Automotive EMC: Practices Of Today And Perspectives For .

Automotive EMCIEEE EMC SocietyEastern North Carolina SectionFebruary 9, 2010ByMark SteffkaIEEE EMCS Distinguished LecturerEmail: msteffka@ieee.orgIEEE1

Automotive Systems “Past andPresent” Today’s vehicles contain three centuries oftechnology 19th century internal combustionengines combined with 20th century electricalsystems and 21st century electronics .Automotive EMC.from Spark toSatellite 2

Automotive EMC Goals Highest priority is toexceed expectationsof the customer. Meet challenges oftechnology contentin vehicles. Develop organizationthat supports EMC.MarketplaceDemandsTechnicalOrganizational3

Automotive EMC Case Studies Emissions: Microprocessor clock harmonic wason two way radio frequency – rendering radiocommunication impossible. Immunity (the Automotive characterization ofsusceptibility): An engine and transmissionseemed defective due to control systemmalfunctions – cause was a change from ametal to a non-conductive componentpackage.4

Vehicle Generated Radiated“Noise” Vehicle systems can be responsible foronboard noise generation as a by-product ofvehicle operation. In the automotive industry, this noise hasbeen classified into two categories:– Broadband (typically due to electrical arcing)» Typically referred to as “Arc and Spark”– Narrowband (typically due to active electronics)» Typically used to refer to all items NOT “Arc and Spark”5

Representation Of plitudeAmplitudeFrequencyFrequencyNarrowband NoiseBroadband Noise Broadband noise is greater than the “width” ofreceiver of the energy Narrowband noise is less than the “width” of thereceiver.6

Typical Sources Of BroadbandNoise Sources include ignition components and similarpulse-type systems Electric motors (both the traditional and the new“brushless”).7

Consequences Of BroadbandNoise Sources BAD –Due to functions that are required forbasic vehicle operation (such as ignition orinductive devices). BAD – Can have both conducted AND radiatedcoupling path. GOOD – Energy spread out – may have minimaleffect on potential receivers (intentional andunintentional).8

Microprocessors And NarrowbandNoise Common source ofNarrowband noise. Logic states depend onclocking from a squarewave source. Square waves containmany frequencies which extend far intothe radio spectrum9

Consequences Of NarrowbandNoise Sources BAD -May be many sources on a vehicle due toproliferation of active devices. BAD - Receivers can appear to function “almostnormal”. GOOD - Can be addressed in component designprocess.10

Immunity: Auto Industry Practices The Automotive industry ensures product immunityby first planning to “design in” appropriate immunitycharacteristics to meet both “Off Board” and “OnBoard” source of electromagnetic energy. System and component testing can be conducted bysimulating “external” sources either by radiation orconduction (such as “bulk current injection”) toensure immunity characteristics.11

Examples of “Off Board” RF New wireless technologies demand morespectrum and more energy Many rural areas are now populated Vehicle must operate in this new environment12

“On-Board” Vehicle Sources Automobiles can have“on-board” sourcessuch as “two way”radio systems – withpower levels of 50 –200 watts ERP. Resulting fieldstrengths can impactfunctionality of vehicleelectronic systems.13

Bulk Current Injection (BCI)Test Method Consists of injection of RF orpulse energy on wiringharness. Typical BCI testing is to 400MHz. General rule: 1.5 mA of RFcurrent induced on a cableis equivalent to ½wavelength cable in a fieldstrength of 1 V/M.14

Role Of Wiring In ConductedEMC Issues Energy may escape or be brought into/from themodules by conduction with wiring harness Wiring can act as a coupling mechanism15

Why Wiring is Important toAutomotive EMC Early systems (and vehicles) had fewcomponents to be connected - recent systemshave increased wiring complexity, similar tomany non-automotive systems. Many automotive engineers consider wiring“just a piece of wire” and the chassis is“GROUND” (this is not true – impedance exists). Wiring will still be used for many systems in thefuture and we need to understand relevantphysical parameters.16

Automotive Wiring InductiveCoupling Inductive couplingfrom the wiring ofsystem 1 to the wiringof system 2. Noise is induced insystem 2 by “di/dt” ofsystem 1 and it’s load. Is frequently thesource of inductivelycoupled transients.17

Automotive Wiring CapacitiveCoupling Capacitive couplingfrom system 1 wiring tosystem 2 wiring manytimes due to closeproximity of wires in abundle. Noise is induced insystem 2 by “dV/dt” ofsystem 1 - is frequentlythe source of capacitivecoupled transients.18

ESD TestingBatteryGround Strap ESD “gun” can be usedto test devices/systems. High voltage isintroduced to identifysensitivities (typicallyfrom 4kv – 25 kv). Simulates natural andhuman-body inducedcharges.SimulatorESDPower SupplyInsulator (Optional)DUTGround Plane19

Automotive EMC Is Changing Global shift towards new propulsion systemsis changing the content of vehicles. These new systems will need appropriate EMCmethods, standards, and utilization of EMCapproaches from other specialties. Many of these systems will utilize high voltagecomponents and have safety aspects that maymake automotive EMC more difficult andsafety takes priority!20

Automotive Systems of the Future Incorporation of high power electric drivesystems as well as today’s conventional ones. EMC techniques from other industries willbecome important in automotive EMC.21

Why Use Electric Drives? Advances in power electronics as well as motordesign and manufacturing have made electric drivesvery attractive. The benefits of electric drives include high efficiencywith lower mass as a result of implementation ofadjustable/variable speed or frequency drives(ASD/VSD/VFD). Provide energy efficiency and flexibility over existing“conventional” drive systems.22

Electric Drive Control Systems Control systems for electric drives typically consist ofactive switching of the primary current for the motor(similar to basic switching power supply). Output voltage is determined by switching speed and“on” duration of the drive transistor's). Multiple phases can be obtained by utilizing multipledriver transistors with appropriate timing.23

Schematic of Three PhaseController and Motor Circuit IGBT’s generate three-phase motor drive currentwhich is supplied to “Wye” stator windings.24

Examples of Electric DriveController Figures (a) and (b) show the control electronics. Figure (c) shows an EMC shield over the IGBT’s toprevent noise from affecting low-level signals. Figure (d) shows the driver IGBT’s.25

Steps in the Construction of ADrive Motor A stator is producedthat contains anumber of “poles”that are used to holdthe windings. Application of drivecurrent for each phasegenerates magneticfield.26

Actual Stator Construction Figure at right shows atypical stator from avariable speed drivemotor. Significant portion ofthe stator (and it’smass) is due to thelarge number ofwindings required.27

Permanent Magnet RotorConstruction Rotor contains high-strength permanent magnetsarranged around the perimeter. “Movement” of field in stator causes magnets totry to track the field – resulting in rotation.28

Typical Electric Drive MotorSpecifications The motor shown atleft has an outputcapability at 1500RPM of:– 50 kW (approximately67 hp)– 400 NM(approximately 300 ftpounds).29

Balancing EMC andPerformance Requirements Important to understand the speed of operation ofelectro-mechanical devices compared to fast “slewrate” power signals from power drive devices such asInsulated Gate Bipolar Transistors (IGBT). The switching operation results in low powerdissipation (in the drive devices) along with:– Semiconductor operation at an order of magnitude fasterthan the response time of electromechanical devices.– Causing radiated/conducted emission issues.30

New Requirements May Apply? Continuing vehicle evolution may result innew requirements / regulations. “Plug In” Vehicle – classified as a householdappliance for EMC?(Vehicle Figure Is Courtesy of Argonne National Laboratory)CISPR 15110DO-160D level assumes 50-ohm LISN impedanceDO-160D: Cat B100Limit -- dB(µV)90CE102FCC Part 15: Class A80CISPR Class A70FCC Part 15: Class B605040 410FCC, Part 18UltrasonicDO-160D: Cat L ,M&HCISPR Class B &CISPR 14 householdappliances105610Frequency (Hz)10710831

Summary Automotive EMC has been continuallyevolving to meet the challenges that newtechnology brings. The automotive industry in undergoing acomplete “re-invention” of itself to meetdemands of today’s world. Understanding of the basics of these newtechnologies and will enable Automotive EMCto meet these challenges!32

Automotive EMC Is Changing Global shift towards new propulsion systems is changing the content of vehicles. These new systems will need appropriate EMC methods, standards, and utilization of EMC approaches from other specialties. Many of these systems will utilize high voltage components and have safety aspects that may make automotive EMC more difficult and safety takes priority! 20 .