Electric grid measurements

Only equipment which abides by regulations for electromagnetic compatibility (EMC) are typically allowed to connect to the electric grid. One part of the EMC directive relates to flicker and harmonics caused by the appliances. Harmonics are typically caused by high power electronics typically found in the main power supply of the equipment. WiCh investigated Evatran’s L2 inductive chargers’ and found them to cause significant harmonics and thereby requires further investigation by the grid owner prior to connecting to the grid.

State of the Art

The countries that are influential in the development of inductive technology and standardization are the United States, Germany and Japan. Some renowned car manufactures aim towards 2018 to provide inductive charging equipment for home charging at low-power and high efficiency that meet a standard that should be ready by then. In the current situation it is only Evatran Plugless equipment made for retrofit that is available. Continued work is now focused on offering lower cost and higher power.

Tests related to CE marking

Many consumer products within EU are marked with CE, an abbreviation of ”Conformité Européenne”. The CE mark means that the product fulfills EU legislations and can thereby be freely sold within the European Economic Area. Typically the product is CE marked by the manufacturer or the importer.

For the WiCh project, the related directives and legislations were the low voltage directive, electromagnetic compatibility and reduction of hazardous substances. The project therefore used the independent party SP Technical Research Institute of Sweden to evaluate compliance.

Magnetic fields

Many people are concerned with magnetic fields. The Swedish Radiation Authority (SSM) has measured the magnetic fields in and around the inductively charged vehicles in the WiCh project.

Although the magnetic fields at charging can be quite high close to the rear of the vehicle and even higher underneath it, inside the vehicle the magnetic fields are quite low. Apart from close to the charging equipment, the magnetic fields are below what is allowed by the Swedish Work Environment Authority, which means that the equipment could be used in the project.

These results only apply to this specific combination of vehicle and charging system and are not generic to other induction charging systems.

Efficiency measurement

To get as little energy loss as possible on the energy transfer a high efficiency is desired. In the Wich project Test Site Sweden at Lindholmen Science Park has measured the efficiency of the inductive systems used in Wich. The purpose of the measurements was to investigate how well the wireless charging transfers energy to the car and how this varies with the distance between the car and the coil at the ground.