Advanced conduction angle control of permanent magnet brushless motor drives

A novel advanced conduction angle control scheme for permanent magnet brushless motor drives is presented in this paper. The originality of this scheme is to employ the transformer EMF in stator windings to counteract the rotational EMF by controlling the advanced conduction angle when the motor drive operates above the base speed. Hence the constant-power operation region can be extended considerably, even though the current regulator is in saturation. The attractive feature of the proposed control scheme is that it has better controllability and easier to implement than conventional flux-weakening control scheme because of the absence of coordinate transformation. It can be applied to all PM brushless motors, including conventional, phase-decoupling, sinusoidal-fed and rectangular-fed types. An Intel 8098-based digital controller and a phase-decoupling rectangular-fed PM brushless motor are employed to implement the scheme. The hardware and the software are simple and flexible. Both computer simulation and experimental results of a 1-kW motor drive system verifies that the proposed control scheme works well.