Recent Developments of Electrical Drives - Part 24. The book stating the recent developments of electrical drives, can be useful for engineers and researchers investigating and designing electrical and electronic devices as well as for students and young researchers dealing with electrical and electronic engineering, computer sciences (advanced computer modelling, sophisticated control systems with artificial intelligence tools applied, optimal design bye use of classical and genetic algorithms employed), applied mathematics and all the topics where electromagnetic, thermal, mechanical phenomena occur | 222 Schlensok and Henneberger Table 3. Maximal levels of the estimated air-borne sound-pressure sl stator excitation left-hand rotation sr stator excitation right-hand rotation srr stator rotor excitation right-hand rotation f Hz Lsl dB Lsr dB LSrr dB 420 16 26 9 520 23 23 23 620 9 6 14 720 27 25 27 940 28 29 28 1 040 11 21 22 1 140 9 10 10 by the forces amplify the axial component. Therefore it is of advantage to take the rotor excitation into account to get more exact results concerning the structure-borne sound. Acoustic simulation The last step is to estimate the air-borne noise generated by the different excitations. For this reason a boundary-element model of the entire machine structure is applied. The air-borne sound-pressure is estimated on an analysis hemisphere around the machine at a distance of d 1m. Fig. 17 shows the result for stator-rotor excitation at f 420 Hz. The maximum sound-pressure levels L reached for the three cases taking the stator excitation into account are listed in Table 3. Figure 17. Sound-pressure distribution at f 420 Hz for stator-rotor excitation and right-hand rotation. II-7. Comparison of Stator-and Rotor-Force Excitation 223 The results show that the direction of the rotation has a significant effect on the noise generation. Except for f 720 Hz and f 620 Hz all orders are amplified up to AL 10 dB. If the rotor-force excitation is taken into account some orders become louder and some quieter. The air-borne sound-levels do not suit the acceleration measurements as well as those of the structure-borne sound. Conclusion In this paper the structure- and air-borne noise of an induction machine with squirrel-cage rotor are estimated. For this different types of surface-force excitations and rotational directions are regarded for the first time. In general the calculated structure-borne sound-levels suit the acceleration measurements of the industrial partnervery well. The acoustic-noise levels differfrom those. The comparison of the
