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: An exemplary method for determining a flow rate of a pump, includes measuring and storing the flow rate (QMean) when the pump is in operation, storing rotational speed (nMean) and torque (TMean) of the pump during measurement of the flow rate (QMean), determining torque (TManufacturer) corresponding to the measured flow rate (QMean), calculating a bias value of the torque (TBias) by comparing the torque determined from the characteristic curve (TManufacturer) and the stored torque (TMean) of the pump, and determining an operating point of the pump based on the bias value of the torque (TBias).

Abstract: The present disclosure is directed to a method and apparatus for approximating a static head of a fluid transfer system including a fluid transfer device. The method can include determining a rotational speed and a power consumption of the fluid transfer device, determining a first set of data points, calculating a second set of data points on the basis of the first set of data points, determining a minimum rotational speed producing flow through the fluid transfer device on the basis of the second set of data points, and determining the static head on the basis of the minimum rotational speed.

Abstract: A method and arrangement for determining the flow rate (Q) produced by a pump, when the pump is controlled with a frequency converter, which produces estimates for rotational speed and torque of the pump, and the characteristic curves of the pump are known. The method includes determining the shape of a QH curve of the pump, dividing the QH curve into two or more regions depending on the shape of the QH curve, determining on which region of the QH curve the pump is operating, and determining the flow rate (Q) of the pump using the determined operating region of the characteristic curve.

Abstract: A method and apparatus for optimizing energy efficiency of a pumping system includes at least one pump that controls a fluid level in a reservoir. The method includes a system identification stage and an energy efficiency optimization stage. The system identification stage includes determining pump characteristics for the pump, operating the pump with a range of flow rate conditions, determining a set of data points, and calculating energy efficiency optimization characteristics. The energy efficiency optimization stage includes determining a present static head value, choosing a value for a pump control parameter, and operating the pump on the pump control parameter.

Abstract: Exemplary methods and systems of determining stall of a fan are disclosed, when the fan is controlled with a frequency converter. The method includes estimating a rotational speed (n) and the torque (T) of the fan. Transferring characteristic curves of the fan to the estimated rotational speed (n) of the fan, determining the stall region of the fan. Determining an operation point of the fan from the estimated rotational speed (n) and estimated torque (T) using the characteristic curves. Calculating RMS values of the low frequency components of the torque and rotational speed estimates (TRMS, nRMS) to obtain a low frequency parameter (S), and determining an occurrence of stall based on at least one of the operation point and the low frequency parameter (S).

Abstract: A method includes selecting the branch of a ventilation system with the greatest pressure loss, opening a control valve in the selected branch and closing control valves in all other branches, controlling a fan to produce the desired air flow rate into the selected branch by using fan characteristic shaft power to air flow rate curves, and a shaft power estimate from the frequency converter and by adjusting the rotational speed of an electric motor to achieve the desired air flow rate, calculating the fan pressure corresponding to the desired air flow rate from fan characteristic fan pressure to air flow rate curves, saving the calculated fan pressure as a reference pressure, and adjusting the control valves in each of the remaining branches so that the desired air flow rate to each branch is delivered while the fan is controlled by the frequency converter to produce the reference pressure.

Abstract: A method and apparatus are disclosed for monitoring accumulation of dirt on an air filter of a ventilation system including the filter and a fan controlled by a frequency converter. An initial value for an operating parameter is determined. A present operating point is determined based on a characteristic curves, and the mechanical power and rotational speed of the fan. A present value for the operating parameter is determined based on the present operating point, and accumulation of dirt is determined on the air filter based on the initial and present values of the operating parameter.

Abstract: An exemplary frequency converter and method are directed to estimating an operation point of a pump when the QH characteristic curve of the pump is known. The frequency converter controls the pump, and a process curve is estimated when a first operation point of the pump is in the nominal range. The process curve defines a head as a function of volumetric flow. A rotational speed of the pump is determined and a QH characteristic curve of the pump is converted to a current rotational speed of the pump based on affinity laws. A second operation point of the pump is estimated by determining an intersection point of the converted QH characteristic curve and the estimated process curve.

Abstract: A method and an arrangement for detecting wear of a pump are disclosed, which pump is controlled with a frequency converter providing rotational speed and torque estimates, characteristic curves of the pump being known. An exemplary method includes obtaining a value representing the operating point of the pump by measuring the flow (Qact) or the head (Hact) produced by the pump; estimating the operating point of the pump by using a calculation based on the characteristic curves of the pump, the estimated rotational speed (nest) of the pump, and the estimated torque (Test) of the pump; calculating an estimation error from the value representing the operating point and from the estimated operating point; repeating the above steps during the use of the pump; and detecting the wear of the pump from the amplitude of the estimation error.

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 and a control arrangement are disclosed to measure a total flow rate through a pump device before a pump pressure or rotational speed change; and to change at least one of: the pump pressure by a predetermined pressure step or the pump rotational speed by a predetermined rotational speed step. The arrangement can measure a total flow rate through the pump device after the pump pressure or rotational speed change; and determine a need for a further pump pressure or rotational speed change step based on total flow rate measurements carried out before and after the pump pressure change.

Abstract: The present disclosure is directed to a method and apparatus for approximating a static head of a fluid transfer system including a fluid transfer device. The method can include determining a rotational speed and a power consumption of the fluid transfer device, determining a first set of data points, calculating a second set of data points on the basis of the first set of data points, determining a minimum rotational speed producing flow through the fluid transfer device on the basis of the second set of data points, and determining the static head on the basis of the minimum rotational speed.

Abstract: A method includes selecting the branch of a ventilation system with the greatest pressure loss, opening a control valve in the selected branch and closing control valves in all other branches, controlling a fan to produce the desired air flow rate into the selected branch by using fan characteristic shaft power to air flow rate curves, and a shaft power estimate from the frequency converter and by adjusting the rotational speed of an electric motor to achieve the desired air flow rate, calculating the fan pressure corresponding to the desired air flow rate from fan characteristic fan pressure to air flow rate curves, saving the calculated fan pressure as a reference pressure, and adjusting the control valves in each of the remaining branches so that the desired air flow rate to each branch is delivered while the fan is controlled by the frequency converter to produce the reference pressure.

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: An exemplary method for determining a flow rate of a pump, includes measuring and storing the flow rate (QMean) when the pump is in operation, storing rotational speed (nMean) and torque (TMean) of the pump during measurement of the flow rate (QMean), determining torque (TManufacturer) corresponding to the measured flow rate (QMean), calculating a bias value of the torque (TBias) by comparing the torque determined from the characteristic curve (TManufacturer) and the stored torque (TMean) of the pump, and determining an operating point of the pump based on the bias value of the torque (TBias).

Abstract: A method and an arrangement for detecting wear of a pump are disclosed, which pump is controlled with a frequency converter providing rotational speed and torque estimates, characteristic curves of the pump being known. An exemplary method includes obtaining a value representing the operating point of the pump by measuring the flow (Qact) or the head (Hact) produced by the pump; estimating the operating point of the pump by using a calculation based on the characteristic curves of the pump, the estimated rotational speed (nest) of the pump, and the estimated torque (Test) of the pump; calculating an estimation error from the value representing the operating point and from the estimated operating point; repeating the above steps during the use of the pump; and detecting the wear of the pump from the amplitude of the estimation error.

Abstract: Exemplary methods and systems of determining stall of a fan are disclosed, when the fan is controlled with a frequency converter. The method includes estimating a rotational speed (n) and the torque (T) of the fan. Transferring characteristic curves of the fan to the estimated rotational speed (n) of the fan, determining the stall region of the fan. Determining an operation point of the fan from the estimated rotational speed (n) and estimated torque (T) using the characteristic curves. Calculating RMS values of the low frequency components of the torque and rotational speed estimates (TRMS, nRMS) to obtain a low frequency parameter (S), and determining an occurrence of stall based on at least one of the operation point and the low frequency parameter (S).

Abstract: A method and arrangement for determining the flow rate (Q) produced by a pump, when the pump is controlled with a frequency converter, which produces estimates for rotational speed and torque of the pump, and the characteristic curves of the pump are known. The method includes determining the shape of a QH curve of the pump, dividing the QH curve into two or more regions depending on the shape of the QH curve, determining on which region of the QH curve the pump is operating, and determining the flow rate (Q) of the pump using the determined operating region of the characteristic curve.