| 摘要 |
PURPOSE: A scale preventing device is provided to remove scale inside a boiler inner pipe by generating ultrasonic waves according to the resonant operation of a resonance unit, thereby preventing environmental contamination. CONSTITUTION: A scale preventing device includes a first switch (104), a resonance unit (108), and an operation control unit (110). The resonance unit is connected to the first switch. The operation control unit operates the first switch. The first switch is a field-effect transistor. An end portion of an output part of the operation control unit is connected to a gate of the first switch. The other end portion of the output part is electrically connected to a source of the first switch. Control signals inputted to the gate of the first switch have a periodical pulse waveform. [Reference numerals] (110) Driving control unit |
