|A system for static wireless charging. Source: HaloIPT. Click to enlarge.|
HaloIPT’s wireless charging systems use inductive power transfer (IPT) to transfer power over gaps of up to 400mm (15.75 inches) and are tolerant to parking misalignment with power transfer efficiencies that can match a plug-and-cable. The company is currently delivering units in the range 3 to 7kW and is also developing higher power 3-phase systems for public charging.
IPT systems work by taking electrical power from the grid and energizing a coil (the primary coil), with current typically in the range 5-125A. The coil is inductive; compensation using series or parallel capacitors may be required to reduce the working voltages and currents in the supply circuitry. Pick-up coils are magnetically coupled to the primary coil. Power is transferred by tuning the pick-up coil to the operating frequency of the primary coil with a series or parallel capacitor. The power transfer is controllable with a switch-mode controller.
HaloIPT’s Wireless IPT System thus comprises three distinct hardware components:
A high-frequency generator or power supply. The high-frequency generator takes voltage input (240VAC at 50/60Hz) and produces a high-frequency (>20kHz) current. The output current is controlled and the generator may be operated without a load. The efficiency of the generator is greater than 94% at 2kW. The generator comprises a filter (to reduce EMI); rectifier; bridge (MOSFETs) converting DC to high frequency; combined isolating transformer /AC inductor; tuning capacitors (specified for frequency and output current); and control electronics (microcontroller, digital logic, feedback and protection circuits).
A magnetic coupling system or transmitter/receiver pads. The coupling circuits are tuned through the addition of compensation capacitors. The pad construction provides shielding of magnetic fields to prevent EMI within the vehicle and ensures levels of MF exposure are within suggested international guidelines (ICNIRP).
- A pick-up controller/compensation. The pickup controller takes power from the receiver pad and provides a controlled output to the batteries, typically ranging from 250V to 400V DC. The controller provides an output that remains independent of the load and the separation between pads. Without a controller, the voltage would rise as the gap decreased and fall as the load current increased.
The main components in the pickup controller are: tuning capacitors; transistors (MOSFETs) for power control and protection; rectifier; DC inductor; capacitors to smooth output voltage; and control circuit, including sensors for voltage and current.
HaloIPT’s system is battery-agnostic; the pick-up controller interfaces directly with the proprietary battery management system on the vehicle.
We are delighted to provide our wireless charging technology for this trial. Industry feedback so far tells us that the automation advantages of wireless charging make it the best charging solution for luxury electric vehicles and will be the key to unlocking the potential of this exciting market. Users don’t need to get out of their vehicles and hunt for a cable to plug-in, they will just park and walk away while their car starts charging automatically … the ultimate in modern convenience.—Dr Anthony Thomson, CEO of HaloIPT
The technology is designed to function beneath asphalt, and works under water or covered in ice and snow. IPT systems can be configured to work with all road-based vehicles from small city cars to heavy-goods vehicles and buses. With IPT technology embedded into roads, cars could also be charged on the move. This dynamic in-motion charging would reduce battery size requirements as well as providing charging convenience, the company suggests.
HaloIPT is a technology development company founded by Auckland UniServices (NZ) and Arup (UK).