| 摘要 |
PURPOSE:To reduce the size of a cooler and the capacity of a controller by dividing a group of coolers into two or more groups, the first group connected to a variable speed controller and the second group connected directly to a power source, and using the second group gradually in accordance with the load factor. CONSTITUTION:Power led in a cooler control cubicle from a power source 5 is supplied to an A.C. variable speed controller 8 through a main electromagnetic contactor 6 and also to the commercial sides of electromagnetic contactors 9B, 10B, 11B for switching to a commercial power source for rated operation. At the first stage, all the commercial side contactors 9B, 10B, 11B are opened and only the first stage variable speed control contactor 9A is closed for speed control operation. If the load factor is raised to the value of the second stage starting, the second stage commercial contactor 10B is closed and the second group motors 13 are operated at rating. The variable speed controller 8 is also once returned to the minimum rotation and again controls the speed of the first group motors 12 through the electromagnetic contactor 9A. |
