Electric vehicles - the hidden battlefield of electromagnetic compatibility

In the hot summer, in this high-tech electronics production factory in the Yangtze River Delta, the automated production line is in full swing completing product assembly and testing.

Automated assembly lines in factories perform complex tasks involving precise signal transmission and wireless communications. The raging lightning and the electromagnetic interference it generated spread to the inside of the factory, destroying some key communication links and seriously affecting the factory's production process. Robot downtime causes production delays and reduced throughput, conveyor belt failures impede the transportation and assembly of products, and quality control sensor failures can lead to the production of defective products. This series of problems seriously threatens the normal operation of the factory and product quality.

At this moment, you are driving your car on your way home after get off work, and your favorite radio music is playing in the car. Suddenly, the sweet music is mixed with some noise and static squeaking, and for a moment, your good mood is gone...

This phenomenon is called electromagnetic interference (EMI), which is noise or interference in an electrical path or circuit caused by external sources. EMI is caused naturally or man-made and can cause electronic products to operate poorly, malfunction, or stop working altogether.

Below we discuss the causes and classification of electromagnetic interference (EMI), how electric vehicles achieve electromagnetic compatibility, and what developments will be expected in the future.

EMI occurs due to the close relationship between electricity and magnetism. The movement of charges creates an electric current, which creates a magnetic field. Likewise, a moving magnetic field produces an electric current, which is how electric motors and generators work. At the same time, all electrical conductors may also become radio antennas. High-power power supply plus wireless signal transmission can have an impact on remote devices, thus forming electromagnetic radiation interference EMI. As electronics become smaller, faster, more compact and more sensitive, they become more susceptible to these factors.

The sources of EMI can be roughly divided into two categories: natural occurrence and man-made occurrence.

In nature, there are sources that generate electric fields strong enough to affect electronic devices. Lightning can produce powerful electrostatic discharges and magnetic pulses. Solar storms and solar flares release high-energy, charged particles that can cause problems for satellites and ground-based communications. Cosmic radiation is known to cause bit-flips in electronics.

Man-made EMI can come from many places. High-power radio and electrical sources can cause unwanted EMI. Poorly functioning or poorly designed consumer devices can cause EMI in other devices. The use of electromagnetic pulses to deliberately induce EMI failures in victim equipment is also an attack.

To form electromagnetic interference (EMI), there must be three elements, namely an interference source, an interference path and a receptor (or victim). According to the different interference paths, we can divide electromagnetic interference EMI into the following three categories.

Radiated EMI: Radiated EMI occurs when radio frequencies generated by a high-power transmitter or electrical device are picked up and cause unwanted effects in another device. If the source of interference and the receptor are far apart, then it is probably radiated EMI. For example, a broken kitchen microwave causes your computer to reboot, or an old cordless phone causes Wi-Fi performance to degrade.

· Conducted EMI electromagnetic interference: Conducted EMI occurs when there is a physical electrical path from the interference source to the receptor. Conducted EMI is usually conducted along power transmission lines, and the source may be a large motor or power supply. For example, turning on a treadmill or clothes dryer causes a computer on the same power circuit to restart.

· Coupled EMI electromagnetic interference: This type of EMI occurs when the interference source and receiver are close to each other, but there is no electrical contact and connection. Coupled EMI can be transmitted through induction or capacitance. For example, when the power cord and audio cord are close to each other, a buzzing sound can be heard on the audio cord. Capacitively coupled EMI requires conductors to be in close proximity, and this type of EMI is most common on electronic circuit boards or in groups of closely spaced wires over long distances.

Electric vehicles (EVs) are vehicles powered by electric motors and rechargeable batteries. Due to the presence of high-voltage electrical and complex electronic systems, as well as potential electromagnetic radiation and susceptibility, electric vehicles require special considerations in terms of electromagnetic compatibility.

· Electric motors and electronic appliances: Electric vehicles rely on high-power electric motors and related electronic and electrical equipment, such as inverters and converters, to control the operation of the motor and the vehicle. These components can produce electromagnetic radiation, especially in the high frequency range, that may interfere with nearby electronic systems such as radio receivers or wireless communications equipment.

· Battery Management System (BMS): The BMS in electric vehicles is responsible for managing the charging, discharging and overall operation of the vehicle's battery pack. It involves various electronic circuits and sensors that may emit electromagnetic energy or be susceptible to external electromagnetic interference. Optimized design and shielding of BMS components is necessary to ensure its reliable operation and prevent interference with other systems.

· Charging infrastructure: Electric vehicle charging stations and equipment can also cause electromagnetic interference (EMI). Charging cables, connectors, and charging station electronics can all produce electromagnetic radiation that can affect the functioning of nearby communication systems, such as Wi-Fi or cellular networks.

In order to prevent or minimize electromagnetic interference, electric vehicle manufacturers can use various electromagnetic compatibility technologies to reduce or eliminate electromagnetic interference EMI during the vehicle design, development and testing stages.

Common practices and techniques include:

· Shielding: Using conductive materials or enclosures to contain or block electromagnetic radiation and protect sensitive components from external interference.

· Filtering: Use filters such as capacitors, inductors, and ferrite beads to attenuate unwanted high-frequency noise and provide cleaner power to sensitive components.

· Grounding and Bonding: Establish proper electrical grounding and bonding to minimize ground loops and noise coupling and provide a reference point for electrical currents.

· Optimize PCB layout: When designing a printed circuit board (PCB), have proper routing, separate analog and digital components, and control impedance to reduce radiation and sensitivity.

· Compliance testing: EMC testing according to industry standards and regulations to ensure devices comply with required emission and sensitivity limits.

At the same time, relevant international and national regulatory agencies have also formulated EMI emission standards and restrictions to ensure that electronic equipment, including electric vehicles, do not interfere with each other. These standards ensure that the electronic devices we use can work together without causing interference with each other.

For electric vehicles, it can be both a source and a receiver of electromagnetic interference. This requires that both electric vehicle manufacturers and consumers should understand EMI to ensure the normal operation, safety and electromagnetic compatibility of electric vehicles with the surrounding environment.

For electric vehicle manufacturers, the following aspects need to be considered.

· Electromagnetic compatibility EMC design: Electric vehicle manufacturers need to consider EMC from the early stages of vehicle design. This involves proper circuit and system layout, shielding, grounding and filtering techniques to minimize emissions and increase immunity to interference.

· Comply with EMC standards: Manufacturers must comply with EMC standards and regulations applicable to electric vehicles. These standards define emission and sensitivity limits and provide test methods to ensure compliance with the standards.

· Testing and certification: Manufacturers should conduct comprehensive EMC testing during the development and production stages to verify that electric vehicles meet the required standards. This results in certification and compliance documentation to demonstrate EMC compliance.

· Documentation and user guidance: Manufacturers should provide consumers with clear documentation and guidance regarding EMC considerations. This includes information on potential interference risks, recommended precautions, and instructions for the proper installation and use of electric vehicles and associated charging infrastructure.

Similarly, consumers of electric vehicles should also have a basic understanding of the concept of electromagnetic compatibility and its significance to electric vehicles. This knowledge can help them identify potential problems, take appropriate preventive measures, and seek professional help if necessary.

· Charging infrastructure compatibility: Consumers should understand the compatibility of EV charging equipment with local regulations and standards. This ensures that the charging system does not introduce electromagnetic interference to the grid or interfere with other communication systems.

· Proper use and installation: Consumers should follow manufacturer’s guidelines for the proper installation and use of electric vehicles and related equipment. This includes avoiding modifications that may affect EMC performance and ensuring proper grounding and shielding of the charging infrastructure.

· Report electromagnetic interference EMI: If consumers experience interference problems or suspect EMI-related problems, they should report them to the manufacturer or the relevant regulatory agency. This feedback can help improve EMC standards, identify potential risks, and ensure the continued reliability and safety of electric vehicles.

By understanding and addressing EMC considerations, both manufacturers and consumers can contribute to the overall electromagnetic compatibility of electric vehicles, minimizing the risk of interference and promoting reliable and efficient operation of electric vehicles in a variety of environments.