Correct installation is one of the prerequisites for the normal operation of the centrifugal fan. At the same time, the use and maintenance of the operator is also an important factor affecting the normal operation of the centrifugal fan. In many cases, due to improper fan operation, the centrifugal fan is directly caused. The overload of the centrifugal fan, specifically, what is the cause of the overload of the centrifugal fan? How to deal with it?
Reasons for overloading of centrifugal fans
The main reason for the overload of the centrifugal fan is that the rated wind pressure value of the fan exceeds the actual value too much. Simply put, the difference between the system resistance and the external residual pressure is too much, so the running current of the fan exceeds the rated current too much:
1. When the centrifugal fan is started, the inlet air door is opened too much, the aerodynamic torque of the motor becomes larger, and the current increases, which causes the centrifugal fan to be overloaded.
2. When the voltage is low, the output power of the three-phase motor is reduced, that is, the output torque is reduced. If the centrifugal fan is heavily loaded, the motor will be blocked. If the motor is blocked, there will be no back electromotive force, and the motor will be over-current. When the voltage drops within the 10% floating range, the current will increase to maintain the rated power, and overload is prone to occur.
3. The frictional operation of the stator and rotor of the centrifugal fan will increase the operating load of the motor. Even if other conditions meet the operating requirements, long-term high-load operation will cause the motor to heat up and cause serious overload.
The situation of overloading the centrifugal fan motor is more complicated. In addition to the above common situations, when the ambient temperature is too high, the voltage is too high, the voltage three-phase uneven deviation is large, frequent starting or braking, and poor wiring, etc. The centrifugal fan is overloaded, so the fan should be inspected more comprehensively to determine the specific cause of the overload.
The treatment method of centrifugal fan overload
1. If the centrifugal fan is under high pressure for a long time, the pressure relief operation should be carried out, or the motor with suitable power should be replaced.
2. If the power supply voltage of the centrifugal fan is too high or too low, it is necessary to install a three-phase power supply voltage stabilization compensation cabinet.
3. If the bearing of the centrifugal fan is seriously worn, the bearing should be replaced and lubricated to reduce the wear of the bearing.
4. Before starting the machine, close the inlet damper of the centrifugal fan, fully open the outlet damper, then start the motor to run, and then gradually open the inlet damper when the motor reaches the specified speed.
5. If conditions permit, install the motor inverter, so that the centrifugal fan can start the fan when the inlet and outlet air doors are fully opened, but the premise is that the motor cannot be set to full speed.
6. If the temperature rise of the motor of the centrifugal fan is not high, check whether the preset electronic thermal protection function of the inverter is reasonable. If the inverter has a margin, the preset value of the electronic thermal protection function should be relaxed;
7. If the temperature rise of the motor of the centrifugal fan is too high, it means that the load of the motor is too heavy. At this time, it should be considered whether the transmission ratio can be appropriately increased to reduce the load on the motor shaft. Otherwise, the capacity of the motor should be increased.
8. If the three-phase voltage of the motor of the centrifugal fan is unbalanced, check whether the three-phase voltage at the output end of the inverter is balanced. If it is unbalanced, the problem is inside the inverter.
9. If the voltage at the output terminal of the inverter is balanced, the problem lies in the line from the inverter to the motor. Check whether the screws of all terminals are tightened.
10. If there is a contactor or other electrical appliances between the inverter and the motor, you should also check whether the terminals of the relevant electrical appliances have been tightened, and whether the contact condition of the contacts is good enough.
Precautions for the use of centrifugal fans
1. When the centrifugal fan is started at full pressure, the starting current should be 5 to 7 times the rated current; when it is started at a reduced voltage, there should be a proportional relationship between the reduced voltage starting torque and the square of the voltage.
2. If the centrifugal fan runs when the air inlet is fully open, the motor may be damaged. Therefore, the valve on the pipeline should be closed first, and then gradually opened until it reaches the required working position, not all at once. Fully open.
3. Before starting the centrifugal fan, you should pay attention to whether the ambient temperature is within the normal range, especially the temperature of the internal bearing and the lubrication and cooling conditions.
4. It is strictly forbidden to overload the centrifugal fan. Use an ammeter to detect the load status of the motor, and not be in an overloaded working condition for a long time.
5. If it is a centrifugal fan used for dust removal, pulverized coal and other environments, you should pay attention to check whether the change of dust and ash particles meets the requirements of fan operation.
