tailieunhanh - High Performance Driver P5b

Some characteristic simulation and experimental results are given in this Section, that illustrate behaviour of rotor flux oriented induction machines. Current-fed indirect rotor flux oriented machine is discussed at all times. Both the scheme of Fig. with indirect vector control and the scheme of Fig. with direct vector control are under consideration. Consider at first the scheme of Fig. | HIGH PERFORMANCE DRIVES 56 Fig. - Indirect feed-forward voltage fed rotor flux oriented induction machine. . PERFORMANCE OF A ROTOR FLUX ORIENTED INDUCTION MACHINE Some characteristic simulation and experimental results are given in this Section that illustrate behaviour of rotor flux oriented induction machines. Current-fed indirect rotor flux oriented machine is discussed at all times. Both the scheme of Fig. with indirect vector control and the scheme of Fig. with direct vector control are under consideration. Consider at first the scheme of Fig. . Simulation results are presented in what follows. Rated rotor flux reference is applied at time instant zero. Speed reference and the load torque are equal to zero. Once when the rotor flux is established a speed reference is applied. The simulation results are given in Fig. . As can be seen from Fig. the initial excitation of the machine follows exponential law. When the flux settles and speed command is applied actual speed follows reference speed with a very small delay caused by inertia of the drive. Torque rises almost instantaneously and reaches the maximum value determined by the imposed limit and hence the stator current is in the limit as well. Note that rotor flux remains constant during the torque variation indicating that flux and torque control are fully decoupled change of stator q-axis current does not cause any variation in the rotor flux . When the reference speed reaches steady-state value the actual speed overshoots due to action of the speed controller which is PI and hence torque rapidly goes out of the limit reduces and becomes negative which means that electric braking operation takes place. Once when the speed settles at the value equal to the reference value torque falls to zero because the case shown in Fig. is acceleration with zero load torque. Comparison of Fig. with Fig. shows that the responses are identical hence the rotor flux orientation .