Abstract: A method of determining a rotational state of a three-phase alternating voltage supply which is connected to a converter and rotating in an uncontrolled manner, wherein the converter is connected to an intermediate voltage circuit and comprises phase-specific upper and lower controllable switches, which are connected in series between the intermediate voltage circuit, free-wheeling diodes connected in parallel with each of the controllable switches, and resistive circuits connected in parallel with the lower controllable switches.

Abstract: Exemplary embodiments for controlling a switching branch for a three-level converter, and a switching branch are disclosed. A first semiconductor switch and a second semiconductor switch, a first diode and a second diode, a third semiconductor switch and a fourth semiconductor switch, a third diode, and a fourth diode, a fifth semiconductor switch and a sixth semiconductor switch, a fifth diode, and a sixth diode, and a control arrangement for controlling the semiconductor switches are provided. The first semiconductor switch, the first diode, the fifth semiconductor switch and the fifth diode reside in a first switching branch-specific semiconductor module, and the fourth semiconductor switch, the fourth diode, the sixth semiconductor switch and the sixth diode reside in a second switching branch-specific semiconductor module.

Abstract: A switching branch for a three-level rectifier and a method for controlling a switching branch for a three-level rectifier are provided. The switching branch includes a first diode and a second diode connected in series, a third diode and a fourth diode connected in series, a first controllable switch connected between a neutral DC output pole and a connection point between the first and the second diode, and a second controllable switch connected between the neutral DC output pole and a connection point between the third and the fourth diode. The switching branch includes means for controlling the first controllable switch to be in a conductive state during a reverse blocking state of the first diode and the second diode, and means for controlling the second controllable switch to be in a conductive state during a reverse blocking state of the third diode and the fourth diode.

Abstract: A method of controlling a brake chopper and a control arrangement, the brake chopper being connected between the positive and the negative rails of an intermediate voltage circuit feeding an inverter bridge, wherein current measurement means are arranged between a DC voltage source and the brake chopper and adapted to measure DC current flowing in the intermediate voltage circuit, which method comprises steps of forming with the inverter bridge an output voltage to a load connected to the output of the inverter bridge, determining a time instant when the DC current of the intermediate circuit is sampled, and preventing the use of the brake chopper at the determined time instant.

Abstract: A DC inductor comprising a core structure (11) comprising one or more magnetic gaps (12), a coil (14) inserted on the core structure (11), at least one permanent magnet (15) positioned in the core structure, the magnetization of the permanent magnet (15) opposing the magnetization producible by the coil (14). The core structure is adapted to form a main flux path and an auxiliary flux path, where the main flux path is adapted to carry the main magnetic flux producible by the coil, wherein the auxiliary flux path comprises a magnetic gap and is adapted to lead magnetic flux past the at least one permanent magnet (15).

Abstract: A two-level or multi-level inverter are supplied with a positive auxiliary voltage (Ug+) and a negative auxiliary voltage (Ug?). A bootstrap technique provides a first positive auxiliary voltage and a first negative auxiliary voltage from the supplied potentials. The bootstrap technique provides at least one additional negative auxiliary voltage to a switch driver of at least one semiconductor switch from the first negative auxiliary voltage. At the start up of an inverter, the inverter can perform a startup sequence to provide auxiliary voltages to the respective auxiliary voltage inputs of the switch drivers by turning the power semiconductors sequentially on and off.

Abstract: A DC inductor comprising a core structure (11) comprising one or more magnetic gaps (12, 13), a coil (14) wound on the core structure (11), at least one permanent magnet (15) positioned in the core structure, the magnetization of the permanent magnet (15) opposing the magnetization producible by the coil (14). The DC inductor further comprises at least one magnetic slab (16) inserted to the core structure which forms the one or more magnetic gaps (12, 13), at least one supporting member (17) made of magnetic material extending from the core structure inside the core structure and supporting the at least one permanent magnet (15), and that the at least one supporting member (17) is arranged to form a magnetic path for the at least one permanent magnet.

Abstract: A method in connection with a frequency converter for correcting the power factor of the frequency converter, and a power factor correction unit. The method includes connecting the power factor correction unit between a rectifier bridge of the frequency converter and the supplying AC voltage network, generating with the power factor correction unit DC voltage from the AC voltage of the supply network and feeding the generated DC voltage to the frequency converter via the rectifier bridge of the frequency converter.

Abstract: A method in connection with a frequency converter for correcting the power factor of the frequency converter, and a power factor correction unit. The method includes connecting the power factor correction unit between a rectifier bridge of the frequency converter and the supplying AC voltage network, generating with the power factor correction unit DC voltage from the AC voltage of the supply network and feeding the generated DC voltage to the frequency converter via the rectifier bridge of the frequency converter.

Abstract: A method of controlling a brake chopper and a control arrangement, the brake chopper being connected between the positive and the negative rails of an intermediate voltage circuit feeding an inverter bridge, wherein current measurement means are arranged between a DC voltage source and the brake chopper and adapted to measure DC current flowing in the intermediate voltage circuit, which method comprises steps of forming with the inverter bridge an output voltage to a load connected to the output of the inverter bridge, determining a time instant when the DC current of the intermediate circuit is sampled, and preventing the use of the brake chopper at the determined time instant.

Abstract: A system and a method for compensating harmonic components or a reactive power of an electrical network. The system comprises a measurement unit (1) configured to measure an electrical quantity to be compensated, a control unit (2) configured to determine harmonics contents or a reactive power need of the measured electrical quantity to be compensated as well as to determine, as relative values, desired values corresponding with the harmonics to be compensated or the reactive power to be compensated, one or more compensation units (5, 6) configured, responsive to the desired values provided by the control unit (2), to generate harmonic components or a reactive current according to the desired values given as relative values, and a communications connection (3) configured to communicate the desired values determined by the control unit (2) to the compensation units (5, 6).

Abstract: Single-phase to three-phase converter comprising a rectifier stage, a DC link and an inverter stage, wherein the rectifier comprises a filter choke, one controllable switch for power factor correction, rectifying diodes arranged in a diode bridge configuration having input terminals and output terminals, the controllable switch being connected to the output terminals of the diode bridge, an upper blocking diode arranged between the positive output terminal of the diode bridge and the positive input of the DC link and a lower blocking diode arranged between the negative output terminal of the diode bridge and the negative input of the DC link, the DC link comprises a capacitor bank connected between the DC link, which capacitor bank has a center point.

Abstract: A DC inductor comprising a core structure (11) comprising one or more magnetic gaps (12), a coil (14) inserted on the core structure (11), at least one permanent magnet (15) positioned in the core structure, the magnetization of the permanent magnet (15) opposing the magnetization producible by the coil (14). The core structure is adapted to form a main flux path and an auxiliary flux path, where the main flux path is adapted to carry the main magnetic flux producible by the coil, wherein the auxiliary flux path comprises a magnetic gap and is adapted to lead magnetic flux past the at least one permanent magnet (15).

Abstract: A DC inductor comprising a core structure (11) comprising one or more magnetic gaps (12, 13), a coil (14) wound on the core structure (11), at least one permanent magnet (15) positioned in the core structure, the magnetization of the permanent magnet (15) opposing the magnetization producible by the coil (14). The DC inductor further comprises at least one magnetic slab (16) inserted to the core structure which forms the one or more magnetic gaps (12, 13), at least one supporting member (17) made of magnetic material extending from the core structure inside the core structure and supporting the at least one permanent magnet (15), and that the at least one supporting member (17) is arranged to form a magnetic path for the at least one permanent magnet.

Abstract: A method of determining a rotational state of a three-phase alternating voltage supply which is connected to a converter and rotating in an uncontrolled manner, wherein the converter is connected to an intermediate voltage circuit and comprises phase-specific upper and lower controllable switches, which are connected in series between the intermediate voltage circuit, free-wheeling diodes connected in parallel with each of the controllable switches, and resistive circuits connected in parallel with the lower controllable switches.