| 摘要 |
<p>Provided is a variable-speed hoisting machine using an electric motor having a pull-rotor brake as a hoisting motor and capable of supplying the electric motor with an electric current that can reliably release the pull-rotor brake at the time of starting an operation even in the case of a variable-speed hoisting machine such as an electric chain block, which has a short acceleration time, without reducing the output frequency at the start of overvoltage application. In a variable-speed hoisting machine having an electric motor with a pull-rotor brake and an inverter controlling the speed of the electric motor in a soft-start manner, the inverter is set to operate according to a predetermined voltage-frequency (V-F) pattern. At the time of starting the electric motor, the acceleration (output frequency increase rate) in the time interval during which the frequency reaches from f1 to f2 is set smaller than the acceleration (output frequency increase rate) in the time interval during which the frequency reaches from f2 to f3, thereby supplying the electric motor with sufficient electric power to release the pull-rotor brake.</p> |
