The paper introduced the hazard of large turbine generator operation under abnormal frequency and technical requirements and criteria for low frequency protection.

介绍了大型汽轮发电机组频率异常运行的危害和对低频保护的技术要求及准则；

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Consider of water ecosystem protection and characteristics of ultrasonic technology, low frequency and low power ultrasonic especially suit to control algal growth in water body.

超声波的空化作用能够抑制藻类生长，从保护水体生态系统以及超声波技术本身的特点考虑，低频率、低功率的超声波更适合于水体抑藻应用。

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Applications: Low Voltage, High Frequency Inverters, and Polarity Protection Applications.

主要用途：低电压整流，高频转换开关和极性保护。

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