The centrifugal fan is essentially a constant pressure device with variable flow rate in use. When the speed of the centrifugal fan is fixed, the theoretical curve of pressure and flow of the centrifugal fan should be a straight line. Due to internal loss, the actual characteristic curve is curved. The pressure produced in centrifugal fan is greatly affected by the change of inlet air temperature or density. For a given intake, the pressure generated at the highest inlet temperature (the lowest air density) is the lowest. For a given pressure and flow characteristic curve, there is a power and flow characteristic curve. When the blower is running at constant speed, the required power increases with the decrease of inlet temperature for a given flow rate.
Centrifugal fans are allowed to start at full voltage or lower voltage by electric power, but the rated current at full voltage starting is about 5-7 times, the starting torque is proportional to the square of voltage, and when the power network capacity is insufficient, Start by lowering the pressure. The centrifugal fan should read the product specification carefully and check whether the wiring method is in accordance with the wiring diagram. It is necessary to carefully check whether the working voltage of the power supply to the fan is in accordance with the requirements, whether the power supply is lacking in phase or in the same phase, and whether the capacity of the components of the distribution apparatus is in accordance with the requirements.
The number of centrifugal fans should not be less than two during the test run. One of them controls the power supply. One person observes the unit rotation of the fan. If an abnormal phenomenon is found, the check should be stopped immediately. First, check whether the direction of rotation is correct or not. When the centrifugal fan starts to operate, it should immediately check whether the running current of each phase is balanced or not, whether the current exceeds the rated current; If there is any abnormal phenomenon, stop checking. After five minutes of operation, stop to check if the fan is abnormal and confirm that there is no abnormal phenomenon before starting the machine.