Abstract: A method for the operation of a centrifugal pump (2) driven by an electric motor (5) with variable frequency, wherein too small a flow through the pump (2) is ascertained by monitoring electrical quantities, and a pump arrangement (1) having a centrifugal pump (2), an electric motor (5) which drives the centrifugal pump (2), a controlled frequency converter (6) which feeds the electric motor (5), a sensor device (12, 13) and an evaluating device (15-19) are described. It is desired to detect, by simple means, when no through-flow is present. For that purpose, the electrical power is ascertained and compared to a control quantity formed as a function of the frequency of the motor (5). The sensor device ascertains values for determination of the electrical power, and the evaluating device has a dynamic limit value former (18), which forms a control quantity as a function of the frequency of the motor (5).

Abstract: The invention relates to an RFI filter used for avoidance of mains retro-action in the form of radio noise. RFI filters are connected to frequency converters in order to reduce radio noise transmitted via conductors. These filters comprise large noise-decoupling capacitors which are connected to earth, and during start up of the frequency converter the capacitors cause leakage currents to earth. This gives rise to problems in those circumstances, where a circuit breaker is connected to a frequency converter and an RFI filter, because the leakage current is higher than the trigger current for the circuit breaker. The solution to this problem is to place a resistor in series with the noise-decoupling capacitor and parallel with the resistor to place a switch, which can be opened or closed with a control signal from a controller. The invention also concerns a method for activation of an RFI filter.

Abstract: Inrush currents in the dc intermediate circuit of a motor controller necessitate the incorporation of protection circuits. These circuits usually take the form of a resistor inserted in series with the intermediate circuit, and the resistor is short-circuited after completion of inrush by a switch positioned in parallel with the resistor. To reduce cable-transmitted electrical noise an earthed noise-decoupling capacitor is added to the intermediate circuit, but it also requires protection against inrush currents. To minimise the number of components, a protection circuit is described which combines noise filtration and inrush protection.

Abstract: A cooling apparatus for power semiconductors, which apparatus is essentially box-shaped, has two extruded cooling sections (14, 15) joined to each other. One of the cooling profiles (14) forms a first heat-conducting side wall (16), and the other cooling profile (15) forms a second heat-conducting side wall (17), opposite the first side wall (16), of the cooling apparatus (1). The side walls (16, 17) have cooling partitions (18, 19) formed on the inner sides of the latter, which cooling partitions bound cooling channels through which a cooling fluid can be conducted. Power semiconductors (4, 5) are to be attached to the outer sides of the side walls (16, 17) in a heat-conducting manner. In order to achieve the largest possible cooling surface of the cooling apparatus, the cooling partitions (18) formed on the first side wall (16) project between the cooling partitions (19) formed on the second side wall (17).

Abstract: A method for the operation of a centrifugal pump (2) driven by an electric motor (5) with variable frequency, wherein too small a flow through the pump (2) is ascertained by monitoring electrical quantities, and a pump arrangement (1) having a centrifugal pump (2), an electric motor (5) which drives the centrifugal pump (2), a controlled frequency converter (6) which feeds the electric motor (5), a sensor device (12, 13) and an evaluating device (15-19) are described.

Abstract: In a known method for regulating a delivery variable of a pump, which is driven by an electric motor operated with alternating current of variable frequency, especially via a converter, the input power of the motor is measured as the actual value for the delivery variable and is regulated by comparison with a desired value. To avoid the influence of the temperature of the motor on the delivery variable at constant input power, according to the invention upon a change in the temperature in the motor a corresponding compensating variable is taken into account in the control for the purposes of correcting the input power. As an alternative, associated values of the input power and the speed of the motor at a predetermined desired pressure value are determined empirically and stored as a table, and during operation a value of the input power belonging to a measured or approximately calculated speed of the motor is retrieved from the table as desired for regulating the input power.

Abstract: A method for monitoring a rotational angle sensor on an electrical machine. It is desired to provide a method that enables fault detection at both high speeds and low speeds of the rotor. The electrical power of the machine is measured and a power value is estimated using the output signal of the rotational angle sensor, a residual being formed from the measured power and the estimated power and the time curve of the residual being monitored.

Abstract: A cooling apparatus for power semiconductors, which apparatus is essentially box-shaped, has two extruded cooling sections (14, 15) joined to each other. One of the cooling profiles (14) forms a first heat-conducting side wall (16), and the other cooling profile (15) forms a second heat-conducting side wall (17), opposite the first side wall (16), of the cooling apparatus (1). The side walls (16, 17) have cooling partitions (18, 19) formed on the inner sides of the latter, which cooling partitions bound cooling channels through which a cooling fluid can be conducted. Power semiconductors (4, 5) are to be attached to the outer sides of the side walls (16, 17) in a heat-conducting manner. In order to achieve the largest possible cooling surface of the cooling apparatus, the cooling partitions (18) formed on the first side wall (16) project between the cooling partitions (19) formed on the second side wall (17).