BLDC Motors, we hear this terminology frequently in appliances like washing machines, air conditioners, and even ceiling fans. What exactly is BLDC technology, and what are its advantages and applications. First, let’s discuss how a conventional motor works and understand how BLDC technology is better for saving electricity.
The Conventional Motor
A conventional electric motor develops torque because it keeps the magnetic fields of the rotor (rotating part) and the stator (fixed part) misaligned at all times. It uses electromagnets made of wires wound around an iron core. As the current passes through the wire, it creates the magnetic field providing the necessary power to run the motor.
The misalignment of the magnetic fields is necessary for generating the torque. As the rotor moves, the fields come into alignment. Hence, you need a device known as a commutator that ensures maintaining the misalignment to generate movement. The conventional motor has a set of stationary contacts known as brushes made of graphite that press against the commutator to make sliding electrical contact as the rotor turns. These brushes provide selective electric current to the windings and ensure that the magnetic fields remain misaligned to create torque in a specific direction.
Disadvantages of the conventional motor
The disadvantages of the conventional brushed motor led to the invention of brushless motors. Here are the disadvantages in brief.
- The brushes sliding against the commutator cause friction and, therefore, result in power losses.
- Friction wears down the brushes and creates dust, thereby necessitating their replacement frequently.
- The electrical resistance of the brushes can cause a voltage drop. Hence, such motors consume more energy.
- The abrupt switch of the electric current through induction can cause sparks at the commutator’s contacts. Hence, it results in a fire hazard.
Using AC synchronous motors is a viable alternative, but the drawbacks remain, limiting its use in electrical applications.
What is BLDC technology?
A Brushless DC motor(BLDC) motor has permanent magnets that rotate around a fixed armature. Thus, it eliminates the problems with connecting current to the moving armature present in the conventional motor. In addition, instead of a commutator assembly, the BLDC motor has an electronic controller that switches the phase of the windings to keep the motor running. In a BLDC motor, the rotor is a permanent magnet. The coils do not rotate because they are fixed on the stator. Therefore, there is no need for brushes and a commutator.
BLDC Motor vs Brushed Motor
A brushed motor achieves rotation by controlling the magnetic fields generated by the coils on the rotor, whereas the magnetic field generated by the stationary magnets remains fixed. As you alter the voltage, the rotation speed changes. In a BLDC motor, a permanent magnet rotates by changing the direction of the magnetic fields. Therefore, controlling the magnitude and direction of the current into these coils helps control the rotation speed.
Advantages of a BLDC Motor
Here are some advantages of a BLDC motor over a conventional brushed motor.
- BLDC motors are efficient because they control continuously at maximum torque. In contrast, the brushed motors reach maximum torque at specific points in the rotation. Therefore, a brushed motor will require larger magnets to achieve the same efficiency level as a BLDC motor. It explains why small BLDC motors deliver more power than conventional motors.
- BLDC motors are easily controllable using a feedback mechanism to deliver the desired torque and rotational speed. Thus, it reduces energy consumption and heat generation.
- BLDC motors are highly durable and make less noise because of the absence of brushes. In brushed motors, the brushes and commutator wear down due to friction. Unfortunately, they also produce sparks at the points of contact, thereby creating more electrical noise.
Hence, BLDC motors are preferable because of their higher efficiency and durability.
BLDC Technology Applied
As BLDC motors offer higher efficiency and controllability than conventional motors, they have a longer operating life. Therefore, these motors are excellent for use in devices that run continuously. Some examples include domestic appliances like Ceiling fans, air conditioners, refrigerators, washing machines, etc.
BLDC motors are also useful to drive vacuum machines because of their superior controllability. BLDC motors are useful in electric vehicles because of their higher efficiency levels. In addition, you can find these motors in cordless tools because of their low weight and higher efficiency.
Today, you have BLDC motors for spinning hard disc drives. Their durability and power efficiency helps reduce energy consumption. BLDC motors have a bright future because they can be used in service robots, especially in fields other than manufacturing. They are also ideal for use in drones because of the higher degrees of precision control.
