X2Y Attenuators, LLC
DC Motor EMI Suppression
Presented at Ford Motor Company July 27, 2004
By Jim Muccioli
DC Motor EMI Suppression
1.
Why Do DC Motors Need EMI Suppression?
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2.
Designing DC Motors for EMI
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3.
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7/19/2004
Filtering Elements
Building EMI suppression Filters
Filtering Examples
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5.
Motor Housing Design
End Cap Design
Connector Design
Applying EMI Suppression to DC Motors
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4.
System integration
Understanding EMI Noise Sources in DC Motors
Compliance with specs.
Radiated Emissions
Conducted Emissions
Transients
Summary/Questions
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2
System Integration
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Integrating increased number of electronic
devices and electrical systems in a single
automobile fuels Electromagnetic
Compatibility (EMC) issues such as:
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Reliability
Anomalies
Functionality
Safety
Cost
Guaranteed EMC requires the suppression
of or immunity from electromagnetic noise
sources within a system (automobile).
This presentation examines DC motor
suppression for EMC
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Understanding EMI Noise Sources in DC Motors
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Electrical Current Loop (antenna)
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Power leads
Brushes
Commutator
Wire coil around armature stack
Brush/Commutator Contact Bounce (arc)
Power leads
Brushes
Armature
Polarized
magnets
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=
_+++ -_ + +
Commutator
+
Housing
Shaft
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Compliance with Specs.
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7/19/2004
Ford Emissions Requirements
(From ES-XW7T-1A278-AC)
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DC Motor EMI Suppression
1.
Why Do DC Motors Need EMI Suppression?
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2.
Designing DC Motors for EMI
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3.
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7/19/2004
Filtering Elements
Building EMI suppression Filters
Filtering Examples
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5.
Motor Housing Design
End Cap Design
Connector Design
Metal Joint Design
Applying EMI Suppression to DC Motors
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4.
System integration
Understanding EMI Noise Sources in DC Motors
Compliance with specs.
Radiated Emissions
Conducted Emissions
Transients
Summary/Questions
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6
Motor Housing Design
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Housing should be metal or metalized to
provide shielding.
Slots should be eliminated or minimized to
keep from making them “slot antenna”.
Slots
Metalized motor housing
Plastic motor housing
Improved
7/19/2004
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Motor Housing Design (Example)
7/19/2004
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End Cap Design
End caps should be metal or metalized to
provide shielding.
Crimping tabs should not electrically connect
inside and outside surfaces.
Noise can couple outside the motor
case when using a plastic end cap.
A metal end cap works as a shield to
contain the noise within the motor case.
Improved
Crimping tabs
7/19/2004
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Connector Design
Leads/connector pins should exit the housing
close together to reduce current loop.
Improved
7/19/2004
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Exit points of Power Leads
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Metal Joint Design
Metal joints are typically only design with
mechanical strength.
Electrical conductivity and shielding should
also be considered.
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Joints should overlap and be interlocking.
Oils and paint should be removed.
Oxidization and galvanic action should be prevented at
the joints.
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DC Motor EMI Suppression
1.
Why Do DC Motors Need EMI Suppression?
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2.
Designing DC Motors for EMI
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3.
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7/19/2004
Filtering Elements
Building EMI suppression Filters
Other Considerations for EMI Filtering Elements
Filtering Examples for Electronics Inside Motors
Filtering Examples
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5.
Motor Housing Design
End Cap Design
Connector Design
Applying EMI Suppression to DC Motors
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4.
System integration
Understanding EMI Noise Sources in DC Motors
Compliance with specs.
Radiated Emissions
Conducted Emissions
Transients
Summary/Questions
Copyright© X2Y Attenuators, LLC
13
Filtering Elements
Element
Disadvantage
Low cost, some transient suppression
Narrow filtering band, Limited to under
800MHz
Broad filtering band
Cost, Failure mode is a short
Easy Implementation, Filter more than 1
line, CM & DM configurations
Heat can cause saturation, Cost,
Moderate filtering performance
Effective below 300-500MHz
Heat can cause saturation, Quality
material and tolerance add cost
Filter 2 lines at once
Heat can cause saturation, Quality
material and tolerance add cost
MOV
Transient suppression
Cost, no filtering
X2Y
Broadband filtering (DC – 6GHz), low
cost, Filter 2 lines, Good Tolerances,
transient suppression
Surface mount only, Location in the
circuit is critical
Capacitor
Feed Thru Capacitor
Ferrite Beads
Inductor
Common Mode Choke
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Advantage
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How to Spec. a Filter Element
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Typical Electrical Testing provided by manufactures
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Test Standards
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Capacitance distribution.
Capacitance balancing.
DC Voltage Breakdown testing.
Impulse/surge testing.
ESD testing.
Reliability testing.
Stress Test.
ISO 9001:2000
ISO 14001
OHSAS-18001
AEC-Q200
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Example Test Summaries – Filter Element Testing
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ESD Test Summary
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Up to 6KV on Contact Discharge Test.
Up to 8KV on Air Discharge Test.
Reliability Test Summary
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Upper Category Temperature +125°C
Voltage 1.5 x Rated Line to Ground voltage
Number of Components
Test hours
Number of Failures
Note: These test summaries are courtesy of Syfer Technology Ltd.
7/19/2004
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Other Considerations for EMI Filtering Elements
For broadband filtering consider:
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G1
Placement of a filter into a motor consider:
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A
B
G2
Option
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X2Y
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G1
A
B
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G2
Component’s parasitics
Trace/lead length parasitics – widen path, avoid sharp 90° turns
Location, Location, Location – prevent noise from coupling
around filter.
Failure mode (open/short)
Performance over temperature
“Brush Dust” – filter may need a non-conductive coating to
protect from shorting.
Some filter technologies require housing to be “grounded”.
Improved
X2Y
G1
A
B
G2
Best
7/19/2004
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17
Filtering Examples for Electronics Inside Motors
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Hall Effect Sensor
Leads
Exiting
Housing
Leads
Exiting
Housing
A
A
VS
VS
Hall Sensor
Q
B
Hall Sensor
GND
Q
B
GND
G1
B
A
G2
7/19/2004
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Building EMI Suppression Filters
(2) Caps + (2) Ferr. Beads + (1) 0.47 Hi-Cap Varistor
(5) element Filter
(4) element Filter
(2 ) C a p s + (2 ) In d u c to r s + (2 ) B e a d s + (1 ) H i-C a p V a r isto r
X2Y
(2) 0.22 uF, L-L
(1) 0.47 uF, L-G
Motor
(7) element Filter
7/19/2004
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12 V
(1) element Filter
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Radiated Emission Filtering Performance
DC Motor Filter Performance Comparisons
60
50
dBuV
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30
20
10
0
0
100
200
300
400
500
600
700
800
900
1000
Freq MHz
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No Filter on Motor
Four Component Filter
Seven Component Filter
Five Component Filter
KuTEM-Cell Ambient
One Component Filter
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DC Motor EMI Suppression
1.
Why Do DC Motors Need EMI Suppression?
¾
¾
¾
2.
Designing DC Motors for EMI
¾
¾
¾
3.
¾
¾
¾
7/19/2004
Filtering Elements
Building EMI suppression Filters
Filtering Examples
¾
5.
Motor Housing Design
End Cap Design
Connector Design
Applying EMI Suppression to DC Motors
¾
4.
System integration
Understanding EMI Noise Sources in DC Motors
Compliance with specs.
Radiated Emissions
Conducted Emissions
Transients
Summary/Questions
Copyright© X2Y Attenuators, LLC
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Radiated Emissions - ABS Motor
7/19/2004
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Radiated Emissions - Air Compressor Motor
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Radiated Emissions - Blower Motors
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Blower Motor #1
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30dB pre-amp was used.
Blower Motor #2
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Radiated Emissions - Lift Gate Motor
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7/19/2004
30dB pre-amp was used.
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Radiated Emissions - Mirror Motor
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7/19/2004
30dB pre-amp was used.
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Radiated Emissions - Radiator Fan Motor
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7/19/2004
30dB pre-amp was used.
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Radiated Emissions - Seat Motors
Seat Motor #2
Seat Motor #3
Seat Motor #1
Note: 30dB pre-amp was used on Motor #1
7/19/2004
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Radiated Emissions - Throttle Body Motor
7/19/2004
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Radiated Emissions - Washer Pump Motors
Washer Pump Motor #1
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Washer Pump Motor #2
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Radiated Emissions - Window Lift Motor
7/19/2004
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Radiated Emissions - Wiper Motor (3-brush, 2-speed)
7/19/2004
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Conducted Emissions – Radiator Fan Motor
7/19/2004
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Conducted Emissions – Fuel Pump Motor
cap & 2 ind’s
No Filter
X2Y
7/19/2004
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Transient Testing – 12v Brake Pedal Motor
12V Motor
7/19/2004
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Transient Testing – Seat Motor (UL Tested)
CCW-stalled-off to on
CCW-stalled-on to off
CW-stalled-on to off
CW-stalled-off to on
7/19/2004
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Questions?
Please Contact:
X2Y Attenuators, LLC
37554 Hills Tech Dr.
Farmington Hills, MI 48331
248-489-0007
x2y@x2y.com
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For more information on EMI filtering of DC motors go to www.x2y.com
and refer to Application Notes:
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4001 - DC Motor Design with X2Y® Technology
4002 - DC Motor Design with X2Y® Example A
4003 - DC Motor Design with X2Y® Example B
4004 - DC Motor Design with X2Y® Example C
“Suppression Techniques Using X2Y as a Broadband Filter”, Symposium
Record – Workshops and Tutorials, 2003 IEEE Symposium on
Electromagnetic Compatibility.
“Using Image Planes on DC Motors to Filter High Frequency Noise.” 2004
IEEE EMC Symposium, Santa Clara, CA. Aug 9-13, 2004.
www.jastech-emc.com