tailieunhanh - Recent Developments of Electrical Drives - Part 41

Recent Developments of Electrical Drives - Part 41. 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 | . Comparison Between Sinusoidal and Trapezoidal Waveforms 401 Figure 4. . currents electromagnetic power and torque for a three-phase trapezoidal waveform system. For the . the width of the interval corresponding to the peak value depends on the width of the magnet. It could vary between 100 and 150 . Deviation from the ideal forms of . and current implies torque ripple. Finite element models Due to the fact that the ideal waveforms are not achieved numerical models are elaborated to calculate the harmonic content of the current and . If the shape of the magnet is defined it is possible to use a finite element model to calculate the air-gap magnetic field. High power disk PM synchronous generators have large diameters and a flat representation of the machine is used to represent a symmetry period. Finite elements models are elaborated for the sine-wave and trapezoidal squarewave machines. The models are built for an average value of the diameter. The magnetic characteristics are introduced for each region of the machine the stator the rotor the magnets and the air-gap. Due to the symmetry of the machine s geometry only halfstator and one rotor are designed. The magnetic periodicity is 9. For each model boundary conditions are imposed the tangential component of the magnetic induction is equal to zero for the line delimiting the two stators and the normal component of the magnetic induction is equal to zero for the inferior limit of the rotor. Sinusoidal waveforms For the sinus machine the slot pitch is slots pole the width of the magnet reported to the pole pitch is and a 5 6 short-pitch winding is used. The flux for each coil is determined 402 Vizireanu et al. Figure 5. Flux lines for nominal charge conditions. and consequently the phase . Fig. 5 presents a zoom of the geometry over three poles and the flux lines for nominal charge conditions. For the sinusoidal waveforms machine the . obtained for no-load conditions .