Articles written in Sadhana

    • Comparative analytical and experimental study of fabricated identical surface and interior permanent magnet BLDC motor prototypes


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      This paper presents a novel and exhaustive investigation involving in-depth analysis, performance evaluation and comparative study of two 0.75 hp, 4-pole, 1500 rpm laboratory prototypes of Brushless DC (BLDC) motors of identical nominal ratings with surface and interior permanent magnet rotor structures havingthe same stator and winding (integral slot distributed winding). Both the motors were designed and developed in the lab. The major electrical variables (such as rated power, speed, voltage, current, number of poles, etc.) and the stator (such as core material, stator lamination, stack length, winding pattern and wire gauge) of the fabricated prototypes have also been kept identical to pin-point the direct influence of the two different rotor configurations (viz., surface vs interior permanent magnet) on the parameters, performance and operation ofthese BLDC motors. Additionally, to ensure unbiased basis for appropriate comparison, the overall volumes of magnets/pole in both the motors have also been kept similar. A detailed comparison of different quantities likeair-gap flux density distribution, THD in induced voltage, torque ripple, losses and efficiency, torque–speed characteristics with field-weakening capability, steady state parameters at different operating conditions, etc. has been conducted for the said motors and the salient points duly highlighted. The vulnerability of the permanent magnets to demagnetisation based on armature reaction, particularly during a sudden fault, has also been investigated in both the cases. The theoretically determined parameters and analytically evaluated performancefigures have been verified through standard FEM packages, and later validated experimentally on the fabricated prototypes. Very good mutual agreement has been observed between predicted and experimental values.

    • Design, analysis, parameter evaluation and testing of a laboratoryfabricated brush-less DC motor prototype


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      This paper presents detailed steps and procedures for the design of a 4-pole, 0.75-hp, 1500-r.p.m. surface-mounted permanent magnet brush-less DC (SPM-BLDC) motor. The motor has been fabricated at the works of a local manufacturer. The parameters of the machine have been analytically evaluated and subsequently compared to the experimentally determined values. Its practical performance on load has been experimentally evaluated in the laboratory and verified against analytical predictions too. Low-cost M45 electrical steel laminations, as used for commercial induction motors (IMs), have been used from considerations of cost and availability. This also enables direct comparison of important parameters (e.g. torque density, power density and efficiency) between the fabricated prototype and commercially available fractional-hp 3-phase and 1-phase IMs of similar rating. This study is significant since electrical motor manufacturers need not change their stator stamping production line for BLDC motor vis-a-vis IM in case of mass production. Such an approach is hardlyreported in the available technical literature. Analytical methods adopted include both conventional hand calculations and finite-element analysis using commercially available software package(s). Excellent agreementsbetween analytical and experimental values uphold the correctness of the design process, precision of fabrication and accuracy of experimental investigations

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