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Understanding SAE J551-5: Performance Levels for EV Emissions (150 kHz – 30 MHz) ⚠️
SAE J551-5 was a recommended practice defining measurement procedures and performance levels for magnetic and electric field emissions from electric vehicles. However, as of November 2017, this standard has been cancelled. In this article, we review its historical context, technical content, and the rationale behind its cancellation.
Overview and Key Technical Details
The standard covers radiated emissions in the frequency range 150 kHz to 30 MHz for vehicles with electric propulsion (BEV, HEV, PHEV). It also addresses conducted emissions from on-vehicle charging systems with switching frequencies above 9 kHz, referencing FCC Part 15. Induction charging systems are excluded.
The standard specifies peak and average limits for radiated emissions, with frequency-dependent formulas. Below is a summary of the peak electric field limits:
| Frequency (MHz) | Level (dBμV/m) |
|---|---|
| 0.15 to 4.77 | 88.89 – 20log10(f) |
| 4.77 to 15.92 | 116.05 – 60log10(f) |
| 15.92 to 20 | 67.98 – 20log10(f) |
| 20 to 30 | 41.96 |
Measurement requires antennas per CISPR 16-1-4, including a 1 m vertical monopole for electric field and a 60 cm loop for magnetic field. Scanning receiver parameters are specified for peak and average detectors.
Engineering Design Insights and Cancellation
The limits exhibit a mixture of constant and logarithmic slopes, emphasizing that EMC design must address different frequency bands with tailored filtering and shielding. The derivation from legacy limits involved distance scaling and bandwidth normalization removal, providing historical context for limit setting. However, since the standard is cancelled, engineers should now reference CISPR 36 for low-frequency EV emissions.
SAE J551-5 was cancelled because it was considered redundant and outdated compared to CISPR 36, which was drafted to harmonize low-frequency measurements globally. The cancellation notice warns against using J551-5 for new designs. Engineers should adopt CISPR 36 or other current standards for EMC compliance.
⚠️ Important: Cancelled Standard
Do not use SAE J551-5 as a current requirement for new vehicle designs. It is superseded by CISPR 36. Always check the latest applicable standards from CISPR, SAE, or other regulatory bodies.
🛠️ Historical Reference
Despite cancellation, SAE J551-5 remains available for historical reference. Understanding its content can help engineers interpret legacy test data and appreciate the evolution of EMC requirements for EVs.
Frequently Asked Questions
- What are the specific emission limits for electric and magnetic fields in J551-5?
Limits are frequency-dependent and provided in Tables 1-3 of the standard. For example, the peak electric field limit from 20-30 MHz is 41.96 dBμV/m. Always refer to the original document if needed, but remember it is cancelled. - How are conducted emissions measured for on-vehicle chargers?
Conducted emissions follow FCC Part 15 limits. Measurement is performed using a LISN on the AC power lines while the vehicle is charging. The standard specifies in-vehicle or subsystem testing. - Why was J551-5 cancelled?
The document was deemed redundant and outdated compared to the emerging global standard CISPR 36, which is designed to harmonize low-frequency measurements for electric vehicles. - What should engineers use instead of J551-5?
Engineers should refer to CISPR 36 for radiated emissions and relevant parts of CISPR for conducted emissions. For the US, FCC Part 15 continues to apply for conducted emissions. Always verify the latest requirements.
This article is for informational purposes. Always consult official standards for compliance.
