In order to make the operation more reliable, more efficient, and less noisy the recent trend has been to use brushless D.C (BLDC) motors. They are also lighter compared to brushed motors with the same power output. This article gives an illustrative introduction on the working of BLDC motors.A detailed webpage version of the video is given below.
Why BLDC motors ?
The brushes in conventional D.C motors wear out over the time and may cause sparking. This is illustrated in the Fig.1. As a result the conventional D.C motors require occasional maintainance. Controlling the brush sparking in them is also a difficult affair.
The Basic working
The rotor and stator of a BLDC motor are shown in the Fig.2. It is clear that, the rotor of a BLDC motor is a permanent magnet.
Further improving the BLDC Performance
Even though this motor works, it has one drawback. You can notice that, at any instant only one coil is energized. The 2 dead coils greatly reduce the power output of the motor. Here is the trick to overcome this problem. When the rotor is in this position, along with the first coil, which pulls the rotor, you can energize the coil behind it such a way that, it will push the rotor.
Use of an ECU
That’s how a BLDC works. But, you might have some intriguing doubts in your mind. How do I know which stator coils to energize? How do I know when to energize it, so that I will get a continuous rotation from the rotor? In a BLDC we use an electronic controller unit (ECU) for this purpose. A sensor determines the position of the rotor, and based on this information the controller decides, which coils to energize.
Types of BLDC design
The BLDC design we have discussed so far is known as the out-runner type. Here the runner if fitter around the stator. In-runner BLDC design is also available in the market.