• Progress in Superconductivity and Cryogenics
• /
• v.6 no.3
• /
• pp.33-37
• /
• 2004

This paper presents the construction and test results of an HTS induction motor. End rings and short bars were made of HTS tapes, To increase the efficiency and starting torque, HTS tapes can be used as the rotor bars. Because large current is induced in the rotor circuit, HTS tapes quench and high starting torque can be obtained. As the speed of rotor builds up. HTS tapes which are used as short bars become superconducting state again. After the HTS tapes recover from quench, resistance of the rotor circuit is nearly zero. In that case, power loss in rotor circuit is eliminated. Stator of the conventional induction motor was used as the stator of the HTS motor. Rated capacity of the conventional motor was 0.75 kW. Performances of the HTS induction motor were compared with those of the conventional motor with same volume and specification. Test result showed that the speeds of the HTS induction motor were the same with synchronous speed up to 2.6 Nm and 1.788 rpm at 9.7 Nm. It guarantees the high efficiency of the HTS motor. Starting torque of the HTS motor was more than twice of the conventional motor.

• Proceedings of the KIEE Conference
• /
• 1994.07a
• /
• pp.208-210
• /
• 1994

In this paper, the design sensitivity evaluation based on the 2-dimensional finite clement discretization is presented for the voltage source and eddy current problem. And it is applied to the two shape design problems of the rotor slot of 3-phase squirrel cage induction motors. The first is to increase the starting torque while keeping the rated torque fixed. The other is only to increase the torque at the rated speed while keeping the starting torque fixed. As an optimization method, the Gradient Projection method is used to control casily the torques for various speeds of rotor. One fourth of rotor is analyzed by using a semi-periodic boundary condition. Because the shape of rotor slot has much influence on the slip torque characteristic, the 10 design parameters are taken on the interface between rotor core and rotor bar. The initial shape of rotor slot is the trapezoidal typo with rounding corners.

• Journal of the Korean Society for Precision Engineering
• /
• v.27 no.4
• /
• pp.53-62
• /
• 2010

This study introduces about development of multi-DOF ultrasonic motor that are composed of a bar-shaped stator and a spherical rotor. The ultrasonic motor is a motor which is operated by vibrations over frequency of 20kHz. The multi-DOF ultrasonic motor will be developed by expanding the basic theory of existing 1-DOF ultrasonic motor. It can generate 3-DOF rotation of the rotor around perpendicular axes using 3 vibration modes of stator. By using finite element methods, the optimal dimension of stator is decided and made the components of stator. When we apply the multi-DOF ultrasonic motor composed of rotor and stator to the driving test system, it will be checked whether the motor can be driven at the direction of 3-DOF or not. And it is proposed how the simulation of square bar shaped multi-DOF ultrasonic motor is accomplished.

• Journal of Power Electronics
• /
• v.8 no.3
• /
• pp.228-238
• /
• 2008

Many induction motor broken bar diagnosis methods are based on evaluating special components in machine signals spectrums. Current, power, flux, etc are among these signals. Frequencies related to a broken rotor fault are slip dependent, therefore, correct diagnosis of fault - especially when obtrusive frequency components are present - depends on accurate determination of motor velocity and slip. The traditional methods typically require several sensors that should be pre-installed in some cases. This paper presents a diagnosis method based on only a vibration sensor. Motor velocity oscillation due to a broken rotor causes frequency components at twice slip frequency difference around speed frequency in vibration spectrum. Speed frequency and its harmonics as well as twice supply frequency, can easily and accurately be found in a vibration spectrum, therefore th motor slip can be computed. Now components related to rotor fault can be found. It is shown that a trained neural network - as a substitute for an expert person - can easily categorize the existence and the severity of a fault according to the features extracted from the presented method. This method requires no information about th motor internal and has been able to diagnose correctly in all the laboratory tests.

• Proceedings of the KIEE Conference
• /
• 2002.07b
• /
• pp.867-869
• /
• 2002

A method for the time step analysis of single phase induction motors is proposed. The unknown variables in differential equations are the currents flowing through rotor bars. They are coupled with the distributed magnetic flux densities in the airgap instead of inductance matrix while applying Kirchhoff's and Faraday's induction laws. Two patterns for magnetic flux densities are necessary. One is given by ideal stator winding distribution. the other is produced by currents flowing a rotor bar with unit magnitude and is calculated by FEM. Formulated set of equations are solved for a simple three phase and single phase example model and the resultant speed torque curve is shown in this paper.

• Proceedings of the KIEE Conference
• /
• 2011.07a
• /
• pp.1079-1080
• /
• 2011

This paper deals with the operating characteristics of induction motors with broken rotor bar, stator winding inter-turn short and their complex fault conditions. The considered operating characteristics are phase current, torque and speed. Since the operating characteristics of induction motors are directly related to their slip conditions, this paper built the experimental set to adjust the speed of induction motor with a permanent magnet synchronous generator connected to a load bank. From the various experimental results, it is shown that the faults do not highly affect on the operating characteristics of induction motors in low slip conditions, but the fault characteristics can be easily found in larger slip conditions.

• Proceedings of the KIEE Conference
• /
• 2007.04c
• /
• pp.21-23
• /
• 2007

It is well known that the characteristics of the induction machine depend on a great degree on the leakage reactance. And the leakage reactance is different according to a level of slant. So in this paper, we calculated the inductance per coil side. And the torque and speed characteristics are analyzed using a method base on the two-dimensional (2-D) finite element method (FEM) and on the circuits theory to model the rotor bar in a induction machine. The variable values of bar angle of slant are considered.

• Proceedings of the KIEE Conference
• /
• 2015.07a
• /
• pp.713-714
• /
• 2015

유도전동기에서 회전자에 대한 진단은 소형, 저압전동기의 실험결과 위주의 논문이 주를 이루어 수도사업장의 용수 공급을 위한 고압 유도전동기의 회전자 진단에 대해서는 많은 관심을 갖지 않은 실정이다. 본 논문에서는 MCSA(Motor Current Signature Analysis) 방식을 이용한 장비를 이용하여 전류 스펙트럼과 기동전류 특성 통해 회전자의 건전성을 평가하는 방법을 기술하였다. 문제가 발생한 유도전동기를 대상으로 분해점검 후 실제 문제가 발생하였음을 확인하였고 문제 해결후 정상인 것을 확인하여 회전자 결함판정기준으로 전류 스펙트럼과 기동전류 특성이 타당함을 설명하였다.

• Journal of international Conference on Electrical Machines and Systems
• /
• v.3 no.1
• /
• pp.7-14
• /
• 2014

Aircraft variable frequency power and a new application of induction motor under the aero-power are introduced. The transient models and simulation of induction motor are reviewed. A new transient model and simulation method is presented that includes deep-bar effect and magnetic saturation. Dynamic magnetizing inductance, rotor resistance and leakage reactance are considered as varying parameters in state-space model. Base on known rotor structure and speed, these parameters can be calculated.

• Proceedings of the KIEE Conference
• /
• 1999.07a
• /
• pp.176-178
• /
• 1999

The Synchronous Reluctance Motor(SynRM) was made and experimented. Salient type SynRM was manufactured by cutting two sides of the three phase squirrel case rotor. So this prototype motor has same stator and capability with the counterparts of the induction motor. The airgap flux density, inductance and torque characteristics was inspected by Finite Element Analysis (FEA). The static torque experiments was accomplished. The paper proposed the effect of rotor bar by comparing two models.