Abstract: A method and an apparatus for measuring the output currents of a frequency converter, preferably a vector-controlled frequency converter, which comprises a mains bridge (10) connectable to an alternating-current network and a load bridge (11) connectable to an alternating-current load and between these a direct-voltage intermediate circuit, by using current samples obtained from a current measuring sensor in the intermediate voltage circuit, wherein a sample is taken from the signal of the current measuring sensor substantially simultaneously with a point of change of the output voltage vector and upon the lapse of a predetermined delay after the point of change after the switching effects have settled.

Abstract: A method and a system for measuring a quantity, such as current, of a power converter apparatus including parallel-connected power converter units. A component quantity, of each power converter unit is measured, transmitted digitally in serial communication format to a control unit (CU), and summed to produce a summed quantity. The component quantity data are transmitted to the control unit with the least significant bit (LSB) first. The summing is started as soon as the LSBs of the component quantities have been received. The LSB of the sum is transmitted further as soon as the LSBs of the component quantities have been summed. After this, the rest of the bits are summed in the order of arrival, with the most significant bit (MSB) last. The respective summing data are transmitted further in the order of arrival as soon as the corresponding bits of the component quantities have been summed.

Abstract: A method and an apparatus for charging a filtering capacitor in the direct-voltage intermediate circuit of a voltage-controlled PWM frequency converter comprising a rectifier (20) connected to an alternating-current source (UR, US, UT), a direct-voltage intermediate circuit and an inverter unit (11)/inverter units for feeding a multi-phase alternating voltage (UU, UV, UW) of variable frequency into a load/loads (12), said rectifier bridge having controlled semiconductor switches (V1–V3), especially thyristors, in one arm, preferably in the upper arm, and diodes (D1–D6) in the other arm, preferably the lower arm, and said direct-voltage intermediate circuit being provided with a capacitor unit (CDC) of a relatively high capacitance for filtering the voltage.

Abstract: A method and a system for protecting the power semiconductor components used in the powerstages of power electronics devices, such as frequency converters, wherein calculation modeling the degree of heating of the semiconductor junction of the power components (V11–V16) is used, wherein the degree of heating of the power components between the measurable outer surface or cooler and the internal semiconductor junction is determined on the basis of the dissipation power and a thermal network model of the component, wherein the temperature of the outer surface of the power component or the temperature of the cooler is measured, wherein the modeled temperature of the semiconductor junction is the sum of the measured temperature of the outer surface or cooler and the calculated degree of heating, and wherein, based on the modeled junction temperature, an alarm is issued or some other protective action is taken.

Abstract: A method and system for the measurement of energy in an alternating-current motor drive containing a frequency converter or an equivalent stepless rotational speed regulator provided with semiconductor switches. In this regulator, the power taken by the motor drive from the mains is determined, and based on the power taken by the motor drive from the mains, the energy taken from the supply mains, especially the accumulated energy consumption after a given instant is determined.

Abstract: An arrangement and method for monitoring a frequency converter, said frequency converter being a voltage-controlled PWM frequency converter provided with a control unit (12) and having an uncontrolled or a mains-frequency controlled mains bridge (10) connectable to an alternating-current source (UL1, UL2, UL3), a direct-voltage intermediate circuit and a controlled load bridge (11) for producing a variable-frequency multi-phase output voltage (UU, UV, UW), which direct-voltage intermediate circuit of the frequency converter is provided with a small-capacitance direct-voltage capacitor, the mains bridge (10) being connected to the load bridge (11) directly without a large-capacitance direct-voltage capacitor functioning as an intermediate energy storage, and which arrangement comprises a measuring unit for measuring the direct voltage of the intermediate voltage circuit.

Abstract: An overvoltage protection system for the intermediate circuit of frequency converter, said frequency converter being a voltage-controlled PWM-frequency converter comprising an uncontrolled mains bridge (10) to be connected to an alternating-current source (UL1, UL2, UL3), a direct-voltage intermediate circuit and a controlled load bridge (12) for producing a multi-phase alternating voltage (UU, UV, UW) of variable frequency, wherein the direct-voltage circuit of the frequency converter contains a low-capacitance direct-voltage capacitor, the mains bridge (10) being connected to the load bridge (12) directly without a high-capacitance direct-voltage capacitor serving as an intermediate energy storage, and which overvoltage protection system contains a varistor (R1).

Abstract: A method and an apparatus for controlling the mains bridge of a four-quadrant PWM frequency converter provided with a DC intermediate circuit when the power is flowing in the direction towards the supply network, said frequency converter being provided with an AC inductor (9) to be connected to an alternating voltage source (UU, UV, UW), a controlled mains bridge (10), a DC intermediate circuit (14) and a controlled load bridge (11) for feeding a variable-frequency alternating voltage (US, UR, UT) into a load (12), and said mains bridge being provided with controlled semiconductor switches (V1–V6) and shunt diodes (D1–D6), and wherein the mains bridge (10) is mainly controlled in such manner that the controlled semiconductor switch in the upper branch of the phase having the highest supply voltage instantaneous value and the controlled semiconductor switch in the lower branch of the phase having the lowest supply voltage instantaneous value are conducting.

Abstract: A method of arranging frequency converters in a cabinet including placing the frequency converters one above the other in a first section of the cabinet, and passing a cooled medium from a second section to a third section of the cabinet such that the cooled medium flows substantially across parts included in the respective frequency converters. Further, the second and third sections are on adjacent sides of the first section. The method also includes arranging supply voltage and load cabling connected to the frequency converters in at least one of the second or third sections of the cabinet.

Abstract: 1.

Abstract: Method of controlling a voltage controlled PWM (Pulse Width Modulated) frequency converter comprising a single phase rectifier bridge (10) connectable to a sinusoidal single phase supply, a DC intermediate circuit (11) and a controlled inverter bridge (12) for generating an AC output voltage with varying amplitude and frequency to a load, said inverter bridge (12) having PWM controlled semiconductor switches (V11–V16) and flywheel diodes (D11–D16) connected in inverse-parallel with the semiconductor switches, wherein the DC intermediate circuit (11) is provided with a DC capacitor unit, and wherein the frequency converter is controlled so that the supply line current (Iin) is essentially sinusoidal and in phase with the supply line voltage (Uin).

Abstract: A method and a system for protecting the power semiconductor components used in the powerstages of power electronics devices, such as frequency converters, wherein calculation modeling the degree of heating of the semiconductor junction of the power components (V11-V16) is used, wherein the degree of heating of the power components between the measurable outer surface or cooler and the internal semiconductor junction is determined on the basis of the dissipation power and a thermal network model of the component, wherein the temperature of the outer surface of the power component or the temperature of the cooler is measured, wherein the modeled temperature of the semiconductor junction is the sum of the measured temperature of the outer surface or cooler and the calculated degree of heating, and wherein, based on the modeled junction temperature, an alarm is issued or some other protective action is taken.

Abstract: A method and an apparatus for charging a filtering capacitor in the direct-voltage intermediate circuit of a voltage-controlled PWM frequency converter comprising a rectifier (20) connected to an alternating-current source (UR, US, UT), a direct-voltage intermediate circuit and an inverter unit (11)/inverter units for feeding a multi-phase alternating voltage (UU, UV, UW) of variable frequency into a load/loads (12), said rectifier bridge having controlled semiconductor switches (V1-V3), especially thyristors, in one arm, preferably in the upper arm, and diodes (D1-D6) in the other arm, preferably the lower arm, and said direct-voltage intermediate circuit being provided with a capacitor unit (CDC) of a relatively high capacitance for filtering the voltage.

Abstract: A method and an apparatus for compensating reactive power and/or harmonic currents in an alternating-current network by means of a frequency converter (1) feeding an alternating-current load (3), which frequency converter has a mains bridge (10) and at least one load bridge (11), said bridges being provided with controllable semiconductor switches. In the method, the reactive power and/or harmonic currents in the alternating-current network are measured, the load of the mains bridge of the frequency converter is measured, and the reactive power and/or harmonic currents in the alternating-current network are compensated by means of the frequency converter when the mains bridge is running at less than full capacity or has no load.

Abstract: A method and system for the measurement of energy in an alternating-current motor drive containing a frequency converter (10, 11) or an equivalent stepless rotational speed regulator provided with semiconductor switches, in which regulator the power taken by the electric drive from the mains is determined, and in which, based on the power taken by the electric drive from the mains, the energy taken from the supply mains, especially the accumulated energy consumption after a given instant is determined.

Abstract: Method of controlling a voltage controlled PWM (Pulse Width Modulated) frequency converter comprising a single phase rectifier bridge (10) connectable to a sinusoidal single phase supply, a DC intermediate circuit (11) and a controlled inverter bridge (12) for generating an AC output voltage with varying amplitude and frequency to a load, said inverter bridge (12) having PWM controlled semiconductor switches (V11-V16) and flywheel diodes (D11-D16) connected in inverse-parallel with the semiconductor switches, wherein the DC intermediate circuit (11) is provided with a DC capacitor unit, and wherein the frequency converter is controlled so that the supply line current (Iin) is essentially sinusoidal and in phase with the supply line voltage (Uin).

Abstract: A method and an apparatus for controlling the mains bridge of a four-quadrant PWM frequency converter provided with a DC intermediate circuit when the power is flowing in the direction towards the supply network, said frequency converter being provided with an AC inductor (9) to be connected to an alternating voltage source (UU, UV, UW), a controlled mains bridge (10), a DC intermediate circuit (14) and a controlled load bridge (11) for feeding a variable-frequency alternating voltage (US, UR, UT) into a load (12), and said mains bridge being provided with controlled semiconductor switches (V1-V6) and shunt diodes (D1-D6), and wherein the mains bridge (10) is mainly controlled in such manner that the controlled semiconductor switch in the upper branch of the phase having the highest supply voltage instantaneous value and the controlled semiconductor switch in the lower branch of the phase having the lowest supply voltage instantaneous value are conducting.

Abstract: An inverter control unit having a bridge circuit provided with controllable semiconductor switches in upper and lower circuit arms, which bridge circuit converts a direct voltage to be fed to the inverter into an alternating voltage of variable frequency and amplitude, said control unit controlling the semiconductor switches by pulse-width modulation (PWM) to generate an inverter output voltage, and said control unit comprising a first control section (21) at ground potential and a second control section (22) at the potential of the semiconductor switches, galvanically isolated channels being provided between said sections for serial transmission of control data from the first control section to the second control section and of feedback data from the second control section to the first control section.

Abstract: Placement of the units of frequency converters, especially the power units (PU#21-PU #24, PU#31-PU#34) of frequency converters in a switch cabinet (21-23, 31-33) or equivalent, wherein the power units are placed one above the other in at least one section (22, 32) of the switch cabinet or equivalent, and wherein the cooling air or liquid circulation of the power units has been directed to flow substantially horizontally through their parts requiring cooling, in such manner that on at least one side of the section (22, 32) housing the power units is provided a section, such as a bay or an otherwise protected space, through which space/spaces cooling air or liquid is passed into the power units and likewise passed out.

Abstract: A method and an apparatus for compensating reactive power and/or harmonic currents in an alternating-current network by means of a frequency converter (1) feeding an alternating-current load (3), which frequency converter has a mains bridge (10) and at least one load bridge (11), said bridges being provided with controllable semiconductor switches. In the method, the reactive power and/or harmonic currents in the alternating-current network are measured, the load of the mains bridge of the frequency converter is measured, and the reactive power and/or harmonic currents in the alternating-current network are compensated by means of the frequency converter when the mains bridge is running at less than full capacity or has no load.