EFFECT OF PARTIAL ROTOR-TO-STATOR RUB ON SHAFT VIBRATION
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The effect of partial rotor-to-stator rubbing is studied both experimentally and analytically.The measured vibration signal is distorted showing a flattenned portion of the waveform.'Spectral analysis indicated that light rubbing induced vibration is characterized by harmonics at frequencies equal to 1/rev., 2/rev.and 3/rev.Severe rubbing is identified by a spectrum containing subharmonics at 1/3, 2/3 of the rotational frequency.The synchronous component is generally attenuated as a result of rubbing introduced friction.Because of the stiffening effect of rubbing on the rotor, the resonance frequency is further delayed.The results obtained analytically show good qualitative agreement with the experimentally obtained ones.The behavior of an induction motor with off-center rotor is investigated. The Maxwell stress between rotor and stator of an induction machine with static and dynamic eccentricity of the rotor is calculated for two types of connection between stator coils. Theoretical and laboratory results show that connections of coils of the stator winding in parallel, with equalizing branches, lead to drastic reduction in unbalanced magnetic pull. This reduction prevents problems of magnetic pull in machines with imperfectly centered rotors. A secondary effect of minor importance is the appearance of a vibrational component in the magnetic pull, with an amplitude less than 26% of that of the fundamental force component.< >
Squirrel-cage rotor
Component (thermodynamics)
Wound rotor motor
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Noise of automotive alternators can be classified into mechanical noise, aerodynamic noise and electro-magnetic noise. which is the same as for electric motors. Previous studies show that the elect ro-magnetic noise takes a maw peak at the rotating frequency multiplied by the number of stator slots. It has not been proved clearly so far, however, that the major peak is wholely due to the stator slots. On the contrary it is well known that noise of motors. which has a mechanism similar to the alternator except that the number of stator slots in automotive alternators is in gene\integer multiple of that of rotor segments, is closely related to the number of rotor slots. Therefore, the statement that only the stator slots is the source of the major peak in the noise spectrum of alternators is suspicious although not easy, to show theoretically, that the statement is incorrect. In this paper. effects of the stator slots on the noise in an automotive alternator are experimentally investigated by intentionally modifying the number of stator slots in such a way that the number of the states is not an integer multiples of the rotor slots. It is shown that both the stator slots are not so much influential as the rotor slots and claimed that the major peak in the noise spectrum of conventional alternators is due to superposition of a component caused by the stator and a higher harmonic component caused by the rotor
Alternator
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The characteristic of rotor and stator vibration signals under run-impact status is studied.Firstly,the characteristic and rules of rotor and stator vibration signals under rub-impact status are studied.Rotor and stator vibration feature with different rotor speed is analyzed through experiment.Through the analysis of stator vibration characteristic,the pulse force from rub-impact may lead to stator resonance,so it can be brought out to diagnose rubimpact faults.Results reveal that the stator resonance signals can indicate rub-impact faults.The conclusions can give basis for the vibration character of the stator and the detection of rub-impact signals for the rotor system.
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This paper addresses itself to the inter-influence on the stator and rotor fault detection in induction motors. The reason why the detection of stator fault is influenced adversely to a certain extent by rotor fault is clearly revealed by study based on the electromagnetic mechanism. Rotor fault results in edge frequency components emerged in stator current. The conventional algorithm of negative sequence component of stator current, which is usually regarded as the most typical indicator of stator fault, gives rise to a false negative sequence component due to the modulation of edge frequency components in stator current, and might influence the detection of stator fault. The problem whether stator fault influences the detection of rotor fault or not is quantitatively discussed on the standpoint of electromagnetic mechanism, and a few interesting conclusions have been drawn. Namely, stator fault indeed results in edge frequency components emerged in stator current, which is usually regarded as the most typical indicator of rotor fault, and thus influence the detection of rotor fault in theory. However, the amplitudes of the edge frequency components derived from incipient even some severe stator fault are rather small with respect to those derived from rotor fault, and not be detectable from the practice’s point of view, and thus do not confuse the indicator of rotor fault.
Wound rotor motor
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When the rotary traveling wave type ultrasonic motor working, the piezoelectric ceramic excites the stator vibration to produce traveling wave, then the elliptical motion of the particle is formed. Under the function of the pre-pressure between the rotors and stator, the rotor rotates by the friction between the rotors and the stator; finally it realizes that the rotational speed and the torque of the motor are taken out. Therefore, the pre-pressure between the rotors and stator has essential influence on the ultrasonic motor performance,many researchers have carried on research to these. According to the documents, it is indicated by most scholars that the pre-pressure has effect on the contact between the rotor and stator, and the conclusion is difference from the experiment because it is neglected that the pre-pressure has effect on the stator vibration. In the paper, the ultrasonic motor model is derived from analyzing the force on the interface between the rotors and stator and founding stator dynamic equations and rotor dynamic equations. Under different pre-pressure, the stator vibration characteristic and the ultrasonic motor output performance are studied by means of the motor model. The result shows that the pre-pressure affects the ultrasonic motor output performance, because it changes the contact area between the stator and the rotor, and the other that the pre-pressure has influence on the performance with the resonant frequency of the stator increasing, the stator vibration changing and the contact area varying. It is indicated from the result that no-load speed and the stall torque are non-monotonic changing with the pre-pressure increasing, and the changing law is connected with the frequency of the excitation voltage on the stator.
Ultrasonic motor
Piezoelectric motor
Squirrel-cage rotor
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Stators for the formerly developed multi-degree-of-freedom ultrasonic motors are not small enough compared with their rotors. In this study, a new type of multi-degree-of-freedom ultrasonic motor, whose stator is relatively small, is developed. First, the stator is designed in detail using a finite element analysis. An outline of the stator is square plate, which has four projections to be in contact with a spherical rotor. The rotor rotates around three perpendicular axes using three natural vibrations of the stator. Second, the designed stator is actually produced, and motion tests of the rotor are conducted. As a result, it is confirmed that the multi-degree-of-freedom motion of the rotor is experimentally produced.
Ultrasonic motor
Degree (music)
Square (algebra)
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Stator and rotor vibration characteristics of generator are analyzed when the rotor winding inter-turn short circuit fault and the imbalance fault occur. The rotor vibration of fundamental frequency increases and the stator vibration of second frequency decreases when the rotor winding inter-turn short circuit fault occurs. But when the imbalance fault occurs, the rotor vibration of fundamental frequency increases and the stator vibration of second frequency increases too, so the stator vibration characteristics are different from that of the rotor winding inter-turn short circuit fault. Considering the differences of the stator vibration, a new diagnosis method of rotor fault, based on stator and rotor vibration characteristics, is developed. Comparing to the traditional method that only considering the rotor vibration signals, the rotor winding inter-turn short circuit fault and imbalance fault can be effectively diagnosed. Finally, the vibration data of a type of SDF-9 generator are measured in the laboratory to verify the theoretical analysis presented above.
Wound rotor motor
Squirrel-cage rotor
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This paper deals with the identification of the stator and rotor resistances. The originality of this work is that it considers both rotor and stator resistances as time-varying parameters. Two schemes for the rotor resistance identification and one scheme for both stator and rotor resistances identification are outlined. The first and the third schemes use the measured stator current, voltage command and rotor speed while the second scheme uses only stator current and voltage commands. All schemes are based on the sliding mode observer and the convergence of the estimates to their true values does not required the persistence of excitation conditions to be satisfied by the input signal.
Identification
Observer (physics)
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The paper presents the results of investigations concerning choioe of the optimal shape (from the viewpoint of acoustical efficiency) of the holes of the rotor and stator of a dynamic axial generator, the horn and pressure chamber of which are common to all the stator channels.
Compared to the sound power and the efficiency for a generator operating with the rotor preferred hitherto a doubling of the values of the parameters was achieved for a generator which has an approximate rectangular function for the time-dependence of the active surface area of the inlet holes of stator channels.
Electric generator
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