| |
DETERMINATION OF MECHANICAL RESONANCES IN INDUCTION MOTORS BY RANDOM MODULATION AND ACOUSTIC MEASUREMENT
| [View]
[Download]
|
| Author(s) |
Frede Blaabjerg; John K Pedersen; Ewen Ritchie; Peter Nielsen |
| Abstract |
Acoustic noise emission from PWM-VSI inverter driven induction motors is a well known problem. The generated noise depends mainly on two factors: The harmonic content of the supply voltage waveform and the mechanical resonance frequencies of the induction motor. lt is necessary to know the mechanical resonances to optimize the switching scheme of the inverter to reduce the noise emission. Measuring the resonance frequencies is normally a laborious process. This paper introduces a new method for estimating the mechanical resonances from acoustic noise measurements. By random modulation of the output voltage of the inverter, the voltage spectrum can be spread over a wide frequency range. By FFT-analyzing the measured acoustic noise, the resonances can easily be estimated as the dominant frequencies of the acoustic noise spectrum. The method is tested on a 2.2 kW induction motor at no load and full load. Some of the mechanical resonances of the motor at no load are calculated by the Holzer method. The calculations show some agreement with the sound measurements. The influence of the fan cowl is investigated and it is concluded that this can be an important factor in the acoustic noise emission. Finally, it is observed that new mechanical resonances appear at load operation when the induction motor is mounted on a pump system and they are estimated by the measurement technique. |
| Download |
| Filename: | Unnamed file |
| Filesize: | 3.387 MB |
|
| Type |
Members Only |
| Date |
Last modified 2019-05-23 by System |
| |
 |