| 摘要 |
PURPOSE:To improve a regenerative capability by a method wherein the inverter is released when differences beween a number of rotations of the motor and frequencies of the inverter are made smaller than a reference level on regenerating, in controlling an induction motor by a variable voltage variable frequency inverter. CONSTITUTION:A tacho-generator 6 detects a number of the rotations of the induction motor 5, and the differences between the output VTG1 of the motor and the frequency level VINV of the inverter are operated by an operator 7. During the normal regeneration being performed, it is represented by 1-VTG1>1VINV1, and the operator 7 carries out the operation of VTG1-VINV1 and feeds a positive output VDELTAFS. The output is compared with a negative pattern-VPFS by a comparator 9. With the decrease of the speed, the inverter reaches an oscillation limit and VDELTAFS decreases. When VDELTAFS becomes smaller than the negative pattern -VPFS, the output of the comparator 9 is turned to negative and a transistor 11 and a relay 12 are turned OFF, and the inverter is released by the contact point 2 of a line breaker 14. |
