EVs and the Quest for Electromagnetic Compatibility
In a hot summer, a high-tech factory in China's Yangtze River Delta is using automation to produce products efficiently. Its automated production line works around the clock with remarkable speed and accuracy. Then lightning strikes and causes electromagnetic interference that damages communication links inside the factory. Production abruptly stops.
Automated assembly lines in factories perform complex tasks that involve precise signal transmission and wireless communications. When lightning strikes, it can generate electromagnetic interference (EMI) via electromagnetic waves that spread to the inside of the factory. This can destroy key communication links and seriously affect production. The knock-on effect is extensive. Robot stoppages cause production delays and reduce capacity. Conveyor belt failures delay product shipment and assembly. Quality control sensor failures can result in defective products.
As you can see, EMI can trigger a series of unfortunate events that can cause costly shutdowns and compromise product quality.
Another example of the impact of electromagnetic interference is when you’re listening to music on the radio and reception is suddenly disrupted by static and other unwelcome noises.
In summary, EMI refers to undesirable noise or disturbance in an electrical path or circuit caused by an external source. EMI can cause electronics to run poorly, malfunction, or stop working altogether.
For obvious and not-so-obvious reasons, EMI poses potentially serious problems for electric vehicles (EVs) and other electronic products and systems in their vicinity. Let’s look at the various causes of EMI, and see where EVS are today in their quest for electromagnetic compatibility.
What causes EMI?
EMI is a result of the close relationship between electricity and magnetism. The movement of a charge creates an electric current, and an electric current creates a magnetic field. Likewise, a moving magnetic field creates an electric current. This is the principle behind motors and generators. At the same time, any electrical conductor may also become a radio antenna. High-power electrical supplies and wireless transmissions can have undesirable effects on distant equipment – namely interference from electromagnetic radiation, or EMI. As electronic products become smaller, faster, more compact and more sensitive, they become more susceptible to EMI.
EMI has both natural and human causes.
Several natural sources can generate electric fields strong enough to affect electronic devices. For example, lightning can generate powerful electrostatic discharges and magnetic pulses. Solar storms and solar flares can release highly charged particles, leading to disruptions in satellite and ground communications. In addition, cosmic radiation has the potential to induce electronic bit errors.
EMI caused by humans can come from many sources. High-powered radio and electrical sources can cause unwanted EMI. Consumer devices, if poorly functioning or poorly designed, can cause EMI in other devices. Using electromagnetic pulses to intentionally generate EMI failures in a target's equipment is a form of terrorism.
Types of EMI
To form EMI, three elements must be present. They are: an interference source, an interference path, and a receptor (or target). We can divide EMI into the following three categories, based on interference path.
- Radiated EMI: Radiated EMI occurs when radio frequencies generated by a high-powered transmitter or electrical equipment are picked up, and cause unwanted effects in other equipment. If the source and receiver (target) are far apart, it is most likely radiated EMI. Examples of radiated EMI include a broken kitchen microwave oven causing a computer to reboot, or an old cordless phone degrading Wi-Fi performance.
- Conducted EMI: Conducted EMI occurs when there is a physical electrical path from the source to the receiver. Conducted EMI is usually along power transmission lines, and the source may be a large motor or power supply. For example, turning on a treadmill or clothes dryer can cause a computer on the same circuit to reboot.
- Coupled EMI: Coupled EMI occurs when the source and receiver (target) of the interference are in close proximity, but there is no electrical contact or connection between them. Coupled EMI can occur through induction or capacitance. For example, an audible buzz occurs on the audio cable when the power cable and the audio cable are in close proximity. Capacitively coupled EMI requires the conductors to be in close proximity. It most commonly occurs on electronic circuit boards or in closely spaced wires over long distances.
EVs and EMI
- Motors and Electronics: EVs are powered by electric motors and rechargeable batteries. Given their complex, high-voltage electronic systems, they have the potential to generate high volumes of electromagnetic radiation, especially in the high-frequency range. This may interfere with nearby electronic systems such as radio receivers or wireless communications equipment. Hence their ongoing quest for electromagnetic compatibility.
- Battery Management Systems (BMS): The BMS in an EV manages the charging, discharging and overall operation of the EV's battery. The BMS involves various electronic circuits and sensors that may emit electromagnetic energy or be susceptible to external EMI. Therefore developers are focusing their efforts on developing an optimal design to ensure that BMS components operate reliably and do not interfere with other systems.
- Charging infrastructure: EV charging stations and equipment also cause EMI. Charging cables, connectors, and electronic equipment in the charging station can all generate electromagnetic radiation that can affect the normal operation of nearby communication systems, such as Wi-Fi or cellular networks.
In order to prevent or minimize EMI, EV manufacturers are using electromagnetic compatibility technologies to reduce or eliminate EMI during the vehicle design, development and testing stages.
Current practices and techniques include:
- Shield: Masks use conductive materials or enclosures to contain or block electromagnetic radiation and protect sensitive components from external interference.
- Filters: Filters such as capacitors, inductors and ferrite beads are used to attenuate unwanted high-frequency noise and provide cleaner power to sensitive components.
- Grounding and bonding: Adequate electrical grounding and bonding minimizes ground loops, reduces noise coupling, and provides a reference point for current.
- Optimized PCB layout: Proper wiring, separate analog and digital components, and control impedance when designing a printed circuit board (PCB) reduces radiation and susceptibility.
- Conformance testing: EMC testing is performed according to industry standards and regulations to ensure that equipment complies with required emission and sensitivity limits.
Meanwhile, national and international regulatory agencies have established EMI emission standards and limits to ensure that there is no interference between electronic equipment, such as EVs. These standards ensure that our electronic devices can work efficiently together, without interference.
Common challenges for EV makers and consumers
To ensure the smooth operation, safety and electromagnetic compatibility of EVs with the surrounding environment, EV manufacturers and consumers must be mindful of the fact that EVS can be both a source and a receiver of EMI.
Key considerations for EV manufacturers include:
- Electromagnetic compatibility (EMC) design: EV manufacturers need to consider EMC requirements from the early stages of vehicle design. This involves proper circuit and system layout, shielding, grounding, and filtering techniques to minimize emissions and improve anti-interference capability.
- Compliance with EMC standards: Manufacturers must comply with EMC standards and regulations for EVs. These standards define emission and sensitivity limits and provide test methods to ensure compliance.
- Testing and certification: Manufacturers are required to conduct comprehensive EMC testing during the development and production stages to ensure that EVs meet standards. Certification and compliance documents serve as proof of EMC compliance.
- Documentation and user guides: Manufacturers are required to provide consumers with easy-to-understand documentation and guidance on EMC considerations. This includes information on potential interference risk, recommended precautionary measures, and instructions for the proper installation and use of EVs and charging infrastructure.
Similarly, EV consumers should have a basic understanding of the concept of EMC and what it means for EVs. Equipped with this knowledge, they can identify potential problems, take appropriate precautions, and seek professional help when necessary.
Key considerations for consumers include:
- Compatibility of charging infrastructure: Consumers should be aware of EV charging equipment compatibility with local regulations and standards. This ensures that the charging system does not introduce EMI into the grid or cause interference with other communication systems.
- Proper use and installation: Consumers should install and use their EV and equipment in accordance with the manufacturer's guidelines. This includes avoiding modifications that could affect EMC performance and ensuring proper grounding and shielding of charging infrastructure.
- Report EMI: Consumers should report interference or suspected EMI problems to the manufacturer or the regulatory agency. Feedback can help improve EMC standards, identify potential risks, and ensure the ongoing reliability and safety of electric vehicles.
In summary, both manufacturers and consumers can work together to help improve the EMC of EVs, minimize the risk of interference, and promote the smooth operation of EVs in a wide range of environments.
Ultimately, nothing should interfere with the growth of EVs as they approach the inevitable point in time when they overtake petrol and diesel vehicles for good – least of all, electromagnetic interference.