Abstract: Measures of a torque and rotational speed of a pump or fan are obtained, from which a mechanical input power can be calculated. By further using predetermined relations between mechanical input power and flow rate through the pump or fan, a measure of the flow rate can be derived without use of in-line flow or pressure sensors. In preferred embodiments the torque and/or rotational speed is obtained by measuring the input current and voltage of a motor driving the pump or fan and using predetermined relations between on the one hand current and voltage and on the other hand torque and rotational speed. Furthermore, also other flow properties, such as pump head, pump efficiency and total efficiency can be determined in this manner.

Abstract: The present invention discloses devices and methods for improved starting and stopping of rotary motors. A rotary electrical machine (3) is supplied with a voltage from a voltage supply (10). The magnitude of a phase current is measured. The measured current value (IM) and applied voltage (U) is compared with what is expected for a predetermined target slip (ST), by means of a relation between phase current, applied voltage and slip. The comparison gives a discrepancy value, which is used to create a regulation signal (?U) to the voltage supply (10). To start and stop the machine, the target slip is increased and decreased, respectively, in a predetermined manner. The means for regulation may be provided as a separate add-on unit to existing soft starter equipment.

Abstract: Measures of a torque and rotational speed of a pump or fan are obtained, from which a mechanical input power can be calculated. By further using predetermined relations between mechanical input power and flow rate through the pump or fan, a measure of the flow rate can be derived without use of in-line flow or pressure sensors. In preferred embodiments the torque and/or rotational speed is obtained by measuring the input current and voltage of a motor driving the pump or fan and using predetermined relations between on the one hand current and voltage and on the other hand torque and rotational speed. Furthermore, also other flow properties, such as pump head, pump efficiency and total efficiency can be determined in this manner.

Abstract: The present invention discloses devices and methods for improved starting and stopping of rotary motors. A rotary electrical machine (3) is supplied with a voltage from a voltage supply (10). The magnitude of a phase current is measured. The measured cuurent value (IM) and applied voltage (U) is compared with what is expected for a predetermined target slip (ST), by means of a relation between phase current, applied voltage and slip. The comparison gives a discrepancy value, which is used to create a regulation signal (&Dgr;U) to the voltage supply (10). To start and stop the machine, the target slip is increased and decreased, respectively, in a predetermined manner. The means for regulation may be provided as a separate add-on unit to existing soft starter equipment.