Line-start synchronous machines (LSSMs) emerged as an efficient alternative for induction machines in numerous constant speed applications. This study reviewed evolution, technological advancements, design concepts, optimisation techniques, and possible applications in a comprehensive manner. A case study on the reviewed LSSM has been carried out based on its suitability in agricultural applications in India. Further, the performance comparison and significant advantages between the existing induction machine and LSSM are finally discussed.

Summary The efficiency of the motor is of paramount importance during selection and operation as well as energy consumption. In countries like India, international efficiency class (IE2) is versatile in use. Prominent efficiency improvements can produce very large energy savings across the country. Induction motors (IMs) are widely used for pump applications in India. IM exhibits high rotor (I2R) losses due to the presence of rotor current. This results in less efficient, more energy consumption compared with energy‐efficient motors. Energy‐efficient motor such has single phase direct‐on‐line synchronous reluctance motor (DOL‐SynRM) would be a right alternative for IM due to the absence of rotor current. DOL‐SynRM has been designed, optimized, and tested for a centrifugal pump application. Initially, single phase SynRM with capacitor start and capacitor run is modeled using equivalent circuit parameters and simultaneously simulated using MATLAB. The machine parameters like rib width, length, and thickness are optimized using genetic algorithm technique. The optimized rotor structures are taken to numerical analysis platform for performance prediction. The flux distribution, moment of inertia, air gap flux density, the effect on the inductances, starting torque, average torque, and torque ripple are thoroughly investigated using this analysis. The high‐efficiency rotor structure is fabricated and configured with a centrifugal pump. Experimental results reveal that the overall system efficiency has been improved compared with the existing induction motor. Moreover, thermal analysis is carried out for two types of frame structures (conventional and proposed) to study the hot spot in the proposed motor.

Summary Self‐start (often called line start) synchronous reluctance motor (a type of synchronous motor) designed with different rotor structures have been analyzed and compared. The torque, output power, rotor mass, and efficiency are calculated through theoretical study. A genetic algorithm is performed to attain optimal machine parameters. The flux distribution, effect on the inductances, starting torque, average torque, power factor, efficiency, and torque ripple are completely examined by the numerical study. The energy consumption comparison of self‐start synchronous reluctance motor and induction motor are calculated. Further, a study on the effects of end‐ring resistance is discussed for starting and steady‐state conditions. Experimental results reveal that the fabricated high efficient rotor structure is closely correlated with the numerical and theoretical studies.

The interaction of spatial harmonics of electrical loading and the rotor anisotropy causes torque ripple in line start synchronous reluctance motor (a type of synchronous motor). A novel design technique for torque ripple reduction is presented in this study. Initially, synchronous reluctance motor filled with conducting material inside the flux barrier (called cage barrier) is optimised using a genetic algorithm (GA) technique. The optimised design is further verified using finite element analysis (FEA) and tested. To reduce the ripple content, the rotor has been introduced with an additional d-axis cage. Six rotor structures with an additional cage have been designed and optimised using FEA. The numerical analysis results are compared for all rotor structures. The optimised rotor structures with and without d-axis cage are fabricated and tested. Experimental results reveal that the fabricated rotor with an additional cage has reduced torque ripple and high efficiency. Finally, the acoustics test is carried out for both the fabricated structures and results are compared.

A permanent magnet assisted synchronous reluctance generator (PMA-SynRG) and an induction generator (IG) were compared for portable generator applications. PMA-SynRG with two rotor configurations, namely rotors with ferrite magnet and NdFeB, were designed. Furthermore, a design strategy for both PMA-SynRG and IG is presented with their geometrical dimensions. The machine was designed and results were analyzed using finite element analysis. Results such as flux density, open circuit and full load voltages, torque in generating mode, weight comparison and detailed cost analysis were investigated. In addition, thermal analysis for various ambient conditions (−40 °C, +30 °C, +65 °C) was evaluated for both PMA-SynRG and IG. Furthermore, acoustic versus frequency plot and acoustic pressure level were investigated for both the generators. Finally, the results confirmed that the machine with a higher power-to-weight ratio was the right choice for military applications.

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