| 摘要 |
PURPOSE:To contrive the improvement of adaptability by increasing an exciting current command value in accordance with rotating speed when the rotating speed exceeds a predetermined value. CONSTITUTION:An exciting current amplitude control circuit 41 is provided and rotating speed Va is supplied to the input terminal in the control circuit 41 to feed an exciting current command signal Im from the output terminal in the control circuit 41. Then, Imsinphi, Imcosphi are fed from D/A converters 9, 10 and an exciting current command value rises in accordance with rotating speed Va at base speed Vb or over. Therefore, when the rotating speed of an induction motor arrives at a predetermined value Vb or more, the exciting current command value is to increase in accordance with the rotating speed. In this way, even if the rotating speed reaches high speed in vector control, the current as commanded can flow into the induction motor to improve adaptability and overexcitation will also not be occurred even if a power voltage varies and the generation of heat in the motor can be prevented. |
