Noise Of Induction Motors Research Articles

Pulse-Width Modulation Technique With Harmonic Injection in the Modulating Wave and Discontinuous Frequency Modulation for the Carrier Wave for Multilevel Inverters: An Application to the Reduction of Acoustic Noise in Induction Motors

An implementation of a harmonic injection pulse width modulation frequency-modulated triangular carrier (HIPWM-FMTC) control strategy applied to a multilevel power inverter feeding an asynchronous motor is presented. The aim was to justify the reduction in acoustic noise emitted by the machine compared with other strategies in the technical literature. In addition, we checked how the THD at the inverter output was reduced compared to the other control techniques used as a reference. The proposed strategy is based on frequency modulation of the triangular carrier. The main advantage of the proposed method is that only one control parameter is required for modifying the electrical spectrum. Therefore, the mechanical natural frequencies and spatial harmonics of the machine can be avoided, and acoustic noise can be reduced. The effectiveness of the technique was demonstrated after laboratory validation by comparing the acoustic results for a 1 kW motor. The results obtained from the laboratory tests are presented and compared with those of other acoustic measurements using different PWM strategies.

A Study on the Design Process of Noise Reduction in Induction Motors

Noise of induction motors can be classified in three main parts, which consist of mechanical source, aerodynamic source, and magnetic source. The magnetic noise is defined as noise generated from vibrations due to electromagnetic excitation force. In this paper, the electromagnetic excitation force is analyzed and design process of noise reduction is proposed. Firstly, the harmonic components which are generated from combination of pole and slot are analyzed in the initial design. Moreover, the lower space harmonic components are reduced in this design stage. Secondly, 2-D transient analysis is conducted to consider the saturation effect and harmonic components of current in detail design. Fourier series has been addressed according to time and space considering harmonic component of electromagnetic excitation force. In the mechanical part, the natural frequency modes of motor components such as bracket, stator and rotor cores are calculated using finite element analysis (FEA) to avoid resonance. Lastly, the skewed rotor is adjusted to reduce the harmonic components of force, and the spectrums of motor according to skew effect are analyzed. The noise of skewed model is analyzed using FEA and compared with experimental result. In order to verify proposed method, the skewed model is manufactured and experimented at no-load condition.

Losses, torques and magnetic noise in induction motors with static converter supply, taking multiple armature reaction and slot openings into account

A system of n complex equations, for which n=14, … , 30 suffices, is used to determine the n unknown stator—and rotor current harmonics for each of the given terminal voltage harmonics. Correct superposition of harmonics yields the air-gap field, losses, torque and radial force. As an illustrative example, the systems of simultaneous equations are solved for an eight-pole squirrel-cage motor with different numbers of rotor slots. Parasitic effects such as supplementary losses, synchronous torques, magnetic noise or line-current harmonics depend highly on the slot number difference Z1−Z2 and on winding connections. Owing to the voltage distortion of the static converter, copper losses increased by 61%. In the case of parallel winding branches, equalising currents with 511 Hz and 37% magnitude occurred, which increased the copper losses by 152%. With Δ-connected windings, circulating currents with a magnitude of 33% have been detected, thus increasing the losses by 21%. Rules to avoid these additional losses are given. Parasitic synchronous torques are increased and emerge at additional speeds. Asynchronous dips in the torque–speed curve because of voltage harmonics are of minor importance, even for large supply voltage harmonics. The accurate determination of radial force waves enables the prediction of core vibrations and the magnetic noise, even at resonance frequency. It has been found by experiments that sound radiation of an oscillating sphere or cylinder seem not to be equivalent to that of an induction motor.

Characteristic analysis of an induction motor with an unequal slot pitch cage rotor

AbstractRecent developments in induction motors have been moving forward reducing the size and weight of motors. At the same time, there are demands for much quieter operating conditions. Various design methods have been applied to reduce the vibration and acoustic noise of induction motors. One method is to make the slot pitches of the cage rotor unequal, to avoid the resonance with the natural frequencies of the stator frame. In this paper, our purpose is to create guidelines for reducing noise. As the first step for this purpose, we developed a method to analyze the voltage and torque equations of an induction motor with an unequal slot pitch cage rotor and discussed the characteristics from the analyzed currents. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 140(2): 44–52, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10032

Electromagnetic noise of induction motors driven by PWM inverters

When a squirrel cage induction motor is driven by a PWM inverter, electromagnetic noise different from that during commercial power source drive is experienced. This is because of sideband wave voltage induced in PWM inverter output voltage. This paper first describes the mechanism of electromagnetic noise generation in commercial power source drive, and then electromagnetic force considering the sideband frequency and voltage content and the mechanism of electromagnetic noise generation in PWM inverter drive. It also refers to the sideband frequency and voltage content because of operating time control. © 2000 Scripta Technica, Electr Eng Jpn, 133(3): 55–62, 2000

Comparison of different methods for calculating the air-gap field of induction motors

In this paper different methods for calculating the air-gap field of induction motors are compared. A “modified one-dimensional field calculation” is proposed, combining the advantages of short computing times and high accuracy of the one- and two-dimensional field calculation, respectively. The different methods are checked against experiments: The total leakage coefficient and the radiated audible noise of induction motors are investigated. Both, the modified one-dimensional and the two-dimensional theory give results which are in good agreement to the measurements.

Magnetic noise of induction motors

A digital computer program is described which predicts the acoustic noise generated by the magnetic field in an induction motor. The motor air gap may have static or dynamic eccentricities, and the squirrel cage rotor may be skewed or unskewed. Besides calculating the sound power in decibels at any motor speed, other important performance parameters such as steady and harmonic (cogging) torques, magnetic side pulls, currents, and the variation of the magnetic field along the stack are computed. The sound power spectrum predicted for a particular motor is compared with laboratory measurements.

Harmonic theory of noise in induction motors

Harmonic theory of noise in induction motors

Harmonic Theory of Noise in Induction Motors

This paper presents a theory of noise generation particularly adapted to use with small motors. Since single-phase motors predominate in the small-motor field, a single-phase point of view has been employed. The underlying philosophy of the paper is to reduce the theory to simplest terms and to concentrate attention upon the most probable sources of noise. While the results are shown as a large collection of numbers representing force waves the development steps of the theory are really simple and easily understood. The resultant air-gap flux wave in an induction motor is the difference between the fundamental stator flux plus its harmonics and the fundamental rotor flux plus its harmonics. The difference between the two fundamental fluxes is usually less than the larger one and often less than either one but the harmonics, with few exceptions, are neither of the same velocity nor space order and, therefore, do not add or subtract from each other It follows that the resultant flux wave has more harmonics of much greater per-unit amplitude than does either the stator or rotor flux wave alone. It is the interaction of two large harmonic flux waves of slightly different space order and traveling at high frequency with respect to each other that causes high-frequency magnetic-force waves of long space pitch which are effective in producing noise. The theory has been used for some time in noise investigations and has been found to bear out test results on a large number of motors.

Harmonic theory of noise in induction motors

This paper presents a theory of noise generation particularly adapted to use with small motors. Since single-phase motors predominate in the small-motor field, a single-phase point of view has been employed. The underlying philosophy of the paper is to reduce the theory to simplest terms and to concentrate attention upon the most probable sources of noise. While the results are shown as a large collection of numbers representing force waves the development steps of the theory are really simple and easily understood. The resultant air-gap flux wave in an induction motor is the difference between the fundamental stator flux plus its harmonics and the fundamental rotor flux plus its harmonics. The difference between the two fundamental fluxes is usually less than the larger one and often less than either one but the harmonics, with few exceptions, are neither of the same velocity nor space order and, therefore, do not add or subtract from each other It follows that the resultant flux wave has more harmonics of much greater per-unit amplitude than does either the stator or rotor flux wave alone. It is the interaction of two large harmonic flux waves of slightly different space order and traveling at high frequency with respect to each other that causes high-frequency magnetic-force waves of long space pitch which are effective in producing noise. The theory has been used for some time in noise investigations and has been found to bear out test results on a large number of motors.

Quiet Induction Motors

Magnetic noise in induction motors is caused by the vibration of magnetic parts produced by the varying forces associated with the changing flux density in the adjacent air parts of the magnetic circuit. Torsional vibration of the motor is caused by unbalanced windings or applied voltages. Vibration of the rotor simulating a mechanically unbalanced rotor is caused by two fields differing by two poles and not of the same frequency or direction of rotation. Vibration of the stator by distortion from a circular shape results from the presence of other simple combinations of fields. Teeth tend to vibrate axially at double applied frequency. The magnetic noise produced by a motor can be predicted from a qualitative analysis of the air-gap field supplemented by an approximate quantitative analysis and consideration of the stiffness of the parts.