Drivetrain – The Electric Motor

The most important part in the drivetrain of the electric vehicle, the electric motor is used. It has a long history and has been applied in many other applications as well. The implementation in a vehicle has happened quite early on, but do to the (created) popularity of oil and internal combustion engines, the electric motor was not applied at a large scale back then. With the current process of making everything we do more sustainable, the electric motor gets full attention again as the prime mover in a vehicle.  The very first electric motor was constructed by Jedlik, in Hungary, 1827. It was not very practical and only suitable for demonstrations. Following that, the electric motor was put in a vehicle many years later (1855) after improvements on the design. The electric motor has found many applications since, varying from the powering of fans for cooling, elevators and vehicles.  

The classic distinction between electric motors is in AC and DC types, depending on which type of current is used to power the electric motor. With the development of the brushless DC motor and the stepping motor, this distinction has become less clear; historically a stepping motor was driven by DC and switches, but can now be operated using AC power.

 The materials used to manufacture an electric motor vary per type. For the hybrid Toyota Prius for example, a permanent magnet motor is used, which requires rare earth metals in their magnets. For the GM EV1, the Toyota RAV4 EV and the Tesla Roadster for example, AC traction motors are used which require mostly copper and aluminium. These types require some rare earth metals, but a lot less.

 The main benefit of an electric motor over an internal combustion engine is the efficiency and the torque it can deliver. The efficiency of the motor is defined as the ratio between the output of mechanical power and the input of electrical power (or the energy equivalent of gasoline in case of the internal combustion engine). In an internal combustion engine a lot of energy is wasted as heat which exits the vehicle through the tail pipe. Conventional internal combustion engines would have an efficniency of 30-40%, with current technology perhaps around 50% now. An electric motor has an efficiency of 90% easily, and that is not affected by the speed (RPM) it is operated at. The other huge benefit is the torque. With an internal combustion engine, you first use the clutch so the engine rotates and only after it is from standstill can the engine be used to power the vehicle. The torque is highest at the low speeds and drops down at higher speeds (as does the efficiency by the way). With an electric vehicle and the electric motor, it is just a matter of pressing down the throttle and off you go! There is instant torque at the moment you press down the pedal and the torque is almost constant for all speeds!

An electric motor is not only more friendly for the environment, but is also a lot more fun to drive. It seems therefore fairly obvious they will now take over the lead from the internal combustion engine with all the attention they are getting.