Abstract: A condition monitoring method for a pump assembly, wherein the method includes estimating a large number of system curves for the pump assembly over a long period of time in order to detect a change in an operating state of the pump assembly for assessing whether the pump assembly requires maintenance. The method includes a curve fitting procedure, in which estimated system curves are fitted on operating point data of the pump assembly. The curve fitting procedure includes providing estimated system curves for a plurality of fitting time windows, wherein each of the plurality of fitting time windows includes a plurality of operating points of the pump assembly.

Abstract: An arrangement for monitoring an antifriction bearing of a rotating shaft of a rotating electric machine. The arrangement includes: one or more capacitor electrodes to measure a capacitive shaft displacement parameter; one or more of the following additional measurement sensors; a microphone to measure a bearing noise parameter, a voltage sensor to measure a bearing current parameter, and/or an optical pyrometer to measure a shaft heat parameter; and one or more processors configured to evaluate a condition of the antifriction bearing based on the capacitive shaft displacement parameter and one or more of the following: the bearing noise parameter, the bearing current parameter, and/or the shaft heat parameter.

Abstract: An apparatus for estimating electrical properties of an electrolyzer includes a data processing system for estimating electrical values, for example a membrane resistance, of the electrolyzer based on a difference voltage, a current, and an initial value and an attenuation time constant of a double-layer capacitance voltage of the electrolyzer during a shutdown of the electrolyzer. The difference voltage is a difference between a voltage of the electrolyzer and a total reversible voltage of the electrolyzer. The initial value and the attenuation time constant of the double-layer capacitance voltage are estimated based on values of the difference voltage when the current is zero and thus the difference voltage equals the double-layer capacitance voltage. The electrical values can be estimated even if a stepwise interruption of the current of the electrolyzer is not possible.

Abstract: A field of electric drive devices, drivetrain systems and electric machines, such as electric motors and electric generators for industrial applications, and more particularly to a method, an arrangement, and a frequency converter for identification of torsional natural frequencies of a drivetrain system.

Abstract: A system for alkaline water electrolysis includes electrolysis cells, a hydrogen separator tank, a first piping from the electrolysis cells to the hydrogen separator tank, an oxygen separator tank, a second piping from the electrolysis cells to the oxygen separator tank, and a third piping for conducting liquid electrolyte from the hydrogen separator tank and from the oxygen separator tank back to the electrolysis cells. The system includes an ultrasound source for applying ultrasound on the liquid electrolyte contained by the first piping. The ultrasound enhances the separation of dissolved hydrogen gas from the liquid electrolyte contained by the first piping, and thus energy efficiency of the alkaline water electrolysis is improved. Furthermore, a safe control range of the alkaline water electrolysis is broadened because crossover of hydrogen gas to an oxygen side of the system is reduced.

Abstract: A system for an electrochemical process includes an electrochemical reactor, a converter bridge for supplying direct current to electrodes of the electrochemical reactor, and serial inductors connected to alternating voltage terminals of the converter bridge. The converter bridge includes bi-directional controllable switches between the alternating voltage terminals and direct voltage terminals of the converter bridge. Forced commutation of the bi-directional controllable switches enables reduction of current ripple in the direct current supplied to the electrochemical reactor. The forced commutation enables also to control a power factor of an alternating voltage supply of the system.

Abstract: An arrangement for monitoring an antifriction bearing of a rotating shaft of a rotating electric machine. The arrangement includes: one or more capacitor electrodes to measure a capacitive shaft displacement parameter; one or more of the following additional measurement sensors; a microphone to measure a bearing noise parameter, a voltage sensor to measure a bearing current parameter, and/or an optical pyrometer to measure a shaft heat parameter; and one or more processors configured to evaluate a condition of the antifriction bearing based on the capacitive shaft displacement parameter and one or more of the following: the bearing noise parameter, the bearing current parameter, and/or the shaft heat parameter.

Abstract: A method is provided for detecting the correct rotational direction of a centrifugal apparatus. The method includes rotating the centrifugal apparatus in a first direction, acquiring first frequency data relating to the step of rotating the centrifugal apparatus in the first direction, rotating the centrifugal apparatus in a second direction, which is opposite to the first direction, and acquiring second frequency data relating to the step of rotating the centrifugal apparatus in the second direction. The method also includes detecting the correct rotational direction of the centrifugal apparatus based on comparing the first frequency data with the second frequency data, the comparison being carried out with respect to at least one significant frequency range. In each of the at least one significant frequency range, a smaller magnitude is interpreted as an indication of the correct rotational direction.

Abstract: A method for determining a change in a mass of a fan impeller. The method includes inducing a torque to the fan impeller and determining a change in the angular speed of the fan impeller, induced by the torque. A value for a first parameter representing a present mass of the fan impeller is determined on the basis of the change in the angular speed and the torque. The change in the mass is then determined on the basis of the first parameter and a second parameter representing the reference mass of the fan impeller.

Abstract: A method is disclosed for detecting the correct rotational direction of a centrifugal apparatus. The method can include detecting the correct rotational direction of the centrifugal apparatus based on an acceleration test and/or a deceleration test. The detecting of correct rotational direction of the centrifugal apparatus can include comparing an acceleration time (t1,acc) for a first direction with an acceleration time (t2,acc) for a second direction, whereby shorter acceleration time can be interpreted as an indication of correct rotational direction; and/or comparing a deceleration time (t1,dec) of the first direction with a deceleration time (t2,dec) of the second direction, whereby longer deceleration time can be interpreted as an indication of correct rotational direction.

Abstract: A method for determining a change in a mass of a fan impeller. The method includes inducing a torque to the fan impeller and determining a change in the angular speed of the fan impeller, induced by the torque. A value for a first parameter representing a present mass of the fan impeller is determined on the basis of the change in the angular speed and the torque. The change in the mass is then determined on the basis of the first parameter and a second parameter representing the reference mass of the fan impeller.

Abstract: A method of correcting the stator flux estimate midpoint in alternating-current systems, the method comprising the step of determining a stator flux estimate (&PSgr;s, est?).

Abstract: A method for controlling an electrical machine while it is connected to an inverter comprising phase-specific switching components generating an output voltage, an optimum switching table arranged to select a switching combination for the switching components on the basis of the stator flux and torque of the electrical machine, the method comprising steps of defining the stator current vector (is) of the electrical machine, and determining the rotation speed of the electrical machine. The method also comprises the step of defining a switching combination for the switching components on the basis of the stator current vector (is) and stator current reference vector (&psgr;s, ref) of the electrical machine when the determined rotation speed is lower than a predefined limit.

Abstract: The invention relates to a method of correcting the flux midpoint in flux-controlled alternating current systems, the method comprising the steps of determining a stator flux estimate (&psgr;s,est) and determining the magnitude of stator current (is).