| 摘要 |
PURPOSE:To accelerate a crane smoothly up to maximum speed by varying output frequency from an inverter to an approximate S-shape. CONSTITUTION:A general-purpose induction motor 7 driving a driving wheel 6 for travelling for a crane is variable-speed controlled by an inverter 10 controlled by a speed command value transmitted through a D/A converter 9 from a microcomputer 8. A gradient (acceleration) is maximized near rated frequency (60Hz), where output torque is maximized, in an acceleration control program memorized to the microcomputer 8, and the gradient is reduced in a frequency region lower than rated frequency and a frequency region higher than rated frequency, and approximate S-shaped frequency-time characteristics in which each region is compensated by straight lines each having different gradients are acquired. |
