| 摘要 |
PURPOSE:To obtain a regulator which can turn ON a synchronizing speed operating circuit when a rotational speed drops to become a predetermined speed by operating a pole change converter on the basis of the signal from a rotation sensor and changing the number of poles. CONSTITUTION:A motor 11 connects with 4 poles, and operates to rotate a cooling fan at a high speed, thereby quickly cooling the interior of a furnace. Then, a drop start switch 31 is closed to turn OFF the 4-pole operating circuit of a pole change converter 1 through a controller 25. The rotational speed of the motor 11 is gradually decelerated while rotating due to its inertia, and the rotational speed is read out by a rotation sensor 2. Since a voltage corresponding to the synchronizing speed in case of 8 poles is applied as a reference voltage to a comparator 24, when the rotational speed of the output shaft 12 becomes the synchronizing speed of 8 poles, it is detected. The controller 25 turns ON the 8-pole operating circuit of the pole change converter 1 by the compared output. As a result, a cooling fan is rotated as a low speed to gradually cool the interior of a furnace. |
