# Status of Pure Electric Vehicle Power Train Technology and Future Prospects
## 3 Electric Vehicle Powertrain Architecture
### Pure Electric Vehicle Architecture  
There are different feasible EV architecture systems due the variations in electric drive systems [55; 60; 62]. Six alternatives architecture that are possible in the EVs as shown in Figure 3. These six alternatives are illustrated in Figure 3.  
* Figure 3a presents an electric motor architecture system which has an electric motor, a clutch (C), a gearbox, and a differential (D). The clutch engages or disengages the power flow from electric motor to the wheels like it does in internal combustion engine powered vehicles. The wheels have low speed with high torque in the lower gears and low torque with high-speed in the higher gears. This architecture setup was mostly used in conversion of ICE powered vehicles to EVs utilizing the existing components.
* Figure 3b presents a single electric motor architecture with fixed gear. The advantage of this architecture is that the transmission weight is reduced as transmission and clutch have been omitted. Some vehicle conversion using electric machine without transmission system utilize this configuration.
* Figure 3c presents an EV architecture using one electric motor. It is an EM with rear wheel drive architecture with fixed gearing and differential integrated into a single assembly, and has been preferred by most of the electric vehicle manufactures at present scenario. Figure 4a shows similar rear wheel drive system used by Mahindra electric e20.
* Figure 3d presents a dual-motor architecture. In this configuration, the differential action can be electronically controlled provided by two electric motors that operates at different speeds. In this dual-motor architecture, the driving wheels are derived separately by two separate electric motors separately via fixed gearing.
* Figure 3e shows an architecture with a fixed planetary gearing system employed to reduce the motor speed to the desired wheel speed. This architecture is called an in-wheel drive system and the planetary gearing in this system offers the advantages of a high-speed reduction ratio along with an inline arrangement of input and output shafts [55; 60].
* Figure 3f presents an EV architecture without a mechanical gear system. A low-speed outer-rotor electric motor has been installed inside the wheels. The gearless arrangement with outer rotor mounted directly on the wheel rim makes equivalent speed control of the electric motor with the wheel speed and, hence, speed of the vehicle [64; 65; 66; 67].  
Figure 3: Electric vehicle (EV) drivetrain architecture alternatives based on drivetrain configuration [53].  
The above architecture set up depends on the required size and application of EVs, considering compactness, performance, weight, and cost of the vehicles. Presently, the popular configurations are as shown in Figure 3b or Figure 3c, mostly Figure 3c has been widely used in present electric vehicles to drive the both wheels using a single motor. The Nissan Leaf, Chevrolet Spark, Kona and Ioniq from Hyundai, Soul EV, Verito from Mahindra, and Niro from Kia uses front wheel drive system. While EVs can be built with the rear wheel drive system with the same configuration, the Tesla Model S, BYD E6, Reva, E20, E20 sport from Mahindra use rear wheel drive with single speed transmission to drive rear axle.  
Figure 3e or Figure 3f have been used in project demos or production at lower scale. The Nissan Blade Glider involves a rear wheel drive system with in-wheel motor arrangement to the application of different amount of torques at two rear wheels to for better cornering performance.  
All-wheel drive (AWD) architecture set up utilizes two motors to drive the front and two motors to drive the rear axles. An all-wheel drive architecture system is shown in Figure 4b. AWD configurations provide better traction control and avoids slipping. Torque vectoring can be used for better cornering performance [62; 67; 68; 69]. AWD architecture systems with in-wheel motor systems can be utilized in cars like Nissan IMX as shown in Figure 4b providing an efficient driving performance.