| 摘要 |
PURPOSE:To always hold the target rotating speed of a motor by comparing with a set rotating speed when an AC motor varies due to the variations in a load or a power source voltage, and correcting the phase angle in response to the compared result. CONSTITUTION:The rotation of a fan motor 1 is controlled to coincide with the rotating speed stored in an ROM 16. When a fan motor 1 varies its rotating speed due to a variation in a load, the varied rotating speed is input to an ROM 15 to become incoincident to the content of the ROM 16, the content of an RAM 19 is added or subtracted in the incoincident amount, the counting time of a timer 20 increases or decreases in response to the content of the RAM 19, the conduction timing of a triac 6 varies by the increase or decrease of the counting time to control the phase so that the content of the RAM 15 coincides with that of the ROM 16. |
