真乄科技業的頂尖投資團隊

近一、兩年，包括插電式混動車在內的電動車在市場的發展速度明顯加快。Tesla、各傳統車廠加大對市場的混動車投放，這些現象讓我們看到，一個新的汽車時代步步逼近。

跟智慧手機一樣，時下主流的電動車充電方式也是有線充電，而一些車廠正在探尋無線充電技術，試圖通過改善用車體驗來推動電動車的發展。

寶馬近日宣佈，已與戴姆勒簽署合作協定，將共同研發用於純電動車和插電式混動車的新一代無線感應充電標準化技術。寶馬表示，該技術未來將可用於旗下的 i 系列電動車，屆時充電會變得更有效、方便和安全。

寶馬和戴姆勒研發的無線充電系統包含兩個部分：安裝在汽車底盤上的次級線圈和安裝在地上的初級線圈。電能通過線圈間的交變磁場傳遞。充電速率可達 3.6 kW 每小時，未來則有望提升至 7 kW 每小時。寶馬稱這一系統的充電效率可達到 90% 以上。

簡單來說，司機只需將車開到充電器位置，然後按下車上的專用按鈕即可充電。與此同時，你也可以通過手機 app 來獲取汽車當前的充電狀態。

據寶馬介紹，得益于優秀的保護措施，這個感應充電系統不受天氣狀況的影響，這意味著你可以將充電器安裝在戶外。一旦充電過程中系統檢測到干擾因素，那麼就會立刻停止充電。

BMW has granted an insight to its development of inductive charging schemes for electric vehicles. In the medium term, the company plans to launch series production for the technology. The project is conducted along with competitor Daimler; both companies plan to provide a uniform charging technology for the garage at home.

The system consists of two components: A primary coil integrated into a base plate which itself is placed beneath the vehicle, for instance in the floor of a garage or parking lot. This coil induces electric energy to the secondary coil in the car floor.
The arrangement of the coils, and consequently of the field pattern, is based on a design derived from their circular shape that offers a number of benefits such as a compact yet light construction as well as an effective spatial confinement of the magnetic field - a feature important to maintain high efficiency. The alternating magnetic field between the coils transmits the electric energy wirelessly at a power of up to 3.6 kW. BMW specifies the energy efficiency of this arrangement at 90%. The system aims at charging high-voltage batteries for plug-in hybrid and battery electric cars.

One of the design goals was achieving the shortest possible charging time. At a charging power of 3.6 kW, many plug-in hybrids can be charged completely in less than three hours. The BMW i8, the company's current technology flagship, can be charged in less than two hours. The i8 has, unlike its smaller sibling i3, a plug-in hybrid powertrain while the i3 is a battery electric car. To take higher battery capacities for purely electric vehicles into account, the future wireless charging technology standard offers the option to increase the charging power to 7kW which would make it possible to charge the batteries of the i3 over night.

BMW has granted an insight to its development of inductive charging schemes for electric vehicles. In the medium term, the company plans to launch series production for the technology. The project is conducted along with competitor Daimler; both companies plan to provide a uniform charging technology for the garage at home.

To charge up a vehicle with the system, the car needs to be positioned exactly over the primary coil. A software in the head unit and a WiFi data link between charging station and vehicle supports the driver during this task. In addition, a smartphone app allows users to monitor the charging progress and informs about the remaining charging time.

Fig. 1: This is how the components for wireless charging are arranged in BMWs system (Stromversorgung = power supply; Sekundrspule = Secondary coil; Gleichrichter = rectifier, Energiespeicher = energy storage).
The system is weather-independent; it works also if the surface is covered with snow or water. The electric stray field is reduced to the minimum possible, says BMW - without however specifying how strong the field is. The gap between primary and secondary coils is monitored constantly; if any foreign particle enters the gap, the charging process is stopped immediately - potentially saving the live of any curious pet cat.
Related articles and links:
What EV charging technologies to watch for in 2014
Inductive e-car charging emerges as alternative to conductive charging

Source:EE Times