Abstract: A double-stator PM machine having: an outer stator generating an outer electromagnetic field dependent on an outer three-phase supply current; an inner stator generating an inner electromagnetic field dependent on an inner three-phase supply current; a PM rotor rotated by the outer and inner electromagnetic fields between the outer and inner stators; and a control arrangement controlling the outer and inner supply currents. There is an electrical connection between neutral points of the outer and inner stators. The control arrangement is configured for controlling the outer and inner supply currents such that there is a relative angle shift of 30° between the outer and inner supply currents and such that a third order current harmonic component is circulated between the outer and inner stators.

Abstract: A method of controlling an electrical machine, wherein the method includes: a) injecting a first voltage waveform (uhx) with a first fundamental frequency into the electrical machine in a first axis of a rotor reference frame, combined with a voltage signal for controlling the electrical machine, b) determining a second axis current component (iqhx) of a second axis of the rotor reference frame, having the first fundamental frequency, generated in response to the injection of the first voltage waveform (uhx), c) controlling based on the second axis current component (iqhx) a second axis voltage component (uqhx) of the second axis, having the first fundamental frequency, to obtain an adjusted second axis voltage component for controlling the second axis current component (iqhx) towards zero, d) feeding back the adjusted second axis voltage component to combine the adjusted second axis voltage component with the voltage signal and the injected first voltage waveform (uhx), and repeating steps b)-d) until the se

Abstract: A method for continuous operation of a rotating machine, the method is performed in a rotating machine having an inner stator and an outer stator.

Abstract: A double-stator PM machine having: an outer stator generating an outer electromagnetic field dependent on an outer three-phase supply current; an inner stator generating an inner electromagnetic field dependent on an inner three-phase supply current; a PM rotor rotated by the outer and inner electromagnetic fields between the outer and inner stators; and a control arrangement controlling the outer and inner supply currents. There is an electrical connection between neutral points of the outer and inner stators. The control arrangement is configured for controlling the outer and inner to supply currents such that there is a relative angle shift of 30° between the outer and inner supply currents and such that a third order current harmonic component is circulated between the outer and inner stators.

Abstract: A method of controlling an electrical machine, wherein the method includes: a) injecting a first voltage waveform (uhx) with a first fundamental frequency into the electrical machine in a first axis of a rotor reference frame, combined with a voltage signal for controlling the electrical machine, b) determining a second axis current component (iqhx) of a second axis of the rotor reference frame, having the first fundamental frequency, generated in response to the injection of the first voltage waveform (uhx), c) controlling based on the second axis current component (iqhx) a second axis voltage component (uqhx) of the second axis, having the first fundamental frequency, to obtain an adjusted second axis voltage component for controlling the second axis current component (iqhx) towards zero, d) feeding back the adjusted second axis voltage component to combine the adjusted second axis voltage component with the voltage signal and the injected first voltage waveform (uhx), and repeating steps b)-d) until the se

Abstract: A method of detecting a permanent magnet rotor of a synchronous machine, includes: injecting a voltage waveform to the stator windings of the synchronous machine, measuring two phase currents in the stator winding, transforming the two phase currents to a rotor reference frame to obtain a current waveform, sampling the current waveform to obtain positive and negative portion values, constructing first and second periodic waveforms by using the sampled positive and negative portion values, performing a frequency analysis of a first and second spectrums of the periodic waveforms, and determining whether a permanent magnet is present in the synchronous machine based on the spectrums.

Abstract: A method of detecting a permanent magnet rotor of a synchronous machine, includes: injecting a voltage waveform to the stator windings of the synchronous machine, measuring two phase currents in the stator winding, transforming the two phase currents to a rotor reference frame to obtain a current waveform, sampling the current waveform to obtain positive and negative portion values, constructing first and second periodic waveforms by using the sampled positive and negative portion values, performing a frequency analysis of a first and second spectrums of the periodic waveforms, and determining whether a permanent magnet is present in the synchronous machine based on the spectrums.

Abstract: A method for determining an undesired condition in an electrical drive system including an electrical machine and an electrical drive, wherein the method includes a) obtaining a measured signal of an electrical or mechanical parameter, b) obtaining a frequency spectrum of the measured signal, that contains a measured frequency component, c) determining whether the measured frequency component is within a predetermined distance from a trend line, which trend line is associated with only one specific frequency component of the electrical or mechanical parameter present during a specific undesired condition, d) on the condition that the measured frequency component is within the predetermined distance from the trend line increasing a counter associated with the trend line, e) repeating steps a) to d), wherein in case the counter reaches a predetermined number determining that the electrical drive system is subjected to the undesired condition associated with the trend line.

Abstract: A self-commissioning method for estimating differential inductances in an electric machine, such as e.g. a synchronous reluctance machine or interior permanent magnet machine, with cross-magnetization effects is provided. The electric machine is driven with PWM voltages to explore current plurality of operating points of the currents in the electric machine while keeping the electric machine at standstill or quasi-standstill. At each operating point PWM switching voltage transients are used as a small-signal excitation. Currents of the electric machine are measured by means of oversampling, which permit the reconstruction of the waveforms including the current ripple within a PWM period caused by the PWM switching transients. Finally, the differential inductances at each operating point are determined based on the determined direct and quadrature current waveforms and voltages.

Abstract: A method for determining an undesired condition in an electrical drive system including an electrical machine and an electrical drive, wherein the method includes a) obtaining a measured signal of an electrical or mechanical parameter, b) obtaining a frequency spectrum of the measured signal, that contains a measured frequency component, c) determining whether the measured frequency component is within a predetermined distance from a trend line, which trend line is associated with only one specific frequency component of the electrical or mechanical parameter present during a specific undesired condition, d) on the condition that the measured frequency component is within the predetermined distance from the trend line increasing a counter associated with the trend line, e) repeating steps a) to d), wherein in case the counter reaches a predetermined number determining that the electrical drive system is subjected to the undesired condition associated with the trend line.

Abstract: A self-commissioning method for estimating differential inductances in an electric machine, such as e.g. a synchronous reluctance machine or interior permanent magnet machine, with cross-magnetization effects is provided. The electric machine is driven with PWM voltages to explore current plurality of operating points of the currents in the electric machine while keeping the electric machine at standstill or quasi-standstill. At each operating point PWM switching voltage transients are used as a small-signal excitation. Currents of the electric machine are measured by means of oversampling, which permit the reconstruction of the waveforms including the current ripple within a PWM period caused by the PWM switching transients. Finally, the differential inductances at each operating point are determined based on the determined direct and quadrature current waveforms and voltages.

Abstract: A method of estimating inductances and flux linkages of an electrical machine supplied with drive currents via current regulators. Drive current values are measured and fed back to the regulators for closed-loop control. The method includes providing one current regulator with an alternating current value either for a direct axis current reference i*d or for a quadrature axis current reference i*q of the machine current vector, while providing another current regulator with a predetermined direct current value for the remaining one of the two current references i*d and i*q. After a predetermined time, a varying signal is superimposed onto an output signal generated by the current regulator in response to the AC value. Finally, a contribution signal, which corresponds to the contribution of the superimposed varying signal to the drive currents, is determined, and the machine inductances and flux linkages are estimated on the basis of the contribution signal.

Abstract: A method of estimating inductances and flux linkages of an electrical machine supplied with drive currents via current regulators. Drive current values are measured and fed back to the regulators for closed-loop control. The method includes providing one current regulator with an alternating current value either for a direct axis current reference i*d or for a quadrature axis current reference i*q of the machine current vector, while providing another current regulator with a predetermined direct current value for the remaining one of the two current references i*d and i*q. After a predetermined time, a varying signal is superimposed onto an output signal generated by the current regulator in response to the AC value. Finally, a contribution signal, which corresponds to the contribution of the superimposed varying signal to the drive currents, is determined, and the machine inductances and flux linkages are estimated on the basis of the contribution signal.

Abstract: A method for finding an operating point of an electric motor which includes the steps of generating a perturbation signal, combining the perturbation signal with a current magnitude related to a drive system of the motor or combining the perturbation signal with a power magnitude related to the motor, yielding a combined signal, and sending, based on the combined signal, a flux adjustment signal to adjust a flux of the motor. An apparatus for finding an operating point of an electric motor comprising is also presented.

Abstract: A method for finding an operating point of an electric motor which includes the steps of generating a perturbation signal, combining the perturbation signal with a current magnitude related to a drive system of the motor or combining the perturbation signal with a power magnitude related to the motor, yielding a combined signal, and sending, based on the combined signal, a flux adjustment signal to adjust a flux of the motor. An apparatus for finding an operating point of an electric motor comprising is also presented.