| 摘要 |
A pump arrangement 1 includes a centrifugal pump 2, an electric motor 5, sensing means 12,13 and evaluation means 15-19. The sensing means 12,13 are used to monitor parameters such that a value for the electrical power being used by the motor 5 can be determined. The evaluation means 15-19 is then used to compare this value with a control value, which is dependant on the frequency of a supply to the motor 5. This comparison may then be used to determine when there is no, or a low, flow rate through the pump 2. The control value may include a product which has a user specified factor, such that it can be adjusted by the user to vary the sensitivity to different rates of flow through the pump 2. The control value may be based on at least two measurements of the power being used by the motor 5, at different frequencies, with no flow through the pump 2, and the electric motor 5 may be fed by a controlled frequency converter 6.
|
