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: Invention concerns a machine fault diagnostic system. Sensors are provided for sensing an operational parameter of the machine over time in use and outputting corresponding sensor signals. A machine operation diagnosis tool is arranged to receive the sensor signals and has a data store for operational parameter data indicative of a normal mode of machine operation and operational parameter data indicative of one or more known machine faults. The diagnosis tool has one or more processor arranged to compare the received sensor signals with the operational parameter data in the data store in order to determine a match with either the normal mode of operation or the one or more known machine fault, and wherein the processor sentences an unknown fault in the event that said match is not established. The system may record unknown faults and update the diagnosis tool as unknown faults become recognizable faults.

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 for detecting a fault in an exciter circuit, suitable for use in a brushless generator, the exciter circuit including (a) an exciter armature winding, having a plurality of armatures, arranged to generate a multiphase AC signal, each armature of the plurality of armatures providing a respective sub-signal component of the multiphase AC signal, and (b) a rectifier circuit for receiving the sub-signals via the respective armatures, the rectifier circuit comprising a plurality of components arranged to rectify the sub-signals to provide a rectified output signal, wherein the method includes the steps of: acquiring a respective operational sub-value for a first characteristic of each of at least two of the respective sub-signals; deriving an operational value indicative of a relationship between the acquired respective operational sub-values; determining whether a fault has occurred in the exciter circuit on the basis of the derived operational value.

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 thermal controller for driving a gate control unit of a gate-driven semiconductor switching device, the thermal controller comprising a junction temperature estimation module for generating an estimated junction temperature for the switching device, a gate voltage control module for modifying a gate voltage of the switching device, a switching frequency control module for modifying a switching frequency of the switching device, and a duty cycle control module for modifying the duty cycle of the switching device. In use, the thermal controller is adapted to activate one of the gate voltage control module, switching frequency control module and duty cycle control module dependent upon the estimated junction temperature in order to maintain the actual junction temperature below a pre-determined limit.

Abstract: A thermal controller for driving a gate control unit of a gate-driven semiconductor switching device, the thermal controller comprising a junction temperature estimation module for generating an estimated junction temperature for the switching device, a gate voltage control module for modifying a gate voltage of the switching device, a switching frequency control module for modifying a switching frequency of the switching device, and a duty cycle control module for modifying the duty cycle of the switching device. In use, the thermal controller is adapted to activate one of the gate voltage control module, switching frequency control module and duty cycle control module dependent upon the estimated junction temperature in order to maintain the actual junction temperature below a pre-determined limit.