This page was created by E-LIX Elektromobile GmbH. All statements without guarantee.
drive
The drive of an electric vehicle can be the same as with the conventional one
Vehicles can be divided into many categories. But they work
all based on the same principle (shown here on the right).
The electrical energy is stored in the battery as direct current (DC).
In an internal combustion engine, the power electronics would be the carburetor or
the injection. It turns direct current (DC) into the necessary
Three-phase current (three-phase alternating current) and doses this according to specifications
of the driver. The VCU processes these specifications: Using the data
the battery as well as the data of the rest of the vehicle calculates this
the required power or the torque and the speed and
passes these specifications on to the power electronics.
The biggest differences in the drive are with the motor: AC asynchronous motor, AC synchronous motor, several motors, wheel hub motor, etc ...
The AC asynchronous motor is the simplest construction. Here the windings are firmly attached to the housing on the outer wall of the motor (stator). Inside is the rotating axis (rotor), which is made of magnetizable material. The different energization of the coils induces a current in the rotor. The stature and the rotor then repel or attract each other through magnetic forces.
The asynchronous motor is completely maintenance-free and robust. In addition, it can briefly deliver 5 times its nominal output. The efficiency changes depending on the speed and load, is roughly just over 90%.
The AC synchronous motor does not work via induction, because very strong magnets are built in here, which react directly to the magnetic forces of the coils. There are again different variants: external rotor and internal rotor, external excitation, etc ... The synchronous motor is also maintenance-free and has a higher degree of efficiency than the asynchronous motor. Due to the variable design, the synchronous motor can also be used as a wheel hub motor.
The DC motor with brushes is hardly used in electromobility because it is very maintenance-intensive.
The principle of multiple motors is very popular with more expensive electric cars. On the one hand, both axles can be controlled independently of each other and ultimately result in a super all-wheel drive, on the other hand, motors with different torque characteristics or gear ratios can be installed, whereby the torque is better distributed over the speed.
The torque of an electric motor is crucial for the propulsion of the vehicle. Electric motors have a different torque characteristic than internal combustion engines. The torque is applied from speed 0 and remains constantly high up to a certain speed, then drops linearly. With the correct design of the electric motor, a gearbox is not necessary.
Recuperation is a major advantage of the electric drive. Every electric motor can also be operated as a generator. When "braking", the vehicle's kinetic energy can be fed back into the battery. This also protects the brakes.
The power electronics are also an important part of the drive. However, there are no different types here. The power electronics must always be adapted to the motor in order to achieve the best possible result. In simpler applications with low battery voltage, the VCU and power electronics are often merged, resulting in a compact design. These are then called motor controllers or simply controllers.
The details of the electric drive are of course much more complex, but thanks to components that have already been developed, they are simpler than the combustion drive. In addition, there is the very high efficiency of 80% -90% (combustion engine comparatively below 25%) and the lack of wear. The driving comfort is also pleasant, there is no engine noise, no vibrations and the recuperation can also be used to brake with the accelerator pedal.