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A new measurement system for measurements at vehicle inductive charging stations

Electric car

EMPIR project enables new power measurements to support safe and efficient charging of low carbon electric vehicles

Inductive charging is a promising charging technology that is being deployed by some manufacturers of electric vehicles and has the potential of being widely used in the near future. This technology offers many advantages, such as the possibility of charging along the road while driving, small batteries and high-efficiency power transmission, as well as a reduction in CO2 emissions and oil consumption. Reliable, accurate and traceable electric power measurements are needed for inductive power transfer applications. This includes electric vehicle manufacturers, as they are subject to strict international requirements concerning accuracy, safety and, in the near future, energy billing.

EMPIR project Metrology for inductive charging of electric vehicles (16ENG08, MICEV)  has been working to accurately measure the efficiency of inductive power transfer, and provide the means to reliably demonstrate compliance with existing safety standards for human exposure. These results will support safe and efficient charging of low carbon electric vehicles.

A Power Measurement Unit (PwMU) developed in the project is the first measurement system designed explicitly for measurements at inductive charging stations. It was built at INRIM, with collaboration from PTB and RISE on the calibration part of the power measurement system.

The PwMU is a modular system consisting of three modules:

  • a module for current, voltage and power measurements from the electricity grid, so-called Grid Unit (GU)
  • a module for on-board measurements, so-called on-Board Unit (BU)
  • a module for the magnetic field measurements, so-called Magnetic Unit (MU).

All three modules are synchronised using a GPS system. The GU, as well as the BU, was conceived with two measurement systems, so as to have redundancy and better reliability during in-field measurements.

A meter for magnetic field measurements has also been calibrated in the new facility at NPL.

The PwMU measurement system was designed to perform the following functions:

  • to measure the power absorbed from the charging station by the load (batteries)
  • to measure the power absorbed by the charging station from the electric grid
  • to determine synchronised ratio between the two power quantities listed above (efficiency)
  • to determine the magnetic flux density levels in the charging station
  • to record measured values and waveforms in their measurement time interval

Project Coordinator Mauro Zucca from INRIM said

‘This is a new and traceable testing system which improves the ease and ability to perform accurate in-field and laboratory test of wireless power transfer charging stations. The system accurately measures all the electrical parameters and waveforms, it determines the efficiency of the charging station and it simultaneously measures the magnetic field levels of inside and outside the vehicle for the evaluation of the human exposure to magnetic fields. The system is quite complex, nevertheless the control and management software has been designed to make it easy to use. It will be a useful development tool in this field.’


This EMPIR project is co-funded by the European Union's Horizon 2020 research and innovation programme and the EMPIR Participating States.

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