| 摘要 |
PROBLEM TO BE SOLVED: To reduce a noise generated by a cooling fan and to make the circumstance comfortable by providing two cooling fans of which driving motors are connected with a common power source circuit, and by connecting a power source phase adjusting circuit between the power source circuit and one of any driving motors. SOLUTION: A noise reduced cooling fan 1 is provided with two cooling fans 2a and 2b and each fan is equipped with driving motors 3a and 3b. A power source circuit 4 is connected with each driving motor and a power source phase adjusting circuit 5 is connected with the middle of the power source circuit 4 and one of any driving motors. A driving power source voltage of the driving motor 3b is shifted at a phase differenceϕby the power source phase adjusting circuit 5, and the cooling fan 2b is made to rotate by the driving voltage. As noise waves generated by each cooling fan has the same sine wave, the cooling fan 2b connected with the phase adjusting circuit 5 is made to reverse by delaying at the phase differenceϕ, each wave form is soften by obstructing each other to become a low level noise.
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