What is the cause of motor overload after a centrifugal fan is started?
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Our facility has an old-fashioned centrifugal blower; the inlet damper is set to half position. Once it is started, the motor overheats. What could be the reason?
When the outlet door opens, the motor requires a high starting torque and high starting current. Check whether the outlet door is open at startup.
Thank you for the advice! :handshake
1# *ang0826 So how should it be done? Should all the outlets be closed, one half of the inlets opened, the motor started, and then the outlets opened? How can this be resolved? The shaft power of the fan is at its lowest when the flow rate is minimal, and the starting current of the motor is also at its lowest. Analysis: Based on the N-Q curve of centrifugal pumps (or centrifugal fans), where N represents the shaft power of the pump and Q represents the flow rate, it can be seen that the shaft power of the fan is at its lowest and the starting current of the motor is at its lowest when the flow rate is minimal
1. The inlet damper should be fully closed and the outlet damper fully open before starting up; once the motor has reached the specified speed, the inlet damper should be gradually opened. This is because the motor itself draws high current when starting, and due to the heavy weight of the fan rotor, overcurrent occurs even under light load. If this persists for too long, the relay will activate the protection mechanism, which results in the circuit breaker in the distribution cabinet tripping. 2. If conditions permit, it is recommended to install an inverter for the motor; in this case, the inlet and outlet dampers can be left fully open when starting the fan, but the motor should not be set to its full speed. The reason is that when the inverter starts, it undergoes a soft start process, meaning that the current and voltage increase gradually, which prevents the motor from being overloaded. This also simplifies the operation steps, making it very convenient for adjustments during normal production.
I think the inlet valve is opened too wide, or in other words, the flow rate is too high. Under normal circumstances, the inlet valve of a fan does not need to be closed completely; if it is closed fully, it can easily cause the system to shut down.