EMC FOR AUTOMOTIVE – WHAT ELECTROMAGNETIC COMPATIBILITY REQUIREMENTS APPLY TO THE AUTOMOTIVE INDUSTRY – PART 1.

 

The car industry is a huge industry. Not only in terms of the number of products (cars), but also in terms of the variety of systems and components. Current vehicles are packed with electronics and there is probably no need to convince anyone that this trend is only becoming more popular and constantly growing.

Literally saying the other side of the power is the costs associated with high-volume production. Because, as you can hear from experienced electronics experts: „it is not hard to build a device that meets the EMC requirements but the trick is to do it in a very very cheap way”. That is why project optimization, engineering tests, and verifications are so crucial. In addition, there are environmental restrictions and the measurement of the behavior of systems (objects) under various temperature and humidity conditions, etc. After all, this affects the properties of the object, also in terms of EMC.

What is EMC testing about?

In a nutshell, it can be said that we want to check if the device (system):

A: EMISSION: It does not emit too high levels of disturbances that may penetrate into the external environment (external compatibility) or disrupt the systems inside the system (internal compatibility).

B: IMMUNITY  (also called RESISTANCE): We want to see how it reacts to certain disturbances  that are known (with some probability) to occur in the target work environment.

EMC in automotive is the specification of test conditions for this specific work environment.

How do we know what exposure to test our products for? You have to see what other devices and systems work in the immediate surroundings and what may appear along the way – identification of the sources of disturbances. Obviously, in order not to do it, certain norms, test standards are created each time. It is a set of rules, conclusions, measurements and good practices for certain environments.

Note: Remember that standards are created with a delay in relation to technical progress. Therefore, the use of standards must be conscious and supported by analyses of the current situation in reality.

Please note that EMC is part of environmental testing (electromagnetic environment) with regard to safety. It is probably obvious that we test the device (especially resistance) to make sure that it will work as intended, and even if there are errors, they will not cause any danger.

POPULAR COMMUNICATION SYSTEMS IN MODERN CARS:

  • CAN (Controller Area Network)
  • Ethernet (AVB, TSN)
  • FlexRay
  • LIN (Local Interconnect Network)
  • MOST (Media Oriented Systems Transport)
  • OBDII (On-Board Diagnostics II).

We have kilometers of cable harnesses in our current cars. Dozens of microcontrollers and many communication, assistance, data collection and security systems. Below you will find  examples of sources of disturbances in modern cars.

SOURCES OF POTENTIAL DISTURBANCES IN CARS:

  • Engine ignition (spark, timing)
  • Entertainment systems
  • Fuel injection
  • Braking systems (anti-lock brakes)
  • Emissions controls
  • Control, steering (steering assist, 4-wheel steering)
  • Collision avoidance systems
  • Positioners – Seat & pedal positions
  • Heating, cooling / air conditioning
  • Communication systems
  • Navigation systems
  • Safety systems
  • Suspension systems
  • Noise cancellation
  • Lights 
  • Signaling indicators, defrosters, horn, wipers, etc.
  • Battery charging systems
  • Built-in electric car chargers.

 

EMC PROBLEMS IN CARS MAY APPEAR AT DIFFERENT LEVELS, HERE THEY ARE:

  1. Integrated Circuits Level (IC Level)
  2. Module level
  3. System level
  4. Vehicle level.

 

UNCLE-GOOD-ADVICE:

Eliminate problems at the source! EMC solutions applied at the source are the cheapest and most effective. EMC solutions used on the coupling path or load are very expensive and sometimes impossible to implement.

METAPHORS: IF YOU HAVE A MONSTER, IT IS BETTER PUT HIM IN A CAGE, THAN BUILDING FORTS, SHELTERS FOR THE POPULATION. HIRING ONE WITCHER TO KILL A MONSTER IS CHEAPER THAN KEEPING AN ARMY OF GUARDS, PROTECTING THE POPULATION.

VEHICLE DESIGN PROCESS – THE ENTIRE SYSTEM:

In the automotive industry  we will always have at least two approaches: to the entire system (vehicle) and particular components (system components). To properly implement the system we use the so-called The model of the big „V”, that is, a process that first decomposes the entire system, where we develop designs, plans and requirements for ever smaller components and modules. Secondly, we start testing the devices built from individual modules to their connections, until we come to the entire system – i.e. the vehicle.

 

Most of the EMC requirements are very similar when it comes to the entire vehicle and components. That is, the range is more or less the same. The same aspects should be checked. However, this approach, particular methods, positions or connection methods will differ at various stages.

Fortunately, it is quite precisely defined by the appropriate standards. And there are many of them but more on that you will read in a moment.

TYPES OF EMC TEST IN AUTOMOTIVE:

EMISSION:

  • Conducted emission from components, modules:
    • Frequency: 150kHz-108 MHz
    • Voltage – measurement on an artificial network (AN-Test)
    • Voltage – Capacitive Coupling Clamp (CV-Test)
    • Current – current probe (CP-Test)
  • Radiated emission:
    • Frequency: 20MHz-1GHz (2 or 3 GHz)
    • ALSE, (Absorber Lined Shielded Enclosure)
    • TEM CELL (TEM-Test, optional)
    • Stripline (SL-Test, optional).

TYPES OF DISTURBANCES IN AUTOMOTIVE:

  • Broadband – this usually comes from „sparking” switches, arcs, electric motors.
  • Narrowband – all the clocks, transmitters, signals, communication

Broadband – when the measured signals are noisy and the distance between potential stripes is smaller than the receiver bandwidth (usually RBW).

Narrowband – The disturbance stripes are narrower than the receiver bandwidth (RBW) and single disturbance frequencies can be picked up.

 

IMMUNITY:

  • Radiated Immunity:
    • Frequency: 20 MHz – 1 GHz, with limit levels (EC); 10 KHz – 18 MHz, multi-class of limit levels (ISO),
  • Conducted Immunity:
    • ISO 7637: Part 1 – 12V power, Part 2 – 24V power, Part 3 – signal / control lines;
    • Transient  immunity: power line transient and signal / control line transients.
  • ESD – electrostatic discharge – Immunity to Electrostatic Discharge (ESD):
    • Levels: +/- 2 KV – +/- 25 KV

STANDARDS IN AUTOMOTIVE:

Here I will provide a simplified chart, requirements in Automotive are a complex topic, however well described. At least we have specific and quite explicit requirements, good descriptions and precise drawings. Sometimes it is determined by contracts between the supplier (subcontractor) and the recipient (car manufacturer), rather than it is only the result of legal requirements, as these may be lower. This happens when a corporation wants to increase safety margins and reduce risks. Each corporation also adjusts its requirements by negotiating with suppliers, and it usually provides very detailed requirements and even its own measurement support.

EMC standards in Automotive – there will be a separate article. Here are just examples of corporations that have their EMC standards.

INTERNAL REQUIREMENTS ARE SUCH CORPORATIONS AS:

  • Jaguar Land Rover
  • Daimler-Chrysler
  • FORD Motor Company
  • General Motors – GM
  • Lotus
  • PSA
  • Renault
  • MG-Rover
  • Volkswagen
  • Porsche
  • BMW
  • Nissan

+ SAE – Society of Automotive Engineers

TYPICAL TEST METHODS IN AUTOMOTIVE:

The chart listing the test method standards for the various EMC aspects to already point out what it entails to meet the requirements. The reference to the methods below may be made from a variety of standards. There may be differences in emission or exposure levels between the standards.

Whole Vehicle Compability Assessment:
Emission: CISPR 12 (EN 55012), CISPR 25 (EN 55025)
Immunity: ISO11451-2 – Radiated immunity
ISO11451-3-8 – Radiated immunity (wireless)
ISO11451-4 – RF Injection Method, BCI
ISO10605 – ESD
ISO 7637-1 –  Impulse immunity
ISO 7637-2
Component Compliance Assessment:
Emission: CISPR 25 (EN 55025)
Immunity: ISO 11452-1 – Metody badań na wąskopasmowe zaburzenia
ISO 11452-2 – Odporność na pole promieniowane
ISO 11452-3 – Komora TEM
ISO 11452-4 – BCI – Bulk current injection – kalmra prądowa
ISO 11452-5 – Stripline
ISO 11452-7 – DPI
ISO 10605 – ESD
IEC 61000-4-21 – Komora rewerberayjna
ISO 7637-1 – Odporność impulsowa
ISO 7637-2 – Odporność impulsowa
ISO 7637-3 – Odporność impulsowa

 

SAMPLE GRAPH WITH DIFFERENT EMC REQUIREMENTS FOR CONDUCTED EMISSIONS:

Graph: Conducted emission – limits from different standards. Source: Automotive EMC – IEEE EMC Society – Eastern North Carolina Section, February 9, 2010, Mark Steffka, IEEE EMCS Distinguished Lecturer.

INTERNATIONAL STANDARDS AND ORGANIZATIONS:

  • EN – European standard (in Poland – PN-EN), e.g. EN55032, EN61000-4-x itd.• ISO – International Standard Organization np. basic in automotive: ISO7637, ISO10605, ISO16750, ISO11452 itd.,
  • ETSI – European Telecomunications Standards Institute – devices with a transmitter and / or receiver (e.g. ETSI 300 328 – BT, WLAN),
  • GOST – Russian standards, e.g. GOST 28751-90 (equivalent to ISO7637-2),
  • JASO – Japanese Automotive Standard Organisation – Japanese standards,
  • SAE – Society of Automotive Engineers – US standards, np. SAE J 1113-11 (equivalent to ISO7637-2),
  • CISPR 12 (EN 55012) – Vehicles, boats and internal combustion engines – Radio disturbance characteristics – Limits and methods of measurement for the protection of off-board receivers,
  • CISPR 25 (EN 55025) – Vehicles, boats and internal combustion engines – Radio disturbance characteristics – Limits and methods of measurement for the protection of on-board receivers,
  • ISO 7637 (all parts), Road vehicles — Electrical disturbances from conduction and coupling,
  • ISO 8854, Road vehicles — Alternators with regulators — Test methods and general requirements,
  • ISO/TR 10305 (all parts), Road vehicles — Calibration of electromagnetic field strength measuring devices,
  • ISO 10605, Road vehicles — Test methods for electrical disturbances from electrostatic discharge,
  • ISO 11451 (all parts), Road vehicles — Vehicle test methods for electrical disturbances from narrowband radiated electromagnetic energy,
  • ISO 11452 (all parts), Road vehicles — Component test methods for electrical disturbances from narrowband radiated electromagnetic energy,
  • UL94, Tests for Flammability of Plastic Materials for Parts in Devices and Appliances,
  • 16750 – Road vehicles — Environmental conditions and testing for electrical and electronic equipment Part 2: Loads,
  • ISO 7637-1 Road vehicles — Electrical disturbances from conduction and coupling — Part 1: Definitions and general considerations.

 

Recently, we have trained electronics designers (Hardware Design Engineers) for one of the large companies in the automotive industry.

BELOW WE PRESENT A FEW MOST IMPORTANT CONCLUSIONS OF THE SPECIFICATIONS OF THE AUTOMOTIVE SECTOR IN TERMS OF ELECTRONICS:

  • the car industry is a large volume (large series) so the costs  limit the imagination of designers,
  • requirements (including EMC) very strongly depend on the customer, i.e. a given car manufacturer,
  • requirements can be much higher than in domestic or industrial standards (depends on the test),
  • the reliability of the systems is very relevant because they affect safety,
  • more and more often we see very fast communication buses, which requires training under HIGH SPEEED DESIGN,
  • electronics are very different from the purpose and place of application in the car,
  • cable harness and system compatibility are challenging,
  • evaluation criteria are difficult to prepare and verify during testing.

EMC FOR AUTOMOTIVE Training – DESIGN, TEST AND COMPLIANCE

EMC for vehicles – design, testing and requirements

requirements, phenomena, tests, system design for electromagnetic compability (EMC) in an automotive enviroment.

interesting links:

Author: Tomasz Utkowski, EMC Engineer, Consultant, Trainer