| 摘要 |
PURPOSE:To prevent the noise of a duct system by setting the upper and lower limit value of a variable voltage variable frequency unit (VVVF) operating voltage, thereby preventing a duct from vibrating. CONSTITUTION:The upper and lower limit values of a VVVF operating voltage are set by upper and lower limit voltage generators 3, 5 having variable resistors, an input voltage from a controller 102 is compared by upper and lower limit voltage comparators 4, 6 for comparing it with the upper and lower limit voltages, an input voltage, upper and lower limit voltages are selected by a multiplexer 7, its output voltage is set to VVVF operating voltage of the range that the output voltage does not arrive at sound pressure level or higher having the noise of a duct system, and supplied through a sample-holding circuit 8 to a VVVF unit 103. |
