• Journal of KSNVE
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• v.10 no.6
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• pp.977-984
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• 2000

Vibration of disk drive spindle is one of the major limiting factors in achieving higher track densities in hard disk drives. Vibration of a BLDC motor is a coupled phenomenon between mechanical characteristics and magnetic origins through the motor air-gap. In this paper, radial magnetic forces for symmetric and asymmetric BLDC motor are calculated with respect to the various rotor eccentricity using analytic method. Based on the results of the radial magnetic forces, transient whirl responses of the spindle motor are analyzed using finite element and transfer matrices. Results show that an asymmetric motor has a worse effects on unbalanced magnetic forces and vibration when mechanical and magnetic coupling exists.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.8
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• pp.675-683
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• 2004

The motor current signature provides an important source of the information for the faults diagnosis of three-phase induction motor. The theoretical principles behind the generation of unique signal characteristics, which are indicative of failure mechanisms, are Presented. The fault detection techniques that can be used to diagnose mechanical Problems, stator and rotor winding failure mechanisms, and air-gap eccentricity are described. A theoretical analysis is presented which predicts the presence of unique signature patterns in the current that are only characteristics of the fault. The predictions are verified by experimental results from a special fault Producing test rig and on-site tests in a steel company. And this study have made new diagnostic algorithm for the operating induction motors with the test results. These developments are including the use of monitoring and analysis of electric current to diagnose mechanical and electrical problems and gave the precise test results automatically.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.4
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• pp.739-745
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• 2011

This paper proposes a method for reducing the negative spatial harmonics of the radial flux density of an interior-type permanent magnet (IPM) motor. The reliability of the motor is increased by minimizing its vibrations under dynamic eccentricity (DE) state and normal state due to reduction of a negative spatial harmonics component through the influx of a zero spatial harmonics component in the radial flux density. To minimize the vibrations, optimal notches corresponding to the distribution shape of the magnetic field are designed on the rotor pole face. The variations of vibration computation by finite element method (FEM) and the validity of the analysis and rotor shape design are confirmed by vibration and performance experiments.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.816-821
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• 2002

It is getting more important that energy efficiency and manufacturing cost of the electric motor in appliance. The SRM has been alternative choice. But acoustic noise and harshness in this motor was widely known. So this paper had been studied on the noise reduction of a SRM in air conditioner. This works include some parameters regarding to blown noise sources like a reluctance torque ripple, air gap eccentricity, Especially, it was focused on dynamic characteristics of the system based on mechanical viewpoint. It came to successful results. Besides, this gave us a validity of phase excitation in experimental measurements.

• Proceedings of the KIPE Conference
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• 2004.07b
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• pp.862-865
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• 2004

Faults such as broken rotor bars, static and dynamic eccentricity are often reported in induction motors. These faults increase the down-time of equipment, which causes major loss of earnings to the industry. This paper presents a result of the finite-element(FE) analysis of air-gap flux variation in induction motors when rotor vibration conditions occur, An accurate modelling and analysis of rotor vibration in the machine are developed using FE software packages, and measuring the flux are made using the search coils. In the FE analysis, an induction motor with 380 [V], 5[HP], 4 Poles, 1742 [rpm] ratings is used. The results of FE analysis can be used for on-line vibration monitoring of the induction motors.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.50 no.1
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• pp.1-9
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• 2001

In this paper, the general research on the analysis of the vibration due to magnetic exciting force in the small brushless DC(BLDC) motor, which is used in the Digital Versatile Disk(DVD) ROM driving system, is performed. The first part of the study is the analysis of the magnetic exciting force in the air gap region. As a verification of the exciting force by numerical analysis, the magnetic exciting force distribution in the air gap region is computed by using Reluctance Network Method(RNM). In addition, the effect of the eccentricity on the magnetic exciting force is discussed. The other part of the research is the structural analysis of the rotor structure of the BLDC motor. The matural mode analysis of the rotor structure is performed, and the vibration response due to magnetic exciting force is found. As a result of the procedures, the basic estimation of the effect of the magnetic exciting force on the vibration of BLDC motor is suggested.

• Proceedings of the KIEE Conference
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• 2006.04b
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• pp.182-184
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• 2006

A down-scaled simulator is developed to simulate typical faults in induction motor such as short-turn stator winding, broken rotor bar, dynamic and static air-gap eccentricity, bearing trouble, and mechanical unbalance. The simulator is used as an initial builder to develop design algorithm for real-time faults detecting system by processing an abnormal signal and characteristics in each fault.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.12 no.4
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• pp.287-293
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• 2002

The unexpected failure of the induction motor makes the downtime of production, and the cost of the process cessation enormous. To reduce the downtime and increase the reliability of the motor, the vibration measurements for the fault detection have been used previously. Recently motor current signature analysis(MCSA) has been adapted for the fault detection and diagnosis of the motors. MCSA provides a powerful analysis tool for detecting the presence of mechanical and electrical faults in both the motor and driven equipment. In this paper, the fault severity of the rotor bar has been derived in terms of the resistance change which is calculated from the equivalent circuit model. Results show that the fault of the rotor can be easily detected and the measured value of the resistance change is verified by the detected fault from on-site tests using MCSA for the induction motors in an iron foundry.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.48 no.11
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• pp.604-610
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• 1999

Vibration of a rotor-bearing system driven by an electric motor is a coupled phenomenon between mechanical characteristics and magnetic origins through the air-gap. With the advent of new high-energy magnets together with high precision motor applications, magnetic sources of vibration are becoming more serious. This paper investigates the transient whirl responses of a rotor system with purely mechanical origins and compares it with that of magnetically coupled origins. A perturbation method is applied to model the magnetic field associated with rotor eccentricity. Electromagnetic forces are obtained by the Maxwell stress method, which utilizes the analytical expression of radial flux density distribution. The FEM was applied to a rotor-motor system to illustrate magnetically coupled effects in rotor dynamics. Results show that magnetically coupled sources significantly affect the vibration of the rotor-motor system.

• Journal of Magnetics
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• v.21 no.4
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• pp.554-560
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• 2016

This paper presents a general analytical model to calculate the characteristics of axial-flux permanent-magnet machines with axis eccentricities. The radial and tangential magnetic flux densities in the air gap under normal conditions were first obtained using a combination of Maxwell's equations and Schwarz-Christoffel (SC) transformation. Next, equations for the radii were deduced to investigate the static/dynamic eccentricities. The back electromotive forces (EMFs) were calculated and compared with those obtained from finite element (FE) analysis. The analytical predictions show good agreement with the FE results. Detection approaches were obtained by comparing with normal conditions, and the analytical model was verified experimentally.