Monthly Archives: May 2023

Journey to the Centre of an EV – How Traction Inverters and DC-DC Converters Evolved Over the Years?

The journey of traction inverters in electric vehicles (EVs) has been a fascinating one. From the early days of simple DC-DC converters to the modern, sophisticated, and highly efficient inverters, the development of these power electronics has played a crucial role in making EVs a viable transportation solution. In this article, we will explore the journey of the traction inverter and DC-DC converters in an Electric Vehicle, from early developments to the present day.

Early Developments: DC-DC Converters

The first electric car of the 19th century relied on a series of batteries to provide power to the motor. However, these batteries were not powerful enough to generate the kind of speed and acceleration required for practical use. As a result, the first inverter-based electric cars were developed in the 1960s, which used silicon-controlled rectifiers (SCRs) to convert DC to AC power.

SCR-based inverters were large and heavy, and they had limited efficiency. However, they represented a significant improvement over the previous designs, and they paved the way for further developments in the field.

The earliest Electric Vehicles were powered by DC motors, and the power for these motors was supplied by DC-DC converters. These converters would take the battery voltage, usually 12V, and step it up to the required voltage for the motor. This approach was simple and effective, but it had some limitations.

First, it was inefficient, as the converter would waste a significant amount of energy in the form of heat. Second, it did not allow for regenerative braking, as the converter was not designed to handle the reverse flow of current.

Introduction of AC Motors and the Need for Inverters

With the introduction of AC motors in EVs, a new type of power electronics was required to drive them. AC motors require an alternating current to function, while batteries provide direct current. To convert the DC voltage from the battery to AC voltage, an inverter is required.

The first generation of inverters used a simple pulse-width modulation (PWM) technique to convert the DC voltage to AC voltage. While this approach was more efficient than the DC-DC converters, it had its share of limitations. The PWM technique resulted in a high level of harmonic distortion, which caused motor noise and reduced efficiency.

Improvements in Inverter Technology

To address the limitations of the first-generation inverters, significant improvements were made in the design and construction of the inverter. The second-generation inverters used more sophisticated control algorithms, such as space vector modulation (SVM), to reduce the harmonic distortion and improve the efficiency of the inverter in an Electric Vehicle.

These inverters also introduced the concept of regenerative braking, which allowed the motor to function as a generator, and the energy recovered during braking could be stored back in the battery.

Development of Power Electronics

The development of power electronics in the 1980s and 1990s led to significant improvements in the performance and efficiency of traction inverters. Power electronics allowed for the development of smaller, lighter, and more efficient inverters, which made it possible to build more practical electric vehicles.

The use of insulated-gate bipolar transistors (IGBTs) and metal-oxide-semiconductor field-effect transistors (MOSFETs) made it possible to switch the inverter at high frequencies, which improved efficiency and reduced size and weight. Additionally, the use of digital signal processors (DSPs) allowed for more precise control of the inverter, which improved performance and reliability.

The Emergence of Hybrid Electric Vehicles:

The emergence of hybrid electric vehicles (HEVs) in the 1990s and early 2000s led to further advancements in the design of traction inverters. HEVs used a combination of electric and combustion power to improve efficiency and range, which required more advanced inverters that could switch between the two power sources seamlessly.

The use of multi-level inverters made it possible to switch between the DC battery and AC generator seamlessly, which improved the efficiency and reliability of HEVs. Multi-level inverters used multiple switches to generate a staircase waveform that approximated a pure sine wave, which reduced harmonic distortion and improved efficiency.

Present-Day Innovations

Today, traction inverters continue to evolve, with a focus on improving efficiency, reducing size and weight, and increasing reliability. Some of the most notable innovations in recent years include:

• Silicon Carbide (SiC) Power Electronics: SiC power electronics offer higher efficiency and lower losses than traditional silicon-based electronics. SiC-based inverters can operate at higher temperatures, which reduces the need for cooling and allows for more compact designs.
• Integrated Power Modules: Integrated power modules combine the inverter, motor control, and other components into a single package. This reduces the size and weight of the inverter and improves reliability by reducing the number of connections and components.
• Wide Bandgap (WBG) Power Electronics: WBG power electronics, such as gallium nitride (GaN) and SiC, offer higher switching speeds and lower losses than traditional silicon-based electronics. WBG-based inverters can operate at higher frequencies, which reduces the size and weight of the inverter and improves efficiency.
• Digitalization: The use of digital technology in inverters allows for more precise control and monitoring of the system. Digital inverters can adjust their output in real-time based on changes in driving conditions, which improves efficiency and performance.

Current Trends in Inverter Design

The current trend in inverter design is to use wide bandgap (WBG) semiconductors, such as SiC and gallium nitride (GaN), to improve the efficiency and performance of the inverter.

WBG semiconductors have several advantages over traditional Si technology, including higher switching frequencies, higher operating temperatures, and reduced switching losses. This allows for higher power densities, smaller form factors, and improved thermal management.

Another trend in inverter design is the integration of the inverter with the motor, known as an Integrated Motor Drive (IMD). An IMD combines the inverter and motor into a single unit, which reduces the number of components and simplifies the design. IMDs are also more efficient than separate inverters and motors, as there is less power loss during the conversion process.

The Road Ahead

The journey of electric vehicles has been marked by significant improvements in efficiency, size, weight, and reliability. The early developments of SCR-based inverters in the 1960s were followed by significant advancements in power electronics in the 1980s and 1990s. The emergence of hybrid electric vehicles in the 1990s and early 2000s led to further advancements in the design of traction inverters.

As we continue to see improvements in the design of traction inverters, it is likely that we will see further advancements in the performance and efficiency of electric vehicles. This will be driven by ongoing innovations in power electronics, digital technology, and other related fields.

Finally, the success of electric vehicles will depend on a range of factors, including advances in battery technology, improvements in charging infrastructure, and changes in consumer behaviour. However, the journey of the traction inverter in an EV is a critical part of this story, and it will continue to play a key role in the ongoing evolution of electric vehicle technology.

Motor Controllers: Making Automobiles Much More Than a Set of Wheels

With electric vehicles making their presence felt in the global automotive market, the discussion on electric motors has shifted completely towards the EV powertrain. Understandably so, since electric motor and motor controllers have replaced the mighty internal combustion engines that have been driving automobiles since their invention.

However, electric motors have also been widely used in hundreds of automotive components. The use of small motors in automobiles can be traced back to the early 20th century.
 

The Ford Model T, for example, used a small electric motor to power its horn. Over the years, the use of small motors and actuator systems has become more prevalent in automotive design. Today, these systems are used in almost every aspect of automotive operation, from power windows to engine control.

As the modern automobile is embracing automation in every way possible, the role of electric motors has become even larger. For instance, your regular seats have become automated and can now adjust themselves to your favorite seating position.

Even the humble parking brake now comes in its electronic avatar. Several technologies are at play making these automations possible, but at the core of it all is an electric motor and a motor control system. These are small motors that go unnoticed but play a huge role in ensuring comfort and ease of driving.

All of this sounds great, but why are we suddenly discussing small motors and motor controllers?

The short answer to the question is that these motors are quite important, and their advancement helps build better automobiles. The longer answer to the question is what we will explore in the subsequent sections of the blog.

So, let’s start by asking the question,

How Do Small Motors and Actuator Systems Impact Overall Driving Experience?

Small motors and actuator systems are ubiquitous in a vehicle and play a crucial role in the overall driving experience. These systems are responsible for controlling various functions such as windows, mirrors, doors, and seats. They also play a critical role in safety features such as airbags, ABS brakes, and stability control systems.

At every moment spent in a modern vehicle, there is some sort of human interaction with a motor. A driver using the electronic steering wheel is being assisted by a small motor driven by a smart motor control system. The algorithm embedded inside the motor controller has been designed to understand the optimum amount of torque provided to the steering wheel.

Here are some ways in which small motors and actuator systems impact the driving experience:

• Enhanced comfort and convenience: Small motors and actuator system allow for easy adjustment of seats, windows, and mirrors, making it easier to find a comfortable driving position. This enhances the overall driving experience by reducing fatigue and making long drives more comfortable.
• Safety of the vehicle occupants: Actuator systems such as airbags, ABS brakes, and stability control systems are essential safety features in modern automobiles. They use small motors to deploy the airbags quickly and accurately or activate the braking system, enhancing safety and reducing the risk of accidents.
• Overall vehicle performance: Small motors and actuator systems are also critical to the performance of the automobile. For example, the engine control module uses small motors to control the amount of fuel injected into the engine, ensuring optimal performance and fuel efficiency.

Looking at the functionality perspective of the motors alone will not give a clear picture of how they are actually able to perform their task. Its imperative that we delve a little deeper and understand,

How Control Algorithms and Application Programs Work Together to Drive Actuator System?

Let’s take an example of a seat control ECU. The electric motor that moves the seat is mostly a DC motor driven by a motor control system. If we go into technical aspects of a motor controller, especially its software, there are two major components- control algorithm and applications programs.

1. Control algorithms: Control algorithms are sets of rules or instructions that govern how the motor operates. They are typically implemented using software and run on a microcontroller or other digital processing unit. Control algorithms take input from various sensors in the vehicle, such as the accelerator pedal position, engine speed, and vehicle speed, and use this information to adjust the motor’s operation accordingly.

   The most common control algorithms used to drive automotive motors are Field control algorithm and field weakening control.

2. Application programs: Application programs are software modules that interact with control algorithms to achieve specific functions, such as controlling the engine speed, or the torque delivered to the wheels. Application programs may also incorporate other features such as fuel injection management, emissions control, and other functions that help to optimize the motor’s performance.

Taking the example of a seating control ECU again, some of the common application programs are:

• Soft Start/Stop: Soft start/stop is an application program that provides a smooth and gradual acceleration and deceleration of the seat motor. It is designed to minimize jerky movements and provide a more comfortable ride.
• Seat Memory: This application allows the driver and passengers to store and recall their preferred seating positions. This feature is commonly used in vehicles with multiple drivers or passengers to ensure that the seat position can be quickly and easily adjusted to the user’s preferences.

Similarly, for an electronic power steering, the application programs that work together with motor control algorithms comprise:

• Variable steering assist: Variable steering assist is an application program that adjusts the level of assistance provided by the EPS system based on the vehicle speed, steering angle, and other factors.
• Lane keeping assist: Lane keeping assist is an application program that uses sensors to detect the vehicle’s position within the lane and provides steering assistance to keep the vehicle centered in the lane.

The amazing things an actuator system in an automobile performs are only due to the sophisticated control algorithms that work in tandem with advanced application programs.

Conclusion

Whether it is comfort, convenience, safety or performance, there is mostly an electric motor or motors helping to achieve them. The automotive industry as a whole has taken immense strides in advancements in the development of motor control algorithms as well as applications to support modern features.

However, the dream of a fully autonomous car or migration to vehicles with fully automated functions takes more than just a few strides in motor controller technology. The combined use of AI, machine learning, sensor technologies, semiconductors, etc. is going to take us where we visualise the automotive industry to be in the future.