Recent Developments of Electrical Drives - Part 26. 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 | II-9. Diagnosis of Induction Machines 243 flux L sensor Ls Figure 2. Measured flux. 2P If the sensor has n turns and it has a rectangular shape of 5 area and considering that I X r then the h k flux components regarding to the external flux density ones are expressed by h k r sin hpfi a nS hpp bnh kr cos k - 31 Then to obtain the component at the km angular frequency it is necessary to add the different terms which have this same frequency. x k h M 32 The terms which compose k r are very numerous but many do not contribute significantly. Actually relation 30 shows that only the terms with a small value of h will have a prominent effect. This property is enhanced by the quantity sin hpfi hpfi which appears in expression 31 . The data given by the coil is a voltage which results of the Lenz law. Consequently the ek r components of the corresponding measured . are obtained by the following relation Bk r d k r dt sin hp g ek r -kmnS Kh r bD. sinl l h - x npP 33 It can be noticed that the electro-motive force spectra amplify the high frequencies what permits to distinguish the slot spectral lines more easily. 244 Thailly et al. Figure 3. Experimental device. Principle of measurements The synoptic of the Fig. 3 shows the experimental device that allows performing the measurement of the radial magnetic field component. The principle is to pick up the sensor signal with an analyzer via an acquisition card. A small winded flux sensor with nS 30 x 10 3 has been realized. It is located at a distance r equals to 100 x 10 3 m. The tests are made considering a star connected 4 poles 4 kW 380 660 V 50 Hz squirrelcage induction machine with 36 stator slots and 44 rotor bars. For this machine Rsint 60 x 10 3 m Rsext 90 x 10 3 m. The stator is supplied by 380 . phase to phase voltage. The supply current is equal to I A. In order to neglect the magnetic effects generated by the rotor the slip is close to 0. Results In the measured spectrum of the . only the .
