A PID control loop can be configured for forward-curved stainless steel centrifugal fans to stabilize furnace negative pressure. In response to fluctuations in furnace negative pressure, the PID controller automatically adjusts the frequency output of the frequency converter, changes the air volume delivered by the forward-curved stainless steel centrifugal fan, and thereby maintains stable negative pressure inside the furnace.

For boilers burning wood chips as fuel, uneven fuel feeding will trigger drastic fluctuations in furnace negative pressure, degrade the control performance of the whole system, and further result in abnormal regulation of the forward-curved stainless steel centrifugal fan.

High-power frequency converters supporting forward-curved stainless steel centrifugal fans generate a large amount of heat during operation. If the heat cannot be dissipated in a timely manner, the frequency converter will trigger overheating protection, which threatens the safe operation of the boiler. Accordingly, cooling exhaust fans are equipped inside variable-frequency control cabinets; an air conditioner shall be installed if the ambient temperature around the cabinet exceeds 40 ℃.

Excessive dust accumulation will accelerate the aging of electronic components inside the frequency converter and eventually lead to converter failure. For this reason, filter screens shall be installed at the air intake vents of the variable-frequency control cabinet, and regular cleaning maintenance of these filter screens is required.