A device for detecting alternating-current components i.sub.AC of an electric current i.sub.ACDC flowing in a direct-current circuit includes an inductor arranged in the direct-current circuit, and an AC path arranged electrically in parallel with the inductor, wherein the AC path comprises a series circuit made up of a capacitor and a primary winding of a transformer. The device further includes a voltage measuring device, wherein a secondary winding of the transformer is connected to the voltage measuring device via a low-pass filter circuit.

A motor drive apparatus includes a converter, a DC link capacitor, a plurality of inverters, a diagnosis command unit configured to give a command to one of the plurality of inverters to perform power conversion, an AC voltage detection unit configured to detect a peak value of AC voltage on an AC input side of the converter, a DC voltage detection unit configured to detect a value of DC voltage across the DC link capacitor, a calculation unit to calculate a difference between the value of DC voltage and the peak value of AC voltage, a storage unit configured to store the difference in association with the inverters, and a leakage current determination unit configured to determine that the inverter associated with the largest of the differences stored in the storage unit is the inverter that has caused the largest leakage current.

A magnetic core is electromagnetically coupled to two conductors that allow an AC current to flow through. An exciter is configured to supply a winding with an excitation current that is an alternating current. A current detector is configured to detect a current flowing through the winding. A DC component detector is configured to detect a DC component level from the current detected with the current detector. Two contact elements are respectively disposed along the two conductors. A discrimination controller is configured to: turn the two contact elements on when the DC component level detected with the DC component detector is less than or equal to a threshold; turn the two contact elements off when the DC component level detected with the DC component detector is greater than the threshold; and turn the two contact elements off in de-energized condition.

A circuit for alternating current and direct current leakage detection. The circuit can achieve multiple functions such as direct current leakage detection, alternating current leakage detection, and leakage sampling link self-check. The circuit mainly comprises: an LDO module for converting an externally input power supply voltage into a voltage required for leakage detection; a frequency divider module for performing frequency division on a high-frequency clock signal; a logic control module for driving an MOS transistor and controlling the switching of different working modes; an MOS transistor driving module for driving an external leakage detection coil; a leakage detection coil for inducing alternating current and direct current leakage signals and a leakage self-check signal; a sampling resistor for converting the current signal flowing through the leakage detection coil into a voltage signal; a PGA module for amplifying a sampling signal; a gain control module for controlling a PGA amplification factor; an ADC module for performing digital-to-analog conversion of the signals; a DSP module for processing the alternating current and direct current leakage signals and the leakage self-check signal; and a current limiting module for limiting a loop current.

The disclosure relates to a device for measuring electrical current in an electrical conductor (2), the device comprising: a measuring circuit configured to be connected to the electrical conductor, the measuring circuit comprising: a resistor based measuring circuit comprising a resistor (10), a transformer based measuring circuit comprising a current transformer (20) comprising a primary coil (20a), connected in series with the resistor (10) of the resistor based measuring circuit, a first inverter (12) configured to transform a first digital signal using a transfer function being an inverse of a transfer function representing the resistor based measuring circuit; a second inverter (22) configured to transform a second digital signal using a transfer function being an inverse of a transfer function representing the transformer based measuring circuits; and a signal combiner (5) configured to combine the transformed first and second digital signals, thereby providing a digital signal representing the electrical current in the electrical conductor. The disclosure also relates to a method for measuring electrical current in an electrical conductor.

In the field of Rogowski coils for the measurement of current within a conductor there is provided an electrical interface for connection to a Rogowski coil arranged around a primary conductor. The electrical interface includes an input that is configured to sample an input voltage signal from the Rogowski coil. The electrical interface also has an integrator circuit which includes an integrator module that is configured to integrate the sampled input voltage signal to provide an output voltage signal from which can be derived a primary current flowing through the primary conductor. The integrator module employs a transfer function that includes an attenuation factor.

A method for determining a direct current component in an electric device that is connected to a high-voltage supply network. The method includes the following steps: acquiring operating noises of the electric device with the aid of acoustic sensors that are part of a portable unit and that provide acoustic signals at the output; breaking the acoustic signals down into their frequency components by a Fourier transformation, yielding a frequency spectrum; determining odd and even frequency components of the frequency spectrum in dependence upon a basic frequency of the high-voltage supply network and setting them in a ratio to one another; concluding that a direct current component is present if the ratio exceeds a predefined threshold value.

A method for detecting a direct current component in an inductive device, for example in a transformer or choke, includes using a computer for recording an oscillation signal, either of sound emitted from the device or of mechanical oscillation of the device, determining the frequency range of the oscillation signal, determining the value of at least one odd frequency in the frequency range, comparing the value of the odd frequency with the value of at least one even frequency in the frequency range, and determining a direct current component when the value of the odd frequency differs from the even frequency by a predefined amount. The method can be carried out without measuring equipment in the interior of an inductive device and without the involvement of an expert. A computer program product for carrying out the method is also provided.

A device and method for detecting the number of revolutions of a sensorless electric park brake (EPB) motor. The device for detecting the number of revolutions of a sensorless motor includes: an actuator driving motor used to set and release a parking brake of an EPB system; an electronic control module for controlling the motor, a vehicle battery for supplying power to the motor and the electronic control module; and a main processing unit for receiving an output signal of the electronic control module and estimating the number of revolutions of the motor, wherein the electronic control module further includes a ripple measuring unit for receiving an output signal of the motor and measuring a ripple of the motor.

A current detecting apparatus measures an input current or an output current of an electronic apparatus. The current detecting apparatus includes a current detecting module, a direct-current measurement module and a current detecting module. The current detecting module includes a coil configured to electromagnetically couple to a path of an input or a path of an output of the electronic apparatus to obtain a first voltage signal. The direct-current measurement module measures the path of the input or the path of the output to obtain a second voltage signal. The current detecting module converts the first voltage signal into a first current command, and converts the second voltage signal into a second current command. The first current command is an alternating-current component of the input current or the output current. The second current command is a direct-current component of the input current or the output current.