fig. 18
has been shown to be beneficial
in reducing CM noise
voltage on signal level components. CMCS around the 120
Vac power feeding susceptible interface equipment may also
reduce EMI interference, if lead separation from unshielded
referenced
from
high
to ground.
dv/dt power
07803-4070-1/97/$10.00 (c) 1997 IEEE
Spacing
wires
control
and signal
is a good
practice
wires
and
apart
will
reduce the capacitive
coupling
problem.
Predictable
noise
accidental conduit contact.
control from power wires is best done using four conductors
in a conduit, or better yet a four conductor
shielded / armor
(2) Shielded Cable Controls
Conducted Noise Current Path:
cable with an insulated PVC jacket.
in
Shielded / armor drive output power leads in Fig. 20 reduce
the amount of capacitive coupled CM IaO ground current
Conduit: Fig. 19 shows this condition with transient CM
current ZaOsourced from the drive as before. The conduit is
flowing in a ground grid system, where conducted EMI noise
problems can occur. Shielded or armor cables with insulated
bonded to the drive cabinet and motor junction box and the
green ground PE wire is connected to the drive cabinet PE
outer jackets, on both output and input sides, provide an
isolated predictable metallic CM noise current path to and
(1) Better Wiring Practice:
bus and the motor
cable capacitance
ground
Three Conductors plus ground
stud. Part of l.O flows
to the grounded
conduit
wall
through
and part
through motor stator winding capacitance to frame ground.
The green wire and conduit absorb most of this capacitive
current and return it back to the drive out of the ground grid,
thereby reducing “ ground noise” for the drive to motor run
shown. However, conduits
ground grid structure due
resistance characteristics
of
Thus, it is unpredictable how
the wire,
conduit
wall
may accidentally
contact the
to straps, support, etc. AC
earth are generally
variable.
noise current divides between
or ground
grid.
Thus,
inadvertent
from the drive,
so noise is not re-introduced
back into the
ground grid by accidental contact.
High ffequency
CM line to ground currents (1=0, Zbo, l..)
sourced from the drive during PWM voltage transition have
three return path options back to the drive, the 60 Hz green
safety wire, the cable shield/armor or customer ground grid.
Predominant return path is the shield/armor,
since it is the
lowest
impedance
to the high
frequency
noise. The
shiekl/armor is isolated horn accidental contact with grounds
by an insulating PVC outer coating so that the majority of
noise current flows in the controlled path of the cable and
conduit grounding at Potential #2 will induce CM voltages
for users referencing this node in Fig. 19. Also, if drive PE
very little noise goes into the customer PE ground grid. Thus,
cabinet wire is grounded to building
building
structure steel, then CM
currents returning back from the motor conduitignd will go
into the ground grid at Potential #l, through feed transformer
Xo and back to the drive through input phase conductors.
CM
interface
Potential
voltage problems may still exist for susceptible
equipment
referenced between Potential
#l or
#2 (which are noisy compared to structure steel)
and interface TE zero voltage ground Potential
on Fig. 6, the drive risetime
chart.
vs. critical
#4, dependent
interface
distance
Thus, 3 wire plus gnd wire in a conduit from the feed
transformer
source is recommended
with conduit
and green
wire bonded to secondary Xo neutral and another wire from
Xo to the ground grid structure. This presents the CM noise
current a low impedance predictable metallic return path out
of the ground grid. Locating the drive isolation transformer
closer to drive cabinet will shorten ground noise current paths
and help contain noise. Using CMC in high risk applications
eliminates concern over noise leakage to ground through
ground
potential
differences
structure
conducting.
If
drive
ground grid pollution
Jr
J
feed
transformer
is far
away,
At
short
output
cable
lengths,
50%
of
return
noise
shield and 5°/0 in the customer grid in Fig. 21. Zero sequence
Iao, Ibo, Ico source currents return in the opposite direction on
SHIELD MOTOR
w
~
lao-lxl---
X=lo
D .10
REIURN
aRCE
COAXIAL LCWINOUCTANCE
STRUCTURE
FOR ZERO SEQUENCE CLWRENT
10
95%
SHIELD PREDOMINATES
1
AC MOTOR
,Y
#
PE GRID
PE TIE IN
USER #n
Figure 20. Solution: Shield controls EMI noise path
then
at User #1 exists and use of drive input
current flows through the safety ground wire path and 50°/0
thru the shieklhrmor.
At long cable distances, the safety
ground wire inductance looks like an open circuit to high
frequency noise and 95% of total noise current flows in the
I
PE TIE IN
USER #2
at
shielded power cables back to the main supply is desirable.
r--l”
DMVE
4
true
User #1 and then to source transformer Xo grounded neutral.
Noise return path back to the drive dc bus source is via input
phase A, B or C , depending on which bridge diode is
SHIELD
:Jgm@l
between
and customers grounding
Users #2 and User #N points.
Noise current returning on the shield or safety ground
wire is routed to drive PE terminal, to cabinet PE ground bus,
out the cabinet PE ground wire, to customer ground grid at
AR~M,R
DRIVE FRAME
are minimized
earth ground
Figure 21. Shield controls conducted & radiated noise
07803-4070-1/97/$10.00 (c) 1997 IEEE
the shield braid/armor
to form a coaxial low inductance
structure. Continuous welded aluminum armor was found to
have lower zero sequence inductance
cable. Thus, the shield
than interlocked
is the predominant
armor
conducted
high
,.
G. . . .
Y,%*’”’
fi-equency noise return path as compared to the customer
ground grid. Thus, the use of CMC to attenuate the noise
combined
to
control
mitigation
with drive input and output shielded/armor
the
noise
path
are effective
noise
reduction
termination
power
(3) Shielded Cable /Conduit
Control Radiated Emissions:
(a) Magnetic Field: Drives generate perfectly balanced phase
voltages so that fundamental
frequency phase currents are
also a balanced set, e.g. la + zb + ZC= O. External magnetic
field emissions radiated
from
frequency
of the high frequency
a shielded
cable are minimal
currents sum to zero and 95°/0
zero sequence currents sourced by the
drive return in opposite
direction
on the shield.
antenna area between magnetic galvanized
Thus loop
steel or aluminum
Im
Figure 22. Filter controls EMI path& magnitude
cables
methods.
since fundamental
PE
of control
cables
wire,
and CM
interface
leads fix
However,
an additional
use of shielded
cores
on drive
the majority
EMI
and drive
EMI
problems.
of drive
input filter
input/output
power
may be required
to
reduce EMI conducted and radiated emissions low enough
for European CE Class A and Class B conformity
standards
or for drives installed in residential areas where potential
radio and TV interference problems exist.
Previously,
be transiently
AM
CM line to ground current Zao was shown to
sourced from the drive output during
semiconductor
inverter
rise and fall times, with ZaOreturning
ground grid to supply transformer
X. connection
via the
and back to
the drive, via one or all of the three phase input lines. CM
since cable currents are almost
cores on the drive output reduced lao peak and slowed the
balanced. Magnetic field emission efficiency is also reduced
with shieldlconduit
systems, since drive output CM current
returns in a small loop area, either to the green wire or
armor/conduit wall.
effective di/dt risetime to ground. Shielded drive input cables
to transformer supply X. and shielded output motor leads
armor selection is not critical,
(b)
Radiated
Electric
Field:
field
perpendicular
from phase conductors
attenuated with continuous
welded
aluminum
armor type MC
emissions
radiate
and are completely
galvanized
steel or
cable for frequencies
ffom
the
collected most of Iao and kept it out of the ground grid where
CM voltages maybe developed.
An EMI filter plus output shielded cable of Fig. 22 work
on the same series path described. However, instead of a high
impedance CM core to limit ground current at the drive
output
leads, the EMI
filter
inductance
and individual
impedance
“blockers”
contains
phase
a large
inductors
CM
that
core
are high
drive carrier frequency up to the 6 MHz noise current
frequency Jn. Thus, the capacitive coupling noise to signal
ground return current to extremely
and control interface is reduced. Braided shields and conduit
wall systems are also effective in attenuating emitted electric
field noise.
supply. EMI filters also contain CM line to ground capacitors
which fimction as low impedance bypass capacitors to reroute most of the high ti-equency ground noise current Iao ,
returning
D. Capture and Return Noise to the Source (drive)
The fourth
mitigation
noise back to the drive
step is to capture and return the
source. Shielded
cables or conduit
returns noise out of the ground grid and back to drive PE as
shown in Figs. 19 and 20. CM capacitors
connected
from
drive PE to drive input lines or from PE to (+) and (-) dc bus
terminals act as high frequency noise bypass capacitors. They
short circuit the noise path from drive PE through the ground
grid and to transformer Xo connection. They are used in
extreme cases of CM noise problems.
VI. REGULATIONS
A. How
Do
Proper
EM1
Filters
grounding
FOR EMI
Work
and
COMPLIANCE
and out of ground grids.
Stabilization
Impedance
Network
(LISN)
at the EMI filter input detects noise voltage ( Vn )
developed
in the plant ac mains supply. LISNS measure CM
noise voltage, since CM is greater than normal
and is the predominant field problem.
B. Conducted&
mode noise
Radiated Emission Levels
Maximum
allowable
without
interference
drive
P’n conducted
to external
line
into
power
equipment,
is
ratio’s
of Table H. A 100 pV noise level above 1 pV is expressed as
40 dBflVusing
proper
series
equipment
lines,
layout,
frequency
low values in the ac mains
defined in dBV or dBp z due to large noise attenuation
?
cabinet
the high
on the output shielded cable, back to drive ac input
R,S,T terminals
Line
to limit
shield
V n (dB)
(1) with Vin = 1 ~V, Vout = 100 VV .
z
20 Log10 (Vout / Vin)
07803-4070-1/97/$10.00 (c) 1997 IEEE
(1)
dB(uV)
lMHZ
100KHZ
I
120
Table III.
IOMHZ 30MHZ
I
Allowable
Conducted
110
Emission
Class
Limits
150 kHz –
500 kHz
AV (66),
QP (79)
AV (56-46),
QP (66-56)
A
B
Radiated Emission
30 I
I Ill
lllllllr’ll\l J’nl
!Wrtlllllll
+++twt+~
10
2
46810
2
46810
2
46810
2
3
EMI
Performance
C. Frequency
vs. Noise Level
Attenuation
(Voltage Ratio)
1:1-3:1
3:1-30:1
30:1-1000:1
1000:1
Attenuation
(dBV)
Oto 10
loto30
30 to 60
> 6(I
PWM
EMI
Protection
Poor
Minimum
Average
Good
output
Output
risetime
to 150 kHz are proposed but not required at this time. Quasipeak (QP) detectors streamline EMI measurement time but
have higher QP dBp V limits than Average dBuV of Table III.
dBuVvs. frequency.
Radiated electric
field
emissions
limits
are expressed
in QP
in dB
pV/m, rather than V/m, for EMI standard comparison. Thus, 1
m V/m using Vout = 1000 pV and Vin = 1 pVin (1) results in
60 dB p V/m. Radiated
noticeable
on AM
emission
radio,
more so than for industrial
TV
interference
problems
and radio-controlled
instrumentation.
are
devices
Radiated troubles
begin at 0.1 to 3 V/m [ 5 ].
European Union basic EMC standards applied to drives
are listed
in EN550 11, while
specifications
that
/m] over 30MHz
-1 GHz
230 MHz -1 GHz
37
37
30MHz -230 MHz
30
30
of Noise Source
internal
voltage,
Switch
Mode
Power
switching
voltage
of Fig. 4 and Fig.
19 induce
CM currents to ground through stray capacitances that drive
input LISNS detect. Spectrum analysis of Fig. 4 indicates a
dBp V units
over the sanctioned
conducted
emission
frequency band of 150 kHz to 30 MHz. Limits fi-om 10 kHz
emission
[ dBpV
5–
30 MHz
AV (60),
QP(73)
AV(50),
QP(60)
I
Supplies (SMPSS), and drive semiconductor transients are the
main EMI noise sources in the 150 kHz to 30 MHz range.
LISNS measure V. and spectrum analyzers convert it to
conducted
I
Characteristics
ffequency
40 dBldecade
Fig. 23 shows allowable
0.5 –
5 MHz
AV (60),
QP (73)
AV (46),
QP (56)
CLASS A = EN 50081-2, CISPR 11, GROUP 1
CLASS B = EN 50081-1 , CISPR 22, GROUP 2
Figure 23. Conducted emissions vs. frequency
(A) No filter (B) Std. Filter (C) Std. Filter/ shielded cable
(D) Special filter / shielded cable
Table II.
Levels
] over 150 kHz -30 MHz
[ dBpV
Limits
Class
A @30 Meters
B 6? 10 Meters
1111
20
CE Emission
I
declare
emission limits are found in gene~ic EMC standards applied
to drives listed in EN50081 -1 and EN5008 1-2 [11]. Class B
component
at fr = 0.321tri~e, decaying
above fr. Thus, EMI
components
= 50-100
MHz range for IGBT trj~e
(~)
changes
corresponding
which
over
a cycle,
decay -20 dB/decade
cause spectrum “smearing’
components
of fc
ns are seen. Pulse width
from
to f. components
at -
in 3.2 -6.4
400
ns
to
200
us,
= 800 kHz to 1.6 kHz and
above fr
Pulse width
over a wide frequency
centered at drive fc
variance
range. EMI
(1 to 12 kHz) and harmonics
are also seen.
Other noise sources are semiconductor
recovery
voltage
spikes, creating noise in the 20 - 30 MHz range that exits
both input and output power leads to ground. Logic board
SMPSS powered tiom
vokage waveforms
drive dc bus power, also
have PWM
similar to Fig. 4. Thus, fr, f, , and fc ( 10
kHz to 100 kHz) noise ffequency
components
may also exit
drive input and output power leads to ground.
D. Line Impedance Stabilization
Network
LISNS in Fig. 22 stabilize line impedance at 50 Cl for Vn
limits for residential, commercial and light commercial sites
follow EN50081- 1 while Class A limits for heavy industry
sites follow EN50081 -2. Class B limits are mostly needed to
eliminate AM radio and TV interference problems.
‘m.
Figure 24. Single phase schematic of LISN
07803-4070-1/97/$10.00 (c) 1997 IEEE
Figure 25. Standard 3 phase EMI filter schematic
measured
>
1 MHz.
Variations
in measured
Vn due to
different user line impedances or EMI filter interactions are
thus eliminated. Fig. 24 shows a CISPR 16 single phase
schematic of a three phase LISN with Drive Under Test
(DUT)
and ac mains
phase to ground
connections.
Frquency
[Hz]
Figure 26. Typical radiated emissions with filters
Components change with current rating and frequency range.
LI simulates typical line inductance of 50 PH. L2, C3, R.j, C2,
is reduced in amplitude
by the Xjload bypass capacitors.
inductors
insert minimal
inductance
R3 form
an ac mains filter
inductors
and X2~ine capacitors attenuate line to line noise to
affecting
10 kHz to 150 kHz DUT Vn measurements.
preventing
external
noise ftom
In the
CM
line to line, so that phase
required dB,u V levels.
150 kHz to 30 MHz range, L2, C3, Rj are not used and R3 =
O. LISNS measure conducted
drive noise via high frequency
bypass capacitor Cl, which routes CM high frequency
RI + R2 = R = 50 Cl measuring
device. In the 2nd range,
LISN impedance is a parallel L1 inductor
and resistor R = 50
Cl at frequencies >1 MHz.
filters
are comprised
of single
each with 40 dB/decade attenuation
A=
stage L-C
filters,
from resonant frequency
1 / (27c(LC)05 ). Thus, if 40 dB attenuation
at undesirable
noise ffequency fn is desired, then filter L and C are selected
for f, = J. / 10. EMI
Ileahge
to
ground
filter
for
designs must minimize
safety
of Conducted Emissions
Fig. 23 shows measurements of conducted emissions for
various cases with /without filters and shielded cables:
(1) No Filter:
Curve A shows the ASD exceeds Class A & B
margins. The wide band of noise frequency is due to PWM
E. Typical EMI Filter Schematic
EMI
F. Measurement
V. to
reasons
and
capacitor
insure
filter
resonates with drive noise sources do not occur under any
pulse width changing over a given cycle. Noise frequency
spectrum related to drive output 50-100 ns Iao risetime, peaks
at 3-6 MHz and decays at an expected -40 dB/decade.
(2) Standard
Filter:
Curve B shows the ASD
prevalent.
A 12 MHz peak is due to semiconductor
of the switchmode
(3) Standard
capacitors
to 30 dB,u V improvements
noise
ground
bypass capacitors
to CM IaO
generated during drive output switching.
Line to
impedance (Zc = 1 /(2 n y. CY )) is lower here, than
a CM current path from transformer
XO , to three phase ac
main lines and through the high impedance blockers of the
filter inductors (ZL = 2 n fn L ). yjload capacitor in series
with XzlOad line to line capacitor also is a CM line to ground
bypass filter for IaO. Thus, L1’ line to ground noise voltage is
very low and equal to Iao times ZC . Differential
and CM
inductors along with Ylline, Xjlfne, and Y21ineform a CM line
to ground
filter
that attenuates
required dBp V levels.
Line to line high frequency
VLI ‘-ground
noise
volt%
to
& Shielded Cables:
Curve C shows 20
by using shielded cable on ASD
input and output power leads. The IGBT
risetime
peak at 5
MHz is reduced 30 dBpV, as well as 20 dBp V attenuation
of
the switchmode risetime peak at 12 MHz. This indicates that
the low impedance of the co-axial shielded armor takes
almost all CM ]aO current directly to the EMI filter CM caps
and back to the drive input as expected, leaving little high
ffequency noise current coupled into the ground grid and ac
mains supply before the LISN. Continuous welded aluminum
armor
Type Metal
Clad cable has reduced “EMI
emissions
over both conducted and radiated ffequency range. The coaxial nature reduces conducted emissions while the seamless
characteristic
noise sourced from the drive
Filter
risetime
power supply.
operating condition to prevent underdamped oscillations.
In the multistage EMI filter of Fig. 25, load side yll~ad
are high frequency
still exceeds
Class A & B margins even with a standard EMI filter. The 5
MHz noise frequency correlated to lao risetime is now more
attenuates radiated
by eddy current shielding.
07803-4070-1/97/$10.00 (c) 1997 IEEE
electric
fields due to noise
H. Jelinek who worked
(4) Special Filter
& Shielded
Cables: Class B requirements
are met using a special designed EMI
filter
through
the CE and common
mode
noise issues.
matched to the
ASD, shielded armor cable on drive input and output power
References
leads, solid wire bonding practices to metal of both drive and
EMI filter, and using a metal cover for the drive.
[1]
W. Ott, Noise Reduction
Systems, Wiley,
G. Measurement
of Radiated Emissions
[2]
EMI
Techniques in Electronic
1976, ISBNO-O-471-65726-3
filters
meeting
conducted
emission
limits
are
essential to passing the specified 30 MHz to 1 GHz frequency
band radiated
emission
test requirements
in Fig. 26.
However, logic board clock transitions, shielded logic cables
and PC board layout are a dominant influence at these ultra
H.
Schlicke,
Principles
Electromagnetic
of Cost Effective
Interference
and Hazards)
Compatibility
Control
(Applied
of Electromagnetic
, Marcel Dekker,
[3]
B. Kaiser, Princ@les of Electromagnetic
Artech, Massachusetts, 1983,79-12032
[4]
M.
1982
Compatibility,
high frequencies.
VII.
Generation
of Common
sourced from the ac PWM
Mode (CM)
EMI
Noise
coupling
noise that is
paths
for
the
current that is
grid is a major
CM
voltages
instrumentation
Conducted and
generated
in detail
noise
for various
conduit.
Output
leads using three wires plus ground in a shielded/armor
with an insulating
provides
R. Kerkman,
G. Skibinski,
were
cores on drive output leads and interface leads, (3) Shielding
the noise away from sensitive equipment
by physically
separating drive power and signal control wires, using three
in output/input
Radiated
IEEE guide for the installation
[6] D. Anderson,
Emission
“Modem
Solutions
Tutorial”,
Industry
Conference
by
1992
of electrical
equipment
to
from
IEEE
L. Saunders, D. Schlegel, and
Drives
Application
Issues and
IEEE-IAS-Petroleum
and Chemical
(PCIC),
PA, Sept. 26,
Philadelphia,
1996.
industrial
control systems.
Solutions to control the EMI involved discussions on: (1)
Proper grounding of drives along with proper panel layout of
drives and controls, (2) Attenuating the noise source with CM
plus ground
Controlling
minimize
electrical
noise inputs to controllers
external sources , ANSI / IEEE Std 518-1982,
Press, John Wiley
of the noise source were analyzed.
discussed and demonstrated
wires
[5]
drive’s high dv/dt output voltage
waveform was discussed in this paper. CM
capacitively conducted into the system ground
noise component.
CM
current
induces
throughout
the plant ground grid, making
reference to a “quiet” ground a difficult task.
radiated characteristics
Mardiguian,
Design, Van Nostrand Reinhold,
CONCLUSION
[7]
“Installation
Issues for IGBT
AC
Gary Skibinski,
Drives”,
Allen-Bradley,
Rockwell
Automation,
Duke
Power Seminar, May 8, 1996
[8]
G. Skibinski, “Installation
Considerations for IGBT AC
of Energy
Drives - A Summary Paper”, Association
Engineers
power
GA,
cable
conference,
Plant & Facility
Expo,
Atlanta,
7, 1996
Nov.
outer jacket to isolate ground noise current
the most predictable
control
over the noise path
[9]
G. Skibinski,
J. Pankau, and W. Maslowski,
“Installation
taken. These solutions are found to fix the majority of drive
related EMI problems.
FCC
and CE regulations
constraining
allowable
Considerations
For IGBT AC Drives”, IEEE Annual
Textile, Fiber, and Film Industry Technical Conference,
May 5, 1997
conducted and radiated emission levels were defined and
typical EMI filter and shielded cable approaches to meet
these more stringent EMI levels were demonstrated.
[1 O] Russel J. Kerkman, “Twenty Years of PWM AC Drives:
When Secondary Issues become Primary Concerns”,
IEEE
Acknowledgment
is given to Prof. Geza Joos of Concordia
University, who encouraged me to write this summary article.
Thanks also goes to the Allen Bradley internal EMI/CE team
consisting of R. LaPerriere, J. Meier, B. Weber, J. Erdman,
Dr. R. Kerkman, J. Johnson, D. Jaszkowski, R. Nelson, D.
Anderson,
Industrial
Electronics
Conference
(IECON),
Taipei, Taiwan, August 5-9, 1996, pp. Ivii- lxiii.
Acknowledgments
[11] EN55011:
Limits
and
methods
of
measurements
of
electromagnetic
disturbance characteristics of industrial,
scientific
and medical radio fi-equency equipment,
(Modified version of CISPR 11, equivalent to VDE 0875
Tll)
D. Leggate, D. Schlegel, K. Pierce, D. Dahl, and
07803-4070-1/97/$10.00 (c) 1997 IEEE