| 摘要 |
PURPOSE:To provide protective functions by detecting the current of an electric motor for driving a conveyer to discriminate overload of the conveyer from an increase in load due to interference with incidental apparatus. CONSTITUTION:A discrimination switching device 3 is provided with the first relay 5 and the second relay 6, wherein by an intermediate set signal It between the maximum actual load current signal and a no-load current signal of an induction motor 1, a little higher first current signal Ih and a little lower second current signal Il are respectively compared with a load current signal I of the motor 1, to energize the first relay 5 for a limited time more than starting time of the motor when the signal I is greater than the signal Il and de-energize same when the signal I is smaller than the signal Il, and to energize the second relay 6 when the signal I is smaller than the signal Ih for a limited time. A control device MG is adapted to stop the motor in response to an output of a heavy-load protective device 4H or a ligh-load protective device 4L. |
