How does an electric car motor work? — codeitsez
By: Diogo Susano Delgado
Tags: Electric, Motor, Cars, Electric Vehicles, Electric Car

TYPES OF ELECTRIC MOTORS

DC brush motor

The brushed DC motor is a motor powered by direct current (DC) from a battery or some other DC source. It has two elements: the first is the stator — fixed part of the motor — which consists of magnets; the second is the rotor — the rotating part of the motor — which has an electric coil inside.

The magnets inside the stator generate a magnetic field between the north and south poles; when the battery transfers energy to the rotor, the electric current that passes through the coils generates a magnetic force with poles inverted in relation to the stator, producing torque, which forces the rotor to rotate to try to align the poles.

These engines are generally used in cars to open and close electric windows and to retract and expand the mirrors.

Induction motor

Induction motors are considered the most common and best cost-effective on the market. They are alternating current (AC) motors and do not need permanent magnets; instead, the magnetic field is produced by the electric current that passes through the coils fixed to the stator. If an alternating current is connected to the stator, the magnetic field will also be alternated.

The control of this engine is simple and they do not need much maintenance. They are more expensive than DC motors and have low starting torque, but are widely used among manufacturers of electric motors, especially for high-performance electric cars.

In the magnetic field created by the coils in the stator it will induce voltage and current in the rotor winding. Hence the name of the motor — induction. This induction will cause the rotor to produce its own magnetic field which will automatically try to align itself with the magnetic field of the stator. As the stator generates an alternating magnetic field, the rotor will rotate so that its magnetic field tries to follow the stator field.

Electric car models that use this type of motor: Tesla Model S, Tesla Model X

PERMANENT SYNCHRONOUS MOTOR

Permanent magnet motors are also known as synchronous motors, since the rotor rotates at the same speed (synchronized) as the rotating magnetic field; different from the induction motor that rotates at a lower speed than the field. If we build a permanent magnet motor, it will no longer be necessary to induce a magnetic field in the rotor, thus preventing losses and heating in the rotor. In addition, they can offer the same benefits as the induction motor including improved efficiency, high torque at low speeds, as well as being compact and lighter.

This type of motor is commonly used in industry when a mechanism with constant speed and high precision is needed, such as robots, instrumentation, machines and process control. It consists of a coiled stator, usually three-phase winding, and a rotor made up of a magnet.

When the stator winding is energized by an external source, a rotating magnetic field is created at synchronous speed. As the rotor has a permanent magnet, it has its own magnetic field, and when interacting with the stator’s magnetic field the opposite poles of the fields will attract and align themselves causing the rotor to rotate synchronously at the same speed as the rotating field.

RELUCTANCE MOTOR

The reluctance or stepper motor, as it is also known, is one of the electric motors that has been gaining popularity recently and seems to be able to bring together the best of both worlds. It spins at synchronous speed (the rotor spins at the same speed as the rotating magnetic field of the stator) while combining the advantages of permanent magnet and induction motors — robust and fault-tolerant as well as induction, and compact and efficient like permanent magnet .

Its rotor does not have windings like other types, but consists of a set of ferromagnetic blades arranged side by side, and configured in three shapes, as shown in the figure. The stator is similar to the previous ones, wound and with three-phase windings. The reluctance motor operates in the same way as the permanent magnet motor; the stator is powered by an external source generating a rotating magnetic field, while the rotor tends to align synchronously with the stator field, causing it to rotate.

This type of engine can deliver high power at a low cost, making it very attractive for various applications. However, some problems associated with control, manufacturing and low power factor prevent it from being widely used for electric vehicles.

ENGINE CONFIGURATION IN THE ELECTRIC CAR

In simple configuration, only one engine is used, and it can move the front or rear axle.

With the two engine layout, configuration can be done in several ways. One option is to use one of the engines for front-wheel drive only, while the other engine drives the rear axle. Another option is the use of both engines on the front or rear axle, thus providing greater torque, compared to the configuration of a single engine. As an alternative, the engines can pull the wheels, front or rear, independently, ensuring greater control of the car when cornering. Although most electric vehicle manufacturers mainly adopt the single engine layout, the dual engine configuration has been used for models with high torque capacity.

Going beyond one or two engines, one can still think of the concept of having independent engines to move each of the four wheels of the car. This shape is achieved by placing the motors directly on the wheels, and these may or may not be engaged. The gearless option has the ability to improve the overall efficiency of the transmission, however it makes the control more complex, which requires a more elaborate system.

Advantages and disadvantages

On the one hand, one of the great advantages of using the electric motor in vehicles is the free emission of polluting gases, contributing to the reduction of air pollution levels. On the other hand, as these engines are mainly powered by the battery bank, they take a certain time to be recharged and the cars cannot be used while the battery is being recharged in the socket.

What are the differences between an electric motor and an internal combustion engine?

The principle of converting energy to mechanical movement is completely different. While an internal combustion engine relies on thermodynamics to burn fuel, electric motors make this conversion by taking advantage of the electromagnetic forces generated when an electric current passes through a magnetic field. An internal combustion engine has a crank mechanism (cylinders, pistons, valves, crankshaft, etc.), while inside an electric motor we find nothing more than a stator and rotor (and their mutual interaction) to propel the vehicle. This electric motor can act as a generator and, when it locks or slows down, the energy can be directed back to the battery, recharging it.