Precautions for General-Purpose Fans The grounding of the fan housing or motor housing must be reliable. Do not operate in the reverse direction; do not run at currents exceeding the rated value; do not operate with a missing phase. Do not perform maintenance on the fan while it is running.

　　Precautions for General-Purpose Fans

　　The grounding of the fan housing or motor housing must be reliable.

　　Reverse rotation is prohibited; operation at currents exceeding the rated value is prohibited; and operation with a missing phase is prohibited.

　　Do not perform maintenance on the fan while it is running.

　　General Fan Commissioning

　　The fan may be started either at full voltage or with reduced voltage; however, it should be noted that during full‑voltage starting, the inrush current is approximately 5 to 7 times the rated current, while the starting torque is proportional to the square of the current. When the grid capacity is insufficient, reduced‑voltage starting should be employed. (For motors exceeding 11 kW, reduced‑voltage starting is recommended.) During commissioning, carefully read the product manual and verify that the wiring configuration matches the wiring diagram. Also, thoroughly check that the supply voltage meets the specified requirements, confirm that the power supply is balanced and in phase, and ensure that the rated capacity of all associated electrical components complies with the design specifications.

　　During test runs, there must be at least two personnel: one to control the power supply and the other to monitor the fan’s operation. If any abnormal conditions are detected, stop the machine immediately and perform an inspection. First, verify that the rotation direction is correct. Once the fan has started, promptly check whether the operating current is balanced and whether it exceeds the rated current. If any irregularities are observed, shut down the equipment for further examination. After running for five minutes, stop the fan and inspect it for any unusual signs; only restart it once you have confirmed that no abnormalities are present.

　　During commissioning of a two-speed fan, first start it at low speed and verify that the direction of rotation is correct. When starting at high speed, ensure the fan has come to a complete stop before restarting to prevent reverse rotation, which could trip the circuit breaker and damage the motor.

　　When the fan reaches its normal speed, verify that the input current is within the normal range; the operating current must not exceed the rated current. If the operating current exceeds the rated value, check whether the supply voltage is normal.

　　The motor power required for a fan refers to the power needed under specific operating conditions. For centrifugal fans and fan units, the power demand is highest when the inlet damper is fully open. Operating with the inlet damper fully open may lead to motor damage. During fan commissioning, it is advisable to close the valves on the inlet or outlet piping; after starting, gradually open the valves until the desired operating conditions are achieved, while monitoring that the fan’s operating current does not exceed its rated current.

　　General Fan Surge Conditions

　　1. The fan’s operating point lies within the unstable region of the Q–H performance curve, which exhibits a hump-shaped characteristic.

　　2. The air duct system has a sufficiently large volume and, together with the fan, forms an elastic aerodynamic system.

　　3. When the frequency of the entire cycle is in phase with the system’s airflow oscillation frequency, resonance occurs.

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