Electric vehicles are playing an increasingly important role in the mobility solutions of the 21st century, both on a commercial and private level (delivery fleets, transport, etc.).
There are many types of electric vehicles: cars, quadricycles, motorcycles, bicycles or even scooters, which are increasingly present in metropolitan areas and tourist environments.
Categories of electric vehicles
The different categories of electric vehicles are as follows: BEV, HEV, PHEV and FCEV. Below, we explain their characteristics in more detail.
BEV (Battery Electric Vehicle)
Electric vehicles that use batteries, known as BEVs, are all-electric cars. In these cars, propulsion is accomplished using electric motors that use the electrical energy stored in their internal battery system, usually using lithium-ion type technology.
This system is what could be considered a purely electric vehicle but its main feature is that it must be connected to the electricity grid in order to recharge its batteries and thus have sufficient autonomy.
HEV (Hybrid Electric Vehicle) – Hybrid Electric Vehicles
Vehicle types that are known as hybrid-electric (HEV) are called conventional hybrids or also non-plug-in hybrids. This type of vehicle could be considered a mixture between an electric vehicle and a conventional one, since they integrate an internal combustion engine, which uses fuel (gasoline or diesel) and an electric motor system.
The batteries are recharged using the energy generated by the fuel engine and taking advantage of the energy recovered when the vehicle is braked. Operation is mixed, with phases in which electrical energy is used, if there is sufficient energy stored in the batteries, and at other times the combustion engine is used.
PHEV (Plug-in Hybrid Electric Vehicle) – Plug-in hybrid electric vehicles
Plug-in hybrid electric vehicles (PHEV) are a variant of conventional hybrid vehicles that also have energy storage batteries that can be recharged using electrical energy from the grid.
Because they can use electrical energy stored in the batteries, these vehicles have a high range in all-electric mode and also have the position of being able to use the energy stored in the batteries.
FCEV (Fuel Cell Electric Vehicle) – Fuel cell electric vehicles
Fuel cell electric vehicles (FCEVs) are the least developed type of electric vehicle today, although there is increasing research and development in this field. Unlike other vehicles, they use hydrogen as an energy source, and would allow this energy source to be integrated into transport.
These electric vehicles use a hydrogen-powered fuel cell to generate electrical energy that is used to power the electric motor that drives the vehicle. The hydrogen does not generate polluting emissions in this process, so it is an environmentally friendly use, as long as the hydrogen could be obtained in a sustainable way.
Elements of the electric vehicle
An electric car can use different propulsion technologies and usually consists basically of the following elements:
- The internal recharging unit (the external recharging infrastructure is not directly part of the electric vehicle).
- The batteries.
- The conversion systems and inverters for direct current/alternating current (DC/AC) or direct current/direct current (DC/DC).
- The electric motor.
Electric cars have an internal power and charging unit. Its function is to be able to transform into direct current the energy of alternating current coming from the electric network, to be able to charge the battery of the electric vehicle.
The continuous evolution of the capacity of the batteries used by the electric vehicles (20 kWh to 60 kWh) in the last 5 years forces the vehicle manufacturers to make constant improvements in these power control units and to propose new designs of internal filters.
To avoid the emission of harmonics to the electrical network and possible leakage currents in both alternating and direct current.
Batteries
There are many types of batteries, but lithium-ion batteries have become the technology of choice because of their characteristics, which make them ideal: they have no memory, are very durable and can withstand many charging cycles.
Lithium-ion batteries store the energy given to them by the charger (connected to an alternating current network) in the form of direct current.
This main battery is the means by which the whole electric car is powered and therefore, in cars that have a direct current electric motor, this battery is directly connected to the motor.
On the other hand, in the electric cars that have an alternating current electric motor, the battery is connected to an inverter, the equipment that transforms the direct current into alternating current.
Converters and Investors
Converters are equipment that transform the voltage of the electricity supplied by the batteries, generally decreasing its voltage to a level of 12 Volts, the usual operating voltage of the auxiliary elements of the electric vehicle, such as lighting and control systems, among others.
Inverters are used to transform the direct current supplied by the main battery into alternating current, so this equipment allows the electric car’s engine to be powered by alternating current thanks to the use of batteries, which store energy in the form of direct current.
Electric vehicle engines: types, features and benefits
The engine of an electric vehicle is one of the most important elements in its design, operation and functioning, since it determines the existence or not of other components, such as inverters and converters. The motors used in an electric car can be either direct current or alternating current.
Although there are different types of electric motors on the market, they all consist mainly of a stator, the rotor and the housing:
- The stator is the fixed part of the rotating machine, and can be anything from electromagnets to magnetic plates.
- Inside is the rotor, which is the mobile part.
- The two components are surrounded by the metal casing.
These motors can be of various types for each technology, but the most used in electric traction are presented below.
Asynchronous or induction motors
The main characteristic of asynchronous or induction motors is that the rotation of the rotor does not correspond to the speed of the magnetic field produced by the stator and all these components are inside the corresponding housing, which has the task of protecting and containing them.
This type of motor is made up of a rotor that can be either squirrel-cage or winding type, and has high efficiency, low cost and high reliability. However, it has a low power density (low power for its size) and low starting torque. Even so, it is the most widely used engine in the electric vehicle industry; for example, Tesla incorporates this type of engine into its vehicles.
Permanent magnet synchronous motor
Permanent magnet synchronous motors have a constant speed of rotation. There is a model called the in-wheel motor that can be placed directly on the shaft, with the resulting savings in space and weight.
These motors are expensive, but have a wide range of use in electric and hybrid vehicles. Nissan, Opel, Lexus or Toyota, among others, opt for this type of engine.