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Fig. 9. Sound power level of the motor due to mechanical excitation. Fig. 8. Radiation efficiencies of various structural components of the motor.

Figure 9 Sound power level of the motor due to mechanical excitation. Fig. 8. Radiation efficiencies of various structural components of the motor.

Related Figures (11)

Fig. 2. Total radial force acting on the stator calculated by FEM. (a) 450 r/min. (b) 1500 r/min.
Fig. 2. Total radial force acting on the stator calculated by FEM. (a) 450 r/min. (b) 1500 r/min.
Fig. 1. Flowcharts for noise prediction. (a) Deterministic method. (b) Statistical method.
Fig. 1. Flowcharts for noise prediction. (a) Deterministic method. (b) Statistical method.
Fig. 5. Sound power spectra at no load. Fig. 4. Sound radiation efficiency of the motor subjected to random mechanical excitation.
Fig. 5. Sound power spectra at no load. Fig. 4. Sound radiation efficiency of the motor subjected to random mechanical excitation.
Fig. 3. FEM model of staor/casing.
Fig. 3. FEM model of staor/casing.
Fig. 6. SEA model for two subsystems. been obtained from (4) which is only applicable for circumfer- ential modes n > 2, the natural frequencies for a cylindrical shell with both ends free are zero for circumferential modes n = 0 and 1 [18]. Thus, by using (1), (3), and (6b), the input power to an electric motor modeled as a cylindrical shell can be calcu- lated.
Fig. 6. SEA model for two subsystems. been obtained from (4) which is only applicable for circumfer- ential modes n > 2, the natural frequencies for a cylindrical shell with both ends free are zero for circumferential modes n = 0 and 1 [18]. Thus, by using (1), (3), and (6b), the input power to an electric motor modeled as a cylindrical shell can be calcu- lated.
Fig. 7. SEA model for the motor structure.
Fig. 7. SEA model for the motor structure.
where U is the circumference of the plate, and S is the plate area. f. = c2/1.8crh is the critical frequency of the plate, and Ae is the corresponding wavelength. Also, h is the thickness of the plate, co is the sound speed in air, and c; is the longitudinal wave speed of the plate material. Strictly speaking, the radiation efficiency of a plate would be affected by the boundary condi- tions. However, if the critical frequency is not too high, the error incurred in using (16) would not be significant. According to previous studies [16], [20], the sound radiation efficiencies for cylindrical shells and plates can be estimated analytically. For a finite plate in flexural vibration, the modal averaged sound radiation efficiency can be written as [16]
where U is the circumference of the plate, and S is the plate area. f. = c2/1.8crh is the critical frequency of the plate, and Ae is the corresponding wavelength. Also, h is the thickness of the plate, co is the sound speed in air, and c; is the longitudinal wave speed of the plate material. Strictly speaking, the radiation efficiency of a plate would be affected by the boundary condi- tions. However, if the critical frequency is not too high, the error incurred in using (16) would not be significant. According to previous studies [16], [20], the sound radiation efficiencies for cylindrical shells and plates can be estimated analytically. For a finite plate in flexural vibration, the modal averaged sound radiation efficiency can be written as [16]
If the two subsystems are excited in tum, there would be two sets of equations similar to (14b) in which only the coupling loss factors are the unknowns. By combining these two equations, we have any one of the subsystems is excited, the energy balance equa- ‘ions in terms of the coupling loss factors are given by
If the two subsystems are excited in tum, there would be two sets of equations similar to (14b) in which only the coupling loss factors are the unknowns. By combining these two equations, we have any one of the subsystems is excited, the energy balance equa- ‘ions in terms of the coupling loss factors are given by
Fig. 10. (a) Sound power level of the motor driven by the PWM inverter at 450 r/min, no load. (b) Sound power level from each subsystem of the motor driven by the PWM inverter at 450 r/min, no load.
Fig. 10. (a) Sound power level of the motor driven by the PWM inverter at 450 r/min, no load. (b) Sound power level from each subsystem of the motor driven by the PWM inverter at 450 r/min, no load.
Related topics:
EngineeringBoundary Element MethodsElectric MotorBoundary Element MethodAcoustic NoiseStatistical Energy AnalysisInduction Motor
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