Modeling and simulation of sensorless control of PMBLDC motor using zero-crossing back E.M.F. detection

In the present scheme, modeling and simulation of sensorless control of permanent magnet brushless DC (PMBLDC) motor is carried out using zero-crossing back e.m.f technique. Since the neutral point of star connected machine is floating and not accessible to detect zero-crossing points, line back e.m.f information is considered. The motor is commutated at zero-crossing point of back e.m.f at 0deg delay (no delay), 18.5deg delay and 28deg delay instants of commutation from zero-crossing point of line back e.m.f signals. The various waveforms like line back e.m.f, phase currents, rotor position, speed, torque with respect to time at no-load, half-load and full-load are obtained. From the results it is observed that the torque developed by the motor at larger delay angles is more pulsating due to more peak to peak currents