A brief note on BLDC motors and their application in ceiling fans
From Superfan, India’s first super energy efficient ceiling fan
Motors are the primary component in a ceiling fan and this blog throws light on working of ceiling fan motors especially BLDC motors.
Electric Motor And It’s Working
We come across hundreds of motors in our daily life from domestic to industrial applications. Motors are electrical machines that convert electrical energy into mechanical energy (rotational motion). This rotational motion can be translated into linear motions as well based on the application.
All electric motors have the following parts:
Stator – the stationary part
Rotor– the rotating part
Shaft – The rod that connects the motor with the application.
The above parts will have slight modifications based on the power supply or the application. A DC motor is the simplest of all motors and it is easy to understand it’s working.
Brushed DC Motors
DC motors are the simple magnet and coil arrangement that we used to play in our childhood. Where stator is a permanent magnet and rotor is a coil winding.
In DC motors the rotor has windings that are supplied with direct current(i). The stator is a magnetic field, and the rotor has a current-carrying coil. The interaction between the magnetic field and the electric field is the basic principle behind the rotation of the motor. The direction of rotation and flow of electric current is explained using Fleming’s left-hand rule.(ii)
We supply the rotor windings through brushes and commutators (ring-like structures) at the end of the rotating coils. Commutators help the rotor to run in the same direction, although an alternating flux linkage is produced. Commutation is the process of switching the current in the motor to achieve a unidirectional torque.
AC Induction Motors (ACIM)
In the case of AC induction motors, which are commonly used in regular ceiling fans, the stator of the motor is supplied with a 3-phase alternating current. Here is ACIM, the stator has coils wound on electromagnetic core and the rotor is a permanent magnet.
Here the magnetic field in the rotor interacts with the electric field in the stator. This phenomenon is explained using Faraday’s law of electromagnetic induction. In simple terms, the greater the voltage in the current-carrying conductor, the faster the magnetic field rotates.
Brushless DC motors are electric motors that are electronically commutated (or works based on software commands). Simply, it is a DC motor without mechanical commutators and brushes. The rapid adoption of these motors in the fields of multirotor aircraft, electric vehicles and home appliances like washing machines moved brushed DC motors out of the picture. The high speed and efficiency of the BLDC motor overtook all the limitations of brushed DC motors.
It works similarly to brushed DC motors by alternating the polarity of the windings of the rotor windings. The interaction between the magnetic field of the stator and the electrical field of the rotor creates the angular movement making the motor spin. The major drawback in DC motors is the wear and tear of commutator and brushes which is overcome by BLDC motors.
Pros and Cons
Recently BLDC motors are being used in electrical appliances because of the availability of inexpensive controllers in the market. There are various reasons as listed below:
1. No commutators and brushes and hence no mechanical wear and tear.
2. BLDC motors have improved precision in speed control as it requires a micro-controller to keep the motor sequence in a correct
3. Very little friction and so it is efficient than other motors.
The disadvantages of BLDC motor include the complexity in the motor’s construction, and it requires complicated software control. Although the cost of a motor is not as high as expected when the cost of the controller is added it becomes expensive. In a few applications, it requires special gearing arrangements for high rpm operations.
Superfan ceiling fan and BLDC motors
In Superfan ceiling fan, the BLDC motors, the rotor is a permanent magnet and there is a copper winding on the iron core for the stator. Although the motor is very expensive, Superfan ceiling fan can produce an inexpensive ceiling fan since we manufacture all the parts, including the motor and micro-controller in-house. A superfan has its built-in controller for BLDC motor that comes with active power factor correction (Patent No. 2873/CHE/2009). This has helped us to give a quality product at an affordable cost.
Versa Drives Private Limited is the first company in India to launch a BLDC ceiling fan in India (Super Energy Efficient Ceiling fan) in the brand name of Superfan. Today, we have a range of inverter ceiling fans that save over 50% of power and has been recognized as a green product internationally. You can buy Superfan ceiling fans online at www.superfan.in
(i) Since DC is constant and does not have a time-varying field, it cannot develop a rotating magnetic field.
(ii) Whenever a current-carrying conductor is placed inside a magnetic field, a force acts on the conductor, in a direction perpendicular to both the directions of the current and the magnetic field.