Abstract : While high-voltage frequency converters (VFDs) have achieved good energy-saving effects when applied to induced draft fans, their reliability has been reduced due to improper design, use, and commissioning. This paper summarizes practical application experience and proposes corresponding prevention and control measures. Keywords : Frequency converter; Reliability; Tripping In thermal power plants, the power consumption of induced draft fan motors accounts for a large proportion of the plant's power consumption, and their energy-saving potential is also significant. The development of high-voltage frequency converter technology provides a reliable technical guarantee for the energy-saving transformation of high-voltage motors, and the good energy-saving effect after the transformation will bring good economic benefits to the power plant. However, improper use or commissioning can cause induced draft fan tripping, which will reduce the reliability of the induced draft fan and bring safety risks to the power plant. 1. Low Voltage Protection Tripping Problem According to the design manual requirements, in order to ensure the reliable operation of the boiler unit and to enable it to start up according to the procedure and restore normal operation as soon as possible after the accident is cleared, low voltage protection is not installed on the induced draft fan. However, in order to protect its own power devices, the frequency converter is equipped with low voltage protection. This will cause the following problems: (1) If a short circuit occurs in one of the devices connected to the plant bus, the bus voltage will drop instantaneously (the time of the drop is related to the protection action time). Before the application of the frequency converter, the operation of the induced draft fan is not affected. After the application of the frequency converter, the low voltage protection of the frequency converter will cut off the induced draft fan, thereby affecting the operation of the entire boiler and expanding the accident. (2) The medium-speed mill direct-fired system is generally equipped with two sets of fans, whose power supply is taken from two sections of the plant 6kV bus. If an external fault occurs, the system voltage will drop. If the voltage drops below the low voltage protection setting of the frequency converter, both fans may stop, thereby causing the boiler to extinguish. This will further expand the accident. Therefore, when applying frequency converters, the first consideration should be whether the low-voltage protection settings of the frequency converter itself can meet the operational requirements: is the low-voltage protection instantaneous or with a certain delay? Can optional components be added to the frequency converter to avoid tripping and escalating accidents? Frequency converters from different manufacturers have different working principles and settings, so these must be carefully considered when ordering. [b][align=center]For more details, please click: Issues to be Noted When Using High-Voltage Frequency Converters in Power Plant Exhaust Fans[/align][/b]