Brushless DC Motor (BLDC) – Construction, Working.

In this article, we shall learn about brushless DC Motors (BLDC Motors) , their definition, construction, working, and applications.

An electric motor is an electromechanical energy conversion device that converts electrical energy into mechanical energy. Depending on the types of supply, construction, and applications, electric motors are classified into different AC motors, DC motors, induction motors, synchronous motors, etc. This article mainly describes all the concepts of brushless DC or BLDC motors.

Table of Contents

What is a Brushless DC(BLDC) Motor?

A brushless DC motor abbreviated as BLDC motor is an electric motor powered by a direct current (DC) electric supply and is commutated electronically instead of mechanical commutation like in a conventional DC motor.

The BLDC motors use more advanced technology, hence these are more powerful than the conventional DC motors. Consequently, these motors have wide use in several practical applications.

Construction of Brushless DC Motor

A Brushless DC Motor (BLDC Motor) is an advanced type of DC motor that operates without mechanical brushes and a commutator. Instead, it uses electronic control to achieve commutation. Like other types of electric motors, it has two major components — the stator and the rotor — along with several supporting elements that enable precise control and efficient operation.

Construction Diagram of Brushless DC(BLDC) Motor

1. Stator

The stator is the stationary part of the BLDC motor. It consists of laminated steel cores with slots that hold three-phase windings, which are typically connected in either a star (Y) or delta (Δ) configuration.

These windings are energized in a specific sequence to create a rotating magnetic field (RMF).
The stator’s construction is quite similar to that of an induction motor, except that the windings are optimized for DC supply through an electronic controller.
The stator is responsible for generating the electromagnetic field that interacts with the magnetic field of the rotor to produce rotation.

2. Rotor

The rotor is the rotating part of the BLDC motor and is equipped with permanent magnets instead of windings.

These magnets are made from materials such as neodymium, ferrite, or samarium-cobalt, depending on torque and cost requirements.
The number of magnetic pole pairs on the rotor can vary from 2 to 8, depending on the application.

The arrangement of these poles determines the motor’s speed, torque, and smoothness of operation.
Since there are no windings or commutator segments on the rotor, friction and electrical losses are minimized, resulting in higher efficiency and longer life.

3. Hall Effect Sensors

A key feature of BLDC motors is the inclusion of Hall Effect sensors, which detect the rotor’s position.

These sensors send position feedback to the electronic controller, which in turn adjusts the current supply to the stator windings.
This synchronization between rotor position and stator excitation is what replaces the mechanical commutation found in traditional brushed DC motors.
In sensorless designs, back electromotive force (back-EMF) is used instead of Hall sensors for commutation, improving reliability and reducing cost.

4. Shaft and Bearings

The rotor is mounted on a shaft supported by high-quality ball bearings to ensure smooth and quiet rotation.

Bearings help reduce friction, allowing the rotor to spin freely and efficiently.
The shaft is connected to the load, such as a fan, wheel, or pump impeller, to deliver mechanical output.

5. Electronic Controller

A BLDC motor cannot operate directly from a DC supply; it requires an electronic controller (driver circuit).

The controller converts the DC input into a pulsating three-phase AC signal to energize the stator windings in a specific sequence.
It takes input from the Hall sensors to determine which winding should be energized next for proper torque generation.

This electronic commutation makes the motor highly controllable, allowing variable speed, direction control, and efficient torque management.

Read detailed article: How a BLDC Motor Controller Works

Working of Brushless DC Motor

A Brushless DC (BLDC) motor operates on the same fundamental principle as a conventional DC motor — the Lorentz force law. It states that a current-carrying conductor placed in a magnetic field experiences a mechanical force. In a BLDC motor, the stator is stationary with energized coils, while the rotor carries permanent magnets that move due to this interaction.

Let’s understand the working step by step:

Energizing the Stator Windings
When the stator windings receive electrical energy, they act as electromagnets and create a rotating magnetic field in the air gap between the stator and rotor. This field is responsible for driving the rotor.

Electronic Commutation (Conversion of DC to AC)
Although the BLDC motor uses DC supply, it cannot directly create a rotating field. To achieve rotation, the DC voltage is electronically switched using a controller or electronic commutator, which converts DC into an AC-like waveform (often trapezoidal or sinusoidal, depending on motor design).
Magnetic Interaction and Torque Production
The magnetic field generated by the stator interacts with the magnetic field of the rotor’s permanent magnets.
- When opposite poles (N-S or S-N) align, attraction forces are created.
- When similar poles (N-N or S-S) align, repulsion forces occur.
  These alternating attraction and repulsion forces produce torque, causing the rotor to rotate.
Sequential Switching of Windings
The electronic controller energizes the stator coils sequentially, ensuring that the magnetic field rotates in a smooth pattern. This sequential switching keeps the rotor moving continuously in the desired direction — usually clockwise.
Role of Hall-Effect Sensors
To maintain synchronization, Hall-effect sensors are mounted on the stator.
- These sensors detect the rotor’s position as it rotates.
- They generate high or low logic signals based on the proximity of the rotor’s magnetic poles.
- This feedback helps the controller determine which coil should be energized next.
Controller Decision and Timing
The electronic controller receives the feedback from Hall sensors and decides which phase winding to switch ON or OFF at a given moment.
This precise timing ensures accurate rotation, smooth torque generation, and efficient energy conversion.

Continuous Rotation
The process of energizing windings, detecting rotor position, and switching coils occurs continuously and rapidly.
As a result, the BLDC motor provides smooth, efficient, and controlled rotation without mechanical brushes or commutators.
Key Advantage of Operation
Since there are no brushes involved, there is less friction, reduced wear, and lower maintenance. Moreover, electronic control allows precise speed and position regulation, making BLDC motors ideal for automation systems, electric vehicles, drones, and robotics.

Types of Brushless DC Motors

Based on the design, the BLDC motors are classified into the following two types namely-

Inner Rotor BLDC Motor
Outer Rotor BLDC Motor

Inner Rotor BLDC Motor

In this type of BLDC motor, the rotor is present in the center of the motor, and the stator windings surround it as shown in the figure-1. In this motor, the rotor is located in the core, As a result, the rotor magnets do not insulate heat inside the motor, so the heat gets dissipated easily. Therefore, the inner rotor BLDC motors are designed to produce high torque and are widely used in different applications

Outer Rotor BLDC Motor

In the outer rotor BLDC motor, the rotor surrounds the windings that are present in the core of the motor as shown in the figure-2.

In this type of BLDC motor, the rotor magnets lock the heat inside the motor and do not allow it to dissipate. Consequently, these types of BLDC motors are designed to operate at lower currents and torque.

Advantages of BLDC Motors

The following are the main advantages of brushless DC motors:

BLDC motors have high efficiency as compared to brushed DC motors.
There is no problem of sparking in the brushless DC motors due to the absence of carbon brushes and a commutator.

They have relatively quiet operation. Thus, BLDC motors produce less noise while operating.
BLDC motors can operate at high-speed under any operating conditions.
In the case of brushless DC motors, the acceleration and deceleration are easy due to low rotor inertia.

Brushless DC motors are more reliable.
BLDC motors can produce high torques over a wide range of speeds.

Disadvantages of BLDC Motors

The following are some major disadvantages of brushless DC motors:

Brushless DC motors are more expensive than brushed DC motors.

We cannot supply uncontrolled high power to BLDC motors because it could damage the magnets and insulation in the motor.

Applications of BLDC Motors

Present day, brushless DC motors are being extensively used in several applications, some of them are listed below:

Brushless motors are being used in modern home appliances such as fans, pumps, blowers, etc.

These are used in computer hard disc drives, CD or DVD drives, etc.
Brushless DC motors are also used in automotive such as in power steering and many other electric vehicles.
These are also used in robotics, CNC machine tools, belt drive systems, and in many other industrial applications.

Conclusion

The brushless DC motor (BLDC) is a highly efficient and reliable motor widely used in modern applications. Its brushless design reduces friction, wear, and maintenance, while electronic commutation provides precise speed and position control. By converting DC power into a rotating magnetic field, BLDC motors deliver smooth torque and high efficiency, making them ideal for drones, robotics, electric vehicles, and automation systems.

Understanding the construction, working principle, and role of Hall sensors helps engineers and hobbyists choose the right motor for their projects. With their combination of durability, performance, and control, BLDC motors continue to be a top choice in applications requiring precision and energy efficiency.

Brushless DC Motor (BLDC) – Construction, Working. explained

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