|System efficiency at 100mm gap for 3.3kW output plotted against primary coil position relative to secondary coil (mm). Source: INL. Click to enlarge.|
Idaho National Laboratory researchers recently released independent testing results of a wireless charging system designed for plug-in electric vehicles (PEVs). The system tested, Evatran’s Plugless 3.3 kW Level 2 Charging System, uses inductive technology to wirelessly charge a PEV’s traction battery, which powers the vehicle. The Plugless system is the first wireless power transfer technology to be independently documented and published.
INL researchers performed 2,600 separate tests of Evatran’s Plugless Level 2 Charging System, which included testing at different distances and varying alignments, said Jim Francfort, INL’s principal investigator for advanced technology vehicles. INL continues to conduct independent testing of PEVs and charging systems.
Evatran supported the testing process with engineering input. The tests documented efficiency results, magnetic and electric fields and overall system performance.
|Efficiency results at 3.3 kW output|
|100 mm gap||110 mm gap|
|Maximum efficiency [%]||88.8||89.2|
|Nominal efficiency [%]||87.0||88.1|
|Minimum efficiency [%]||86.1||86.2|
The Plugless wireless charging system comprises four elements: (1) the control panel and power electronics which are connected to the commercial/residential wiring and receptacle; (2) the primary coil; (3) the secondary (in-vehicle) coil; and (4) the vehicle adapter/power electronics. System efficiency was defined as the energy out of the vehicle adapter (4) divided by the energy into the control panel (1).
|Impact of coil gap on system efficiency. Source: INL. Click to enlarge.||Impact of charge power on system efficiency. Source: INL. Click to enlarge.|
In addition to avoiding a physical plug-in process, the Plugless system includes parking guidance technology that directs the PEV driver toward optimal alignment and foreign object detection technology to protect against ferrous materials.
INL is expected to continue testing wireless charging technologies with industry participation. Industry, DOE and INL are also conducting research into dynamic vehicle charging technologies that will use wireless power transfer technologies for possibly charging vehicles while they are driven on roadways.
This emerging technology offers the potential for much higher charging participation resulting in more electric miles being driven, helping to reduce our nation’s dependency on foreign oil.—Jim Francfort