The Influence of the Load Condition upon the Radial Distribution of Electromagnetic Vibration and Noise in a Three-Phase Squirrel-Cage Induction Motor

Transcription

1 The Influence of the Load Condition upon the Radial Ditribution of Electromagnetic Vibration and Noie in a Three-Phae Squirrel-Cage Induction Motor Yuta Sato 1, Iao Hirotuka 1, Kazuo Tuboi 1, Maanori Nakamura 1, Akihiko Iguchi 1, Daiuke Hayahi 1, and Youuke Takahahi 2 1 Department of Electrical Engineering, Chubu Univerity, Japan 2 Tohiba Indutrial Product and Sytem Corporation, Japan ABSTRACT The reduction of electromagnetic vibration and noie in three-phae quirrel-cage induction motor (IM) ha become very important from an environmental tandpoint. However, the relationhip between the radial ditribution of the electromagnetic vibration and noie and the force wave that caue them ha yet to be analyzed in ufficient detail. In thi paper, we preent the reult of everal experimental trial and how the analyi of an IM under variou load condition to tudy the caue of the vibration and noie component by examining of their radial ditribution. Keyword: Electromagnetic vibration, Electromagnetic noie, Radial ditribution, Harmonic flux, Slot combination 1. INTRODUCTION In recent year, enhanced environmental conideration have led to an increaed demand for low-noie induction motor (IM). Although the baic theory of IM ha been clarified in numerou tudie [1], the relationhip between the radial ditribution of electromagnetic vibration and noie and the force wave that caue them ha yet to be analyzed in ufficient detail. In thi tudy, we experimentally examine the radial ditribution of electromagnetic vibration and noie in an IM under variou load condition. Becaue the occurrence frequency (f v ) of the vibration and noie component change according to the load condition, the mechanical reonance effect on thee component alo change. Therefore, to eliminate the mechanical reonance effect, f v can be held contant a the load condition varie by adjuting the frequency and amplitude, (f and V, repectively) of the ource voltage ued to maintain the gap flux [2]. In thi paper, we firt dicu the occurrence frequencie and mode aociated with variou type of dominant electromagnetic force generated by the interaction of harmonic fluxe within the IM gap. We then decribe our experimental method, and finally, we how that the radial ditribution of the dominant electromagnetic vibration and noie component in an IM under load condition match the mode hape of the correponding dominant electromagnetic force on the bai of the reult of everal trial. 2. DOMINANT ELECTROMAGNETIC FORCES Figure 1 how a ummary of the caue of electromagnetic vibration and noie in an IM. The electromagnetic noie i caued by electromagnetic vibration, which in turn i caued by the electromagnetic force. The electromagnetic force i generated by the interaction among the air-gap fluxe in an IM toward the radial direction. Thi flux i expreed a the product of the magnetomotive force and air-gap permeance whoe main component i the lot permeance. Furthermore, Figure 1 how that many harmonic component affect the electromagnetic vibration and noie. The electromagnetic noie i alo affected by the mechanical reonance of the IM. Therefore, clarifying the complex relationhip among the electromagnetic vibration, noie, 1 Te @ti.chubu.ac.jp 1

2 electromagnetic radial force, and mechanical reonance i important to deign an IM with leer vibration and noie. The general equation for the primary cauative electromagnetic force of the dominant electromagnetic vibration and noie component in an IM were derived in [2]. Table I lit the ummary of the occurrence frequencie f M (Hz) and mode M for three dominant electromagnetic force type in an IM driven by a inuoidal power upply. Where, n and n are the number of tator and rotor lot, p' i the pole pair, i the lip, and L and K are integer that indicate the order of the tator and rotor lot permeance, repectively. For convenience, each dominant electromagnetic force i allocated a claification number. Thi table alo lit two type of electromagnetic Force -[I] and [II]- that are produced depending on the load condition. Force [I] reult from the interaction between the tator fundamental flux and the rotor harmonic flux at no-load, wherea Force [II] i produced by the interaction between thee two fluxe under loaded condition. Table I clearly how that f M i proportional to f; therefore, f M can be maintained a contant by adjuting f to avoid the effect of the IM mechanical reonance. Supplied voltage Magnetomotive force Flux Interaction of fluxe Electromagnetic force Electromagnetic vibration Electromagnetic noie Effect of waveform Effect of winding ditribution Effect of lot Effect of mechanical reonance Effect of environment Fig. 1. Caue of electromagnetic noie. Table I. Occurrence frequencie and mode of variou dominant electromagnetic force. No. Frequency: f M Mode: M 1 1 Kn p' 2 f 2 1 Kn p' f 3 1 Kn p' 2 f [I] p p Ln Kn ' ' [II] p' Ln Kn p ' [I] p p Ln Kn ' ' [II] p' Ln Kn p ' [I] p p Ln Kn ' ' [II] p' Ln Kn p ' 3. TEST MOTOR AND MEASUREMENT Table II lit the pecification of the tet motor ued in thi tudy. The four-pole motor i rated at 2 V/6 Hz, ha a power output of 1.5 kw, and ha 36 and 33 tator and rotor lot, repective ly. Although thi lot combination i not commercially ued, it i employed in the tet motor becaue it produce appropriate dominant electromagnetic vibration and noie component. The natural frequencie were meaured uing an impact hammer, and we confirmed that they remain approximately contant even if the rotor were exchanged. Figure 2 how the arrangement of the experimental apparatu, and Figure 3 how a photograph of the motor noie laboratory. To minimize the external vibration effect, the tet motor wa et on a damper rubber. A room with pecial acoutic propertie wa contructed to keep the reflected ound and background noie below 4 db. To avoid abnormal tarting phenomena and to allow control of the upplied frequency f, a ine-wave variable-frequency upply wa ued. Two acceleration pickup -one movable and other fixed to the top of the IM- were ued to detect radial vibration and to feed the reulting ignal via charge amplifier into a fat Fourier tranform (FFT) analyzer. Movable and fixed microphone mounted at the upper center poition of the IM tator were ued to detect the electromagnetic noie, and the ound preure level (in decibel) were meaured by the FFT analyzer through ound level meter. To etimate the electromagnetic noie in more detail, the ditance between the center of the tet motor and each microphone wa fixed at.5 m, which wa horter than the ditance tipulated in Japanee Indutrial Standard (JIS) C 421 [3]. Meaurement of the vibration and noie were performed both at no-load and rated-load condition. When the load condition changed, the electromagnetic vibration and noie occurrence frequency f v were altered by varying the lip. A a reult, the mechanical reonance effect on the electromagnetic vibration and noie changed. The vibration and noie component were meaured under ten condition: at a contant upply voltage of 2 V/6 Hz and at a condition where f v wa kept contant by adjuting the upplied voltage while the ratio of the voltage to the frequency wa maintained at 2 V:6 Hz. 2

3 Power upply Eddy current dynamometer Table II. Specification of the tet motor. Rated output 1.5 kw Number of pole: 2p 4 Rated voltage 2 V Rated frequency 6 Hz Number of tator lot: n 36 Number of rotor lot: n 33 Skew of rotor lot No kew Main natural frequencie 625, 99, 111, 198, 21, and 39 Hz FFT Analyzer FFT Analyzer Sound level meter Sound level meter Charge AMP. Charge AMP. Pickup bae Microphone Pickup 3φ 2V IM Signal generator Volt lider Floor Fig. 2. Arrangement of the experimental apparatu. Fig. 3. Motor noie laboratory. 4. EXPERIMENTAL RESULT Figure 4 how the dominant electromagnetic vibration and noie of the tet motor under variou load condition. When the load condition i changed, no change wa oberved in the occurrence frequencie of the dominant component. However, the acceleration level of the vibration and the ound preure level of the noie changed. We alo confirmed that the frequency of the dominant electromagnetic noie component wa the ame a that of the dominant electromagnetic vibration component. The three component hown in Figure 4 were aeed to determine their repective caue (from Table I). The reult lited in Table III. The occurrence frequencie of the 99, 198, and 297 Hz vibration component were caued by the electromagnetic force wave of mode M = 3, 6, and 9, repectively. Figure 5 how the time-continuou graph of the radial ditribution of the vibration and noie component where the occurrence frequency i kept contant at f v = 99 Hz by adjuting the upplied voltage at % load condition. Figure 6 how the radial ditribution when the dominant electromagnetic vibration i kept contant at 99 Hz by adjuting the upplied voltage under 1, 2, 3, 4, 5, 6, 7, 8, 9, and 1 % load condition. The ditribution of the 99 Hz component appear to have M = 3 at no-load [1]. However, we found that the mode changed from 4 % of the load factor from thi meaurement even though the force wa at Mode 3 at thi frequency. Exiting theory ugget that a double-mode ditribution uch a thi would reult when trong mechanical reonance effect occur; our reult confirmed thi effect. Table III. Dominant electromagnetic vibration and noie component. f v contant under variou load condition (Hz) No. M K L

4 Vibratory acceleration fa [m/ 2 ] Vibratory acceleration fa [m/ 2 ] Hz, 1.4 m/ Hz, 1.69 m/ V/6.51 Hz, L p = 2 % 297 Hz,.22 m/ 2 99 Hz, 1.1 m/ Hz, 23.3 V/61.1 Hz, L p = 4 % Hz,.32 m/ m/ Hz,.97 m/ Hz, 2.96 m/ 297 Hz,.36 m/ V/61.56 Hz, L p = 6 % 27.2 V/ Hz, 99 Hz, 2.7 m/ 2 L p = 8 % 198 Hz, 1.15 m/ Hz,.53 m/ Occurrence frequency (khz) Occurrence frequency (khz) Electromagnetic vibration Fig. 4. Dominant electromagnetic vibration at Therefore, the ditribution of the dominant electromagnetic vibration have the ame mode tructure a that of the electromagnetic force in ome cae, a lited in Table III. 5. CONCLUSIONS In thi tudy, an IM under variou load condition wa analyzed to determine the caue of the vibration and noie component by examining their radial ditribution. The radial ditribution of thee component were quantitatively analyzed in detail over a variety of driving frequencie and load condition. We believe that the reult of thi tudy will be ueful in developing vibration and noie reduction method for IM. ACKNOWLEDGEMENTS The author would like to thank the univerity tudent of the Department of Electrical Engineering, College of Engineering, Chubu Univerity, Japan, for their aitance. Thi work wa upported by JSPS KAKENHI Grant Number REFERENCES 1. I. Hirotuka, Y. Sato, K. Tuboi, and Y. Takahahi, The Influence of the Occurrence Frequency upon the Radial Ditribution of Electromagnetic Vibration and Noie in a Three-Phae Squirrel-Cage Induction Motor, ICEMS 213, 2. K. Tuboi, I. Hirotuka, and F. Ihibahi, Caue and Characteritic of the Electromagnetic Vibration of a Squirrel Cage Induction Motor under Load, Tran. IEEJ, Vol. 117D, No. 1, pp. 73-8, January Japanee Indutrial Standard Committee, JIS C 421, 21(in Japanee). 4

5 ±18 1 At bae time 2 After 1/99 1/12 () 3 After 1/99 2/12 () 4 After 1/99 3/12() 5 After 1/99 4/12 () 6 After 1/99 5/12 () 7 After 1/99 6/12 () 8 After 1/99 7/12 () 9 After 1/99 8/12 () 1 After 1/99 9/12 () 11 After 1/99 1/12 () 12 After 1/99 11/12 () (a) Electromagnetic vibration Sound preure level (kg/m 2 ) 1 At bae time 2 After 1/99 1/12 () 3 After 1/99 2/12 () 4 After 1/99 3/12() 5 After 1/99 4/12 () 6 After 1/99 5/12 () 7 After 1/99 6/12 () 8 After 1/99 7/12 () 9 After 1/99 8/12 () 1 After 1/99 9/12 () 11 After 1/99 1/12 () 12 After 1/99 11/12 () (b) Electromagnetic noie. Fig. 5. Radial ditribution when the 99 Hz component i kept contant by adjuting the upplied voltage at %. 5

6 ±18 ±18 ±18 ±18 L p = 1 % L p = 2 % L p = 3 % L p = 4 % ±18 ±18 ±18 ±18 L p = 5 % L p = 6 % L p = 7 % L p = 8 % ±18 ±18 L p = 9 % L p = 1 % Fig. 6. Radial ditribution when the 99 Hz component i kept contant by adjuting the upplied voltage under 1, 2, 3, 4, 5, 6, 7, 8, 9, and 1 %. 6