Understanding How EV Motors Work

As electric vehicles (EVs) continue to gain traction in the automotive and overall mobility industries, understanding the basics of EV motors becomes increasingly important. EV motors lie at the heart of electric propulsion systems, making them one of the most pivotal components to understand. In this beginner’s guide, we’ll embark on a journey to demystify the intricacies of EV motors by shedding light on their inner workings, the different types of motors, and their indispensable role in shaping the future of e-mobility.

How EV Motors Work

Electric motors operate on the principles of electromagnetism, with a rotor and stator encased within a housing. When supplied with an electric current, the motor generates a magnetic field that interacts with the rotor’s permanent magnets (always present magnetic field) or electromagnets (require electric current to generate a magnetic field), propelling the vehicle forward with remarkable efficiency and power. 

  • Basic Components: An electric motor typically consists of two main parts: the stator and the rotor. The stator remains stationary and contains coils of wire wound around an iron core. These coils are connected to a power source, usually a battery or a power converter. The rotor is the moving part of the motor and is connected to the vehicle’s drivetrain.
  • Electromagnetic Induction: When an electric current flows through the coils in the stator, it creates a magnetic field around them due to the principles of electromagnetism. This magnetic field is either attracted to or repelled by the magnetic field produced by the rotor, depending on the motor design and the direction of the current.
  • Magnetic Field Interaction: The interaction between the magnetic fields of the stator and the rotor generates a force on the rotor. According to Newton’s third law of motion, for every action, there is an equal and opposite reaction. Therefore, this force causes the rotor to spin.
  • Rotor Movement: As the rotor spins, it drives the vehicle’s drivetrain, which ultimately propels the vehicle forward. The rotational motion of the rotor is transferred to the wheels through a transmission system, which may include gears, shafts, and differentials, depending on the vehicle’s design.

Most Common Types of Electric Motors

There are two types of electric motors, AC and DC, but we’ll be focusing on the two most common types of AC motors. AC motors are often favored in the automotive industry due to their optimum performance. Each motor type and design offers some unique advantages in terms of efficiency, power output, and cost-effectiveness. 

  • Induction Motor: An induction motor generates motion through electromagnetic induction. Simply put, electromagnetic induction is the process by which motion is produced when a magnetic field moves or changes near a wire or a coil of wires. An induction motor is entirely made up of electrical conductive metal, typically copper, on both the stator and rotor.  This makes the induction motor a cost effective motor design.  This is one of, if not the most, common type of electric motor due to its simplicity, reliability, and efficiency. Making it a popular choice in industrial applications. 

 

  • Permanent Magnet Motor: A permanent magnet motor is a type of electric motor that uses permanent magnets to generate motion. Unlike induction motors that utilize magnets as electromagnets (requiring electricity to generate a magnetic field), permanent magnet motors have magnets that always produce a magnetic field. This type of motor is extremely efficient and has a high power density, but is often more expensive in comparison to induction motors.  This type of motor is widely used in the EV space because of its improved efficiency.

 

Most Common Motor Designs

Radial flux and axial flux motors represent two of the most common designs for both induction and permanent magnet motors. The primary differences are in the arrangement of the magnetic flux lines (the paths along which magnetic fields travel) within the motor and how they interact with the rotor and stator components.

  • Axial Flux Motor: This type of electric motor design is characterized by the magnetic fields running along the same direction as the motor’s shaft. This means they flow parallel to the axis of rotation. They’re commonly used in applications where space and weight are important considerations due to their high power density. This type of motor is relatively new among motor designs and therefore has seen slower adoption due to the complexity and cost. As the technology has been better understood and tools are developed to simulate their usage in systems, axial flux motors have the potential to become more widely used. The axial flux motor has a higher energy density compared to other motors — an important consideration in systems where size and weight are important.

 

  • Radial Flux Motor: A radial flux motor is a type of electric motor where the magnetic flux flows radially outward from the center, perpendicular to the axis of rotation. In simpler terms, the magnetic field lines spread out from the center of the motor, like spokes on a wheel. These motors are commonly used in a wide range of applications due to their simplistic design, wide availability, and versatility. 

 

The Future of Electric Vehicle Motors

Electric motors are pivotal in shaping the future of e-mobility due to their inherent efficiency, zero-emission operation, and versatility. Unlike traditional internal combustion engines, electric motors convert a higher percentage of electrical energy into mechanical energy, making them more energy-efficient. This efficiency translates to increased range and reduced energy consumption, which can help address concerns over fossil fuel dependency and environmental impacts. 

The adaptability of electric motors enables their integration into various types of vehicles and mobility platforms. This versatility supports the diversification of e-mobility solutions, catering to different transportation needs and scenarios. Electric motors are one of the main driving forces in battery technology innovations and power electronics which will continue to push advancements in energy storage, charging infrastructure, and overall vehicle performance. Electric motors have been and will continue to be the core component in the world’s transition towards a cleaner, more efficient, and higher performance world.