Determination of acoustic power of electric machines according to ČSN and according to ISO

Authors: RNDr. B. Madejewski,CSc., Ing. Z. Gela

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The article deals with comparison of differences between the methods given in ČSN 011604 and ISO 1680/1 for determination of acoustic power of electric machines. In theoretical part, and particularly in the results of the measurement it is established that the application of any of the given methods leads to the identical results. The article also draws attention to the conditions that are necessary for achieving correct results.

The acoustic power level of electric machines is one of the most important properties according to which their quality is evaluated. From the point of view of the measuring methodology the standard ČSN 011604 - [1] is valid for the measurement of acoustic power in the Czech Republic. In electric machines being exported, especially to the western countries, the standard ISO 1680/1 - [2] must be complied with, however. These standards differ in various arrangements of measuring surfaces and thus also of positions of the measuring microphone on these surfaces.

The results of the measurement in service conditions of testing laboratories in production plants show that the acoustic power level determined by the first of the given methodologies can differ from the value determined by the second of them. The paper is aimed at giving reasons, on the basis of the theoretical knowledge, for possible differences of the results of the measurement carried out by means of the above mentioned methodologies and at proving them by a suitably chosen experiment on the real machine.
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