Automotive Electronics EMC/EMI Compliance

Depending on the automotive OEM a re-validation may be mandatory whenever an electronic controller production is moved from one manufacturing plant to another (e.g. Mexico to China). This refer to a situation with unchanged design, parts vendors, and even identical manufacturing process flow.

The EMC/EMI related advantages when using SMT pick and place machines are:

• lower the resistance and inductance at the connection ensuring fewer unwanted RF signal effects, a better and more predictable high-frequency performance.
• better EMC performance (lower radiated emissions) due to the smaller radiation loop area (because of the smaller package) and the smaller lead inductance.

However, by using a different type/model of SMT pick and place machine a full EMC/EMI validation of your product might be necessary. The reason for re-validation is that even a small amount of inductance may change the self-resonant frequency of operation significantly, making the capacitor ineffective for optimal or desired performance. A capacitor remains capacitive up to its self-resonant frequency. Above self-resonance, the capacitor starts to appear as an inductor due to lead length and trace inductance. Inductance minimizes the ability of the capacitor to decouple or remove RF energy that exists between power and ground.

The self-resonant frequency of surface mount (SMT) capacitors is always higher, although interconnect inductance may obviate this benefit. Interconnect inductance includes routed traces and the bond wires internal to a component package. Depending on the type of product being designed, as well as on the frequency of operation, a change of inductance in the picohenry range may be too much to tolerate.

SMT 0805 1.0 uF capacitor (lead inductance L = 1 nH) the self-resonance occurs at 5 MHz.
SMT 0805 0.01 uF capacitor (lead inductance L = 1 nH) the self-resonance occurs at 50 MHz.
SMT 0805 100 pF capacitor (lead inductance L = 1 nH) the self-resonance occurs at 503 MHz.

In my EMC laboratory testing experience I've seen such changes in radiated emissions or conducted emissions performance from modules using the same hardware and software design built in different manufacturing plants.

References: Printed Circuit Board Design Techniques for EMC Compliance 2nd Ed. (Mark I. Montrose)

Magnetic Field WPT Input Power Classes (drawn from the grid)

Interoperability is the state of the supply device and the EV enabling wireless power transfer via magnetic field in a safe and efficient manner. Power transfer is allowed to occur only when interoperability is established.

Interoperability Power Classes

The Europeans expect frequency ranges 20-40 kHz, 80-90 kHz, and 119-135 kHz to be reserved for preferred accommodation of fundamental and operation frequencies for “charging stations” for electric vehicles featuring wireless power transfer (WPT). The use of these frequency bands becomes possible via the license exempt conditions granted by Decision 2013/752/EU of the European Commission on harmonization of utilization of radio frequencies for Short Range Devices.

WPT systems and car manufacturers target for these frequency bands is compliance to:

• Conducted Emissions C1 & C2 limits at LV a.c. mains power ports of power electronic equipment with WPT functionality as specified in IEC TS 62578 Ed. 2.0 (TC 22)
• Radiated Emissions limits (magnetic field strength at 10 m distance) specified by Decision 2013/752/EU and EN 300 330-1&2 for WPT interface of the inductive power transfer system comprising the charging station and the electric vehicle.

Abbreviations:
CENELEC: European Committee for Electrotechnical Standardization, Brussels
CD: Committee Draft; ISO, IEC
CDV: Committee Draft for Vote; IEC
CAB: Conformity Assessment Board; IEC
CASCO: Committee on Conformity Assessment; ISO
DC: Document for Comment; EC
DIN: German Institute for Standardization, Berlin
DIS: Draft International Standard; ISO
DK: German Committee
DKE: German Commission for Electrical, Electronic & Information Technologies of DIN and VDE, Frankfurt am Main
DK-IEC: German Committee of IEC
ETSI - EN 300 330-1 PART 1: TECHNICAL CHARACTERISTICS AND TEST METHODS

• ELECTROMAGNETIC COMPATIBILITY AND RADIO SPECTRUM MATTERS (ERM); 
• SHORT RANGE DEVICES (SRD);
• RADIO EQUIPMENT IN THE FREQUENCY RANGE 9 KHZ TO 25 MHZ AND INDUCTIVE LOOP SYSTEMS IN THE FREQUENCY RANGE 9 KHZ TO 30 MHZ;

GA: Gemeinschaftsausschuss (Joint Committee); DIN
IEC: International Electrotechnical Commission, Geneva
IEEE: Institute of Electrical and Electronic Engineers, New York
ISO: International Organization for Standardization, Geneva
JTC: Joint Technical Committee; ISO, IEC
TC: Technical Committee; ISO, IEC, CEN, CENELEC, ETSI
TR: Technical Report; ISO, IEC, CEN, CENELEC
TS: Technical Specification; ISO, IEC, CEN, CENELEC, ETSI
VDE: Association for Electrical, Electronic & Information Technologies, Frankfurt am Main
WG: Working Group; ISO, IEC, CEN, CENELEC

2013/752/EU: Commission Implementing Decision of 11 December 2013 amending Decision 2006/771/EC on harmonisation of the radio spectrum for use by short-range devices and repealing Decision 2005/928/EC (notified under document C(2013) 8776) Text with EEA relevance

DKE / K 353 is responsible for the development of standards for the charging of electric vehicles.  These include interface descriptions and requirements for stations for the AC-charging, DC-charging, wireless charging and battery replacement.

   Working Groups:
   DKE / AK 353.0.6    EMC in the energy supply of electric vehicles
   DKE / AK 353.0.7    Battery change systems
   DKE / AK 353.0.8    User authorization for charging infrastructure
   DKE / GAK 353.0.9   Energy supply of light electric vehicles
   DKE / AK 353.0.6    EMC in the energy supply of electric vehicles
   DKE / GAK 353.0.1   Contactless charging of electric vehicles
   DKE / GAK 353.0.2   DC charging of electric vehicles
   DKE / AK 353.0.3    Communication interface from the vehicle to the power grid (V2G CI)
   DKE / GAK 353.0.4   AC charging of electric vehicles

So far two major NA automotive makers (FCA & Ford) have released updated test specifications for electronic components.

• Chrysler CS-11979:2010 is replaced by CS 00054:2015. This specification is not publically available.
• Ford EMC-CS-2009.1 is replaced by FMC1278:2015. A summary showing what is different and the new EMC Test Plan template are also publically available.
  

The 2015 BMW i3 AM radio was built-in but due to some compliance issues it was disabled, therefore no AM radio local traffic reports or news headlines are possible.

"AM is not offered due to negative performance influences of the electromagnetic interference of the electric drivetrain" said Rebecca K. Kiehne, a BMW product and technical communications spokesperson. Electric motors cause interference on AM which is why BMW decided to remove this option. "While it could be offered, BMW’s performance standards are very high and we don’t offer a product that meets less than those high standards."

MF-WPT is the wireless transfer of energy from a power source to an electrical load via a magnetic field.

Magnetic coupling
The source of a magnetic flux is a coil structure. Power transfer will be initiated by positioning two or more coil structures near each other in a way that the time varying flux generated by the primary coil structure, passes through the windings of the secondary coil structure.

Primary and secondary coil structures for WPT systems interact through an air gap. Usually a centre plane in the air gap can be defined dividing the WPT system whereas the primary coil structure is completely located on one side of this plane and the complete coil structure of the secondary device is located on the other side of the plane. For a primary device and a secondary device to be interoperable, they shall be magnetically compatible.

MF-WPT Functions

• stand by and wake up: the supply device is woken up by the a signal from the EV.
• compatibility check: power classes, the operating frequency, magnetic coupling, circuit topology, tuning.
• initial alignment check: primary and secondary devices are properly well positioned relative to each other.
• start power transfer: transfer the power from the primary device to the secondary device upon the request from the vehicle
• time scheduled power transfer: no perform power transfer until the command and control communication is properly established and the primary device and secondary device are properly positioned.
• perform power transfer: MF-WPT system transfer the power from the primary device to the secondary device in accordance with the power demand of the EV. The maximum transferring power of the off-board MF-WPT system shall not be exceeded. The vehicle can change the requested transfer power.
• stop power transfer: MF-WPT system shall be able to stop transfer the power from the primary device to the secondary device in accordance with the demand of the EV. Th e vehicle can requested stop power transfer.
• user initiated stop power transfer: allow the user to terminate of power supply. e.g. pushing stop button.
• safety monitoring & diagnostics: command & control communication safety monitoring & diagnostics
•    power transfer monitoring
•    thermal monitoring
•    live object protection
• failure conditions: short-circuit, earth leakage, excess temperature, insulation failure, overcurrent, overload
• continuous monitoring of power transfer conditions: the actual output power does not differ from the expected output power by a certain limit; if the limit is exceeded, it shall stop power transfer.
• continuous monitoring of command & control communication
• continuous monitoring of safety conditions
• Verify that the ventilation system of the area is functioning and active
  

CISPR11:2010 (Ed 5.1) applies to industrial, scientific and medical (ISM) electrical equipment operating in the frequency range 0 Hz to 400 GHz. Certain frequencies are designated by the International Telecommunication Union (ITU) for unrestricted radiation from ISM equipment.

AC Power Port    - CISPR 11; Conducted disturbances (150kHz-30MHz)
Table 6 (Class A) - Mains terminal disturbance voltage limits for class A group 2 equipment measured on a test site

Table 7 (Class B) - Mains terminal disturbance voltage limits for class B group 2 equipment measured on a test site

WPT System and Enclosure Port  - CISPR 11; 
 Table 12 - Limits of the magnetic field strength for induction cooking appliances intended for commercial use

WPT System Port   - CISPR 11; 
 Table 6 (Class A) - Mains terminal disturbance voltage limits for class A group 2 equipment measured on a test site
 Table 7 (Class B) - Mains terminal disturbance voltage limits for class B group 2 equipment measured on a test site

NB RF Immunity for EV should be carried out per IEC 61980-1 Annex B - Radiated RF Field 20 MHz - 2 GHz @ 30V/m using the test setup per ISO-11451-2:2005.

Currently the WPT transfer distance is in range of several centimeters. Among the technical challenges to overcome we can mention:

• acceptable power transfer efficiency at high transfer range
• increasing power level
• misalignment tolerance
• safety considerations

Coil-to-coil distance & 30 m working wavelength transfer efficiencies

2-turn copper ribbon coil (3cm wide, 0.14 mm thick) with d=60cm and 5 to 70 pF adjustable high voltage capacitor. The quality factor of the resonator is 1338 in the absence of the metallic plane and 1329 in the presence of a metallic plane.

Source: Safe Wireless Power Transfer to Moving Vehicles: Design of Radiationless Antenna