• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.5
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• pp.949-954
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• 2011

This paper presents a comparative study on motor characteristics with specific consideration of radial vibration force in interior permanent magnet synchronous motors (IPMSM) according to pole/slot combinations. Three IPMSM models, 16-pole/15-slot design, 16-pole/18-slot design and 16-pole/24-slot design are built, in which 16-pole/15-slot and 16-pole/18-slot designs provide high winding factor and 16-pole/24-slot design is known as a general pole/slot combination. By coupling finite element analysis (FEA) with equivalent circuit method, motor characteristics, back electro-motive force (Back-EMF), inductances, cogging torque, etc. as well as machine output performances are analyzed and compared. The radial vibration force (RVF) distribution in air gap causing stator vibration and noise is interested. It is expected that this study help with appropriate choice of pole/slot combination in IPMSM design.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.3
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• pp.257-262
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• 2002

A single-layered radial line slot array (SL-RLSA) antenna etched on a substrate and fad by a rectangular waveguide is presented in the 60 ㎓ band. The design curves are obtained by an efficient electromagnetic coupling analysis using Ewald Sum technique and Shanks transformation. The antenna has rectangular waveguide feed structure using a rectangular waveguide-to-radial line transition. The prototype antenna of 10 cm-diameter was tested and the gain of 31 ㏈i and the efficiency of 38% were measured at 60 ㎓.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.6
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• pp.560-568
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• 2009

Modal vibration characteristics of a thin annular disk containing narrow radial slots are studied numerically and experimentally. Existing analytical solution is examined based on these results revealing that it can not precisely predict eigenvalues of the disk with slots since it does not accurately consider change in the vibration modes and change in strain energy density distributions due to the slots. Parametric study on slot length found that distortions in the mode shape as well as changes in the corresponding natural frequencies are proportional to the slot length. Consequently, errors in the calculated eigenvalues are also proportional to the slot length and accurate data can not be obtained with existing analytical solution above a certain level of slot length. Same phenomena can be observed in both free-free disk and fixed-free disk.

• Journal of Electrical Engineering and Technology
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• v.11 no.6
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• pp.1693-1699
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• 2016

The oscillation character of permanent magnetic motor is highly related to its slot-pole match. By calculating air-gap magnet field and radial electromagnetic force of 6-phase fractional-slot concentrated-winding permanent magnetic motor with slot-pole match of 48/44, 48/46, 48/50 and 48/52 under no load and load status, oscillation character of permanent magnetic motor is analyzed. A 20kW prototype with 48 slots and 44 poles is designed. With many sensors attaching to the corresponding parts, oscillatory acceleration is measured, and spectrum of oscillation frequency is recorded as well. The experiment results give proof to the analysis method for permanent magnetic motor oscillation in this paper.

• Journal of the Korea Institute of Military Science and Technology
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• v.7 no.4 s.19
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• pp.125-132
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• 2004

The radial slot configuration in the solid propellant grain is usually fabricated by the polyurethane foam slot former The foam cannot be easily removed from the solid propellant, some can remain in the slot. Analogue solid propellant rocket motors using polyurethane foam to shape the slot are static fired with the foam former still in place in the slot. The pressure increases at the slot part are measured and there are indications of the propellant cracks at the insulations above the slot. The pressure increase is produced at the beginning of the burning sequence as the foam will hinder the combustion gas of the burning propellant from flowing into the central bore. The pressure increase up to about 300psi is predicted for the motor tested and this pressure increase depends on the gap between the propellant and foam surfaces and remaining foam volume. This amount of pressure increase inside of the slot is estimated to cause the propellant crack. To prevent this pressure increase, minimizing the foam remainder in the slot and making sufficient chamfering at the comer of the slot entrance are suggested.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.04a
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• pp.321-326
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• 2013

This paper investigates the magnetic excitation force of a surface-mounted permanent magnet (SPM) motor according to the change of pole/slot combination. The characteristics of magnetic flux and radial magnetic force (RMF) due to pole/slot combination were analyzed by using magnetic circuit analysis. Also, the RMF of motors with the variable pole/slot combination was numerically simulated by using the finite element analysis to verify the result of the magnetic circuit analysis. This research shows that RMF ripple is reduced when the number of pole is smaller than the number of slot.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.6
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• pp.931-939
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• 2001

The slot coupling characteristics was analysed in a radial-line slot antenna for its design. The previously proposed waveguide model with a periodic boundary condition on its narrow walls and periodically arranged slots on its wide wall was used. The magnetic field integral equation and two dyadic Green\`s functions for respective regions was derived and the method of moments was used. To maximize the efficiency of numerical analysis and to extract singularities, two different kinds of basis functions, the entire domain basis function and the sub-domain one, are used. In addition, the Ewald sum technique for the rectangular waveguide and the Shanks transform for the half space were used to accelerate the computation of the slowly convergent potential Green\`s functions. Simulation results expressed the effects of the various design parameters on the slot coupling.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.11
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• pp.1133-1143
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• 2009

Vibro-acoustic characteristics of a simplified disk-brake rotor containing a narrow radial slot are studied using a semi-analytical procedure. First, modal sound radiations for flexural and radial modes of a generic annular disk having identical key dimension and slot(with free boundaries) are defined using pre-developed analytical solutions based on the modal vibrations from finite element model. The analytical solutions are validated by fully computational methods. Second, sound radiation from a simplified brake rotor simulated using sound radiation solution of the generic disk based on the rotor eigensolutions computed using a finite element code. Predictions by the semi-analytical method matched well numerical calculations using finite element and boundary element method. Finally, sound radiation and vibration characteristics for the example rotor due to a harmonic excitation fixed to the rotor or rotating around the rotor are also obtained.

• Journal of Electrical Engineering and Technology
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• v.7 no.5
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• pp.753-758
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• 2012

This paper deals with the analysis of vibration and noise sources in a modular-type SPM fractional-slot motor. To reduce cogging torque, torque ripple and unequal radial force, which are the main causes of the electromagnetic vibration, the optimal shape of notch and magnet are designed.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1277-1282
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• 2003

The purpose of the present paper is to investigate the noise and vibration characteristics of externally pressurized air proceeding bearings with a circular slot restrictor. To do this, the nonlinear transient analysis including rotor imbalance was performed for a rotor-bearing system. The effects of radial clearance and the width of the bearing and mass eccentricity of the rotor on the noise and vibration characteristics of the bearing are also examined. The results show that the noise and vibration of the rotor-bearing system first increase up to critical speed of the system, and then decrease up to instability threshold speed of the system as the rotational speed of the rotor increases, and the noise of the bearing is markedly influenced by the mass eccentricity of the rotor and the radial clearance and the width of the bearing.