Analytical Design Framework for Torque and Back-EMF Optimization, and Inductance Calculation in Double-Rotor Radial-Flux Air-Cored Permanent-Magnet Synchronous Machines

Abstract

Analytical models have been demonstrated to be effective tools in the analysis of electromagnetic devices by providing fast, yet accurate solutions. In this paper, a comprehensive analytical framework for double-rotor radial-flux air-cored permanent-magnet (PM) machines is developed whereby the average as well as the torque ripples, back-electromotive force waveforms, air-gap flux density distribution, and a number of other characteristics regarding the design of the machine are predicted. Also, closed-form expressions for inductances of the stator coils are analytically derived. All machine parameters and material properties including iron saturation are considered in the model. Moreover, an algorithm in order to optimally design the thicknesses of the rotor yokes based on the utilized steel is presented. Finally, genetic optimizations regarding the enhancement of the produced torque and back-EMF are performed. It is also shown that the results obtained from the proposed model match well with those issued from FEM.Index Terms-finite element method, genetic optimization, inductance calculation, magnetic equivalent circuit, nonlinear modeling, permanent-magnet machine, double-rotor radial-flux machine.

Performance Prediction and Analysis of Adjustable-speed Permanent Magnet Eddy-current Couplings

“…And this is mainly produced by induced current losses dissipated in the conductive plate. The eddy currents induced in the conductive plate can be calculated from Lorentz's equation, (14) Thus, the eddy current loss can be given as follows (15) and the transmission torque is given by (16) where, ω = ω p − ω s . Substituting (14) into (16) yields 173.…”

“…In this condition, the torque is proportional to the slip [21]. However, with the increase of the slip values, the resulting reaction field will not be able to ignore, and tends to distort the original flux distribution produced by the PM, and thus the effective air-gas magnetic field will be the sum of the PM field and the reaction field [3,16,23]. In this condition, the derivation of the torque becomes complicated and (19) will no longer be accurate, but the proposed method can be potentially combined with other method developed in [16,23] to get good results.…”

“…Magnetic equivalent circuit (MEC) is one of the oldest techniques for solving magnetic field problems. The approach has been applied in all sorts of electromagnetic machines, for example, permanent-magnet motor in [16][17][18][19], brushless doubly fed reluctance generator in [22] and induction machines in [20,21]. Due to the similarity in form between magnetic circuit and electric circuit, it is easy to facilitate understanding.…”

Study on Process Derivation and Characteristic Analysis for BLDC Design using Dual Rotor Method with High Torque Density

“…Study on the theory of injecting harmonics to improve torque capacity [4], application of magnet or rotor skew to improve torque ripple [5][6][7], and study on applying magnet splitting [8], harmonics of back EMF research to reduce is being actively conducted. [9][10] However, more discussion is needed to solve the design difficulties due to difficult fabrication and low efficiency due to dual rotor characteristics [11][12][13]. In this flow, this paper aims to complete the basic design process for dual rotors through magnetic equivalent circuits, electromagnetic field finite element analysis, and optimization techniques, and finally realize high torque density, high efficiency and miniaturization.…”

Comparison, With an Analytical Optimization Process, of Two Synchronous Halbach Permanent Magnet Machines, for a Direct Drive Stick Application

“…This change improves the power density and therefore the expected performances of the actuator, as demonstrated in [9]. The second structure is a Double Airgap Rotating synchronous PM Machine with a non-entire arc called DARM, as in [10]. Figure 2 shows the DARM, for one axis (pitch or roll).…”