Abstract: A circuit comprising a first power node for connection to a positive voltage of a DC link, a second power node for connection to a negative voltage of the DC link and a mid-point power node for connection to a mid-point voltage of the DC-link, the circuit further comprising a three-level neutral point clamped converter module and a brake resistor connection.

Abstract: A circuit comprising a first power node for connection to a positive voltage of a DC link, a second power node for connection to a negative voltage of the DC link and a mid-point power node for connection to a mid-point voltage of the DC-link, the circuit further comprising a three-level neutral point clamped converter module and a brake resistor connection.

Abstract: A circuit comprising a first power node for connection to a positive voltage of a DC link, a second power node for connection to a negative voltage of the DC link and a mid-point power node for connection to a mid-point voltage of the DC-link, the circuit further comprising a three-level neutral point clamped converter module and a brake resistor connection.

Abstract: The present invention relates to a method for reducing common mode current in power electronic equipment comprising two or more active front end (AFE) components (1) coupled in parallel between an AC supply grid (2) and a DC-link (3). A duty cycle of pulse width modulation (PWM) for the AFE components (1) is determined, and an error signal is derived based on the determined duty cycle of PWM and on a common mode current of the AFE components (1). A correction voltage is derived, based on the error signal, and a DC voltage control signal is derived based on the derived correction voltage and a measured DC voltage of the DC-link (3) and/or a DC voltage reference. The power electronic equipment is controlled in accordance with the derived DC voltage control signal. The present invention also relates to a method for starting active front end (AFE) components (1) of power electronic equipment comprising two or more AFE components (1) coupled in parallel between an AC supply grid (2) and a DC-link (3).

Abstract: The present invention relates to a method for reducing common mode current in power electronic equipment comprising two or more active front end (AFE) components (1) coupled in parallel between an AC supply grid (2) and a DC-link (3). A duty cycle of pulse width modulation (PWM) for the AFE components (1) is determined, and an error signal is derived based on the determined duty cycle of PWM and on a common mode current of the AFE components (1). A correction voltage is derived, based on the error signal, and a DC voltage control signal is derived based on the derived correction voltage and a measured DC voltage of the DC-link (3) and/or a DC voltage reference. The power electronic equipment is controlled in accordance with the derived DC voltage control signal. The present invention also relates to a method for starting active front end (AFE) components (1) of power electronic equipment comprising two or more AFE components (1) coupled in parallel between an AC supply grid (2) and a DC-link (3).

Abstract: A circuit comprising a first power node for connection to a positive voltage of a DC link, a second power node for connection to a negative voltage of the DC link and a mid-point power node for connection to a mid-point voltage of the DC-link, the circuit further comprising a three-level neutral point clamped converter module and a brake resistor connection.

Abstract: A piston type compressor wherein the position of the piston highest pressure point is indicated and the rotor of the motor at the optimal starting angle aligned prior to the actual compression operation by providing a pre-pulse to rotate the rotor of the motor at least one full rotation at a certain frequency, during rotation measuring the load torque by the frequency converter as well as indicating the maximum load torque point and at the end aligning the rotor of the motor at the optimal starting angle of about 180° from the maximum pressure angle, and at the beginning of the actual compression operation setting the rotor position opposite to the maximum torque angle by feeding direct current to the stator winding and starting the motor by supplying maximum motor current to the motor to give the maximum torque and acceleration.

Abstract: Method and apparatus for measuring an earth fault current in an output circuit of an inverter (INU) operating on the PWM principle and forming alternating-current voltage from direct-current voltage, the output currents (iU, iV and iW) of which inverter are measured, and which inverter comprises at least two phase switches implemented with power semiconductor components (V1-V6, D1-D6), which switches, controlled by a control unit, connect their own output phases to a positive (+) pole and to a negative (?) pole of a direct-current voltage source such that the phase switches are repeatedly both in different positions and also in the same positions, wherein the results of current measurement during two opposite switch position combinations are recorded in memory, and the earth fault current is calculated by forming a difference of the measurement results of said combinations.

Abstract: A piston type compressor wherein the position of the piston highest pressure point is indicated and the rotor of the motor at the optimal starting angle aligned prior to the actual compression operation by providing a pre-pulse to rotate the rotor of the motor at least one full rotation at a certain frequency, during rotation measuring the load torque by the frequency converter as well as indicating the maximum load torque point and at the end aligning the rotor of the motor at the optimal starting angle of about 180° from the maximum pressure angle, and at the beginning of the actual compression operation setting the rotor position opposite to the maximum torque angle by feeding direct current to the stator winding and starting the motor by supplying maximum motor current to the motor to give the maximum torque and acceleration.

Abstract: Method and apparatus to start a frequency converter equipped with a direct current intermediate circuit, particularly when a permanent magnet motor whose rotor is rotating at the start-up time is connected to it, wherein the frequency converter has a network bridge (10) and load bridge (11), and the load bridge has controllable power semiconductor switches of the upper and lower branch (V1-V6) and parallel connected zero diodes (D1-D6), and a direct current intermediate circuit between them, and the said frequency converter uses a current transducer placed in the direct current intermediate circuit, and the analogue current signal composed by it features samples of the measured output currents, and the diverter switches of the frequency converter's upper branch are controlled using the bootstrap method, wherein start-up is initiated by controlling the controllable power semiconductor switch of the lower branch of at least one output phase to a conductive state for one or several periods of time, preferably of

Abstract: Method and apparatus for measuring an earth fault current in an output circuit of an inverter (INU) operating on the PWM principle and forming alternating-current voltage from direct-current voltage, the output currents (iU, iV and iW) of which inverter are measured, and which inverter comprises at least two phase switches implemented with power semiconductor components (V1-V6, D1-D6), which switches, controlled by a control unit, connect their own output phases to a positive (+) pole and to a negative (?) pole of a direct-current voltage source such that the phase switches are repeatedly both in different positions and also in the same positions, wherein the results of current measurement during two opposite switch position combinations are recorded in memory, and the earth fault current is calculated by forming a difference of the measurement results of said combinations.

Abstract: Method and apparatus to start a frequency converter equipped with a direct current intermediate circuit, particularly when a permanent magnet motor whose rotor is rotating at the start-up time is connected to it, wherein the frequency converter has a network bridge (10) and load bridge (11), and the load bridge has controllable power semiconductor switches of the upper and lower branch (V1-V6) and parallel connected zero diodes (D1-D6), and a direct current intermediate circuit between them, and the said frequency converter uses a current transducer placed in the direct current intermediate circuit, and the analogue current signal composed by it features samples of the measured output currents, and the diverter switches of the frequency converter's upper branch are controlled using the bootstrap method, wherein start-up is initiated by controlling the controllable power semiconductor switch of the lower branch of at least one output phase to a conductive state for one or several periods of time, preferably of