| 摘要 |
Method and arrangement of determining stall of a fan, when the fan is controlled with a frequency converter comprising means for providing rotational speed estimate of the fan and torque estimate of the fan and when the characteristic curves of the fan are known. The method comprising estimating the rotational speed of the fan (n), estimating the torque of the fan (T), transferring the characteristic curves of the fan to the estimated rotational speed of the fan ( n ), determining the stall region of the fan in the characteristic curves, determining the operation point of the fan from the rotational speed estimate ( n ) and torque estimate ( T ) using the characteristic curves, calculating the RMS values of the low frequency components of the torque and rotational speed estimates ( T RMS , n RMS ), combining the calculated RMS values of the low frequency components of the torque and rotational speed estimates (T RMS , n RMS ) for obtaining a low frequency parameter ( S ), and determining the occurrence of stall when the operation point of the fan is in the stalling region and/or when the low frequency parameter ( S ) is above a set limit. |
