Wireless Power Transfer for Light-Duty Plug-In/Electric Vehicles and Alignment Methodology


The SAE Recommended Practice J2954 establishes an industry-wide specification that defines acceptable criteria for interoperability, electromagnetic compatibility, EMF, minimum performance, safety and testing for wireless charging of light duty electric and plug-in electric vehicles. The current version addresses unidirectional charging, from grid to vehicle, but bidirectional energy transfer may be evaluated for a future standard. The specification defines various charging levels that are based on the levels defined for SAE J1772 conductive AC charge levels 1, 2, and 3 with some variations. A standard for wireless power transfer (WPT) based on these charge levels will enable selection of a charging rate based on vehicle requirements, thus allowing for better vehicle packaging, and ease of customer use. The specification supports home (private) charging and public wireless charging.

In the near term, vehicles that are capable to be charged wirelessly under Recommended Practice should also be able to be charged by SAE J1772 plug in chargers.

This Recommended Practice is planned to be standardized after the 2018 timeframe after receiving vehicle data. The contents, including frequency, parameters, specifications, procedures and other contents of this Recommended Practice are to be re-evaluated at that time to allow for additional developments and future innovations.

SAE Recommended Practice J2954 is intended to be used for stationary applications (charging while vehicle is not in motion). Dynamic applications may be considered in the future based on industry feedback. This document covers above-ground surface mounted GAs. Flush mounted reference designs have been proposed in the taskforce and it is anticipated that these will be specified in the next version of the Recommended Practice planned for publication in 2018.

SAE Recommended Practice J2954 is meant to be used for interoperability, performance and emissions testing, where a single standard coil-set has been chosen for the WPT Power Class 1 and 2 to 7.7kW, per Z-Classes (1 through 3) which is circular topology. However, there are two reference options for WPT 3 to 11kW per Z-classes (1 through 3) with two topologies. The next revision of the Recommended Practice in 2018 is slated to have one standard coil set for WPT 3. This SAE J2954 Test Station is meant to provide a baseline where compatibility with the content of the Recommended Practices is to be demonstrated.

The future standard, will use this -performance based- J2954 Standard Testing Station to establish a uniform way to demonstrate design for both the electrified vehicle (VA) and WEVSE (GA) components safety, interoperability, performance and EM emissions -through testing-. The goal is to have a common methodology to validate Wireless Power Transfer and Alignment, production designs between different power classes and topologies for both the vehicle and infrastructure.


Electrified powertrains, specifically Battery Electric and Plug-In Electric (BEV/PHEV) vehicles are projected internationally to become more prevalent in production due to environmental factors (such as CO2 emissions), regulations (such as the Greenhouse Gas and the California ZEV Mandate) and the increasing price of fossil fuels. The main benefits of electrified powertrains are eliminating or significantly reducing local emissions while increasing the overall well-to-wheels efficiency. In addition, autonomous vehicles are soon to be more commonplace to allow more convenient and safer transportation especially in traffic settings and long-distance driving. Standardized Wireless Power Transfer (WPT) through wireless charging allows the BEV/PHEV customer an automated and more convenient and alternative to plug-in (conductive) charging. Essentially the customer simply needs to park into a SAE J2954 compatible parking space in order to charge the vehicle. WPT offers the additional advantage to autonomous vehicles enabling autonomous parking with alignment assistance and automated charging (in all weather conditions such as rain or snow).

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