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Recent Developments of Electrical Drives - Part 12

Recent Developments of Electrical Drives - Part 12. 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 | I-9. Torque Ripple in Inverter Driven Induction Motors 97 Drive system model An inverter driven induction motor can be modeled by combining the space phasor model of the machine with the supply model representing the non-sinusoidal voltage source inverter. Fig. 3 illustrates the ensuing model. All electromagnetic terms in 15 and 16 are expressed as space phasors by advancing from the actual three-phase machine model to an orthogonal model with alpha-beta and d-q windings the voltages and currents of which are combined to give a deceptively simple representation of the drive system. Furthermore it becomes possible to assess the effects of supply harmonics by simply including or injecting the significant supply harmonics into UJs of 15 . Simulation results The simulated alpha-beta terminal voltages containing the significant harmonics have been drawn into the simulation. With these voltages the ripple torque for no-load and load conditions shown in Figs. 4 and 5 are predicted obtained by solving the system equations of 15 to 17 . The simulation results show that the torque ripple is already of a considerable magnitude when the motor is not loaded. Under load the ripple band is seen to widen. Electromagnetic quantities not shown here provide supportive evidence for the deterioration. The results are significant in that they indicate that the simulation method used is capable of estimating parasitic torque behavior in advance. Experimental verification The validity of the approach was tested experimentally for an inverter driven three-phase cage induction motor of 1.5 kW rating. Field orientation control with strong overmodulation was employed resulting in supply harmonics both the order and magnitude of which resembled that of the six-step inverter at the motor terminals. Table 1 gives the relevant data for the test motor with which the foregoing simulations were conducted. Fig. 6 depicts the measured torque ripple band under steady state operating conditions with .