| 摘要 |
PURPOSE:To realize downsizing and cost reduction of door motor by providing a highly accurate protective function based on estimation of temperature rise thereby making possible to operate the door motor in the limit of capacity. CONSTITUTION:A motor current measuring means 20 full-wave rectifies a three- phase current signal It fed from a DC current transformer 5. A motor current corresponding to temperature rise of a door motor 3, i.e., a full-wave rectified signal Iis, is fed to a digital circuit 8. An AC converter 88 provided in the digital circuit 8 takes in the full-wave rectified signal Iis converted into a digital signal. A CPU 80 in the digital circuit 8 operates motor current per a predetermined time (an averaged motor current) based on the full-wave rectified signal Iis and thus operated motor current is compared with a first allowable value. When the operated motor current exceeds a first allowable value, the motor current is suppressed to drive the door at a low speed while when the motor current exceeds a second allowable value, the door is fully opened to lower the temperature of the door motor. |
