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Abstract-The zero crossing detection is essential in twelve sensorsless control using back-EMF. To increase output power of Brushless DC motor (BLDCM), traditional twelve step control has extended active angular period. It has drawback which become unstable the performance of the drive system in rated load condition because a period for detecting zero crossing point of terminal voltage is reduced. To solve this problem, this paper proposes the advanced twelve step sensor-less control of a BLDCM using field oriented control (FOC), which combines the traditional twelve step sensor-less drive scheme and single shunt three phase current reconstruction algorithm. The effectiveness of this proposed control is verified by the simulation and experiment result according to the comparison of the output characteristics between the traditional and proposed control.

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Recently Line Start Permanent Magnet Machine (LSPM) is a well-known motor due to its technical advantages in academic and industrial sector. The LSPM combines a permanent magnet rotor that allows higher motor efficiency during synchronous operation, and an induction motor squirrel cage rotor for starting the motor by connecting it directly to an A.C. Source. Such a construction generates important technical advantages like reduced manufacturing costs and better performances. In this paper, we will deal with the efficiency and Power factor improvement of a 3.4kW, 2-pole, three-phase LSPM using the difference in d-axis magnetic inductance (Ld) and qaxis magnetic inductance (Lq). d-axis and q-axis magnetic inductance are nonlinear problem which are varied with current level and current angle. Therefore, nonlinear finite element analysis is necessary to obtain the Ld and Lq. The efficiency improvement can be effectively achieved by designing optimization of the rotor structure using finite element method. The optimized slot shape of PM was selected for the prototype machine, which improves the efficiency and power factor of LSPM.