A Study on Analysis and Improved Methods for Noise and Vibration of Compressor Motor. Xiaoyao Qian, Pingping Wang

Transcription

1 Applied Mechanics and Materials Online: ISSN: , Vols , pp doi: / Trans Tech Publications, Switzerland A Study on Analysis and Improved Methods or Noise and Vibration o Compressor Motor Xiaoyao Qian, Pingping Wang China Jiliang University, Hangzhou , China qianxyy@139.com, happy_wang2008@163.com Keywords: motor, noise, vibration, measurement. Abstract. Motor noise and vibration relect quality control problems or the motor production process,inding out the cause through testing and analyzing the spectrum o motor noise and vibration to educe the main noise sources, thus guiding to improve motor production quality. In this paper by means o noise and vibration measurements, meanwhile carry out statistical and analysis or the measured data to ind the inluence size o various actors with quality analysis tool, and then adopt some corresponding measures to control the motor noise, hoping to improve the motor quality. Introduction Vibration and noise are important parameters o assessing motor quality. Abnormal vibration not only aects the lie o the motor, but is the main cause o noise. From a physical point o view, noise is called inconsistent tone that is irregularly composed o many dierent requencies and strong sound waves which would adversely aect the surrounding environment. Currently, noise, sewage and waste gas are the three major hazards o environmental pollution. Thereore, the motor noise level is measured as an important indicator o its quality, becoming an important actor o aecting their competitiveness in the market. Since 1940, the introduction o new materials has helped to improve induction and the design o synchronous motors, how to identiy noise source and eliminate or reduce noise has become a topic issue. Motor noise is mainly caused by the electromagnetic, mechanical and ventilation in the three reasons, the corresponding noise can be divided into three categories: electromagnetic noise, mechanical noise and aerodynamic noise. Electromagnetic noise is a low requency noise generated in the vibration o the stator, rotor and the whole motor structure caused by magnetic ield pulse in the motor air-gap, the main reason is due to the stator and rotor slot mismatch, the stator and rotor are eccentric or air gap is too small and length is not consistent, its magnitude depends on electromagnetic load and motor design parameters. Mechanical noise is produced in the riction o motor running part, impact, imbalance and structure resonance, types o the noise are many and complex. Noise sources are: Sel-noise source, load-sensing noise source, auxiliary parts o the machinery noise source; in addition, attributed to the processing technology, precision machining, assembly quality problems, noise is usually rom the brush, bearing, rotor, ventilation systems, hereby, mechanical noise can be divided: brush noise, bearing noise, an noise, load noise, etc. Aerodynamic noise is ormed because o the an and some protruding parts o the rotor making air an impact and riction as the motor rotates, its size mainly depends on the size o air volume and pressure. In the case o high speed, this noise occupies a large proportion; aerodynamic noise is the main part o motor noise, about 75%, which mainly has vortex noise and whistle noise. Through the measurement o motor noise and vibration, while the measured data or statistical analysis to identiy the size o the various actors and choose to modiy the methods o motor noise and vibration, hoping to improve the motor quality, meanwhile, increase motor products on the market share. All rights reserved. No part o contents o this paper may be reproduced or transmitted in any orm or by any means without the written permission o Trans Tech Publications, (# , Pennsylvania State University, University Park, USA-12/09/16,02:34:07)

2 Applied Mechanics and Materials Vols Spectral Analysis o Motor Vibration The Spectrum Analysis Role o Vibration. Vibration is the source o noise itsel will damage the body, reduce the perormance o the machine, or even damage the machine. In severe cases, the vibration causes the vibration o the internal organs o human body that can lead to disease and other physiological damage. The sensitivity o the human body depends on the vibration requency, but also on the acceleration or displacement o the vibration. Motor vibration waveorm is not a single sine wave, but is made up o many waveorms with dierent requencies, hence it needs or requency analysis to identiy its composition. Generally analysis vibration and analysis noise are similar, or the low-requency vibration, because the manuacture o low-requency ilter is a little diicult it is oten by means o a detailed analysis o the waveorm in the vibration study. Vibration can use the requency range, displacement, velocity or acceleration to describe. Select the appropriate reerence velocity and reerence acceleration and with the same way which is similar to noise measurement deine velocity and acceleration level class. Make speed grade, acceleration level being consistent with the acoustic pressure level size under the case o large lat panel vibration. In this condition, we are aware o the noise level generated by these vibrations without measuring the sound level ater knowing the surace vibration velocity Y. Thereore, several decibels lower vibration level, noise level will reduce the same decibels. However, the small motor is not as lat radiator, correction should be added when calculates. Low requency vibration (including audio-requency vibration) can stimulate other parts unit vibration, as natural requency h is an integer multiple o vibration requency p, this part is especially strong vibration. Sound intensity I is proportional to 2 2 y.when is small, and Y is large, the increase o material stress can cause damage to mechanical parts. But the sound intensity is not necessarily large, while is large (or example: > 1000Hz), even i Y is not large (or example: a ew microns) which may also cause a great sound intensity. Moreover, due to vibration and noise are closely related, in the study o motor noise, in addition to measure sound power with a sound level meter, but oten need to simultaneously measure the vibration o the motor casing and end caps, etc. Radial Vibration Time-domain and Spectrum Signal. Use experimental instrument CoCo-80CSA dynamic signal analyzer test, igure 1 is the radial acceleration signal o measured sound source as the three-phase asynchronous motor is rotating at ull speed, we can see low and high requency o vibration signal components is considerable large rom the original signal o time domain. Fig.1 Radial acceleration signal o three-phase asynchronous motor Fig.2 Radial vibration spectrum o three-phase asynchronous motor

3 566 Computer-Aided Design, Manuacturing, Modeling and Simulation Observe the spectrum, igure 2 shows sub-power spectrum o radial vibration signal o three-phase asynchronous motor. Motor vibration signal is relatively "clean", the highest vibration energy is during Hz this spectrum region, which can be seen rom the spectrum. Spectrum Signal o Axial Vibration. Figure3 shows the power spectrum o axial vibration signal o three-phase asynchronous motor. The spectrum displays, motor vibration signal is "rich", now compare Fig.3 Axial vibration spectrum Fig.4 Comparative analysis between axial vibration and radial vibration spectrum it with the radial vibration signal (coherence as shown in Figure 4), it is ound that axial vibration spectrum has higher energy value than radial vibration requency spectrum in the 1200Hz ~ 1600Hz, 2000Hz ~ 2300Hz, 3500Hz ~ 4100Hz three places. Spectrum Signal Analysis. Through a series o tests and the actual measurement data, then analyze them. Now start to analyze the source o the noise with cause and eect diagram, namely igure 5. Fig. 5 Noise and vibration causality diagram o three-phase asynchronous motor

4 Applied Mechanics and Materials Vols Draw the main actors o aecting noise and vibration o three-phase asynchronous motor in the experiment are: 1Electromagnetic noise: Harmonic gear noise and vibration 2Bearing noise: bearing its own noise and vibration, bearing axial sound and vibration, axial movement sound (axial movement). 3Other components vibration sound: riction sound o communtator. Improvement Measures and Advice Measures to Reduce Motor Electromagnetic Noise. In the design, the motor electromagnetic noise is mainly gear noise and vibration that are chiely caused by the ollowing reasons:1stator and rotor slot mismatch;2skewed degree o rotor is inappropriate;3stator or cover and tooth harmonic requency resonate;4rectiier quality is not ideal;5case and cover are improperly processing or Bearing assembly is improper, which cause rotor skewed;6rotor is eccentric or air gap is uniorm. Thereore, the main measures to reduce electromagnetic noise are as ollows: (1)Select the appropriate stator slot to match with rotor slot: Slot combination will aect the additional torque, additional losses, vibration and noise o asynchronous motor. Generally speaking, as near slots match, the additional loss is small, but electromagnetic noise is large. While adopt rotor skewed slot, additional torque and noise are signiicantly reduced, however, the additional loss is not necessarily small. (2)Skewed slot and skewed pole: Stator, rotor skewed slot or shaking pole can make radial orce wave occur phase displacement along the length direction o the axis o the motor. Hence the average radial orce along the axial becomes lower, so that reduce vibration and noise. (3)Reduce the intensity 1 Select the appropriate stator winding pitch to weaken compared with the harmonics. rom the angle o reducing the noise, choosing the winding whose harmonic magnetic potential is small, such as sine group, is always beneicial 2 Reduce the opening width o stator and rotor slot, or use closed slot, use the magnetic slot wedge to reduce permeance harmonic in air. 3 Reduce the air-gap lux density. 4 Increase properly air gap to reduce the amplitude o harmonic magnetic ield. (4)Ensure the symmetry o the magnetic ield: 1 Lower the electromagnetic noise o twice slip requency 2 Ensure the running at the garden shape rotating magnetic ield o single-phase motor. (5)Reduce the dynamic amplitude o the stator and control the sound amplitude o television: 1 Prevent resonance2adopt lexible connections. 3 Enhance the stiness o the stator 4Measures to increase the damping orce 5Increase orders o orce wave 6 Decrease sound radiation eiciency. Measures to Reduce Motor Bearing Noise. The causes o bearing noise.owing to the bearing rotates with rotor, and the ball, inside and the surace o the outer ring are not smooth or deormed, moreover the gap between them, the ball's not round or internal mixed debris, which leads to collide and squeeze between them, resulting in vibration and noise. The noise value has a great relationship with the ball, the dimensional accuracy inside and outside the ring groove, surace roughness and geometrical tolerance. Some people think that, as long as use precision bearings, bearing noise could be reduced. Little do they know, instead, the noise will increase,the reason is shat and bearings are too tight, that inner ring deormation o precision bearing is greater than that o the normal bearing, thereby beat, vibration increases, noise rises. Thereore, bearings and bearing chamber with the combination o shat are very important. Methods to reduce motor bearing noise (1)Use normally sealed bearing in order to prevent debris entering; (2)Beore bearing assembly, or bearing production plant, machining o the ball, inside and the outer ring must meet the design requirements, likewise,the assembly should be carried out strictly demagnetization cleaning process, washing away the grease and iron ilings;

5 568 Computer-Aided Design, Manuacturing, Modeling and Simulation (3)The combination o bearing outer ring and the bearing chamber, generally the inner ring and shat should not be too tight, the bearing outer ring and bearing chamber is appropriate to adopt clearance it, whose radial clearance should be 3 to 9 microns in range; Between the bearing inner ring and shat use relative transition it, as well as the cover and chassis; (4)To eliminate axial clearance o the rotor, appropriate pressure must be added on the bearings. Generally use wave spring washers or three-point spring washers, and putting them on the extension o shat is appropriate;during the bearing assembly, irst press bearing into the rear bearing room, and then two bearings are pressed into the rotor, at inal it together with the case. Conclusions Vibration and noise are important indicators o assessing the motor quality. Abnormal vibration not only aects the lie o the motor, but is the main cause o noise, and motor noise and vibration relect the quality o production problems. Thereore, the motor noise and vibration can not only veriy whether the motor can meet the design requirements, but also through the spectrum analysis, ind out the causes and the main noise source, thus improving production quality.in this paper, according to related standards or single-phase capacitor motors and three-phase asynchronous motor vibration and noise measurements, and then analyze the measured data, urthermore select to modiy methods, hoping to improve the motor quality. Reerences [1] QIHui,LI Yong-hui, DUAN Jian-gang. Advances in the Research o Category, Analytical Methods and Countermeasures o Noises in Electric Motor[J].Small & Special Electrical Machines,2007(3): [2] Li Guohua,Huang Shoudao,and Duan Gailin. Analysis o the Noise and Vibration in Induction Motor Fed by Variable-Frequency Power Supply[J]. EXPLOSION PROOF ELECTRIC MACHINE,2006-2,vol.41, [3] Janda,M.;Vitek,O.; Skalka, M. Noise diagnostic o induction machine[j]. Electrical Machines (ICEM), 2010 XIX International Conerence on,2010,1-4. [4] Xin Shangjun,Liang Qingxin. Study on Key Technology or Asynchronous Motors with Low Noise and Low Vibration [J].S&M Electric Machines,2004(4):10-11,35. [5] Cassoret, B.; Corton, R.; Roger, D.; Brudny, J.-F. Magnetic noise reduction o induction machines[j]. Power Electronics, IEEE Transactions on,2003, [6] Diao Liming,Zhangyu. The analysis and noise reduction method o three wire asynchronous motors mechanical vibration and noise[j].shanghai Medium and Large Electrical Machines,2007(3): [7] R.Dalke,R.Achatz,Y.Lo, P. Papazian, and G. Hu ord. Measurement and Analysis o Man-made Noise in VHF and UHF Bands [J].IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, Aug Page(s): [8] Ali Ibrahim, Mohamed El Badaoui, François Guillet, Widian Yousse. Electrical signals analysis o an asynchronous motor or bearing ault detection [J]. IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS Nov Page(s):