This article is an introduction to Electromagnetic Compatibility (EMC) immunity testing in the automotive sector. The automotive industry is one of the biggest industries in the world and it is moving fast due to the shift from traditional combustion engine vehicles to hybrid and electrical ones. Here you will learn about the most important automotive immunity EMC standards and how the immunity tests are executed.
1. Immunity standards
In the automotive sector, different standards are defining the immunity tests. The following list shows some of them. The most important EMC immunity standards are defined by the International Organization for Standardization (ISO) and the Society of Automotive Engineers (SAE). The most important automotive EMC regulation is the United Nations Economic Commission for Europe (UNECE) R10. Besides that, some manufacturers define their own standards for the vehicles they manufacture and for the subassemblies installed in them.
1.1 International standards
UNECE R10 is a regulation of the Economic Commission for Europe of the United Nations (UN/ECE), it gathers all the requirements for components and vehicles to be type-approved.
ISO 11451 [4] defines the test methods, guidelines, levels, for electrical disturbances from narrowband radiated electromagnetic energy. This standard is used for determining the immunity of passenger cars and commercial vehicles to electrical disturbances from narrowband electromagnetic energy, regardless of the vehicle propulsion system. Even only narrowband electromagnetic fields are considered in this standard, a wide frequency range, from 10 kHz to 18 GHz, is covered in it. Generally spoken, the SAE J551-x are equivalent EMC standards to ISO 11451-x.
ISO 11452 [5] defines terms, gives practical guidelines and establishes the basic principles of the component tests used in the other parts of ISO 11452 for determining the immunity of electronic components of passenger cars and commercial vehicles to electrical disturbances from narrowband radiated electromagnetic energy, regardless of the vehicle propulsion system. Many SAE 1113-x EMC standards have an equivalent ISO 11452-x standard.
ISO 7637 [6] specifies test methods and procedures to ensure the compatibility to conducted electrical transients of equipment installed on passenger cars and commercial vehicles fitted with 12 V or 24 V electrical systems. ISO 7637 describes bench tests for both the injection and measurement of transients. It applies to all types of road vehicles independent of the propulsion system (e.g., spark ignition or diesel engine, electric motor).
ISO 10605 [7] applies to electrical systems to be installed in road vehicles. This standard defines the test methods for electrical disturbances from electrostatic discharge (ESD). It describes test procedures for evaluating subassemblies and complete vehicles, regardless of the propulsion system. ISO 10605 applies to discharges in the following cases: ESD in assembly, ESD caused by service staff and ESD caused by occupants. SAE J551-15 and SAE J1113-13 are equivalent to ISO 10605.
1.2 Manufacturer based standards (OEM)
GMW3091 and GMW3097 are General Motors EMC specifications for vehicles, components, and subsystems, respectively. Those standards refer to the ISO 11451-1, ISO 11451-2 and the ISO 11451-8.
FMC1278 and FMC280 are Ford EMC specifications for electrical components and subsystems for Ford Motor Company (FMC). The FMC1278 details EMC requirements for low-voltage and high-voltage components and subsystems during normal vehicle operation. The FMC280 details EMC requirements for high-voltage components and subsystems specifically associated with electric and hybrid vehicles and that are active during HV battery charging while the vehicle is connected to the AC mains power grid or an external DC charging device.
JLR-EMC-CS are Jaguar Land Rover (JLR) EMC specifications for electrical and electronic components and subsystems used by JLR. The requirements affect all active electronic modules and sensors, motors, generators, solenoids and passive modules.
1.3 Acceptance criteria
During the immunity tests, the Device Under Test (DUT) may stop working as expected. Typically, the EMC immunity standards define four levels of reactions to an immunity test based on the loss of performance of the DUT.
Normal operation within the DUT specifications.
Temporary degradation or loss in the operation, the DUT can perform a self-recovery.
Temporary degradation or loss in the operation, the DUT needs to be recovered by the user or performing a restart.
Unrecoverable degradation, components damaged, loss of information.
The entity which defines which level applies to the DUT being tested varies across industries, product types and final use cases.
2. Immunity tests
2.1 Conducted Immunity (CI)
We present here the conducted immunity testing for automotive components based on ISO 11452-4 (component test methods for electrical disturbances from narrowband radiated electromagnetic energy - Harness excitation methods). There are two methods defined in the standard ISO 11452: the Bulk Current Injection (BCI) method and the Tubular Wave Coupler (TWC) method.
There are two methods defined in the standard ISO 11452-4: the Bulk Current Injection (BCI) method and the Tubular Wave Coupler (TWC) method.
CI frequency range:
BCI: 1MHz to 400 MHz.
TWC: 400MHz to 3 GHz.
CI equipment:
A shielded enclosure
Current injection probe(s)
Current measurement probe(s)
Artificial network(s)
A ground plane
A Radio Frequency (RF) generator with modulation capability
A power amplifier
Power measuring instrumentation to measure the forward and reverse power
Current measurement equipment
CI test setup:
Each power supply lead shall be connected to the power supply through an Artificial Network (AN).
The AN(s) shall be mounted directly on the ground plane and the measuring port of each one shall be terminated with a 50Ω load.
The Device Under Test (DUT) shall be placed on non-conductive (εr ≤ 1.4), at 5.0 mm above the metallic surface of the table.
The face of the DUT shall be located at least 100mm from the edge of the ground plane.
The injection probe shall be placed 150 mm from the connector of the DUT, but additional tests at 450 mm and 750 mm may be required.
The current measurement probe shall be placed at 50 mm from the connector of the DUT.
In the case of the TWC method, the coupler shall be placed at 100 mm from the DUT and isolated from the ground plane.
CI test execution
BCI:
There are two ways to specify the power to be applied to the wiring harness: the substitution method and the closed-loop method with power limitation.
Once the power has been calibrated, the current shall be injected over each of the wires of the DUT. If there is more than one branch, the test shall be repeated for all the branches.
TWC:
The power is set by using the substitution method.
Once the power has been calibrated, the current shall be injected over each of the wires of the DUT. If there is more than one branch, the test shall be repeated for all the branches.
2.2 Electrostatic Discharge (ESD)
ESD standards: ISO 10605, Road Vehicles - Test methods for electrical disturbances from electrostatic discharge. This standard is based on IEC-61000-4-2 and describes vehicle-specific requirements.
ESD test equipment:
A generator, usually named “ESD guns”, capable of generating waveforms with the following requirements:
Parameter | Value |
Voltage – Contact discharge | 2 – 15kV |
Voltage – Air discharge | 2 – 25kV |
Voltage accuracy | 5% |
Polarity | Positive and negative |
Rise time of short circuit in contact discharge mode | 0.7nsec to 1nsec |
Interval time | Minimum 1sec |
Holding time | ≥ 5sec |
Capacitance | 150pF to 330pF |
Discharge resistances | 330Ω or 2000Ω |
A ground plane configured as follows:
ESD test execution
Air discharge test:
The generator is placed close to the DUT and the discharge is by arcing on the DUT.
For each voltage level, several pulses of both polarities are applied close to the DUT. The test is started applying low voltage levels and increasing them as long as the DUT passes correctly the test.
Contact discharge test:
The generator is in direct contact with the DUT.
For each voltage level, several pulses of both polarities are applied with the gun touching the DUT surface. The test is started applying low voltage levels and increasing them as long as the DUT passes correctly the test.
The ESD generator circuit simulates a human body that is being discharged. Tests are performed using two resistances:
R=2kΩ represents a human body being discharged through the skin
R=330Ω represents a body being discharged through a metallic object.
Furthermore, there are two capacitances used: 150 pF, which represents a human body outside a vehicle, and 330 pF, which represents a human body inside a vehicle. The equivalent circuit of an ESD test generator and its generated output waveform are shown in the pictures below.
![ESD test generator equivalent circuit [1].](https://static.wixstatic.com/media/ec8386_bf7efdc1c0614c06ab3fddb3d542a1c3~mv2.png/v1/fill/w_47,h_21,al_c,q_85,usm_0.66_1.00_0.01,blur_2,enc_auto/ec8386_bf7efdc1c0614c06ab3fddb3d542a1c3~mv2.png)
![ESD waveform according to IEC 61000-4-2 [2].](https://static.wixstatic.com/media/ec8386_70dbb32442e14b8cb88b7021645b44df~mv2.png/v1/fill/w_49,h_30,al_c,q_85,usm_0.66_1.00_0.01,blur_2,enc_auto/ec8386_70dbb32442e14b8cb88b7021645b44df~mv2.png)
1.3 Radiated Immunity (RI)
RI standards: IEC 61000-4-3, ISO 11452-2
RI frequency range: 100 kHz – 18000 MHz
RI equipment:
A shielded enclosure
Signal generators
RF amplifiers
Antennas
Attenuators
RI test setup:
The DUT should be placed on a non-metallic, non-conductive material.
If wirings are less than 3 m in length, that length should be used. However, if the wirings are longer than 3m, a minimum of 1 m must be exposed to the radiated field.
RI test execution
Field levels up to 200 V/m
Dwell time: not less than the time necessary for the DUT to react, and never less than 0.5 sec.
The test should be performed with the antenna facing each side of the EUT. Furthermore, the antenna must be oriented for horizontal and vertical polarizations.
1.3 Electrical Fast Transients (EFT)
This test, also known as burst testing, has the goal of simulating immunity to switching inductive loads. Transients are a series of high-frequency pulses (transients) provoked by sparking. The origins of such EFTs are various: switches, inductive loads switching, circuit breakers, a power line that is being connected or disconnected.
EFT standards: IEC-61000-4-4
EFT test equipment:
Coupling Network (CDN)
Ground Reference Plane (GRP)
Insulating support
Grounding wirings
Pulse generator
EFT test setup:
The DUT is placed over an insulating support of 0.1 m height.
The insulating support is placed over the ground reference plane.
The ground plane needs to be, at least, 1m x 1m, with a minimum thickness of 0.25 mm.
The minimum distance from the DUT to all other conductive structures shall be 0.5 m.
EFT test execution:
The test voltage shall be applied to power supply ports as well as to I/O and communication ports. The amplitude and repetition rate depends upon the type of equipment.
EFT Immunity Level | On Power Supply Port. Voltage peak (kV) | On Power Supply Port. Repetition rate (kHz) | On I/O signal, data and control ports. Voltage peak (kV) | On I/O signal, data and control ports. Repetition rate (kHz) |
1 | 0.5 | 5 | 0.25 | 5 |
2 | 1 | 5 | 0.5 | 5 |
3 | 2 | 5 | 1 | 5 |
4 | 4 | 2.5 | 2 | 5 |
![EFT waveform according to the standard IEC 61000-4-4 [3]](https://static.wixstatic.com/media/ec8386_efa6e83ab34c42b48ca36e187f801935~mv2.png/v1/fill/w_89,h_54,al_c,q_85,usm_0.66_1.00_0.01,blur_2,enc_auto/ec8386_efa6e83ab34c42b48ca36e187f801935~mv2.png)
3. Conclusion
Immunity EMC tests are one of the most relevant tests to perform before releasing a product with electronic or electric circuits inside. The automotive sector has its own EMC standards to specify test methods and criteria for EMC immunity tests. Furthermore, each manufacturer has its own standards, which apply to the whole vehicle as well as to each of the electronic subassemblies to be installed in their vehicles. Nevertheless, despite the variety of standards, many of them make reference to the harmonized ISO EMC immunity standards: ISO 11451 for cars, ISO 11452 for components, and ISO 10605 for ESD.
References
[1] Texas Instrument: Application ISO 10605 Road Vehicles Test Methods for Electrical Disturbances from Electrostatic Discharge. https://www.ti.com/lit/an/slva954a/slva954a.pdf
[2] IEC 61000-4-2:2008: Electromagnetic compatibility (EMC) - Part 4-2: Testing and measurement techniques - Electrostatic discharge immunity test. https://webstore.iec.ch/publication/4189
[3] IEC 61000-4-4:2012: Electromagnetic compatibility (EMC) - Part 4-4: Testing and measurement techniques - Electrical fast transient/burst immunity test. https://webstore.iec.ch/publication/22271
[4] ISO 11451-1:2015. Road vehicles — Vehicle test methods for electrical disturbances from narrowband radiated electromagnetic energy — Part 1: General principles and terminology. https://www.iso.org/standard/62477.html
[5] ISO 11452-4:2020. Road vehicles — Component test methods for electrical disturbances from narrowband radiated electromagnetic energy — Part 4: Harness excitation methods. https://www.iso.org/standard/74108.html
[6] ISO 7637-2:2011. Road vehicles — Electrical disturbances from conduction and coupling — Part 2: Electrical transient conduction along supply lines only. https://www.iso.org/standard/50925.html
[7] ISO 10605:2008. Road vehicles — Test methods for electrical disturbances from electrostatic discharge. https://www.iso.org/standard/41937.html
[8] Frankonia EMC & Antenna Solutions. https://www.linkedin.com/company/frankoniagroup/posts/?feedView=all
[9] ESD Guns / The EMC Shop. https://www.esdguns.com