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We have a lot of choices to choose a motor that is most suitable for our application. A Brushless DC motor or BLDC motor is the type which is most suitable for applications that require high reliability, high efficiency, more torque per weight etc.

How Does A Brushless DC Motor Works?

Commutator helps in achieving unidirectional torque in a typical dc motor. Here commutator and brush arrangement is eliminated in a brushless dc motor. And an integrated switching circuit is used to achieve unidirectional torque. That is why these motors are, sometimes, also referred as ‘electronically commutated motors‘.

Construction Of Brushless DC Motor

Same as another electric motor, a BLDC motor also has a stator and a rotor. Permanent magnets are mounted on the rotor of a BLDC motor, and a stator is wound with a specific number of poles. This is the basic constructional difference between a brushless motor and a typical dc motor.

There can be two types of BLDC motor on the basis of construction : 

(i) inner rotor design 

(ii) outer rotor design

Brushless DC motor

Working Principle

Before explaining the working of brushless DC motor, it is better to understand the function of the brushed motor. In brushes motors, there are permanent magnets on the outside and a spinning armature which contains electromagnet is inside. These electromagnets create a magnetic field in the armature when power is switched on and help to rotate armature.

The brushes change the polarity of the pole to keep the rotation on of the armature. The basic principles for the brushed DC motor and for brushless DC motor are same. 

Brushless DC motor has only two basic parts: rotor and the stator. The rotor is the rotating part and has rotor magnets whereas stator is the stationary part and contains stator windings. In BLDC permanent magnets are attached to the rotor and move the electromagnets to the stator. The high power transistors are used to activate electromagnets for the shaft turns. The controller performs power distribution by using a solid-state circuit.

Stator windings of a BLDC motor are connected to a control circuit or an integrated switching circuit. The control circuit energizes proper winding at a proper time, in a pattern which rotates around the stator. The rotor magnet tries to align with the energized electromagnet of the stator, and as soon as it aligns, the next electromagnet is energized. Thus the rotor keeps running. 

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