Measurement method and arrangement
2 Assignments
0 Petitions
Accused Products
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.
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Citations
46 Claims
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1-23. -23. (canceled)
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24. A method for measuring a flow in a pump system, in which a liquid flow is generated by means of a pump and the pump is actuated by an electric drive, in which the rotation speed of an alternating-current motor is controlled with a control unit, characterised in that the method comprises:
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measuring (402) a pump power (P) in the pump system, measuring a rotation speed (v) of the pump, measuring (504) a static pressure (Hs), setting an estimate of a dynamic pressure (Hd) to a pre-estimated constant value, determining (506) an estimate of a total pressure (H) on the basis of the static pressure and the estimate of the dynamic pressure, determining a first estimate (410, 416) of the liquid flow on the basis of the measured pump power (P) and rotation speed variables, determining a second estimate (514, 516) of the liquid flow on the basis of the estimate of a total pressure (H) and rotation speed variables, determining a flow measurement result by a logical selection or any other predetermined function on said first estimate of the liquid flow and said second estimate of the liquid flow, determining (520) a new estimate of a dynamic pressure (Hd) on the basis of the flow measurement result, re-determining the estimate of a total pressure (H) on the basis of the static pressure and the new estimate of the dynamic pressure, re-determining the second estimate of the liquid flow on the basis of the estimate of a total pressure (H) and rotation speed variables, and re-determining the flow measurement result by a logical selection or any other predetermined function on said first estimate of the liquid flow and said second estimate of the liquid flow. - View Dependent Claims (25, 26, 27, 28, 29, 30, 31, 32, 33)
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34. An arrangement for measuring the flow in a pump system comprising a pump (240) for generating a liquid flow, an electric drive for actuating the pump, the electric drive comprising an alternating-current motor (230) and a control unit (220) for controlling the rotation speed of the alternating-current motor, characterised in that the arrangement comprises:
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means (221, 223) for measuring a pump power (P) in the pump system, means (221, 223, 228) for measuring a rotation speed (v) of the pump, means (244, 245) for measuring a static pressure (Hs), means (221, 222, 228) for setting an estimate of a dynamic pressure (Hd) to a pre-estimated constant value, means (221, 222, 228) for determining an estimate of a total pressure (H) on the basis of the static pressure and the estimate of the dynamic pressure, means (221, 222) for determining a first estimate of the liquid flow on the basis of the measured pump power (P) and rotation speed variables, means (221, 222) for determining a second estimate of the liquid flow on the basis of the estimate of a total pressure (H) and rotation speed variables, means (221, 222) for determining a flow measurement result by a logical selection or any other predetermined function on said first estimate of the liquid flow and said second estimate of the liquid flow, means (221, 222) for determining a new estimate of a dynamic pressure (Hd) on the basis of the flow measurement result, means (221, 222) for re-determining the estimate of a total pressure (H) on the basis of the static pressure and the new estimate of the dynamic pressure, means (221, 222) for re-determining the second estimate of the liquid flow on the basis of the estimate of a total pressure (H) and rotation speed variables, and means (221, 222) for re-determining the flow measurement result by a logical selection or any other predetermined function on said first estimate of the liquid flow and said second estimate of the liquid flow. - View Dependent Claims (35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46)
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Specification