Wonseok Han

In this paper, an analytical method for predicting the rotor overhang (OH) effect is presented using two types of conformal mappings (CMs), which are the r-θ and zr plane CMs. First, the no-load air-gap flux density (AFD) of a slotted air gap without OH is determined using the rθ plane CM. Second, the complex relative air-gap permeance (CRAP) in the zr plane is obtained by the zr plane CM. This helps in taking the OH effect into account. Finally, the no-load AFD of the slotted and OH air gaps in cylindrical coordinates is derived from the no-load AFD in the rθ$ plane with CRAP along the z-axis. The accuracy of the presented method is verified by comparing the results of no-load analysis with those of 3-D finite-element analysis.

Finite element analysis-based optimal design of electric machines takes up a considerable amount of time for characteristic analyses and the analysis region has many local optima. Thus, selecting the appropriate global search optimization algorithm, known as the with fast convergence characteristics is necessary in the optimal design of electric machines. In this paper, a novel global search optimization algorithm known as the global-simplex optimization (GSO) algorithm, is proposed. The GSO is an optimization algorithm that adopts the characteristics of the simplex method for searching the optimum point but utilizes its global searching capability by scattering many initial points at the beginning of the algorithm. The global searching capability and convergence speed of GSO is validated through a comparison with particle swarm optimization, which has already been proven for its global searching capability through its application in the well-known Goldstein-Price benchmark function. In addition, the GSO has been applied to the optimal design of an interior permanent magnet synchronous machine to reduce the torque ripple and total harmonic distortion in its back electromotive force.

The Brushless DC(BLDC) motor shows different characteristics when it operates on ideal current source of 6-step voltage source. The efficiency characteristics of BLDC motor is different according to its input condition. In this paper, efficiency characteristic analysis is conducted on A-connected BLDC Motor for three kinds of input conditions, that is, ideal current source, 6-step voltage source and hysteresis current control. The core loss characteristics are compared for the three input condition on fixed output and copper loss condition. In detailed, phase currents of each input condition and core losses are competitively analyzed on frequency domain and draw a correlation between phase current and core loss. For validity of this paper, 2D Finite Element Analysis (FEA) is conducted in suggested motor model.