Abstract
There is a necessity to design a three-phase squirrel cage induction motor (SCIM) for high-speed applications with a larger air gap length in order to limit the distortion of air gap flux density, the thermal expansion of stator and rotor teeth, centrifugal forces, and the magnetic pull. To that effect, a larger air gap length lowers the power factor, efficiency, and torque density of a three-phase SCIM. This should inform motor design engineers to take special care during the design process of a three-phase SCIM by selecting an air gap length that will provide optimal performance. This paper presents an approach that would assist with the selection of an optimal air gap length (OAL) and optimal capacitive auxiliary stator winding (OCASW) configuration for a high torque per ampere (TPA) three-phase SCIM. A genetic algorithm (GA) assisted by finite element analysis (FEA) is used in the design process to determine the OAL and OCASW required to obtain a high torque per ampere without compromising the merit of achieving an excellent power factor and high efficiency for a three-phase SCIM. The performance of the optimized three-phase SCIM is compared to unoptimized machines. The results obtained from FEA are validated through experimental measurements. Owing to the penalty functions related to the value of objective and constraint functions introduced in the genetic algorithm model, both the FEA and experimental results provide evidence that an enhanced torque per ampere three-phase SCIM can be realized for a large OAL and OCASW with high efficiency and an excellent power factor in different working conditions.
Highlights
A squirrel cage induction motor (SCIM) requires reactive power for operation
This paper has presented a genetic algorithm optimization method assisted by finite element analysis to obtain optimal air gap length and capacitive auxiliary stator winding values for three-phase squirrel induction machines
The sensitivity analysis in the finite element model showed great results for the torque per ampere, efficiency, and power factor when the air gap length and capacitance auxiliary winding varied, only a single objective function was defined in the genetic algorithm model presented in this paper instead of a multi-objective function
Summary
A SCIM requires reactive power for operation. its power factor is intrinsically poor, and it is especially worse when starting or operating under a condition of light load [1]. This paper is an advanced work based on the analysis outlined in [1,2], it presents an optimization method that would assist with the determination of an OAL and OCASW for an enhanced torque per ampere three-phase SCIM suitable for high-speed applications. It further elaborates on an analytical approach that describes the engineering problem and its solutions based on key design variables and the machine circuit parameters. The experimental and FEA results of the SCIM with OAL and OCASW are analyzed in Section 6, and Section 7 summarizes the paper
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