Abstract:
A method of assessing a condition of a multi-phase power system comprises the steps of: acquiring a voltage signal and a current signal for each phase of the multi-phase power system; calculating a product of the voltage signal for each phase of the multi-phase power system with one of the current signals such that the product is between a voltage signal for one phase and a current signal for a different phase for at least two of the products; summing the calculated products; and identifying the possible existence of a fault in the multi-phase power system based on a frequency analysis of the summed calculated products.
Abstract:
A method of open-switch fault detection in a two-level voltage source power converter comprises the steps of: i. acquiring the waveforms of three-phase alternating current of the two-level voltage source power converter; ii. calculating at least a first time derivative of each acquired waveform; and iii. using the at least first time derivatives to determine whether an open-switch fault is present in the two-level voltage source power converter.
Abstract:
A method of detecting a fault in an induction machine having one or more windings arranged to draw current at a supply frequency, the method including: performing a process of judging whether a respective sideband of one or more selected harmonics of the supply frequency exists at a predetermined fault frequency in a signal in the one or more windings; and determining that a fault has occurred if the judgement is positive; wherein in the judging process each of the selected harmonics of the supply frequency is a harmonic frequency of the supply frequency other than the supply frequency itself.
Abstract:
A method of detecting a diode fault in an AC signal rectifier circuit, the AC signal rectifier circuit including a plurality of diodes, and being arranged to supply a rectified output voltage to a load, wherein the method includes the steps of deriving an operating value indicative of the ratio of the voltage magnitudes of a first harmonic frequency and another harmonic frequency of the rectified output voltage across the load; and determining whether a fault has occurred in one or more diodes on the basis of the derived operating value. The first harmonic frequency is preferably the fundamental harmonic frequency, and/or the another harmonic frequency is preferably the 6th harmonic frequency.
Abstract:
A method of monitoring the health of a semiconductor power electronic switch such as an insulated gate bipolar transistor (IGBT) is provided. The method having the steps of: measuring one or more parameters selected from the group consisting of: a rate of change of voltage ( dV dt ) across the switch; a rate of change of current ( di dt ) through the switch, a charge present on a gate of the switch (QG), a peak overshoot voltage (VPO) across the switch, and a peak overshoot or reverse recovery current (IRR) through the switch; and estimating the health of the switch based on the measured parameter(s).
Abstract:
A method of controlling an inverter, in which the inverter includes a single-phase inverter arrangement comprising a complementary pair of power switches, comprises the steps of:controlling the complementary pair of power switches with a modulating signal to output an AC signal;judging which of the power switches in the complementary pair of power switches is at a higher temperature;determining the magnitude and sign of a DC offset signal to apply to the modulating signal to reduce the total current in the power switch judged to be at the higher temperature; andapplying the DC offset signal to the modulating signal.
Abstract:
A method of detecting rotor and/or stator side faults in an induction motor. Signals indicative of three-phase stator currents of the induction motor are acquired (10) and converted (16) into three-phase current phasors. The three-phase current phasors are combined (16) to obtain a quantity having a DC component and an AC component. A frequency spectrum of the AC component is obtained (18) and compared (20,22) to a frequency spectrum of the AC component under healthy operating conditions in order to determine the presence of a rotor and/or stator side fault in the induction motor
Abstract:
The invention concerns the damping of torsional oscillations/vibrations, particularly during electrical power generation within a gas turbine such as a civil aviation engine. The method of the invention relies on actively generating compensating oscillations in a driveline of a system to actively damp undesirable oscillations existing in the system.