Articles
Engineers in South Korea have developed wireless power technology to rival maglev systems which will be installed on a high-speed train for the first time later this year.
The online electric vehicle (Olev) technology was demonstrated on conventional railway tracks last month. Engineers at the Korean Advanced Institute of Science and Technology (KAIST) plan to fit the wireless power transfer technology to trams by May this year and then to high-speed trains during September.
Professor Dong-Ho Cho of KAIST said the Olev system has advantages over maglev that make it more likely to be commercially successful.
Cho said: “Olev-based trains carry a battery, which means the installation of the track can be more flexible and cheaper than the maglev system, which always needs a power source to be derived from the track. The Olev system can also be retrofitted to conventional railways easily, unlike magnetic levitation, which needs a new structure. Implementation and maintenance costs can therefore be reduced a lot compared to maglev.”
Although Olev technology is similar to maglev in the lack of contact, the two systems use electromagnetic fields in different ways. Magnetic levitation systems use the repulsive force between magnetic flux for motion, whereas Olev uses magnetic flux which is converted into electrical energy to drive motors.
KAIST’s wireless power system uses inductive coupling and shaped magnetic field in resonance technology, and was originally developed for use in electric road vehicles. Engineers install an AC power coil underground with two magnetic poles and shielding. The shape of the magnetic field is determined by the distance between the two poles. An active and passive cancellation system mounted on the vehicle works to minimise the radiation from the magnetic field.
The Olev system supplies 180kW at 60kHz across a gap of 20cm in its rail application, a tripling of the power transmission from earlier versions of the technology. Cho said: “The size and weight of the power pick-up modules have been reduced. We were able to cut down the production costs for major components, the power supply and the pick-up system, and in turn Olev is one step closer to being commercialised.”
The use of wireless power technology on railways would reduce the cost of wear and tear dramatically, said Cho. Other benefits include the removal of the need for power rails and electrical poles, reducing the area needed for railway lines. Tunnels could be built smaller, lowering construction costs.
In addition, the system is quieter than conventional rail, removing a common barrier to the construction of high-speed lines.