In the relentless pursuit of sustainable transportation solutions, the automotive industry has witnessed remarkable advancements over the years. One such breakthrough that has transformed the landscape of electric vehicles (EVs) is the development and application of Brushless DC Motors (BLDC motors).
A Brushless DC Motor, also known as an electronically commutated motor (ECM), is a type of synchronous electric motor that operates using direct current (DC). Unlike traditional DC motors, BLDC motors do not rely on brushes and commutators for the flow of electric current to the rotor. Instead, they utilize electronic controllers to switch the currents in the stator windings, resulting in a more efficient and maintenance-free design.
A BLDC motor consists of the following main parts:
- Stator: The stationary part of the motor, containing electromagnets (coils of wire wound around iron cores) that generate a magnetic field.
- Rotor: The rotating part of the motor, containing either permanent magnets or electromagnets that interact with the stator's magnetic field to produce motion.
- Hall Effect Sensors: These sensors are placed on the stator to detect the position of the rotor's magnets. They provide feedback to the motor controller for proper commutation.
- Electronic Motor Controller: The motor controller is an electronic circuit that interprets the Hall effect sensor feedback and controls the current flowing through the stator windings to achieve smooth rotation.
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A BLDC motor, or Brushless Direct Current motor, is a highly efficient electric motor that operates without brushes. Its design includes a rotor with permanent magnets and a stator with coil windings, generating motion through magnetic interaction. The absence of brushes results in improved efficiency and reduced maintenance requirements. One of the key advantages of BLDC motors is their ability to offer precise speed control, making them ideal for applications where accurate motor speed regulation is crucial.
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There are two different configurations of BLDC motors:
- Inrunner BLDC Motors: In an inrunner BLDC motor, the rotor is located inside the stator. The coils are wound around the stator, and the permanent magnets are fixed to the rotor, which is the central part that spins. When the motor is energized, the rotor rotates within the stationary stator. Inrunner motors typically have higher rotational speeds and lower torque compared to outrunner motors. They are commonly used in applications where high rotational speeds are required, such as cooling fans and some industrial applications.
- Outrunner BLDC Motors: In an outrunner BLDC motor, the rotor is located on the outside, surrounding the stator. The stator is typically fixed at the center, and the rotor, with permanent magnets, rotates around it. Outrunner motors have a stationary outer casing and achieve motion by spinning the outer part of the motor. These motors tend to have lower rotational speeds but higher torque compared to inrunner motors. Outrunner motors are often used in applications where higher torque is necessary, such as in electric scooters, electric skateboards, and some small electric aircraft.
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To regulate BLDC motors, electronic motor controllers are employed. These controllers manage the flow of current to the motor coils, controlling the motor's speed and direction. The continued development and integration of BLDC motors play a vital role in advancing electrification and automation across different sectors. BLDC motors exhibit remarkable versatility, finding applications in diverse fields, from space missions to everyday household appliances like washing machines. Notably, the electric vehicle (EV) industry has also recognized the immense potential of BLDC motors and begun to embrace them for powering their vehicles, harnessing their numerous benefits in this innovative and environmentally conscious sector.
The precise electronic control of BLDC motors enables fine-tuning of torque and speed, leading to improved traction control, stability, and overall driving performance. BLDC motors boast higher efficiency compared to traditional brushed DC motors and even some induction motors. Their precise electronic commutation minimizes energy losses, allowing for improved range and battery life in electric vehicles. Also, BLDC motors exhibit a superior power-to-weight ratio, making them an ideal choice for electric vehicles that require lightweight and compact components to enhance performance and overall efficiency. The absence of brushes in BLDC motors reduces wear and tear, leading to longer lifespans and lower maintenance requirements. This characteristic is particularly advantageous for electric vehicles seeking to minimize operational costs and enhance reliability. BLDC motors can be operated in reverse, allowing electric vehicles to employ regenerative braking. During deceleration, the motor functions as a generator, converting kinetic energy into electrical energy, which is then stored in the vehicle's battery for future use.
In this article, we will explore the patent landscape and delve into the details of how the BLDC motor industry is continuously evolving to meet the requirements of the booming EV sector.
1. Efficient Motor Design:
BLDC motors have seen substantial advancements in their design to optimize efficiency, one of the crucial factors in electric vehicles. Innovators have focused on reducing losses in the stator and rotor, enhancing magnetic materials, and employing improved winding configurations. Patents filed in this area often highlight novel stator and rotor designs, magnetic materials, and winding techniques to achieve higher power densities and improved efficiency.
US Patent Application No. US13/045,482 titled "Direct current motor with independently driven and switchable stator" (Granted on 05.11.2013)
This invention presents an apparatus and method to adjust a motor's torque and speed while staying within the power supply's voltage limit. It involves a brushless direct current motor with independently driven stators, acting as separate motors. Two power electronics units provide energy to the stators, and a commutation electronics unit synchronizes current pulses to create a rotating magnetic field interacting with the rotor. A controller connects the power electronics units in series or parallel for optimizing motor performance.
2. Cooling Systems:
As electric vehicles demand higher power outputs from their motors, effective cooling systems have become critical. Patents related to cooling solutions for BLDC motors include liquid cooling, phase-change materials, and advanced heat sink designs. These innovations ensure the motors can handle the increased power requirements without compromising on reliability and performance.
Indian Patent Application No. 202241077170 titled "A liquid cooling hub for a brushless electric motor" (Granted on 13.07.2023)The invention presents a liquid cooling hub for a brushless electric motor. It consists of two hollow cylindrical components, one housing an inlet and an outlet for liquid coolant flow and a key guided slot. The second component has a groove along its axis, aligning with the inlet and outlet of the first component. With the help of complementary keys, these components fit together cleanly, forming the liquid cooling hub. Additionally, a key guided slot on the first component aligns with the stator for proper coupling.
3. Integration of Power Electronics:
BLDC motors require sophisticated electronic controllers to achieve precise commutation. In recent years, patents have been filed that focus on integrating power electronics directly into the motor structure, reducing overall system complexity and improving power conversion efficiency. This approach simplifies the vehicle's powertrain design and can lead to cost savings in EV manufacturing.
US Patent Application No. 10,903,723 B2 titled "Motor positional sensing" (Granted on 26.01.2021):
This invention features a sensor that significantly improves the motor's efficiency. The sensor measures the leakage flux, enhancing motor performance. The motor comprises a rotor housing, magnets, a stator with multiple poles, and at least one sensor. The main flux extends towards a stator pole in a radial plane, while the leakage flux goes towards the sensor, contributing to increased efficiency
4. Sensorless Control:
Early BLDC motor systems relied on position sensors to achieve electronic commutation accurately. However, the addition of sensors increased the complexity and cost of the motor. In response to this challenge, patent filings reveal advancements in sensorless control algorithms that rely on back electromotive force (EMF) or other methods to determine rotor position accurately. Sensorless control has become a significant area of innovation in the BLDC motor domain, making motors more reliable and cost-effective.
Taiwan Patent Application No. TW103105710A titled "Method and system for determining the position of a synchronous motor's rotor" (granted on 21.05.2018):
To establish the initial position of a permanent magnet rotor, the motor's stator windings are individually energized with voltage, and the time taken for the current to reach a specific value is measured for each winding. This time measurement helps determine the rotor's position within a 60-degree range even before the motor starts. Knowing the rotor position allows identifying the next commutation point in the six-step sequence before actual motor rotation
5. Regenerative Braking:
Electric vehicles benefit greatly from regenerative braking, which allows them to recover energy during deceleration and braking. Patents have been filed to optimize the regenerative braking capabilities of BLDC motors, improving the efficiency of energy conversion and storage. These innovations contribute to extending the driving range of electric vehicles, a crucial factor in consumer acceptance.
Patent Application no. TW98129022A titled "Regenerative Brake Control Method for Salient Brushless DC Motor" (Granted on 11.02.2013):
The invention pertains to a regenerative brake control method for a brushless DC motor with a magnetic field path featuring salient pole distribution. The proposed method aims to control the regenerative braking process for a salient pole brushless DC motor by determining the appropriate backward switching phase angle based on required regenerative braking strength, speed, and rotor position information, leading to highly efficient regenerative braking performance.
6. Noise and Vibration Reduction:
BLDC motors can produce noise and vibration during operation. In the pursuit of quieter and smoother electric vehicles, inventors have filed patents that address noise reduction techniques, such as improved rotor designs, better bearing configurations, and vibration damping methods. These innovations enhance the overall driving experience, particularly in premium and luxury electric vehicles.
China Patent Application No. CN200510015252 titled "Permanent magnet structure for decreasing noise in BLDC" motor (Filed on 04.04.2007)
The invention is a permanent magnet structure for reducing noise in BLDC electrical machinery. It includes a rotating shaft, back yoke, permanent magnets, fixed sub-iron-core, and loop groupware. The loop groupware reduces magnet imbalances and vibration during rotation.
7. Manufacturing and Cost Optimization:
With the growing demand for electric vehicles, cost optimization in BLDC motor manufacturing has become a priority. Patents in this area focus on streamlining production processes, using new materials and manufacturing techniques, and exploring alternatives to rare earth magnets, which are commonly used in high-performance BLDC motors but are expensive and environmentally challenging to extract.
US Patent Application No. US08/875,220 titled "Brushless DC motors"(Granted on 16.11.1999):
This patent describes a novel manufacturing technique for a brushless DC motor. The motor has a rotor and a stator with magnets on one side and teeth on the other. Windings are wrapped around the teeth to generate torque when powered. The tooth angle closely matches the pole angle. The teeth are grouped in sets, with uncoiled teeth placed between each set at an angle equal to twice the pole angle divided by the number of phases.
8. Multi-phase Motor Configurations:
Patent filings have revealed an increasing interest in multi-phase BLDC motor configurations, such as three-phase and six-phase designs. Multi-phase motors offer advantages like reduced torque ripple, smoother operation, and increased fault tolerance. These innovations are especially relevant to electric vehicles, where smooth and reliable power delivery is essential for enhanced driving experience and system reliability.
US Patent Application No. US12/713,224A titled "Six-Phase Firing Circuit For Brushless DC Controls"(Granted on 23.09.2010)
The invention is a six-phase, 12-step firing circuit for brushless DC controllers. It independently distributes current to the six motor stator windings of a six-phase brushless DC motor. The firing circuit utilizes hall sensor rotor position signals, a drive start signal, and pulse width modulation commands to control the motor's rotation with a six-phase power bridge assembly fired at 30-degree intervals.
9. Dual-motor and Axial Flux Configurations:
In pursuit of higher power and torque outputs, dual-motor configurations have gained traction. This approach involves coupling two BLDC motors in the same vehicle, with each motor driving a separate axle. Dual-motor setups provide improved traction control, torque vectoring, and regenerative braking capabilities. Furthermore, axial flux BLDC motors have garnered interest due to their compact design and potential for higher power density. Patents related to these configurations aim to enhance the overall performance and efficiency of electric vehicles.
US Patent No. US20100222953A1 titled "Dual Motor Drive and Control System for an Electric Vehicle" (Granted on 04.05.2013):
The granted patent discloses a method and apparatus for optimizing the torque applied by each motor in a dual motor drive system of an all-electric vehicle. The torque adjustments are made considering factors such as wheel slip and other vehicular operating conditions to enhance overall performance.
10. Intelligent Motor Control:
Artificial intelligence and machine learning have been integrated into BLDC motor control algorithms to optimize efficiency and performance. Smart control systems analyze real-time data from various vehicle sensors and adapt motor performance based on driving conditions, load, and temperature. These AI-driven innovations are reflected in patents that showcase predictive and adaptive motor control strategies, leading to improved energy efficiency and battery management.
Indian Patent Application No. 202227042545 titled "Drive control device for electric vehicle" (Granted on 07/04/2023):
This electric vehicle drive control device consists of a motor part responsible for motor operation and a converter part controlling the motor. The motor part includes a metal motor frame housing a stator and a rotor and having an outer peripheral surface. The converter part, positioned around the motor frame, contains a semiconductor module with semiconductor elements. This semiconductor module is in direct contact or thermal contact with the outer peripheral surface of the motor frame.
11. Modular Motor Systems:
To cater to a diverse range of electric vehicles, inventors have filed patents for modular BLDC motor systems. These systems allow manufacturers to customize the motor's power output, torque characteristics, and form factor, making them suitable for different vehicle platforms, including electric cars, motorcycles, scooters, and e-bikes. Modular motor designs facilitate faster development and reduce time-to-market for new electric vehicle models.
Indian Patent Application No. 415099 titled "Solar power integrated bidirectional non-isolated dc-dc converter for e-rickshaw" (Granted on 30/12/2022):
The disclosed embodiments feature a solar power integrated bidirectional non-isolated DC-DC converter, combining a PV panel buck converter with the bidirectional non-isolated converter. This system includes a flexible mono-crystalline solar panel placed on an e-rickshaw with a 1.5 KW BLDC motor for hilly terrain. The non-isolated bidirectional converter effectively controls regenerative power through the BLDC motor, while the integrated buck converter maximizes power tracking for battery charging using the PV panel.
12. Fault Detection and Diagnostics:
Electric vehicles depend on robust motor health monitoring and diagnostics. Patents have been filed for advanced fault detection systems that can identify and diagnose motor issues proactively. These innovations enable early detection of potential problems, leading to reduced downtime, improved safety, and more effective maintenance strategies.
South Korean Patent Application No. KR1020100119051A titled "Bldc motor fault detection apparatus for automotive and method thereof"(Granted on 07.06.2012)
This invention is a vehicle brushless DC electric motor malfunction diagnosis system and method. It detects counter electromotive force during motor rotation and calculates the distortion rate of the harmonic component. The system informs the driver of any abnormal state in the motor based on the calculated distortion rate.
13. Electromagnetic Interference (EMI) Reduction:
Electric vehicles often face challenges related to electromagnetic interference, which can impact vehicle electronics and communication systems. Patents have addressed this concern by proposing various EMI reduction techniques, including shielding solutions, optimized motor winding patterns, and specialized materials. Reducing EMI ensures seamless operation of vehicle electronics and enhances overall vehicle reliability.
South Korean Patent Application No. KR1020100101245A titled "Motor driving inverter for reducing electromagnetic noise and motor drive apparatus using the same "(Granted on 24.08.2012):
This invention presents a motor driving inverter and a motor driving apparatus that aim to prevent malfunctions caused by electromagnetic interference. It achieves this by reducing electromagnetic noise generated during the high-speed switching operation of power switching semiconductor devices.
14. Wirelessly Charged Electric Vehicles (WCEVs):
As wireless charging technology evolves, there has been a growing interest in developing BLDC motors that are compatible with wirelessly charged electric vehicles (WCEVs). Patents in this area focus on designing motors that align with wireless charging systems, ensuring efficient energy transfer while maintaining the required safety standards.
Japan Patent Application No. JP6314442B2 titled "In-vehicle device controller" (Granted on 25.04.2018)
This is an in-vehicle device control device that functions by providing electrical power to the motor to an in-vehicle battery of an in-vehicle device and other in-vehicle electric devices from an external power source located outside the vehicle.
15. Braking Systems in Electric Vehicles:
Braking systems are a crucial aspect of electric vehicles, ensuring safe and efficient deceleration and stopping. BLDC motors play a significant role in regenerative braking, a feature that has become synonymous with electric vehicles. Regenerative braking allows BLDC motors to act as generators during deceleration and braking, converting kinetic energy back into electrical energy that can be stored in the vehicle's battery for later use.
US Patent Application No. US201662358732P titled "Electronic braking of brushless DC motor in a power tool" (Granted on 08.01.2019):
This invention features a power tool with a brushless DC motor and power switches on the DC bus line. The controller applies electronic braking by closing either high-side or low-side switches. It toggles between switches when the voltage is below a threshold and uses a single switch when the voltage is above the threshold.
The aforementioned illustrations and examples represent exemplary patents, providing references and showcasing the diverse technologies encompassed within. It is important to note that these are only a glimpse of the ongoing advancements in the development of BLDC motors, and we can anticipate even more remarkable technological strides in the future, promising an exciting era of progress in this field.
CONCLUSION:
BLDC motors have become vital components in modern electric vehicles, powering various applications ranging from wipers and air conditioning to propulsion and power steering. It is evident that the automotive industry's relentless pursuit of sustainable transportation solutions is far from over, and we can expect to see further transformative inventions with respect to BLDC motors. These continuous advancements will undoubtedly play a significant role in reshaping the automotive industry, driving the widespread adoption of electric vehicles, and paving the way for a more sustainable and efficient transportation ecosystem in the near future.
Author Details: Uthresh Gobu Naidu, Symbiosis Law School (Pune)
Footnotes:
1. https://robu.in/brushless-dc-motor-working-principle-construction-applications/
2. https://www.tytorobotics.com/blogs/articles/what-is-a-brushless-motor
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