Dae-Hyun Koo

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.

Static characteristics of linear BLDC motor using equivalent magnetic circuit and finite element method

This paper presents the static characteristics of the linear BLDC motor. An equivalent magnetic circuit model is derived for the prototype motor. The air-gap flux density is calculated using the equivalent magnetic circuit and compared with results from finite element analysis. The thrust force is measured for the prototype motor and is also compared with those from derived circuit model and FEA. These values agree well to show the validity of the equivalent circuit model. Using this equivalent circuit model, the thrust force density variation according to change of coil width to pole pitch can be expected at the design stage.

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.

Detent Force Minimization of Permanent Magnet Linear Synchronous Motor by Means of Two Different Methods

The thrust ripple in a permanent magnet linear synchronous motor (PMLSM) is mainly generated by the detent force that is caused by the interaction between the permanent magnet (PM) and the iron core without input current in armature winding. This paper proposes two different techniques to minimize the detent force in a PMLSM. One is to choose an optimal constructive design; the other is to employ a current compensator. In this paper, we investigate the performance of detent force minimization using both of them. The effectiveness is verified by both numerical and experimental results.

Development of a radial active magnetic bearing for high speed turbo-machinery motors

A radial active magnetic bearing system for a high speed turbo-machinery induction motor is presented. In this application, a massive rotor is required in order to make up high power and speed. So radial active magnet bearing should be designed to support this rotor mass. Precise analysis of a radial active magnetic bearing is presented from the point of view of electromagnets design. From the controller design point of view, the radial active magnetic bearing can be thought as a combination of two independent magnetic suspensions, each of which is made up of a differential magnetic actuator. Magnetic suspension system is open-loop unstable. So some control techniques like feedback stabilization with proportional-derivative (PD) controls are required in order to make the closed-loop system stable. In practical applications like high speed rotating machine, the proportional-derivative (PD) controls are compensated by 2n derivative control which reshapes the high-frequency end of the stiffness and damping of the system. In magnetic suspension system, massive rotor can act like static disturbance, which makes the center of the rotor out of the center of rotation. So an integral control algorithm is also required. Finally for the developed active radial bearing in turbo-machinery motor, the proportional-derivative-2n derivative-integral (PIDD) control algorithms are implemented with real-time simulator, and the test results are presented

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.

Investigation of Linear Induction Motor According to Secondary Conductor Structure

This paper presents the analysis of single-sided linear induction motors (SLIMs) for application in various systems demanding direct linear motion. In order to investigate the characteristics of linear induction motors according to secondary conductor structures, five types of secondary slot shape structures, usually used in rotary motors, were set up. The equivalent circuit of a SLIM is proposed and the equivalent parameters are computed. In addition, the characteristics such as the air-gap flux density, thrust, normal force, force ripple, speed response, etc., are analyzed by 2-D FEM with an external circuit, and the results are compared.

Improvement of control characteristics of interior permanent magnet synchronous motor for electric vehicle

This paper describes a method to improve the control characteristics of an interior permanent magnet synchronous motor for an electric vehicle. At the motor for electric vehicle, d- and q-axis inductances are varied to a great extent. So, variation characteristics for d- and q-axis inductance are analyzed as function of current magnitude and also current phase angle. The proposed method makes use of the learning capability of neural networks to implement an adaptive vector control structure. Also, a distribution law of torque reference to improve the driving characteristics of a two motor-driven EV is proposed. A advanced performances are verified through numerical methods and experiments.

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.