What is a BLDC fan, and how does it work?

Ceiling fans running on direct current (DC) save up to 50% of power, making them energy efficient. Therefore, BLDC ceiling fans have become popular in India.

Conserving electricity has become imperative because of two reasons. One is that electricity power generation is limited because of environmental and raw material availability factors. Secondly, power tariffs have increased throughout India. The best way to conserve electricity is to reduce power consumption in the residential sector. While inverter technology helps reduce power consumption in air conditioners and refrigerators, BLDC technology is ideally suited for ceiling fans. This article discusses the concept of BLDC fans and their working.

What is BLDC?

BLDC stands for Brushless Direct Current. A brushless DC motor works on direct current powered by an electronic commutation system. In contrast, the conventional ceiling fan is powered by a mechanical commutator and brushes.

In BLDC, the current to torque and voltage to RPM have a linear relationship. Thus, a BLDC motor is excellent for a ceiling fan. Let us discuss its working and how it benefits users by saving power.

BLDC Ceiling Fan Working Explained

The BLDC fan working can be categorized into two sections: a) Mode Selection and b) Working of the motor.

• Mode Selection – The BLDC ceiling fan motor has three modes of control: manual, automatic, and remote control. The BLDC fan motor’s speed is controlled by the Electronic Speed Controller (ESC) mechanism, which in turn depends on the power output from the microcontroller.
• Manual Mode – The motor’s speed is controlled by adjusting the pulse width, which is controlled by adjusting the reference voltage through the potentiometer.  
• Auto Mode – This controller uses the LM35 temperature sensor that senses the room temperature and adjusts the output voltage accordingly to change the input to the microcontroller. As a result, a change in the room temperature changes the pulse width from the microcontroller, adjusting the motor’s speed accordingly.
• Remote Control Mode – This mode uses an RF remote control option to control the motor’s working speed. The remote has two switches (Up and Down) for controlling the speed. Pressing the Up-speed switch causes the RF module transmitter to send serial data to the microcontroller through the RF receiver. The programming is such that the wave width increases if there is continuous transmission of high value. In contrast, the wave width decreases when it receives a low value.

The BLDC ceiling fans in India generally work using the remote-control mechanism. So, let us discuss the working of the BLDC motor with sensor-less control.

·      The BLDC Fan Working (Without temperature sensors)

We have said that the BLDC ceiling fan motor is powered through electronic commutation. Every commutation step has one phase winding connected to the positive supply, one to the negative voltage supply, and one is kept floating. The back-EMF in the floating phase results in zero crossing whenever it crosses the average of the other two phases.

The zero crossing occurs precisely in the middle of two consecutive commutations. Therefore, the time from one commutation to the zero crossing and subsequently to the next commutation is equal when the motor rotates at constant or low-speed variations. However, the floating phase changes for every commutation step. Therefore, each phase requires an ADC channel for detecting the zero crossing.

The ESC acts as a power-controlling device switching supply to the BLDC motor windings depending on the back EMF produced.

We will not discuss the Block and Circuit diagrams because that would be too technical. So, let us understand the hardware and software in a BLDC ceiling fan to learn how it works and saves power.

BLDC Ceiling Fan Hardware

BLDC ceiling fan hardware comprises various components. We shall discuss each of them in brief.

a.   BLDC Motor

Brushless Direct Current (BLDC) motors are synchronous motors powered by a DC electric source through an integrated inverter or an SMPS that produces an AC signal to drive them. AC is a bi-directional current with no waveform restrictions. Hence, a BLDC motor has additional sensors and electronics control to control the frequency, inverter output amplitude, and waveform.

The BLDC motor has a stationary armature with a rotating permanent magnet. Hence, it eliminates the problems faced by conventional ceiling fan motors, like connecting current to a moving armature. The conventional motor has brushes or a commutator assembly that switches the phase to the windings to keep the motor running. Instead, the BLDC motor has an electronic controller to perform similar timed power distribution using a solid-state circuit instead of a brush commutator system.

BLDC Motor Vs. Induction Motor

Now, let us compare the BLDC motor to the induction motor used in conventional ceiling fans.

1. A BLDC motor is comparatively more efficient and convenient to control than an induction motor.
2. A BLDC motor has linear torque-to-speed characteristics compared to the non-linear relationship for induction motors.
3. A BLDC motor has a higher outpower per frame size than the induction motor. So, it enables achieving a smaller size for any given power output.
4. The rotor inertial levels are low for a BLDC motor. Therefore, it has better dynamic characteristics than an induction motor.
5. A BLDC motor does not require a unique starter circuit because it has a rated starting current.
6. BLDC motors always need a controller as compared to induction motors.
7. BLDC motors do not experience any slip between the rotor and stator frequencies. On the other hand, the rotor in an induction motor runs at a lower frequency than the stator and increases with the motor load.

b.   Electronic Speed Controller (ESC)

This device controls the speed of the BLDC motor. It has six leads: three connected to the motor, two for 12V supply, and one for the input pulse to the ESC from the microcontroller. Six pairs of MOSFETs are provided to carry more current. It also includes a microcontroller, which is programmed for controlling the BLDC motor speed.

c.   Temperature Sensor LM35 series

These precision IC temperature sensors have an output voltage linearly proportional to the Celsius temperature reading. These sensors do not require external calibration or trimming to provide high-level accuracies of 14C at room temperature and 34C over a temperature range of 55C to over 150C. Hence, it reduces the cost. Besides, LM35 sensors have linear output, low output impedance, and precise inherent calibration. They can be used with single, plus, or minus power supplies.

d.   AT mega 16 microcontroller

This low-power CMOS 8-bit microcontroller is based on the AVR-enhanced RISC architecture. This microcontroller helps optimize power consumption versus processing speed because it has a high-performance characteristic with low power consumption.

e.   RF Remote Control

The RF remote control module comprises a transmitter, a receiver, an encoder, and a decoder.

1. RF Transmitter – The RF transmitter operates from a 1.5V to 12V power supply, making it convenient for battery-controlled applications. It has a frequency range of approximately 433.92 MHz and a transmission range of around 100 meters.
2. RF Receiver – The RF receiver is ideal for short-range remote-control apps where cost is a significant factor. This receiver module has no external RF components except for the antenna. The receiver frequency is around 433 MHz, with the supply current at 2.3 mA and an operating voltage of 5V.
3. RF Decoder HT12D – This decoder has an operating voltage of 2.4V to 12V with a low standby current. It can decode 12-bit information with a binary address setting.
4. RF Encoder HT12E – The operating voltage is 2.4V to 12V with high noise immunity and low power demand. It can encode information consisting of N address bits and 12N data bits.

BLDC Ceiling Fan Software

The BLDC motor works with the help of a powerful computing system and interactive software, OrCAD, supplemented by MikroC and Proteus. We will not go deep into the software discussion because of its technicalities.

In short, BLDC ceiling fans are highly efficient, less noisy, durable, and reliable. They have linear torque–speed characteristics. These factors combine to save energy up to 40 to 50%.  

Frequently Asked Questions on BLDC Ceiling Fans

Do BLDC ceiling fans save electricity?

Yes. BLDC fan technology uses a BLDC motor capable of reducing power consumption by nearly 65%. These fans have thick copper cables that ensure durability with fewer noise issues. Besides, BLDE ceiling fans do not get overheated.

Are BLDC ceiling fans expensive?

Yes. BLDC ceiling fans are comparatively more expensive than the conventional ceiling fan models. However, these fans can save up to Rs 1500 to Rs 2000 annually to help recover the pricing difference within one to two years.

How do BLDC ceiling fans save power?

Let us compare the power consumption of BLDC ceiling fans with conventional fans at varying speeds.

This comparison shows that BLDC ceiling fans consume up to 32 to 50% less power than conventional ceiling fans. It translates into savings of Rs 1500 to Rs 2000 annually.

Can a BLDC fan work without a remote?

BLDC fans can work without a remote because the speed can be controlled through a regulator or wall switch. Some BLDC ceiling fans come with a manual speed adjustment feature by pulling the cord or using a pull chain.

What are the primary drawbacks of BLDC ceiling fans?

BLDC ceiling fans cost nearly double the conventional fans. Secondly, they require an RF remote to control the speed. This remote needs AAA batteries, which require frequent replacement.

Which are the best BLDC ceiling fans available in India?

Excellent BLDC ceiling fan models will be available in India in 2023. They include Atomberg Renessa, Atomberg Efficio, Crompton Energion HS, Havells Ambrose, Havells Glaze, and others.

What is the lifespan of a BLDC motor?

The typical DC motor has a lifespan of around 2000 hours under normal conditions. In contrast, a BLDC motor averages around 10000 hours. So, BLDC fans are five times more durable than conventional ceiling fans.

Is Atomberg a Chinese company?

No. Atomberg Technologies is an Indian company founded by fresh graduates from IIT Mumbai.