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BRUSHLESS MOTOR & DRIVE. CONTENTS. INTRODUCTION WORKING OF MOTOR BRUSHLESS MOTOR WORKING OF BLDC TESTING AND TUNING ADVANTAGES OF BLDC MOTOR. INTRODUCTION. What is Motor ? It is a machine can converts electrical energy to mechanical energy.
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BRUSHLESS MOTOR & DRIVE
CONTENTS • INTRODUCTION • WORKING OF MOTOR • BRUSHLESS MOTOR • WORKING OF BLDC • TESTING AND • TUNING • ADVANTAGES OF BLDC MOTOR
INTRODUCTION • What is Motor? It is a machine can converts electrical energy to mechanical energy. It may be DC or AC depending upon the type of power supply. It has mainly two parts- stator & rotor. DC motors are of two types- • Brushed motor –with brushes and commutator and • Brushless motor- without brushes.
INTRODUCTION • What is commutator and brush ? • Commutator is a cylindrical in structure, made of copper or carbon with high conductivity. • Mounted on the rotor part of the brushed motor. • Helps to conduct current through conductor when the brushes comes to contact during rotation. The electrical contacts to the rotating ring called brushes.
BRUSHLESS MOTOR • It has no brushes and commutators. • The rotation of the rotor depends on the accurate position with stator. • Detected by Hall Sensor, mounted on rotor, shifted at 60º or 120º phase shift. • Electronic commutation used to vary the PWM duty-cycle for speed control, using software.
Working of BLDC motor As there is no commutator ,the current direction of the conductor on the stator controlled electronically. Rotor consists the parmanent magnet where as stator consist a no. of windings. Current through these winding produces magnetic field and force. Hall sensor used to determine the position during commutation.
Commutation of BLDC motor • Brushless DC motor requires external commutation circuit to rotate the rotor. • Rotor position is very important. • HALL SENSOR senses the position of the coil accurately
Hall Sensor operation • It embedded into the stator on non-driving end of motor. • Senses accurate position of the rotor to the stator. • Shifts at 60º or 120º phase shift for each of three coils, yet a time two coils work for 3Φ current • Due to the changing of direction of the current & applying Fleming’s Left Hand rule force direction can be determined. • Thus the permanent magnet on rotor moves clockwise , as well as the rotor of the BLDC also moves clockwise.
PWM requirement • To control the speed PWM is required. To vary the speed the Hall output signals should be pulse width modulated. • When the signals marked by PWM switches ON or OFF according to the sequence, the motor will run at the rated speed. • The PWM frequency should be at least 10 times of the max. frequency as thumb rule. • By varying duty cycle, the stator voltage can be increased causes increasing of the speed.
Machine rated speed 1000rpm, commutated with 6 pulses… Required frequency f= 1000×6 = 6000 pulse/min. Therefore, speed in pulse/sec= 6000/60= 100 Hz. And the PWM frequency= 10×100 Hz =1kHz. Thus the speed depends on the switching frequency i.e. switching period. By varying duty cycle PWM freq. varies and switching speed also varies. It is controlled by electronically through software PEWIN32PRO in GMRT rayshed.
Advantages of Brushless Motor • In BLDC motor PM are on the rotor & electromagnets are on the stator controlled by software. Thus the advantages are: • Because of computer control it is more precise & more efficient. • There is no sparking & less electrical noise. • Voltage and current rating is high. • High speed can be achieved. • As there is no brushes it requires no servicing. • It has longer life. • Low Radio Frequency Interference and Electromagnetic Interference.
