Abstract: This invention relates to line frequency synchronisation for use in diagnostics for alternating current electrical circuits. The invention provides a method of synchronising measurement system frequency with an alternating current line frequency comprising the steps of: adjusting the frequency of the measurement system frequency using a frequency locked loop until the measurement system frequency is within a predetermined range of said alternating current line frequency; and when the measurement system frequency is within a predetermined range of said alternating current line frequency adjusting the phase and the frequency of the measurement system frequency using a phase and frequency locked loop.

Abstract: This invention relates to fault detection in electrical circuits. The invention provides an input module for electrically isolating an input signal received via a field sensor to be transmitted to a plurality of processors, in which the input module comprises a plurality of optical coupler/controller circuits; and each optical coupler/controller comprises a light emitting diode drive sub-circuit driving a light emitting diode; and an input sub-circuit; and in which a sensor voltage representing said input signal and a supply voltage are connected to each input sub-circuit; and each of said light emitting diode drive sub-circuits are connected in series between the supply voltage and ground.

Abstract: This invention relates to a speed monitor apparatus for monitoring speed and acceleration of rotating turbine equipment (turbomachinery) and for operating an overspeed trip to shut down the equipment in the event that the speed or acceleration exceed predetermined thresholds. The invention provides a speed monitor module having an input conditioner comprising: a multiplexer; an amplifier; and a comparator; in which the multiplexer selects an input signal from the sensor, or an input signal via a feedback loop from the comparator in dependence upon a test input, such that the input circuit may be tested by confirming that the amplifier oscillates when the feedback loop is enabled by the test signal.

Abstract: This invention relates to a speed monitor apparatus for monitoring speed and acceleration of rotating turbine equipment (turbomachinery) and for operating an overspeed trip to shut down the equipment in the event that the speed or acceleration exceed predetermined thresholds. The invention provides a speed monitor module having an output switch comprising a plurality of armature clamped relays such that first armatures form a first electrical path only when both first armatures are open or when both first armatures are closed and second armatures provide a second electrical path when either or both second armatures are open or closed such that the second electrical path is discontinuous when either first armature is stuck in an open or closed position causing either second armature to remain floating between an open and closed position.

Abstract: This invention relates to line frequency synchronisation for use in diagnostics for alternating current electrical circuits. The invention provides a method of synchronising measurement system frequency with an alternating current line frequency comprising the steps of: adjusting the frequency of the measurement system frequency using a frequency locked loop until the measurement system frequency is within a predetermined range of said alternating current line frequency; and when the measurement system frequency is within a predetermined range of said alternating current line frequency adjusting the phase and the frequency of the measurement system frequency using a phase and frequency locked loop.

Abstract: This invention relates to fault detection in electrical circuits. The invention provides an input module for electrically isolating an input signal received via a field sensor to be transmitted to a plurality of processors, in which the input module comprises a plurality of optical coupler/controller circuits; and each optical coupler/controller comprises a light emitting diode drive sub-circuit driving a light emitting diode; and an input sub-circuit; and in which a sensor voltage representing said input signal and a supply voltage are connected to each input sub-circuit; and each of said light emitting diode drive sub-circuits are connected in series between the supply voltage and ground.

Abstract: This invention relates to fault detection in electrical circuits. The invention provides a switch for a fault tolerant digital output module comprising: an output transistor pair for enabling and disabling an alternating output current; and a current limiter for clamping the output current to a predetermined maximum value.

Abstract: This invention relates to fault detection in electrical circuits, in particular it relates to fault detection for a plurality of adjacent input circuits. The invention provides a method and apparatus for detecting a control or communication fault on an analogue circuit by digitally simulating said analogue circuit; driving the digitally simulated circuit with a control input also used to drive said analogue circuit; and comparing an output of said simulated circuit with a reference output and setting an error condition in the event that the compared outputs differ.

Abstract: This invention relates to a method and apparatus for output current control. The invention provides an output module slice for controlling an output current comprising: an output field interface controller for controlling an input voltage to a first field effect transistor; an analogue to digital converter connected to read the current flowing through said first field effect transistor and to provide a digital signal dependent thereon to said output field interface controller.

Abstract: This invention relates to overload protection for a circuit driving a direct current (DC) load.

Abstract: This invention relates to fault detection in electrical circuits. The invention provides a method and apparatus for testing an input circuit by generating a periodic test signal having a predetermined phase and a predetermined amplitude; summing the test signal and an input signal to provide a summed signal; processing the summed signal to provide an output signal; generating an extracted test signal from the output signal; comparing the extracted test signal with a reference signal representing said periodic test signal; generating an error signal in dependence upon the result of said comparing step. The invention also provides a method and apparatus for testing a plurality of adjacent input circuits.

Abstract: This invention relates to a speed monitor apparatus for monitoring speed and acceleration of rotating turbine equipment (turbomachinery) and for operating an overspeed trip to shut down the equipment in the event that the speed or acceleration exceed predetermined thresholds. The invention provides a speed monitor module having an output switch comprising a plurality of armature clamped relays such that first armatures form a first electrical path only when both first armatures are open or when both first armatures are closed and second armatures provide a second electrical path when either or both second armatures are open or closed such that the second electrical path is discontinuous when either first armature is stuck in an open or closed position causing either second armature to remain floating between an open and closed position.

Abstract: This invention relates to a speed monitor apparatus for monitoring speed and acceleration of rotating turbine equipment (turbomachinery) and for operating an overspeed trip to shut down the equipment in the event that the speed or acceleration exceed predetermined thresholds. The invention provides a speed monitor module wherein the speed monitor module may be may be plugged in to the same chassis as a module which is controlling the speed of the turbine, and wherein the turbine speed monitor is arranged to receive configuration parameters relating to the overspeed threshold and the overacceleration threshold only when the turbine is operating at a speed lower than a predetermined threshold.

Abstract: This invention relates to a speed monitor apparatus for monitoring speed and acceleration of rotating turbine equipment (turbomachinery) and for operating an overspeed trip to shut down the equipment in the event that the speed or acceleration exceed predetermined thresholds. The invention provides a speed monitor module having an input conditioner comprising: a multiplexer; an amplifier; and a comparator; in which the multiplexer selects an input signal from the sensor, or an input signal via a feedback loop from the comparator in dependence upon a test input, such that the input circuit may be tested by confirming that the amplifier oscillates when the feedback loop is enabled by the test signal.