Byung-Chul Woo

Ultra High Speed Motor Supported by Air Foil Bearings for Air Blower Cooling Fuel Cells

As accomplishing the research of the PM synchronous motor driven by 15 kW at the rated speed of 120,000 rpm, this paper represents an approach to minimize eddy current losses which occur prominently at high speed. Various simulation and testing techniques are therefore applied to determine the effect of design parameters. Here, the proposed parameters for analysis are winding types, slot opening width and sleeve thickness. This paper based on the obtained results, evaluates the optimum value of the most critical design parameters responsible for eddy current loss. Finally, this paper studies the developed model which represents a solution for minimizing the cause of eddy current loss by implementation of sinusoidal distribution of air-gap magnetic flux density. It comes to the conclusion that sleeve thickness should be chosen as considering a function of mechanical stress and critical speed of rotor. Furthermore, the critical speed of rotor is evaluated by rotor dynamics. The design efficiency is well accorded with the efficiency test, having a maximum error of 2.7%.

Optimum Design of Transverse Flux Linear Motor for Weight Reduction and Improvement Thrust Force Using Response Surface Methodology

Permanent magnet (PM)-type transverse flux linear motors (TFLMs) are electromagnetic devices which can develop directly powerful linear motion. The unique configuration makes power of output higher than longitudinal motors, but also it makes characteristic analysis difficulties. This paper deals with an effective analysis of PM-type TFLM by 3-D equivalent magnetic circuit network method (EMCNM). This paper presents optimum design of PM-type TFLM to reduce the weight of the machine with the constraints of thrust and detent force using response surface methodology (RSM). RSM was well adapted to make the analytical model of the minimum weight with constraints of thrust and detent forces and enable the objective function to be easily created and a great deal of the time in computation to be saved. Therefore, it is expected that the proposed optimization procedure using RSM can be easily utilized to solve the optimization problem of electric machines.

A Novel Design of Modular Three-Phase Permanent Magnet Vernier Machine With Consequent Pole Rotor

The permanent magnet vernier machine (PMVM) is known to be well suited for direct drive applications due to its high torque characteristics at low speed. This paper introduces a novel design of PMVM comprising a modular stator and a consequent pole rotor. The proposed design magnetically decouples each phase and suppresses the magnetic unbalance caused by the consequent pole rotor.

Fractional Slot Concentrated Winding Permanent Magnet Synchronous Machine With Consequent Pole Rotor for Low Speed Direct Drive

Fractional slot concentrated winding permanent magnet synchronous machines (FSCW PMSMs) are suited for low speed direct drive since they offer comparatively large number of poles, high torque density, and low torque ripple. This paper introduces feasibility study on FSCW PMSMs with consequent pole (CP) rotor for low speed direct drive. A 40 pole-48 slot FSCW PMSM with CP rotor is analyzed and characterized by extensive 2-D finite-element analysis. The analysis reveals the proposed topology can achieve good performance.

Rotordynamics of 120

This paper introduces a rotor with shrink fit and analyzes its rotordynamics by 3-D FEA. An ultra high speed motor prototype is manufactured for fuel cells at the rating of 15 kW, 120000 r/min. First, the stability of the rotor structure with shrink fit is evaluated in non-loading and loading condition (120 000 r/min, 210degC). And then the 3-D rotordynamics analysis and Campbell diagram considering shrink fit are examined for the critical speed of rotor. The analysis shows that the critical speed of the rotor is higher when the rotor is shrink fitted than when the rotor is not shrink fitted. The analysis also shows the increase of shaft stiffness when the rotor is shrink fitted.

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This paper presents optimum design of transverse flux linear motor (TFLM) to reduce the weight of the machine with the constraints of thrust and detent force. Employing penalty functions, each constraint is included in the characteristic function, and the response value is determined by three dimensional magnetic field analyses. Finally, the contribution and effect of the each design variable on the characteristic function is evaluated by the analysis of means (ANOM), and optimum design set is determined. With this procedure, the weight of initially designed TFLM can be reduced 10% with small variation of thrust and detent force

000 r/min 15 kW Ultra High Speed Motor

Permanent magnet linear synchronous motors (PMLSMs) have been successfully adopted in a wide variety of industry applications due to improved servo-capability and outstanding dynamic characteristics. However, the conventional PMLSMs need a large amount of permanent magnet (PM) material in the stator resulting in significant cost rise. This paper proposes and analyzes a new doubly salient PM linear synchronous machine (DSPMLSM). The proposed configuration consists of consequent pole stator to reduce PM material and modular mover structure to reduce force ripples. Four different models are chosen and compared by two-dimensional finite element analysis (FEA). The analysis reveals that the proposed DSPMLSM uses only a half amount of PMs, while retaining almost the same characteristics as the conventional PMLSMs.

Optimum Design of TFLM With Constraints for Weight Reduction Using Characteristic Function

This paper deals with a 44pole-48slot fractional slot concentrated winding permanent magnet synchronous machine (FSCW PMSM) for a low-speed direct drive. Two different rotor topologies, a surface permanent magnet (SPM) rotor and a consequent pole (CP) rotor, are optimized and compared both analytically and experimentally. The experimental results confirmed that an FSCW PMSM with a CP rotor can achieve almost equivalent performance at the rated state when compared to an FSCW PMSM with an SPM rotor with 33% less permanent magnet material.

A Feasibility Study on a New Doubly Salient Permanent Magnet Linear Synchronous Machine

A new method for detecting eccentricity and broken rotor bar conditions in a squirrel-cage induction motor is proposed. Air-gap flux variation analysis is done using search coils, which are inserted at stator slots. Using this method, the leakage flux in radial direction can be directly detected. Using finite element method, the air-gap flux variation is accurately modeled and analyzed. From the results of the simulation, a motor under normal condition shows maximum magnetic flux density of 1.3T. On the other hand, the eccentric air-gap condition displays about 1.1T at 60° and 1.6T at 240°. A difference of flux density is 0.5T in the abnormal condition, whereas no difference is detected in the normal motor. In the broken rotor bar conditions, the flux densities at 65° and 155° are about 0.4 T and 0.8T, respectively. These simulation results are coincided with those of experiment. Consequently, the measurement of the magnetic flux at air gap is one of effective ways to discriminate the faulted conditions o...

Fractional Slot Concentrated Winding PMSM With Consequent Pole Rotor for a Low-Speed Direct Drive: Reduction of Rare Earth Permanent Magnet

The aim of this paper is to provide performance comparisons between conventional longitudinal flux and transverse flux permanent-magnet machines using three-dimensional finite element analysis considering both electro-magnetic and mechanical fields. For a turret application with 2 meters in diameter size, not only electro-magnetic performance but also mechanical structural strength is important. Therefore, the comparison is focused on the torque density, machine efficiency, time constant, magnetic forces, and mechanical equivalent stresses occurred by the magnetic forces. For a specific turret application without an external cooling system, the obtained results provide an indication on which type of the machines is best suited regarding performance and size.