A method for detection of a sub-synchronous oscillation in a power system includes measuring a three-phase measurement signal of an electric system value, analyzing the measurement signal to detect an oscillation component of the measurement signal having an oscillation frequency lower than a system frequency of the power system, deciding whether the detected oscillation component at the oscillation frequency qualifies as a sub-synchronous oscillation, and disconnecting a generator from the power system that might be affected by the sub-synchronous oscillation. To detect sub-synchronous oscillations with low computational effort and good accuracy, an amplitude of each phase of the oscillation component is calculated and compared against a threshold, a sub-synchronous oscillation is detected upon exceeding the threshold during a given time delay, and a fault signal is generated upon detecting a sub-synchronous oscillation. A device having a processing unit is also provided.

A measuring circuit (100) is described, for the voltage of an electric machine comprising a first operational amplifier (20) having its non-inverting input (5) connected to a non-inverting input (10) of at least one second operational amplifier (30), and its output (7) feedback connected, through a resistance (R5), to the inverting input (6), the inverting input (6) of the first operational amplifier (20) being further connected through a resistance (R6) to a first phase (C) of the input current to an electric machine, the output (7) of the first operational amplifier (20) being connected, through a resistance (R8), to the inverting input (2) of a third operational amplifier (40) which has its non-inverting input (3) connected to a reference voltage (VREF), the output (7) of the first operational amplifier (20) being further connected to a first output (VC) of the circuit, which is at a voltage value equal to the voltage of a first phase of the electric machine to be measured, said third operational amplifier (40) having its output (1) feedback connected, through a capacitance (Cl), to the inverting input (2), the output (1) of the third operational amplifier (40) being further connected through a resistance (R10) to the non-inverting input (5) of the first operational amplifier (20) and to the non-inverting input (10} of the second operational amplifier (30); a system and a process for calibrating electric machines using such circuit (100) are further described.

The purpose of the present invention is to provide a device monitoring technique having little restriction even on application to an already-existing device or facilitating monitoring even when a device to be monitored is in variable speed operation or under load variation. One of the representative device monitoring devices of the present invention monitors a device system using, as a power source, an AC electric motor driven by an inverter and is provided with a torque current estimation unit and a state estimation unit. The torque current estimation unit acquires information about AC currents of at least two phases and excitation current of the AC electric motor and calculates a torque current estimated value of the AC electric motor on the basis of the AC currents and the excitation current. The state estimation unit estimates the state of the device system from information including at least one of the feature amounts extracted from the torque current estimated value.

An arrangement for generating electric energy comprises an alternator having a rotor with a winding for being magnetized by an electric current fed therethrough and a stator with at least three stator windings for generation of three phase voltages therein upon rotation of the magnetized rotor in the stator. A rectifier has an input connected to the stator windings. Means is configured to measure the development over time of the difference of two of said phase voltages and an evaluation unit is configured to evaluate the result of this measurement to determine the functionality of the alternator. A control unit located remote to the alternator controls the rotor current.

A state quantity-acquiring unit acquires values of a plurality of state quantities at a certain timing associated with an object device. A state quantity-predicting unit predicts allowable ranges of the values of the plurality of state quantities after a predetermined time has elapsed on the basis of the acquired values of the plurality of state quantities. A display information-generating unit generates display information in which a predicted-value figure which is a figure with a shape corresponding to the allowable ranges of the values of the plurality of state quantities is disposed in a coordinate space with the plurality of state quantities as axes.

Disclosed is a method and apparatus for real-time estimation of full parameters of a permanent magnet synchronous motor. According to this method and apparatus, it is possible to estimate in real time all four parameters of a permanent magnet synchronous motor without additional signal injection. In addition to the state equation, the “stator current ripple model” is additionally used to fundamentally solve the rank deficiency problem in the state equation without injecting additional signals. All four parameters of a permanent magnet synchronous motor can be estimated in real time.

A failure diagnosing device diagnoses failure of a plurality of reduction gears of a mechanical apparatus which includes a plurality of operation parts, a plurality of motors, and the plurality of reduction gears. The failure diagnosing device includes an acceleration/deceleration period identifying module configured to identify an acceleration/deceleration period of operation of one of the plurality of operation parts, a motor current processing module configured to acquire a peak value of an amplitude of a frequency component of motor current in a specific frequency band of one motor that drives the one operation part, in the acceleration/deceleration period, and a determining module configured to determine whether a sign of failure exists in one of the reduction gears.

A motor angle detection and diagnosis apparatus is connected to a drive motor using a resolver. The resolver is configured to output a resolver feedback signal of an electrical angle of the drive motor. An angle sampling and diagnosis system in the motor angle detection and diagnosis apparatus performs two-channel simultaneous sampling on a resolver feedback signal, obtained after adjustment by the resolver feedback processing circuit, separately calculates a first electrical angle and a second electrical angle; diagnoses data obtained after the two-channel sampling of the first electrical angle and the second electrical angle in real time, diagnoses hardware circuits, and controls the motor controller to enter a safe state when a diagnosis result is abnormal. In this solution, sampling is performed by using two sampling channels, so that angle decoding of at least an ASIL C can be implemented.

A device and a system for diagnosing a motor parameter are provided. The device includes a master chip, an excitation conditioning circuit, a motor resolver unit, and a sine and cosine conditioning circuit. The master chip includes a first analog-to-digital converter, a second analog-to-digital converter, a first processing unit, and a monitoring core.

A diagnosis device for diagnosing a diagnosis target machine having a rotary machine on the basis of a measured current during rotation of the rotary machine is provided with: an effective value acquisition unit configured to acquire an effective value of the measured current for each specified number of cycles in a target current waveform which is time transition of the measured current in a first predetermined period; a distribution information calculation unit configured to calculate a target distribution information which represents a distribution state of a plurality of the effective values acquired; and a detection unit configured to perform abnormality detection of the diagnosis target machine on the basis of the calculated target distribution information.