How to Check a Fan’s Actual Power Consumption

Many people see a fan equipped with a 7.5 kW motor and assume that the fan always consumes 7.5 kW. This is not correct.

The motor power is the rated capacity that the motor can handle continuously. It does not mean the fan constantly consumes 7.5 kW. The actual power consumption depends on the fan’s operating airflow and pressure.

For the same fan, the higher the airflow and pressure, the heavier the load and the higher the motor current.

When system resistance is low and the air damper is fully open, the fan operates at a high-airflow point, and the motor current will increase.

If the filter becomes clogged, the airflow decreases, and the current and pressure behavior will change accordingly.

To determine whether the motor power is suitable, you cannot rely on the nameplate alone. You need to check the operating current and compare it with the fan performance curve.

If the current stays close to the rated current for a long time, there is little operating margin left. If the current exceeds the rated value and the fan continues running, the motor may overheat, the protection system may trip, and the load on the bearings may increase, eventually leading to equipment failure.

During fan commissioning, motor current is one of the most direct indicators.

Is the airflow sufficient? Measure it.
Is the pressure correct? Measure it.
Is the current stable? Measure it too.