Abstract: A method for controlling a polyphase inverter that includes a number of half bridges connected into an intermediate voltage circuit and center taps between switching elements. By cyclically switching the switching elements, the respective center taps of the half bridges are connected to an upper intermediate circuit rail or to a lower intermediate circuit rail of the intermediate voltage circuit according to the principle of pulse width modulation. The switching elements of at least one half bridge are driven in a modified manner, at least in some time intervals, in that the switching pulses of at least two consecutive periods of the pulse width modulation are concatenated directly in time as one switching pulse. In this way, the switching frequencies of the correspondingly driven switching elements and thus the switching losses of the latter can be further reduced.

Abstract: A method controls a three-phase converter with a voltage intermediate circuit by pulse-width modulation for supplying a polyphase system, in particular a three-phase machine. The converter is operated with at least two different modulation methods which are selected from among the group of modulation methods which includes single-phase switching, two-phase switching and three-phase switching, and for changeovers to be made between the at least two different modulation methods depending on the operating state of the polyphase system.

Abstract: A method for controlling a polyphase inverter that includes a number of half bridges connected into an intermediate voltage circuit and center taps between switching elements. By cyclically switching the switching elements, the respective center taps of the half bridges are connected to an upper intermediate circuit rail or to a lower intermediate circuit rail of the intermediate voltage circuit according to the principle of pulse width modulation. The switching elements of at least one half bridge are driven in a modified manner, at least in some time intervals, in that the switching pulses of at least two consecutive periods of the pulse width modulation are concatenated directly in time as one switching pulse. In this way, the switching frequencies of the correspondingly driven switching elements and thus the switching losses of the latter can be further reduced.

Abstract: The invention specifies a method for fault identification when driving a polyphase motor by means of a frequency converter, wherein, in a rest state, the frequency converter controls the phase voltages of the polyphase motor and the phase currents of the polyphase motor are measured. In this case, provision is made for, then in the rest state, the phase currents or current variables derived therefrom to be adjusted by closed-loop control to a predetermined setpoint current variable, for the frequency converter to be controlled so as to output an interference voltage variable for the phase voltages, for the response of the adjustment by closed-loop control to the interference voltage variable to be observed, and for a conclusion to be drawn regarding a fault of the frequency converter and/or the phases of the polyphase motor from the response of the closed-loop control. The cited method allows for largely loss-free detection of faults in the drive system of a polyphase motor.

Abstract: A method is specified for fault identification when operating a rotating-field motor by means of a pulse-controlled inverter, wherein electromagnetic state variables of the rotating-field motor are determined by means of a mathematical model in space-vector form, and wherein the pulse-controlled inverter is operated electronically using space-vector variables. In this case, the invention provides that, during the operation of the rotating-field motor, the space vector of an uncontrolled state variable of the rotating-field motor is formed, in that the space vector that is formed is analyzed for a spectral component at twice the frequency of the rotating field, and in that, if the spectral component at twice the frequency is present, a partial turns short is deduced in the stator windings.

Abstract: A method controls a three-phase converter with a voltage intermediate circuit by pulse-width modulation for supplying a polyphase system, in particular a three-phase machine. The converter is operated with at least two different modulation methods which are selected from among the group of modulation methods which includes single-phase switching, two-phase switching and three-phase switching, and for chageovers to be made between the at least two different modulation methods depending on the operating state of the polyphase system.

Abstract: A method for operating an electric motor with at least two motor terminals that are driven by a control device contains the steps of short-circuiting of at least two of the motor terminals of the electric motor by the control device; measurement of the motor phase currents at the short-circuited motor terminals; and identification of a standstill of the electric motor if a magnitude and/or a frequency of the motor phase currents measured lies below a predefined limit value. In the case of such a reliable identification of the standstill of the electric motor, an enable signal can then advantageously be generated in order, by way of example, to enable access to an apparatus driven by the electric motor.

Abstract: The invention specifies a method for fault identification when driving a polyphase motor by means of a frequency converter, wherein, in a rest state, the frequency converter controls the phase voltages of the polyphase motor and the phase currents of the polyphase motor are measured. In this case, provision is made for, then in the rest state, the phase currents or current variables derived therefrom to be adjusted by closed-loop control to a predetermined setpoint current variable, for the frequency converter to be controlled so as to output an interference voltage variable for the phase voltages, for the response of the adjustment by closed-loop control to the interference voltage variable to be observed, and for a conclusion to be drawn regarding a fault of the frequency converter and/or the phases of the polyphase motor from the response of the closed-loop control. The cited method allows for largely loss-free detection of faults in the drive system of a polyphase motor.

Abstract: A method is specified for fault identification when operating a rotating-field motor by means of a pulse-controlled inverter, wherein electromagnetic state variables of the rotating-field motor are determined by means of a mathematical model in space-vector form, and wherein the pulse-controlled inverter is operated electronically using space-vector variables. In this case, the invention provides that, during the operation of the rotating-field motor, the space vector of an uncontrolled state variable of the rotating-field motor is formed, in that the space vector that is formed is analyzed for a spectral component at twice the frequency of the rotating field, and in that, if the spectral component at twice the frequency is present, a partial turns short is deduced in the stator windings.

Abstract: A method for operating an electric motor with at least two motor terminals that are driven by a control device contains the steps of short-circuiting of at least two of the motor terminals of the electric motor by the control device; measurement of the motor phase currents at the short-circuited motor terminals; and identification of a standstill of the electric motor if a magnitude and/or a frequency of the motor phase currents measured lies below a predefined limit value. In the case of such a reliable identification of the standstill of the electric motor, an enable signal can then advantageously be generated in order, by way of example, to enable access to an apparatus driven by the electric motor.