This slide shows the components of the front drive unit. The Tesla model S is an all wheel drive vehicle, has shown on the prior slide. They publish a few numbers in their driver manuals and then leave it to their large group of online enthusiasts to speculate on the rest. There are lots of photos and videos of Tesla electric motors online, but Tesla does not explain the technical details. This slide took me a long time to create. Both versions directly drive the front wheels and neither needs a driveshaft. The battery electric vehicle replaces the gasoline engine with a traction motor. The front wheel drive versions of these cars are similar in architecture. The engine and transmission are located up front and the driveshaft transfers torque to the rear wheels. This architecture contrasts with the gasoline powered rear wheel drive car. This frees up space up front for a nice storage compartment. The rear wheel drive electric vehicle has an electric motor and transmission located in the rear of the car. Front and rear motors are programmed to provide the same speeds to their respective set of wheels, as well as accelerate or decelerate at the same rate. To solve this problem, manufacturers use synchronous AC motors which run at exact speeds. The car would tend to lurch forward, not accelerate smoothly. If you use low cost AC induction motors, they would never power the front and rear wheels and sync with each other. In the electric car, you have two sets of motors which run independently of each other. In the gasoline powered car, you synchronize the front and rear wheels with the mechanical couplings. Therefore you put a second traction motor and transmission in the wheel of the car to power the rear wheels. A driveshaft would drill through the battery packs if you placed it there, there's no way to mechanically transfer torque from the front of the car to the rear. The full volume under the car seats is filled with battery packs. You don't have a driveshaft or differentials in the electric all wheel drive vehicle, you don't have room for this stuff anyway. This latter part changes the axis of rotation by another 90° and transfers torque to the rear wheels. The driveshaft extends to the rear of the car where it meets the rear differential. The center differential changes the axis of rotation by 90° to transfer torque to the driveshaft. The front differential of the gasoline version splits torque between the two front wheels. The gasoline version has one engine and one transmission. The electric version has two sets of attraction motors along with their associated transmissions. There are important differences between this layout and that for the gasoline engine version shown in the lower right. On the left of this slide, you see the motor layout of an all wheel drive electric vehicle. Therefore, a DC to DC converter is used to step down the voltage to 12 volts for the auxiliary battery. The battery pack voltage measures in the hundreds of volts. Gasoline engine cars have 12 volt batteries to power headlights, brake lights, signal lights, dashboard panel and other low voltage circuits in the vehicle. A thermal cooling system circulates cooling fluid around the inverter package to keep its circuit boards at operating temperature. the inverter produces a great deal of excess heat. A high voltage inverter located next to the traction motor, converts DC voltage to AC voltage for the motor. The traction battery packs located under the passenger seats, store energy as DC voltage. Therefore, EV automakers generally use AC induction motors rather than DC motors. The traction motor must supply high power and speed all while packaged in a tight space. In this way, the electric vehicle accelerates the cruising speed in a manner that drivers of gasoline powered cars are accustomed to. The transmission reduces the speed of the motor and increases the torque. The axis of rotation of the traction motor is parallel to the axis of rotation of the two front wheels. In this diagram, you see a front wheel drive electric vehicle. Some electric vehicles use motor generators that both drive the car and regenerate voltage in the traction battery pack. Instead of a gasoline powered engine to propel the car, you have an electric traction motor. Let's review at a high level the architecture of a battery electric vehicle has shown in the slide.
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