How Brushless Motors Work: Fully Explained (Guide)

Industrial applications worldwide commonly use brushless DC motors. DC and AC motors are the two types of motors that can be divided into brushed and brushless. Unlike brush-driven motors, brushless DC motors generate DC current without brushes. Compared to other types of motors, brushless DC motors have many specific advantages. But what exactly are they? What is it used for and how does it work?

What is a Brushless DC Motor?

In BLDC motors, direct current is used to generate motion without brushes, which is what differentiates them from conventional DC motors. Due to their efficiency and precision torque and rotation speed control, brushless motors are becoming more popular over conventional brushed DC motors, and their durability and low electrical noise also make them more popular. The use of BLDC motors in consumer electronics, such as washing machines and air conditioners, allows for high efficiency and long term durability. As well as being used in hard disk drives, RC planes, and cars, they are used in many products as well.

How Brushless DC Motor Works?

Basic Principles

Electric motors, also called brushless DC motors (BLDC), are constructed using electromagnetism as a principle. The commutation of BLDC motors is not conducted by brushes, unlike that of traditional brushed motors. The current flow through the windings is controlled by an electronic controller, which creates a rotating magnetic field. A torque is produced by interacting between these magnetic fields and the permanent magnets on the rotor.

Main Components

Stator: In a motor, the stator contains the windings and is the stationary part. A rotating magnetic field is generated by these windings when current passes through them. In order to create electromagnets, steel laminated stator wires are wound around copper wires to reduce energy losses.

Rotor: Permanent magnets are installed on the rotor, which rotates the motor. Depending on the motor design, magnets can be mounted on the surface or inside. Stator and rotor permanent magnets interact to produce torque through the interaction of their magnetic fields.

Electronic Controller: BLDC motors require a controller to operate. As the current was switched through the stator windings, the magnetic field rotated through electronic commutation. Based on sensor feedback or the back-EMF (electromotive force) generated by the motor, the controller adjusts the timing and magnitude of the current.

Position Sensors (Optional): A Hall effect sensor or another type of position sensor is commonly used to determine the position of the rotor in BLDC motors. By providing feedback to the controller, it is able to maintain motor efficiency and precisely time the commutation.

Working Mechanism

Electronic Commutation: The mechanical commutation used in brushed motors is replaced by electronic commutation in BLDC motors. An electric field is created by energized stator windings that are controlled in a specific sequence. Rotor rotation is caused by the interaction between this field and the rotor's permanent magnets. Sensors or inferred back-EMF can be used to determine the sequence of energizing the windings.

Creation of Rotating Magnetic Field: Magnets on the rotor are attracted or repelled by a magnetic field created by stator windings. In order to create the appearance of a rotating magnetic field around the stator, the controller sequentially energizes different sets of windings. Continuous rotation is achieved by following the rotating magnetic field.

Feedback Mechanism: The controller receives real-time feedback on the rotational position of sensored BLDC motors. As a result of this information, the controller ensures that the magnetic field is always oriented correctly relative to the rotor by adjusting the timing and sequence of current pulses delivered to the stator windings. By using the back-EMF generated by the motor's windings, the controller estimates the rotor position in sensorless BLDC motors.

Control of Speed and Torque: Stator winding voltage and current can be adjusted to control BLDC motor speed and torque. Using Pulse Width Modulation (PWM) techniques, a controller can control the motor's speed and torque by altering the duty cycle of the current pulses. Increasing voltage increases motor speed, and adjusting current adjusts torque.

Advantages of Brushless DC Motors

High Efficiency: As a result of eliminating brushes and commutators, BLDC motors are highly efficient. Electric vehicles and renewable energy systems benefit from their efficiency, making them ideal for energy conservation.

Reliability and Longevity: Motor components wear and tear less because there are no brushes, resulting in a longer lifespan and fewer maintenance needs. Whenever continuous and long-term operation is required, this level of reliability is crucial.

Smooth Operation and High Performance: In applications such as robotics, CNC machines, and drones requiring high performance, BLDC motors provide smooth and precise speed and torque control. A motor's operation can be adjusted quickly and precisely thanks to electronic commutation.

Reduced Noise and Electromagnetic Interference: Medical devices and audio equipment require low noise levels, so the absence of brushes reduces electronic noise and electromagnetic interference.

Choosing a Motor 

The last thing we need to discuss is what to look for when selecting a motor. A motor's Kv, which shows how fast it rotates using a particular power input, is the most important characteristic. Whenever a motor is supplied with electricity, it will spin at 2000 revolutions per minute. The size of a motor is closely related to its Kv. There is a difference between a thin but longer motor with high Kv, and a wide but large motor with high torque, but low Kv and uses a small propeller. Small motors operate at relatively high RPMs, while larger motors operate at relatively low RPMs.

It is also important to consider a motor's maximum power. A motor that exceeds its power limit will heat up, resulting in a drastic drop in efficiency or even damage. It is also possible to change the performance of a motor by changing its brand. There may be a difference in performance between motors from different brands with the same Kv value. That's why you shouldn't build a drone around a motor without testing it first.

Faqs

Question 1: How does a brushless motor work without brushes?

Answer: Where does the current come from in a brushless motor? There are no coils on the rotor, so it doesn't work. Stator coils are fixed into place on the rotor, which is a permanent magnet. Brushes and a commutator are not needed since the coils do not move.

Question 2: What fails in a brushless motor?

Answer: A brushless motor can fail for a number of reasons after only a short period of time. In most brushless motors, corrosion occurs as a result of water or dust contamination, causing the motor to fail early. Similarly, bearing life is affected by issues related to bearing balance.

Question 3: Why brushless over brushed?

Answer: In addition to saving energy, brushless motors can last up to 50 percent longer than brushed motors, according to Consumer Reports. Brushless motors have longer battery life than brushed tools since they do not contain brushes that lose energy to friction. Hours can be spent running many models.

Final Verdict

Featuring an innovative design and an advanced electronic switching system, brushless motors represent an important advancement in motor technology. Their mechanical advantages make them more efficient, reliable, and precise than traditional brushed motors. Electric vehicles, drones, industrial machinery, consumer electronics, and other applications benefit from brushless motors' seamless operation, controlled by electronic controllers. These devices are an excellent choice for modern, energy-conscious applications due to their high efficiency and reduced maintenance requirements. To improve the performance and reliability of motor-driven systems across a wide range of industries, we must understand how brushless motors work.

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