| 摘要 |
PURPOSE:To prevent a rise of primary voltage and the improvement of a primary power-factor in field-weakening control performing operation at constant output under a vector control by a system wherein magnetic flux is weakened in proportion to speed up to a fixed speed, and the magnetic flux is reduced within a fixed change range at speed faster than the fixed speed. CONSTITUTION:A function generator 22, which employs only ¦omegar¦ which is the speed of revolution of an induction motor as input, and has the output of logical signals up to omegarc fixed angular velocity, and whose output changes in attenuation characteristics to ¦omegar¦ at not less than omegarc, is added to a circuit enabling automatic field-weakening control vector-controlling the induction motor by using a pulse width modulating inverter 1. Its output and output from a multiplier 11 are inputted to a comparatot 13 through a multiplier 21. Thus, when the induction motor is operated at constant output within a speed region of not less then omegarp=1 base speed, the speed is changed at PHI2infinity 1/omegar up to omegarc the fixed angular speed, and changed so that PHI2 is controlled within a shaded line range of (2)' and (3)' shown in a graph at omegarc or more, and the reduction of a rise of primary terminal voltage and the improvement of a primary power-factor can be attained. |
