The online electric vehicle system is split into two main parts: the segmented "recharging" road and the "pick-up" modules on the vehicle.
In the Road
In the "recharging" road, slim W-shaped ferrite cores are buried 30 cm underground in a fish bone like structure. Power cables are wrapped around the center of the fish bone structures to make the "primary coils". This design combines the magnetic fields of the two sides of the cables and shapes the fields in a way that maximizes induction. Moreover, the primary coils are placed in segments across certain spans of the road so that only about 5% to 15% of the road needs to be remodeled. To power the primary coils, the cables are attached to the South Korean national power grid through a power inverter. The inverter accepts 60 Hz 3-phase 380 or 440 voltage from the grid to generate 20 kHz of AC electricity into the cables. In turn, the cables create a 20 kHz magnetic field that sends flux through the slim ferrite cores to the pick-ups on the OLEV.
On the vehicle
Attached beneath the vehicle, are "pick-up" modules, or the secondary coils, that consist of wide W-shaped ferrite cores with wires wrapped around the center. When the pick-ups "pick up" the flux from the primary coils, each pick-up gains about 17 kW of power from the induced current. This power is sent to the electric motor and battery through a regulator, thereby charging the vehicle wirelessly.
Models
As seen in the table above, the generation 1 OLEV lacks a realistic margin for error. The lower current means a smaller magnetic field and requires the secondary coil to be very close to the floor, which can be an issue while driving. Moreover, if the primary and secondary coils are vertically misaligned by a distance over 3mm, the power efficiency drops greatly. To fix these issues, KAIST came up with the generation 2 OLEV. In the gen 2 OLEV, the current in the primary coil was doubled to create a stronger magnetic field that allows for a larger air gap. The ferrite cores in the primary coils were changed to a U shape and the cores in the secondary coil were changed a flat board shape to pick-up as much flux as possible. This design allows the vertical misalignment to be about 20 cm with a 50% power efficiency. However, the U shaped cores also require return cables which bumps up the cost of production. Overall, the gen 2 made up for the gen 1's margins but, was more costly. In response to the cost issue of gen 2, the third generation OLEV was developed. The third generation OLEV, uses ultra-slim W-shaped ferrite cores in the primary coil to reduce the amount of ferrite used to 1/5 of gen 2 and to remove the need of return cables. The secondary coil uses a thicker variation of the w-shaped cores as a way to make up for the lesser area for the magnetic flux to flow through compared to gen 2. Overall, the gen 3 OLEV made up for the gen 1's small margins and gen 2's increased cost.
