Brushless Direct Current Motor

Abstract

The development of permanent magnet materials with high magnetic energy product lead to the development of dc machines with Permanent magnet field excitation. A BLDC motor is a motor having stator similar to a synchronous motor and permanent magnets in the rotor, operates in self-controlled mode by the use of position sensors to detect rotor poles and an inverter for controlling the phase currents of stator winding. In conventional dc motor, the commutator and brushes are needed, which are subjected to wear and require maintenance. In BLDC motor, the function of commutator and brushes are implemented by using semiconductor power switches and digital controllers and hence maintenance free motor can be released. This motor is called BLDC motor. The rotor position sensors and the semiconductor power switches in the inverter performs the role of the commutator and brushes of the conventional dc motor. A conventional dc motor has stationary field system which consists of field magnets. It produces magnetic field in the machine. The armature is rotating part and it is the rotor. The armature is free to rotate between the field poles and it is mounted on the shaft. The construction of BLDC motor is similar to the AC motor called Permanent Magnet Synchronous Motor (PMSM). The brushless dc motors offer many advantages as compared to conventional dc motors. BLDC motors have small size rotor, high power density, low inertia, higher efficiency and requires lower maintenance. High speed and torque capability because of absence of commutator and brushes. Presently BLDC motors are the significant contributors for the modern drive technology. They are used for a wide variety of applications in the fields of Electric vehicles, hybrid vehicles, robotics, computer disk drives, servo drives, DVD players, fans, washing machines, pumps, blowers, compressors, Industrial robots and CNC machine tools etc.