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SAE task force agrees on frequency of operation and power classes for wireless power transfer for light-duty plug-in vehicles

SAE International J2954 Task Force for Wireless Power Transfer (WPT) of Light Duty, Electric and Plug-in Electric Vehicles, has agreed upon two key factors for the Technical Information Report (TIR) on interoperability for the first phase of pre-commercial development: a common frequency of operation (85 kHz) and the definition of three power classes for light duty vehicles: WPT 1, 2 and 3.

Made up of OEMs, WPT Suppliers, industry experts and government representatives, the Task Force plans to complete the TIR in early 2014. The SAE Technical Information Report will be followed by publication of SAE J2954 Standard, based on field data confirmation.

A common frequency of operation for WPT is essential for interoperability. After 3 years of international collaboration and investigation within the team, consensus had been reached on a nominal frequency of operation for the light duty vehicle guideline. The SAE team has determined this nominal frequency of 85 kHz for SAE J2954. This frequency lies within an internationally available frequency band. [81.38 - 90.00 kHz].

—Jesse Schneider, Chair J2954 Taskforce

The limits for the three power classes are defined by the maximum input Wireless Power Transfer power rating as shown in the table below:

SAE TIR J2954 WPT Power Classes
Private/Public Parking
LD Fast Charge
Maximum Input WPT Power Rating 3.7 kW 7.7kW 22 kW

The SAE International Task Force is currently working on completing the remaining interoperability topics, including factors such as the minimum coupling factor “k”, alignment, and coil geometries.



This is a good first step towards standardized wireless charge stations. However, future quick charge stations will require much more power, something like 100KW, 150KW and 200KW.

Henry Gibson

If people are allowed to plug in their cell phone chargers every day in Europe and other countries there is no reason to believe that it is necessary to have inductive charging connections for automobiles. Ground fault devices and be supplemented if necessary with other tests of the circuit done by computer processes of great complexity. Connecting the charger with ordinary jumper cables would be far less risky than driving on motorways. Fast charging is not necessary. Sustainable n-butanol can be made at nuclear reactors buried in remote islands at less cost than present fuels for use in tiny range extenders from Bladon jets.

There is much talk about ocean acidification, but the ocean is now somewhat caustic, anti-acid, and it would take unimagined mega-tons of CO2 to even get it neutral. Large machines automatically coppicing large forests and hiding the wood in salt mines forever is cheaper than maize ethanol for reducing CO2 in the air.



I do not know what considerations were used in this frequency choice but it limits substantially the progress in the field. In general, the higher frequency is the smaller passive resonant components can be (integral part of wireless energy transfer). Besides this, shaping the electro-magnetic field is much easier at higher frequencies. In my humble opinion as a power electronics designer, several hundreds of kHz is not the limit. These inverters should not interfere with AM band but otherwise 85kHz sounds too low and limiting. Also, "The SAE International Task Force is currently working on completing the remaining interoperability topics, including factors such as the minimum coupling factor “k”, alignment, and coil geometries"- sounds like framing for the existing products.
Define the allowed radiation ...and that is all. Somebody is definitely trying to prevent the competition from leapfrogging inventions. Mind boggling. For those SAE Bureaucracy "survival of the fittest" is like red color for bulls. Regulate, regulate with no thinking (non required).

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