WHAT IS BRUSH-LESS DC MOTOR ?
Also known as BLDC motor or BL motor, it is the DC motor which does not have brushes. Motor is the heart of an Electric Vehicle. It is called Brushless because it doesn’t have brushes and commutator arrangements. Here the commutation is done electronically.
PRINCIPLE OF BLDC MOTOR:
The working principle of BLDC motor is similar to Brushed DC motor. The reversal of current in Brushed DC motor is done by Commutator and Brushes whereas in BLDC motor sensors are used, mostly hall-effect sensors. The hall-effect sensors generate a high or low signal whenever rotor magnetic poles cross the hall sensors, which can be used to detect the position of the shaft.
TYPES OF BLDC MOTORS:
They are classified based on designing and their working procedure is the same.
- Outer rotor design
- Inner rotor design
OUTER ROTOR DESIGN: The rotor of the motor is situated outside and it surrounds the stator which is located in the center of the motor has multi-phase winding. The windings are fed with current and are controlled(commutated) to effect rotation of the rotor. There is no need of external gear system in this type of design and in few instances the motor itself comes with inbuilt gears. Therefore, without any gear system this design makes the device less bulky. The magnets present in the rotor acts as an insulator and will not allow the heat to dissipate from the motor. Outer rotor designed motor has low torque and operated at low current rates.
INNER ROTOR DESIGN : As in the image the rotor is situated in the centre of the motor and is surrounded by the stator winding. The rotor magnet does not shield the heat inside and the heat will be dissipated effortlessly, thus increasing the torque.
WORKING OF BLDC MOTOR
The BLDC motor has 2 main parts rotor and stator. The rotor is the permanent magnet and is rotating part. The stator is the armature winding and is the stationary part. In BLDC motor coils do not rotate as in Brushed DC motor instead they are fixed onto the stator. There is no need of commutator and brushes since coils are static.
Refer https://futuretronlabs.in/blog/index.php/2019/09/25/electric-motor/ to know more about the working of an electric motor.
Mechanical rotation is produced when the magnetic field generated by the permanent magnets(rotor) comes in contact with the field induced by the current in the stator windings. The magnitude and direction of the current into the coils are adjusted to control the rotation.
Hall effect sensors are mounted on the stator or rotor. As the rotor rotates the hall effect sensors senses the magnetic field and produces a high signal for one pole or low signal for opposite pole. These sensors are connected to the Electronic control unit. Electronic control unit switches the supply voltage between the stator winding as the rotor rotates and energize the correct winding at correct time in such a way that it rotates the rotor around the stator. According to these combinations of signals electronic unit will decide the next commutation sequence or interval to activate.
Some of the advantages of Brushless DC motors are they are highly efficient, exceptional controllability, produce high torque, higher speed range compared to other motors, Operating life is long due to absence of electrical friction losses, Operation is noise-less, high dynamic response. It has power-saving advantages also. Due to its traction characteristics they are most preferred motors in electric vehicle applications.
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