Articles written in Sadhana

    • Recent advances in permanent magnet brushless DC motors

      Bhim Singh

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      This paper deals with the latest developments in Permanent Magnet Brushless DC (PMBLDC) motor drives. A comprehensive account of the state-of-the-art on types of construction of the motor, closed loop controllers in position, speed and current/torque control and recent trends in inverters, sensors etc. are given. Techniques for mechanical sensors elimination are discussed in detail. Special efforts made to reduce torque ripples, noise and vibrations are described. The impact of microelectronics through integrated chips used in the control of PMBLDC motor drives is given. The increasing applications of this drive due to improved performance and its cost reduction are also enlisted.

    • Single-stage unity power factor based electronic ballast


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      This paper deals with the design, modeling, analysis and implementation of unity power factor (UPF) based electronic ballast for a fluorescent lamp (FL). The proposed electronic ballast uses a boost AC–DC converter as a power factor corrector (PFC) to improve the power quality at the input ac mains. In this singlestage UPF based electronic ballast, boost PFC converter and a half bridge series resonant inverter (HBSRI) share a common power switch. Thus one power switch is reduced as compared to the conventional two-stage approach. The design, modeling, analysis and implementation of this topology were carried out in MATLAB-Simulink environment for a T8 36 W, 220 V, 50 Hz fluorescent lamp. The switching frequency was kept morethan the resonant frequency of the inverter, to ensure the zero voltage switching (ZVS) operation of both power switches. This resulted in reduction of high frequency switching losses. The power quality parameters such as displacement power factor (DPF), distortion factor (DF), power factor (PF), crest factor (CF) and total harmonicdistortion of ac mains current (THDi) were evaluated to analyze the performance of proposed electronic ballast. Test results on a developed prototype of PFC electronic ballast were included to validate the design and simulated results.

    • Improvement of torque and permanent magnet operating flux density in a novel flux-intensifying spoke PMSM based on peripheral and internal barriers


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      This paper presents a flux-intensifying spoke permanent magnet synchronous motor (FIS-PMSM) based on peripheral and internal barriers that exhibits enhanced maximum torque, lower torque ripple and higher permanent magnet (PM) operating flux density. The flux-intensifying effect is realized by using internal barriers while the maximum torque is increased through peripheral barriers. Besides, the influences of barrier dimensions on torque, torque ripple and PM operating flux-density are investigated in order to improve these performances. Therefore, the first objective of this work is to present basic concept behind the improvement in performance of FIS-PMSM while the second objective is to enhance the torque and to reduce the torque ripple while improving the PM operating flux density though variation in flux barrier dimensions. Based on this analysis, the final barrier dimensions are selected and the electromagnetic performances of FIS-PMSM like inductance profile, torquecharacteristics and PM flux density plots are evaluated by using finite element method to demonstrate the achieved advantages.

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