Compared to internal combustion vehicles and non-road mobile machinery (NRMM), electric drive presents original equipment manufacturers (OEMs) and their partners with greater electromagnetic compatibility (EMC) challenges.
This is because vehicle and machine frames provide effective electromagnetic shielding and 12V circuits pose less electromagnetic interference (EMI) and safety risks. But electric powertrains require significantly higher voltages to operate.
So, OEMs considering this transition need to familiarize themselves with new design, engineering, and compliance complexities to ensure electrical and electronic subsystems and components will operate without interfering with each other or increasing hazards.
The article below provides an overview to help OEMs learn what they need to know about these EMC challenges.
What is EMC?
All electrical and electronic devices, subsystems, and components emit electromagnetic energy during operation—the natural result of electrons accelerating or decelerating. This energy can cause performance issues (e.g., interrupted circuits, voltage spikes), malfunctions, or failures in other electrical and electronic subsystems and components. And when multiple exist within the same environment, the results may be unpredictable or dangerous.
Therefore, OEMs and their partners must ensure electromagnetic compatibility (EMC)—or the sufficient reduction of electromagnetic energy to ensure electrical and electronic subsystems and components will operate in close proximity without adverse effects.
The Difference Between EMC and EMI
When devices, subsystems, or components emit electromagnetic energy of significant enough magnitude or at disruptive frequencies, it causes electromagnetic interference (EMI) or “noise.” This noise impacts “receivers’” performance (i.e., affected devices, subsystems, and components) and may cause failure. Close proximity or a direct connection between a “source” (i.e., EMI emitters) and a receiver results in greater EMI impacts.
In essence, EMI is the problem and EMC is the solution, which is generally achieved via techniques such as:
- Galvanic isolation
- Wire and cable routing
- Grounding
- Ferrite filters
The Importance of EMC
The potential issues related to EMI-caused performance loss, malfunction, and failure should be apparent—everything from loss of customer confidence due to increased downtime to substantial worker safety risks can occur.
However, what OEMs might not consider is that continual innovations make EMC efforts increasingly difficult.
To make EVs and NRMM more sophisticated, lighter, and compact, OEMs and their partners continually develop and install smaller, more complex, and more powerful electric and electronic subsystems and components. And these subsystems and components operate in closer proximity than ever before, which further exacerbates potential EMI and can result in unpredictable outcomes.
As a result, EMC and compliance testing have become increasingly crucial—especially during design and engineering stages.
Creating Voltage Domains to Achieve EMC
One of the most successful methods for achieving EMC is “galvanic isolation.” This practice separates different electrical and electronic subsystems and components from each other by placing them in dedicated “domains” that don’t share direct conduction paths.
Separating circuits into distinct domains decreases the sources and receivers in that environment, inherently simplifying EMC challenges.
Generally, the electrical and electronic subsystems and components installed on EVs and NRMM should be separated into four domains to mitigate EMI (and safely step down voltages when sharing power):
- AC input power (i.e., the power provided by external sources to charge batteries)
- DC traction power (i.e., the high-voltage or battery domain)
- Auxiliary power (i.e., the low-voltage domain for attached systems and functionality)
- Signaling and communication (i.e., systems such as CAN bus)
Galvanic Isolation Methods
Galvanic isolation does not mean that the different domains are separated entirely—although some EVs and NRMM may utilize a separate battery for auxiliary functions. Instead, installing certain components achieves domain isolation while still enabling communications and safe power transfer.
Isolation components include:
- Isolation transformers – Transfer via the electromagnetic field
- Optocouplers – Transfer via optical signals created with LEDs and photodiodes (also referred to as “photocouplers”)
- Capacitor-based semiconductor isolators – Transfer via differential capacitors or microelectromechanical-based transformers
Capacitor-based semiconductor isolators are suited for EV and NRMM applications, in particular, due to their durability, thermal stability, EMI mitigation, and high switching speeds.
Importance of Dedicated Grounding for Domains
Maintaining isolation between traction power, auxiliary power, and signal domains requires providing each with dedicated grounds. When these domains share grounds, auxiliary power and signal domains lose their protection against accidental connection to DC traction power (and its elevated EMI generation and higher voltage).
Accidental connections between these domains may result in permanent damage to chargers and other subsystems and components, along with an overall reduction in EMC.
Isolation between AC input power and the other domains poses less of a challenge, as EVs and NRMM will not be charging while in motion.
EMC Testing Standards
Ensuring EMC for components and subsystems within a domain and for finished products involves performing dedicated testing in accordance with industry-accepted standards.
Automotive-grade standards applicable to EVs and NRMM that OEMs should consider testing against include:
- SAE J1113 family of standards – Specifications for vehicles, boats (15m or less in length), and machines (not including aircraft)
- ISO 7637-2 – Specifications for 12V and 24V electrical systems
- ISO 11452 family of standards – Specifications for on-road vehicle protections against narrowband electromagnetic energy
- IEC 61000 family of standards – A collection of over 50 “basic” and “generic” EMC specifications
In-house testing should be performed frequently during design and engineering stages. However, final testing processes must be performed by an approved entity, such as CSA Group, Underwriters Laboratories (UL), and the American National Standards Institute (ANSI). Certified compliance with these standards will be denoted by entity-specific marks on product labeling.
Noncompliance with applicable EMC regulations—such as FCC Title 47, Part 15 for North America and UN ECE R10 for Europe—will prohibit OEMs’ entry into global markets.
Partner with Delta-Q Technologies for Optimal EMC
OEMs will need to identify and collaborate with their partners to achieve standard-complying EMC within the different power domains and for finished products. For example, Delta-Q Technologies’ XV3300 on-board charger meets North American, European, and other global regulatory requirements—but that performance will be impacted if OEMs don’t galvanically isolate DC traction power and auxiliary power domains.
Contact Delta-Q Technologies to ensure your on-board chargers meet all applicable EMC regulations and performance requirements.
Sources:
Charged. EMC for EVs: Understanding electromagnetic compatibility. https://chargedevs.com/features/emc-for-evs-understanding-electromagnetic-compatibility/
EE Times. Galvanic Isolation in Electric and Hybrid Vehicle Applications.https://www.eetimes.eu/galvanic-isolation-in-ev-and-hev-applications/
SAE. Electromagnetic Compatibility Measurement Procedures and Limits for Components of Vehicles, Boats (up to 15 m), and Machines (Except Aircraft) (16.6 Hz to 18 GHz) J1113/1_202304. https://www.sae.org/standards/content/j1113/1_202304/
ISO. ISO 7637-2:2011. https://www.iso.org/standard/50925.html
ISO. ISO 11452-2:2019. https://www.iso.org/standard/68557.html
Rohde & Schwarz. EMC Standards. https://scdn.rohde-schwarz.com/ur/pws/dl_downloads/dl_common_library/dl_brochures_and_datasheets/pdf_1/EMC_Standards_overview_list_2020.pdf
