What is an electric car motor made of?
An electric car motor consists mainly of a rotor and a stator. The rotor is the moving part of the motor, generally consisting of a magnetic core surrounded by coils of copper wire.
The stator is the fixed part of the motor that surrounds the rotor and is also made up of copper wire coils arranged around it.
When electric current flows through the stator coils, it generates a magnetic field that turns the rotor. To regulate the speed and torque of the motor, an electronic switch or controller is used to adjust the amount of current sent to the stator coils.
The casing, which forms the external structure of the motor, houses all the internal components and protects the motor from external elements.
Depending on cooling requirements, some electric motors can be fitted with cooling systems such as radiators or fans to remove the heat generated during operation.
What is the difference between an internal combustion engine and an electric motor?
The difference between an internal combustion engine and an electric motor in a electric car lies in the way they operate and the energy source they use.
- Internal combustion engine:
- The heat engine converts heat energy into mechanical energy.
- It works by burning fuel (petrol or diesel) in the cylinders.
- Heat engines generally have a maximum speed of less than 8,000 revs per minute.
- They have a high power and torque range, but only over a small rpm range.
- They emit noise and vibrations when in operation.
- Their maintenance is more complex because of the sensitive mechanical parts and liquids (oil, fuel) to be managed..
- Electric motor:
- The electric motor transforms electrical energy into mechanical energy and vice versa.
- It works thanks to the electromagnetic force generated by magnets.
- There are three types of electric motor: direct current, synchronous alternating current and asynchronous alternating current.
- The electric motors can reach high speeds, sometimes up to 16,000 revs per minute, while maintaining a good level of torque and power throughout this range.
- They are silent, require little maintenance and have fewer sensitive mechanical parts.
- Electric cars use DC or AC motors.
Basically, the internal combustion engine uses fuel combustion, while the electric motor runs on electricity.
The electric cars prefer electric motors for their efficiency, silence and ease of maintenance.
How does an electric motor work in an electric vehicle?
An electric motor in an electric vehicle works by converting the electrical energy stored in the battery into electrical energy. battery of the vehicle into mechanical movement to propel the wheels. Here are the main stages in the operation of an electric motor in an electric vehicle:
- Power supply Electricity is supplied by the vehicle's battery. This battery usually stores electricity in the form of direct current (DC), but it can also be used to store energy in the form of alternating current (AC), depending on the design of the system.
- Conversion to alternating current If the battery supplies electricity in the form of direct current (DC), a direct current to alternating current (DC-AC) converter is used to transform the electricity into alternating current (AC). Most electric motors use alternating current to operate.
- Motor activation Once the electricity has been converted into alternating current, it is sent to the electric motor. The motor is equipped with copper wire coils arranged around a stator and a rotor, usually made up of permanent magnets. When alternating current is applied to the stator coils, this creates a rotating magnetic field.
- Rotating the rotor The rotating magnetic field induces a magnetic force in the rotor, causing it to rotate. This rotary motion is transmitted to the vehicle's wheels via an appropriate transmission system, such as a differential and drive shaft, which ultimately propels the vehicle forward.
- Speed and torque control The electric motor can be electronically controlled to adjust rotor speed and torque output. This optimises the vehicle's performance under different driving conditions, such as acceleration, braking and cruising speed.
Electric car engine: what are the benefits?
Performance and energy efficiency
Electric car engines offer several advantages over traditional internal combustion engines in terms of performance and energy efficiency. Here are some of these advantages:
- High energy efficiency Electric motors convert a greater proportion of electrical energy into motion than internal combustion engines, which dissipate a large proportion of energy in the form of heat.
- Instantaneous torque Electric motors: Electric motors produce maximum torque from start-up, delivering fast, smooth acceleration without the ramp-up time required by internal combustion engines.
- Rapid response Electric motors react quickly to commands, resulting in a better driving feel and immediate throttle response.
- Reduced maintenance Electric motors have fewer moving parts and fewer components subject to wear than internal combustion engines, reducing maintenance requirements and associated costs.
- Silent operation Electric motors are much quieter than internal combustion engines, offering a quieter driving experience and reducing noise pollution.
- No local broadcasts Electric cars produce no harmful tailpipe emissions, which helps to improve air quality in urban areas and reduce greenhouse gas emissions.carbon footprint particularly when they are powered by renewable energy sources.
- Regeneration of energy during braking Braking energy recovery systems convert some of the car's kinetic energy into electrical energy, which can then be fed back into the battery to boost the car's fuel consumption.autonomy of the vehicle.
- Design flexibility Electric motors are more compact and can be arranged more flexibly in a vehicle, giving designers more freedom to create innovative interior layouts and optimise available space.
Fewer moving parts
With fewer moving parts than internal combustion engines, electric car engines offer greater reliability, reduced maintenance requirements, simpler design and a quieter driving experience.
By eliminating the complexity of piston and valve systems, electric cars benefit from a more efficient and sustainable alternative for vehicle propulsion.
Electric battery longevity
The longevity of an electric car battery depends on a number of factors, including battery technology, charging conditions, driving habits and maintenance. Modern lithium-ion batteries are designed to last several years with proper use and maintenance, often covered by warranties of up to 8 years or 160,000 kilometres.
Manufacturers and drivers can adopt practices to extend battery life, such as avoiding repeated full charge cycles and maintaining an optimum charge.
If the battery is damaged, certain replacement or repair options can extend the useful life of the electric vehicle.
Read on: Range, power, battery: how does an electric car work?
What are the different types of electric car motors?
Direct current motors
Direct current (DC) electric motors are electrical machines that convert electrical energy into mechanical energy. They are powered by a DC power source, such as a battery or rectifier. DC motors are used in a wide variety of applications, from small electronic devices to large electric vehicles.
The operating principle of a DC motor is based on the interaction between a magnetic field and a current-carrying conductor. The magnetic field is created by permanent magnets or electromagnets.
The current-carrying conductor is usually wound around a soft iron core. When current flows through the conductor, it creates a magnetic field that interacts with the magnetic field created by the permanent magnets or electromagnets. This interaction creates a force that turns the motor's rotor.
Alternating current motors
The advent of new advances in power electronics has made it easier to integrate AC motors into electric vehicles. To power asynchronous and synchronous motors efficiently, a system must now include a three-phase inverter between the battery and the motor. This inverter must be capable of switching the current in both directions, allowing the machine to be used in generator mode during deceleration.
To control these motors, two key parameters need to be regulated: the voltage and frequency of the AC signal supplied by the inverter. To adjust the frequency, simply control the six switches with a variable frequency. As for the voltage, the inverter must also incorporate a pulse width modulation (PWM) function to regulate it effectively.
The variable reluctance motor
This motor is based on the reluctance principle, with a rotor made entirely of sheet metal and windings located in the stator. The main advantage of this type of motor is its low losses in the rotor, with a minimal amount of induced current and relatively low bearing temperatures.
However, despite its attractiveness in terms of cost and simplicity of manufacture, this motor presents challenges, particularly in terms of complex control, non-sinusoidal currents, reduced air gap and a specific inverter structure (in 4 or 6 phases) specific to this technology. In addition, issues such as the management of generated noise and significant torque oscillations at low speeds must be taken into account.
The asynchronous motor
In this type of motor, the stator is supplied with three-phase sinusoidal currents, which create a rotating magnetic field. This magnetic field induces currents in the rotor, causing it to rotate at a slightly lower speed than the rotating stator magnetic field. The difference in speed between these two elements is called slip, which is the main weakness of asynchronous motors: the greater the difference, the lower the motor's efficiency.
This type of motor operates without brushes or magnets and is fitted with a speed sensor. Although its torque dynamics are less dynamic than those of a machine with magnets, its control is simpler than that of synchronous machines. Asynchronous motors offer satisfactory efficiency at low loads, but require a small air gap, which makes them unsuitable for use in wheel motors. They generate significant losses at high torque levels and low speeds (due to rotor magnetisation) and tend to be bulkier and heavier than magnet machines.
The synchronous motor
Synchronous motors, characterised by zero slip, are currently attracting the attention of electric vehicle manufacturers because of their superior performance in terms of torque/weight ratio, power density and efficiency. These motors fall into two main categories: wound motors and permanent magnet motors.
The wound synchronous motor uses a rotor winding to generate the magnetic field, offering a torque density similar to asynchronous motors. Its control is simpler than that of permanent magnet motors, involving regulation of the rotor field via a low-power electronic regulator and brushes to carry the current to the rotor. Although it has low part-load losses and good efficiency at high load, it takes up more space and offers lower torque dynamics than magnet motors.
Permanent magnet synchronous motors, on the other hand, do not require a rotor winding, which makes them lighter and free of joule losses at the rotor, while stator losses are easier to evacuate. These motors offer maximum mass torque for radial flux machines, high torque dynamics and very fast response times.
However, their control is more complex with sinusoidal currents and a position sensor, and they have significant losses at partial load and high speed. Their cost is also higher due to the price of NdFeB magnets, which account for around 30 % of the total manufacturing cost.
Comparison table between the different types of electric motor
| Direct current machine | Wound synchronous machine | Magnet machine | Reluctance machine | Asynchronous machine | |
|---|---|---|---|---|---|
| Compact | - | + | ++ | + | - |
| Low-speed losses | - | + | ++ | + | - |
| High-speed losses | + | ++ | - | ++ | ++ |
| Acoustics | + | + | + | - | + |
| Reliability | - | + | ++ | ++ | ++ |
| Industrial maturity for automotive traction | ++ | + | ++ | - | + |
| Simple to manufacture | - | - | + | ++ | ++ |
| Cost | - | + | - | ++ | ++ |
Conclusion
In conclusion, electric motors are revolutionising automotive mobility thanks to their efficiency, durability and reduced environmental impact.
With constant innovation and the support of electric mobility experts like Beev, thehe future promises electric vehicles more efficient and more sustainable.
Ready to go electric? Contact Beev today to find out more!
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