 Electric motor 5
A distinction is made between electric motors and generators. The former convert electrical energy into kinetic energy, while the latter does the exact opposite. Electric cars contain motors that can be switched between the
two modes. They can initially generate propulsion and then, during a gentle braking maneuver, simply reduce the vehicle's speed while simultaneously generating electricity. Of course, the same amount of electrical
energy is never returned as was used for propulsion.
The machine becomes a motor when speed and torque are in the same direction, and a generator when their directions are opposite. The torque tends to impede the rotational movement, typical of a braking process.
Incidentally, both processes generate heat, energy that is referred to as lost energy because it has been converted into thermal energy.
The motors for an electric drive always convert electricity into rotational kinetic energy, generating torque that is transferred to the drive axle. In this case, we are dealing with two masses: that of the rotor in the electric motor
and that of the entire vehicle that is to be driven. The former is very small in this ratio. Even if the electric motor were to be engaged and (in exceptional cases) it would be a fluid coupling, the connection must at some point
be considered rigid.
If we also assume a constant processing of electrical energy into kinetic energy, we can determine the efficiency by dividing the energy output by the energy input. This also makes the energy chain in electric cars
increasingly important, because it also determines the core problem of electric drive systems: range.
In addition to the required energy, the mechanical drive power is the primary consideration in an electric car. Positioning within such a vehicle, however, plays a subordinate role. Even the question of front or rear engine
placement, always considered important in combustion engines, is irrelevant here. The position of the batteries appears to be much more important, also due to their weight. The actual electric drive seems to have been
added later, usually at the rear in two-wheel drive systems.
Currently, the single-speed transmission appears to dominate. This is due to the significantly more consistent torque delivery compared to a combustion engine. However, if the center of interest is to be more focused on
efficiency again, several gears could be useful to operate the electric motor optimally. A gear ratio will always be necessary due to the different speed requirements of the electric motor and the drive wheels.
The technology in electric cars is based on so-called brushless motors. The rotary motion generated by an electric motor is only possible when two magnetic fields intersect. One of the two must be electromagnetic;
previously, this was always the rotor. For this purpose, electrical energy was usually supplied to it via two carbon brushes. The motors were prone to wear and tear and heavy.
Brushless motors have permanent magnets in the rotor that don't require any power. They are always powered by a type of three-phase current, which is why they have more than two leads. They usually require a complex
electronic controller, which may be one reason why they were relatively late to gain a foothold in model making. This is another reason why such motors are more expensive. For example, the motor and controller in
modern washing machines often cost about the same as spare parts. However, thanks to new battery technologies, model aircraft, for example, can now be sensibly equipped with electric motors.
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