High efficiency, cutting-edge performance and environmental friendliness are just some of the advantages that Electric Vehicles (EVs) offer over internal combustion engine vehicles.
While internal combustion engine vehicles have a complex network of fast-moving components to make the vehicle operate.
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Whereas, EVs depend on the simple interaction between the electric motor, electronic control units, and a drastically simplified transmission system.
How do electric vehicles work?
At the heart of an electric vehicle propulsion system lies the electric motor.
The electric motor’s underlying operating principle is based upon an electric current flowing through a wire producing an electromagnetic field around it. When it is wrapped in a coil it temporarily exhibits the properties of a conventional magnet.
This coil, now an electromagnet, is placed in the proximity of another magnet, they will attract or repel each other, creating motion. Electric motors are thus constructed by configuring such magnetic elements to produce a continuous rotational motion.
As such, electric motors consist of two fundamental elements – a stator (stationary element) and a rotor (rotating element) – which work together to convert electric current into kinetic energy.
By using a permanent magnet as the rotor and an electromagnet fed by a variable power supply as the stator, the essential electromagnetic field variation was created without the need for additional parts to ensure continuous motion.
Alas, given that batteries provide DC power supplies, EVs were restricted to the less efficient brushed EM designs until the development of power electronics.
The modern electric vehicle motor
Modern EV development has homed in on three electric motor families that best suit these basic requirements:
AC induction motors:
AC induction motors have been the most widely deployed in a diverse range of applications, especially electric vehicles, and are thus the most mature and proven technology. Additionally, they are inexpensive and extremely reliable. However, their efficiency deteriorates at low load levels and they have a narrow constant power range.
While induction motors provide a considerable step-up in efficiency compared to brushed motors, they still do not provide an ideal solution. This is the result of energy being consumed by theinduction of current in the rotor, which is crucial to produce the induction motor’s electromagneticrotor motion. This current flow also heats the rotor, thus requiring more energy to keep it cool.
AC switched reluctance:
AC switched reluctance motors are also proving to be inexpensive and reliable, as a result of their simple construction. They also benefit from good torque/ speed characteristics with wider constant power range. While electric control units (similar to a computer) permit the use of AC supplies in EV applications, however, both induction motors and switched reluctance motors continue to face difficulty in power control.
Permanent magnet motors provide the highest efficiency levels among electric motor rivals. These motors can be broken down into AC synchronous and brushless DC types depending on the power controller used.
Their advantage next to other brushless designs is that their permanent magnet rotor provides very high flux density without consuming any energy (as in the case of induction motors). Furthermore, the high energy density permanent magnet allows for a very compact motor design. On the downside, however, brushless permanent magnet motors are not cheap since the high energy density permanent magnets must be made from expensive rare-earth metals. Furthermore, they too suffer from a narrow constant power range.
For more information, please read on about the key components of an electric vehicle by clicking the button below.