Abstract: A method and an arrangement for controlling a pump station includes measurement of the surface level of a liquid (465) by means of a sensor (452) and controlling the electric drive (401, 420, 430) of the pump (440) to a predetermined speed of rotation when a specific surface level value has been reached. This predetermined rotation speed value is preferably the rotation speed at which the ratio of the flow rate to the consumed power, i.e. the efficiency, is optimal. The measurement of the surface level and the related data processing for control of the pump are performed in a frequency converter (420) in conjunction with the control.

Abstract: The invention relates to a method and an arrangement for measuring a liquid flow in connection with a pump system. The invention is preferably implemented in a pump system where the pump (240) is driven by an alternating-current motor (230), whose rotating speed is controlled by a control unit (220), such as a frequency converter, for instance. In accordance with the invention, the flow is determined without any direct flow measurement by utilizing characteristic data of the pump and parameters that can be easily and reliably measured. Such parameters comprise the rotation speed of the pump, the liquid pressure and/or the motor power. Both the motor power and the rotation speed can be measured i.a. at the frequency converter (220). In addition, the static liquid pressure can be measured by means of a straightforward and reliable pressure sensor (244, 245), which can be integrated in the pump system.

Abstract: Method and arrangement for measuring a liquid flow in connection with a pump system, where the pump is driven by an alternating-current motor, whose rotating speed is controlled by a control unit. The flow is determined without any direct flow measurement by utilizing characteristic data of the pump and parameters that can be easily and reliably measured. Such parameters include the rotation speed of the pump, the liquid pressure and/or the motor power. Both the motor power and the rotation speed can be measured at the frequency converter. The static liquid pressure can be measured by a straightforward and reliable pressure sensor, which can be integrated in the pump system. In implementing the invention, two characteristic curves of the pump can be advantageously used; flow as a function of power and flow as a function of pressure. This achieves high accuracy of measurement both with low and high flow values.

Abstract: A method and an arrangement for controlling a pump station includes measurement of the surface level of a liquid (465) by means of a sensor (452) and controlling the electric drive (401, 420, 430) of the pump (440) to a predetermined speed of rotation when a specific surface level value has been reached. This predetermined rotation speed value is preferably the rotation speed at which the ratio of the flow rate to the consumed power, i.e. the efficiency, is optimal. The measurement of the surface level and the related data processing for control of the pump are performed in a frequency converter (420) in conjunction with the control.