| 摘要 |
A method for the operation of a centrifugal pump (2) driven by an electric motor (5) with variable frequency, wherein too small a flow through the pump (2) is ascertained by monitoring electrical quantities, and a pump arrangement (1) having a centrifugal pump (2), an electric motor (5) which drives the centrifugal pump (2), a controlled frequency converter (6) which feeds the electric motor (5), a sensor device (12, 13) and an evaluating device (15-19) are described. It is desired to detect, by simple means, when no through-flow is present. For that purpose, the electrical power is ascertained and compared to a control quantity formed as a function of the frequency of the motor (5). The sensor device ascertains values for determination of the electrical power, and the evaluating device has a dynamic limit value former (18), which forms a control quantity as a function of the frequency of the motor (5).
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