The electric powertrain is the system responsible for propelling your car. While it’s efficient, it’s more complex than a gasoline engine.
The powertrain of an electric vehicle consists of a battery, motor, transmission and controls – with 60% fewer components than its internal combustion engine (ICE) counterpart.
Battery
Electric powertrains are a rapidly-evolving trend in the automotive industry. They offer superior performance and efficiency as well as reduced tailpipe emissions – making them an attractive alternative to gasoline-powered cars for those who want to reduce harmful emissions or live in areas without access to natural gas.
Batteries are an integral component of electric vehicle (EV) powertrain. They supply energy to run a vehicle’s motor for extended periods, enabling drivers to travel without having to stop for fuel or using charging infrastructure. Batteries provide this vital resource.
A battery consists of multiple voltaic cells connected in series by a conductive electrolyte containing metal cations. When these react with both positive and negative electrodes, they produce electrically charged electrons which travel between each cell via the electrolyte.
Under normal operation, a battery’s capacity increases as its chemical reactions inside it speed up and slow down, commonly referred to as the relaxation phenomenon or recovery effect.
Electric vehicles (EVs) utilize two kinds of batteries: lithium-ion (Li-ion) and nickel-metal hydride (NiMH). Li-ion cells are the most popular choice among EVs due to their high energy density – meaning they pack a significant amount of power into a small package.
NiMH batteries, often found in smaller electric vehicles (EVs), offer lower energy density but offer the advantage of being rechargeable faster than Li-ion batteries. Furthermore, NiMH batteries last longer but require more space due to their smaller size.
The lithium-ion battery is the most popular type of battery used in electric vehicles (EVs). Not only does it boast the highest energy density, but it’s also expensive; production requires special materials not found elsewhere.
The electric vehicle powertrain system consists of the battery, DC/DC converters, onboard charger and traction inverter–each housed separately. Recently however, engineers have adopted an integrated design approach which unites these solutions into a single domain controller and power stage, increasing efficiency and dependability throughout the entire electric system.
Motor
Motors are the main source of power for electric vehicles (EVs). They transform electrical energy into mechanical motion and transfer it to the wheels. Different motor types are employed in EVs depending on their intended use.
When selecting the ideal motor for a particular application, there are numerous factors that must be taken into account. These include performance requirements, cost considerations and operating conditions.
In electric vehicles (EVs), two primary motor types are Induction Motors and Synchronous Motors. Induction motors utilize permanent magnets to generate a magnetic field that causes the rotor to rotate. They differ in speed and torque characteristics.
Induction motors offer high starting torque, low noise and a wide speed range – making them the go-to motor type for electric vehicles (EVs).
These motors can be found in a wide variety of vehicles, such as go-karts, cars, trucks, buses, bicycles and motorcycles. Not only are they efficient but also provide great torque at higher speeds.
Synchronous motors use both permanent magnets and excitation windings, which can be placed either on the rotor surface or embedded inside it.
This motor type is commonly employed in electric vehicles (EVs) due to its compact size and ease of control.
When selecting a motor for this application, several PWM methods exist: space vector pulse width modulation (SVPWM), sinusoidal pulse width modulation (SPWM) and six-step voltage (SSV). All these options have their own distinct advantages and drawbacks.
The SVPWM method is the most efficient, as it effectively reduces harmonic distortion. Unfortunately, it does not produce as much flux-weakening as other PWM methods do. Furthermore, this method cannot be applied for all speed settings, thus its control reliability is low.
Comparatively, the SSV method produces low harmonic distortion and achieves good flux-weakening performance; however, it lacks the advantage of high DC bus voltage utilization. Furthermore, selecting an optimal output current for corner speed may prove challenging.
Synchronous motors can be optimized for dynamic performance, such as acceleration slip regulation and anti-lock braking system, using an axial flux PMSM control system. This method has high control robustness and disturbance rejection that is further improved with a fuzzy model predictive control (FMC) algorithm based on a speed loop.
Transmission
The transmission is a mechanical device that transfers rotational power from an energy source, such as an electric motor or internal combustion engine, to the wheels. It often refers to the gears and differential unit responsible for spinning those wheels but also includes other components which help move your car forward or backward.
Electric vehicles differ from gasoline-powered cars in their transmission. Unlike gas-powered cars, which must burn fuel to produce peak torque, electric motors generate full power on ignition and transmit it directly through the gearbox to the wheels. This eliminates acceleration and deceleration spikes like an internal combustion engine (ICE) and makes for much smoother acceleration and deceleration motion.
Typically, electric cars feature a single speed transmission; however, some high-performance models require more revs for optimal power output. Some EVs even boast continuously variable transmissions (CVTs), which enable drivers to access maximum power at any speed.
Unfortunately, CVT systems require mechanical parts which add weight and complexity to electric vehicles (EVs). Furthermore, they take up valuable space within the car, potentially reducing battery capacity or creating weight issues.
ZF, a German auto parts builder, has designed an electric powertrain concept that integrates an electric motor and two-speed automatic transmission in one package. They claim this technology could be applied by automakers to create an EV transmission with both top speed and low-speed capability.
The company claims it can fit a two-speed system into an existing electric vehicle design, at lower cost than traditional gearboxes since there’s no clutch or synchronizers required. Furthermore, they suggest offering various gear ratios tailored for different applications.
This electric transmission can be utilized in a variety of vehicles, but it may be especially advantageous in sports cars and luxury sedans due to its high-performance torque output at various rpms. As such, shifting gears with this EV transmission is seamless and requires no manual intervention on your part.
Controls
Electric powertrains rely on multiple control systems to maintain efficient energy flow throughout the vehicle. The primary control system is called the vehicle control module, which uses inputs from drivers to decide how much torque should be sent to the motor.
This controller is an advanced system capable of controlling the speed, acceleration and power output of a motor. It combines electronics and microcomputers to convert battery energy into usable mechanical energy for use by the motor.
The electric vehicle’s powertrain control systems are designed to work together with its body control modules and other electronic accessories in order for them to run optimally. To accomplish this task, they must exchange information and synchronize with external systems in real-time.
To make this possible, the electric vehicle (EV) powertrain controls must be intelligent and reliable. That is why they are so essential in an EV.
An electric vehicle’s controller is a complex electronic component that oversees the motor and other parts of the vehicle. It assesses how much power different parts require from the inverter and sends that info back to it.
For the motor, the controller uses a Field-Oriented Control algorithm to calculate how much torque and speed is necessary. This ensures that your motor runs at optimal efficiency and performance levels.
Another controller strategy suitable for an electric vehicle (EV) is the optimal operation line (OOL). This approach aims to maximize performance while also minimizing fuel consumption.
In addition to OOL, there are other strategies that can help reduce energy consumption in an electric vehicle (EV). These include transmission gear ratio control, clutch control and engine on/off.
The proposed approach utilizes dynamic programming and supervised machine learning for optimizing a supervisory powertrain control strategy. This framework is designed to automatically retrain the control strategy when a driving task is complete, so that it can adapt according to user specific driving behaviors without human involvement.
Electromate offers a comprehensive selection of motor controllers for Electric Vehicles from leading manufacturers such as Advanced Motion Controls and Kollmorgen. Each controller is backed by rigorous testing equipment including durability, vibration, temperature and noise tests to ensure quality assurance.