• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.118-121
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• 2006

Stick-slip of belt-pulley system produces vibration which results in the noise problem. Experimental study was carried out to investigate the phenomenon of stick-slip with simple v-belt system. The optical displacement sensor detected the vibration caused by the stick-slip of which the frequency was significantly dependant on tension of the belt. The rotation speed of putties also affected the frequency and magnitude of the stick-slip vibration. Existence of misalignment between the driven and drive pulleys made some difference in the stick-slip frequency, but not much. Further study is necessary to identify the generation of noise from the stick-slip vibration.

• 전기의세계
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• v.31 no.4
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• pp.303-307
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• 1982

This paper describes how to improve a induction moter efficiency by a slip frequency control. Digital filter controlled by microcomputer is introduced in control system of a constant speed-drive and it has prove that the moter can be drived with a high efficiency at a constant slip frequency. The constant slip frequency control method has a merit of simplness.

• International Journal of Railway
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• v.9 no.2
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• pp.41-45
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• 2016

In this paper, a study on the efficiency improvement of the magnetic levitation train using the LIM (Linear Induction Motor) was presented. The maglev train has the advantage of being environmentally friendly since much less noise and dust is produced. However, due to structural limitation, compared to a rotating induction motor, linear induction motor, the main propulsion engine of the maglev train has a relatively greater air gap and hence has the lower operation efficiency. In this paper, the relationship between the operating condition of the train and the slip frequency has been investigated to find out the optimum slip frequency that might improve the efficiency of the magnetic levitation train with linear induction motor. The slip frequency is variable during the operation by this relationship only within a range that does not affect the levitation system of the train. After that, the comparison of the efficiency between the conventional control method with the slip frequency fixed at 13.5[Hz] and the proposed method with the slip frequency variable from 9.5[Hz] to 6.5[Hz] has been conducted by simulation using Simplorer. Experiments of 19.5[ton] magnetic levitation trains owned by Korea Institute of Machinery and Materials were carried out to verify the simulation results.

• Proceedings of the KIEE Conference
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• 1991.07a
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• pp.641-644
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• 1991

Constant slip frequency operation of linear infliction motor is essential for the stable levitation. Control scheme for the constant slip frequency with general purpose frequency inverter is proposed, Speed sensing scheme with proximitity switch for the speed feedback is also proposed. Optimal slip frequency, at which normal force is equal to 0, is selected by the experiment. This slip frequency is a comand to the controller. It shows good characteristic during acceleration and deceleration.

• Proceedings of the KIEE Conference
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• 1991.07a
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• pp.135-138
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• 1991

In this study, a variety of characteristics is considered when LIM for transit is driven with acceleration and deceleration. From the characteristics of constant voltage, with V/f ratio fixed, slip frequency is derived. With slip frequency of 12[Hz] and objective velocity of 40[km/h], the robust control characteristics which are generated constant thrust and normal force, except for open-loop control interval, are obtained.

• Journal of the Korean Society of Safety
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• v.9 no.4
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• pp.42-48
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• 1994

A rotor flux error-based approach for correcting the rotor time constant estimation used in the slip frequency calculator of indirect field oriented controller is presented in this paper. The controller was derived from the d-q induction machine model. Slip frequency gain is dependent on the machine parameter errors. And parameter errors result in rotor flux error. Thus, estimated rotor flux is compared to commanded rotor flux. The error between them is used for the estimation of rotor time constant. Simulation results which demonstrate the performance of this approach are presented.

• Proceedings of the KIEE Conference
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• 1992.07b
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• pp.689-691
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• 1992

In this study, slip frequency control for a single-sided linear induction motor(SLIM) is discussed. We adopted variable slip frequency pattern in stead of constant slip frequency pattern under V/f constant mode, which is effective in improving driving efficiency of SLIM. And the dynamic characteristics are analyzed by using equivalent circuit during the accelerating time.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.1
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• pp.46-51
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• 2018

Constant slip frequency control has been conventionally used in thrust control of the linear induction motor(LIM) for magnetically levitated train. However in this paper variable slip frequency control method is presented to increase LIM efficiency according to change of driving notch. Thrust, attractive force, input power to inverter, regenerative power of the LIM are analyzed by finite element method when the train runs according to the presented control method. As a result it is proved experimentally that the electrical energy to inverter is reduced than the conventional method.

• Ocean Systems Engineering
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• v.4 no.2
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• pp.99-115
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• 2014

When caissons are mounted on a floating transportation barge and towed by a tug boat in waves, motion of the floating dock creates inertia and gravity-induced slip forces on the caisson. If its magnitude exceeds the corresponding friction force between the two surfaces, a slip may occur, which can lead to an unwanted accident. In oblique waves, both pitch and roll motions occur simultaneously and their coupling effects for slip and friction forces become more complicated. With the presence of strong winds, the slip force can appreciably be increased to make the situation worse. In this regard, the safety of the transportation process of a caisson mounted on a floating dock for various wind-wave conditions is investigated. The analysis is done by both frequency-domain approach and time-domain approach, and their differences as well as pros and cons are discussed. It is seen that the time-domain approach is more direct and accurate and can include nonlinear contributions as well as viscous effects, which are typically neglected in the linear frequency-domain approach.

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