A method for monitoring the state of an electric machine includes determining within a defined frequency range, for example in a spectrogram of a current amplitude, a frequency position where a current amplitude has a maximum at the frequency position and where a phase relationship between a current vector and a voltage vector or between two current vectors is located in a predefined interval. The determined frequency position is characteristic; of the state of the electric machine.

A device (9) for protecting a direct current electrical system (1) having one or more modules (2) from electric arcs comprises: a first sensor (10) provided with a first ring of ferromagnetic material configured to generate a first signal, representing a oscillating component of a current flowing through a cable inserted into the ring; a conditioning stage (12), having a bandpass filter, for conditioning the first signal; a first threshold comparator (13); a counter (15); a processor (14); a second sensor (19), configured to generate a second signal representing a direct current component of the current flowing through the cable; a second threshold comparator (20).

Fractional Fourier Transform (FrFT)-based spectrum analyzers and spectrum analysis techniques are disclosed. Rather than using the standard Fast Fourier Transform (FFT), the FrFT may be used to view the signal content contained in a particular bandwidth. Usage of the FrFT in place of the frequency or time domain allows viewing of the signal in different dimensions, where “spectral” features of interest, or signal content, may appear where they were not visible in these domains before. This may allow signals to be identified and viewed in any domain within the continuous time-frequency plane, and may significantly enhance the ability to detect and extract signals that were previously hidden under interference and/or noise, provide or enhance the ability to extract signals from a congested environment, and enable operation in a signal-dense environment.

Fractional Fourier Transform (FrFT)-based spectrum analyzers and spectrum analysis techniques are disclosed. Rather than using the standard Fast Fourier Transform (FFT), the FrFT may be used to view the signal content contained in a particular bandwidth. Usage of the FrFT in place of the frequency or time domain allows viewing of the signal in different dimensions, where “spectral” features of interest, or signal content, may appear where they were not visible in these domains before. This may allow signals to be identified and viewed in any domain within the continuous time-frequency plane, and may significantly enhance the ability to detect and extract signals that were previously hidden under interference and/or noise, provide or enhance the ability to extract signals from a congested environment, and enable operation in a signal-dense environment.

There is provided a broadband lossless partial discharge detection and noise removal device which includes: a partial discharge occurrence timing pulse acquiring unit acquiring a generated timing pulse of a partial discharge signal at the beginning of generation of a partial discharge signal; a partial discharge magnitude pulse acquiring unit acquiring a magnitude pulse of the partial discharge signal; a synchronization comparing unit detecting a partial discharge digital signal determined according to whether the generated timing pulse of the partial discharge signal and the magnitude pulse are synchronized; and a partial discharge signal generating unit detecting a partial discharge pulse obtained by converting the detected partial discharge digital signal into an analog signal.

There is provided a broadband lossless partial discharge detection and noise removal device which includes: a partial discharge occurrence timing pulse acquiring unit acquiring a generated timing pulse of a partial discharge signal at the beginning of generation of a partial discharge signal; a partial discharge magnitude pulse acquiring unit acquiring a magnitude pulse of the partial discharge signal; a synchronization comparing unit detecting a partial discharge digital signal determined according to whether the generated timing pulse of the partial discharge signal and the magnitude pulse are synchronized; and a partial discharge signal generating unit detecting a partial discharge pulse obtained by converting the detected partial discharge digital signal into an analog signal.

Systems and methods relate to electric propulsor fault detection. An exemplary system includes at least a first inverter configured to accept a direct current and produce an alternating current, a first propulsor, a first motor operatively connected with the first propulsor and powered by the alternating current, and at least a noise monitoring circuit electrically connected with the direct current and configured to detect electromagnetic noise and disengage the at least an inverter as a function of the electromagnetic noise.

Systems and methods relate to electric propulsor fault detection. An exemplary system includes at least a first inverter configured to accept a direct current and produce an alternating current, a first propulsor, a first motor operatively connected with the first propulsor and powered by the alternating current, and at least a noise monitoring circuit electrically connected with the direct current and configured to detect electromagnetic noise and disengage the at least an inverter as a function of the electromagnetic noise.

The present invention proposes an arc detector having a multi-band frequency detection function, which divides an arc frequency band using multiple band-pass filters and detects whether or not an arc occurs in each of the divided frequency bands, thereby eliminating switching noise or power supply noise that mainly occurs in a certain frequency band, and consequently increasing the accuracy of arc detection. In addition, the arc detector of the present invention may minimize the use of expensive analog-to-digital converters and increase the accuracy of arc detection through overlapping area detection.

Methods, devices, and systems for coherent time-gated residual spur characterization and correction in signal analyzers. In some cases, the method includes: displaying a signal on the display of the signal analyzer that is present without an input signal being provided to an input of the signal analyzer; establishing a predetermined amplitude threshold above which energy spikes in the signal being displayed on the display of the signal analyzer are considered spurious; automatically identifying one or more spurious energy spikes in the signal being displayed on the display of the signal analyzer based on the predetermined amplitude threshold; and automatically reducing or removing the one or more spurious energy spikes from the signal being displayed on the display of the signal analyzer. The method can be performed using one or more processors, application specific integrated circuits (ASICs), field-programmable gate array (FPGA), or other circuitry on any suitable signal analyzer.