Method for Obtaining the Variable-Frequency Speed Control Waveform for High-Pressure Centrifugal Fan No. 5

Method for Obtaining the Variable-Frequency Speed Control Waveform for High-Pressure Centrifugal Fan No. 5

In the variable-frequency speed control of High-Pressure Centrifugal Fan No. 5, there are two methods for generating rectangular pulse waves with unequal amplitudes and widths. First, based on the frequency and voltage variation requirements of the No. 5 high-pressure centrifugal fan, a microcomputer is used to calculate and determine the turn-on and turn-off times of each high-output transistor. The output voltage of the No. 5 high-pressure centrifugal fan control system is determined by the inverter, resulting in rapid speed adjustment and excellent system dynamic response. Since the DC power supply for the PWM inverter is obtained through rectification, phase-shift control is not required; the power factor is relatively high at 17.5 or 18, reducing reactive power losses. Because multiple inverters can be connected to the same common DC bus, the speeds of multiple motors can be controlled simultaneously. The additional output current of the frequency converter for the No. 5 high-pressure centrifugal fan typically needs to be 111 times the motor’s additional current. When applying heavy loads for short periods or frequently adjusting the motor, the inverter’s capacity must be increased. For high-inertia fans such as the No. 5 high-pressure centrifugal fan, the acceleration and deceleration times must be extended. Otherwise, the fan may shut down due to overcurrent, and an overvoltage alarm may occur during startup. The acceleration time can be adjusted from the factory default of 5 seconds to 30 seconds. The inverter must be installed in a suitable environment. When used in fiber-based air conditioning systems, it must be protected against dust and moisture.