Brushless dc motor | bldc motor

Brushless dc motor is the permanent magnet synchronous electric motor that operates by DC supply. Brushless dc motor is used to convert electrical energy into mechanical energy like other motors. This type of motor is also known as trapezoidal permanent magnet motor.

Construction of BLDC motor

Brushless dc motor consist with stator and rotar like other type of electric motor. It has some similarities like three phase induction motor and DC motor because it has also stator and rotor.

it’s stator core is made up of laminated Silicon Steel Silicon Steel have high permeability that is property of material which supports the magnetic field. Lamination is the arrangement of various thin sheets that combined together for reducing electrical losses. Brushless dc motor can be design single phase , 2 phase or three phase according to application generally 3 phase brushless dc motor are most commonly used.

at the inner peripheri of stator core axially cuts are present where we place stator winding that can be connected in either star or delta. Most of the brushless dc motor prefer three phase Star connection on stator peripheri.

each strater winding constructed with numerous interconnected coil where one or more coil placed in each slots. Generally copper material is used for winding due to their high electrical conducting properties. According to voltage capability we select the correct stator core of motor.

for robotics automation and Small actuating applications we prefer 48 volt or less rating brushless dc motor. Industrial application and automation system in industry we prefer 100 volt or higher BLDC motor.

Rotor : permanent magnet rotor is used in bldc motor that have 2 to 8 poles pair can be possible according to different application. To achieve the maximum torque , flux density of rotor magnet should be high so we select a special magnet material in which flux density of rotor magnet should be high. Generally we use samerium cobalt, neodinium , ferrarite and Boron magnetic material. These material have maximum flux density.

Rotor core : Rotor core configuration can be design of different types like .. circular core with permanent magnet circular core with rectangular magnet etc..

Why do we use permanent magnet as rotor in brushless dc motor ?

since in case of conventional DC motor commutator and process are used to energize the roto winding but in case of brushless dc motor commutator and brushes are not used and with brushes it is not possible to give the supply in rotor winding. That’s why we use permanent magnet as a rotor in bldc motor.

Working principle of BLDC motor

Each phase of brushless dc motor energize separately .

Suppse in starting phase-A has energize and north , south ( N-S) polarity develop on stator pole and we are using permanent magnet Motors so magnetic polarity will be constant so stator pole will attract opposite polarity of rotor pole. If stator phase-A has N-pole then it will attract S-pole of the rotor, rotor will align towards phase-A.

After that phase-B will energize and developed magnetic pole on stator will attract opposite polarity of rotor and rotor will align towards phase-B. Then Phase-C and Phase-D will energize and attract the opposite polarity that develop on rotor pole and rotor will align accordingly .

after half rotation of rotor we change the terminal of each phase so that rotor can rotate continue in clockwise direction. After half rotation we will not change the terminal of different phase than instead of attraction force between rotor and stator repulsion force will be act due to same polarity of rotor and stator .

as you can see in above diagram stator phase (a’) has S-pole and near rotor pole is also S-pole so same pole will repell to each other that’s why we change the terminal of all phases after half rotation.

when we change the terminal then magnetic polarity on stator pole also changes. Now stator phase (a’) has N-pole so N-pole of stator will attract S-pole of rotor and the (b’) , (c’) ,(d’) will energize separately and rotor will rotate in clockwise direction continuously. Thus rotor of brushless dc motor rotates clockwise continuously.

Key points

to energize the different stator phase separately electric speed controller and hole sensor is used
electronic speed controller energize the stator next phase according to rotor position.
Electronic speed controller behave like commutator so brushless dc motor is also known as electronic commutated DC motor.

Applications

brushless dc motor used in hardware devices and DVD / CD players , drive the spindle that rotate the disc.
BLDC Motors are used in household applications like washing machine , dryer , air conditioner , vacuum cleaners and other important appliances.
this type of DC motor is used in drones and other aerial devices where is provide precise control and high efficiency.
bldc Motors are used in industrial automatic and CNC machine uses this type of Motors where it provide precise control and high reliability with low maintenance.
Brushless dc motor is used in medical equipment like it is used in ventilators , CPAP machines and robotic surgical instrument uses this type of DC Motors.

Advantages

Bldc motor provides higher efficiency that is about 85 to 90% compare to other DC Motors that have commutator and brushes. Because heat generated by the brush and commutator.
this type of motor don’t uses carbon brush and commutator so its life is long , and low maintenance is required.
when bldc motor operates it produces less noise and also vibration are minimum so we can say bldc motor provides quite operation.
this type of motor provides the precise and smooth speed control that make it suitable for that type of application where accurate and precise operation is required.
this type of DC motor can deliver high torque for their size and weight ratio that make it suitable for that type of application where space and weight of the motor is important.

Disadvantages

Bldc motor uses electronic speed controller that increases the complexity of the motor operation.
electronic speed control mechanism can generate electromagnetic interference that causing operational risk
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