Ground fault detection circuit
AssigneeLucas Aerospace Power Equipment Corporation
InventorsKevin E. Rice, Ronald W. Roseman
Life of this patent
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Abstract
A controller for a starter/generator used with an aircraft engine, includes means for monitoring field return current in a generator field winding; means for monitoring generator voltage; and microprocessor control means for adjusting generator field current as a function of the field current and voltage and field return current. The field return current and output voltage monitoring functions allow for open field, field integrity, over voltage, field weakening and torque limiting functions to be realized in an integrated programmable system configuration.
Claims13
Apparatus for detecting a ground fault in a generator circuit a load is connected to the generator by a first conductor, being a feeder line and having a feeder current, and a second conductor, being a return line having a return current, comprising:
- a sensing means coupled to each conductor for detecting instantaneous changes in feeder current and return current, where said sensing means producing a first output that corresponds to instantaneous changes in feeder current, and a second output that corresponds to instantaneous changes in return current;
- a differential circuit for differentially combining said first and second outputs and producing a third output for indicating when the ground fault is detected based on a difference between said first and second outputs, and;
- a control means for monitoring said third output and de-energizing the generator when the ground fault is detected.
Apparatus for detecting a ground fault in a circuit which has a load connected to a D.C. generator by a first conductor being a feeder line and having a feeder current and a second conductor being a return line and having a return current, comprising:
- a first current transformer coupled to said feeder line, said first transformer producing a first voltage pulse in response to an instantaneous change in the feeder current;
- a second current transformer coupled to said return line, said second transformer producing a second voltage pulse in response to an instantaneous change in the return current;
- a first differential amplifier having an inverting input and a non-inverting producing an output relative to the difference of the voltages at the inverting and non-inverting inputs;
- a second differential amplifier, having an inverting input and non-inverting input producing an output relative to the difference of the voltages at the inverting and non-inverting inputs;
- means for connecting the inverting input of said first differential amplifier to said first current transformer and receiving said first voltage pulse;
- means for connecting the non-inverting input of said first differential amplifier to said second current transformer and receiving said second voltage pulse;
- means for connecting the inverting input of said second differential amplifier to said second current transformer and receiving said second voltage pulse;
- means for connecting the non-inverting input of said second differential amplifier to said first current transformer and receiving said first voltage pulse;
- a first summing node connected to the output of said first differential amplifier and the output said second differential amplifier whereby the existence of a ground fault may be detected;
- a built in test (BIT) circuit connected to the outputs of said differential amplifiers wherein the operability of said differential amplifier circuits can be tested independent of the application of a test signal, said BIT circuit comprising a second summing node coupled to said first differential amplifier output, said second differential amplifier output and a reference voltage whereby the second summing node voltage indicates a failure of said first or second differential amplifier by a static change in the voltage level at said second summing node;
- a sample and hold circuit coupled to said first summing node;
- a control means for monitoring said first and said second summing nodes and de-energizing the generator when either the ground fault is detected or the failure of the apparatus is detected.
Dependencies are inferred from the claim text.