High level arc fault detector

1. An arc fault detector for detecting arc faults in three phase aircraft power systems, comprising:

three full wave rectifiers, each of the three full wave rectifiers having an input of a load current in the three phase power system and having an output connected to one of a plurality of threshold detectors;

a three input comparator having at least three inputs, each of the least three inputs being connected to an output of one of the plurality of threshold detectors; and

a fault verification circuit connected to an output of the three input comparator.

2. The arc fault detector of claim 1 , wherein each of the plurality of threshold detectors comprises:

a first comparator having: a first input connected to an output of one of the full wave rectifiers; a second input connected to a signal indicative of a predetermined threshold; and

an output.

3. The arc fault detector of claim 2 , wherein each of the plurality of threshold detectors further comprise an integrator configured to integrate the output of the first comparator.

4. The arc fault detector of claim 1 , wherein the three input comparator is configured to generate a signal indicative of the outputs of any two of the threshold detectors differing by more than a predetermined amount.

5. The arc fault detector of claim 1 , wherein the fault verification circuit comprises:

an integrator connected to the output of the three input comparator; and

a comparator connected to the output of the integrator and configured to generate a signal indicative of the detection of a fault, when the output of the integrator exceeds a predetermined threshold.

6. An arc fault detector for detecting arc faults in three phase aircraft power systems; comprising:

means for generating three load currents in the three phase system, where each load current in the three phase system is indicative of each of the three phases;

means for rectifying the generated load currents;

mean for comparing the three rectified load currents;

means for generating a signal in response to the three rectified load currents differing for a time period exceeding a predetermined duration; and

means for detecting that one of the three rectified currents exceeds a predetermined threshold, wherein the means for generating a signal in response to the three rectified load currents differing for a time period exceeding a predetermined duration generates a signal if at least one of the three filtered load current exceeds the predetermined threshold.

7. A method of detecting arc faults in three phase aircraft power systems, comprising:

detecting when at least one of the three load currents in the three phase power system has a current exceeding a predetermined threshold;

detecting differences between the three load currents; and

generating a signal indicative of differences being detected between the three load currents for a time period exceeding a predetermined duration;

wherein the detecting differences comprises generating load currents in the three chase system, each load current indicative of one of the three phases and generating a signal indicative of at least two of the three load currents differing by more than a predetermined amount, and detecting differences further comprises continuously monitoring the load currents indicative of the three phases.

8. The method of claim 7 , wherein detecting differences further comprises continuously sampling the load currents indicative of the three phases.

9. The method of claim 7 , wherein generating a signal indicative of at least two of the three load currents differing by more than a predetermined amount comprises integrating over at least one cycle each of the load currents indicative of each of the three phases.

10. The method of claim 9 , wherein generating a signal indicative of at least two of the three load currents differing by more than a predetermined amount further comprises:

comparing the magnitude of each load current to a predetermined threshold; and

generating a signal for each load current indicative of the magnitude of the load current relative to the threshold.

11. The method of claim 7 , wherein generating a signal indicative of differences being detected between the three load currents for a time period exceeding a predetermined duration comprises:

generating a signal indicative of the time period during which at least two of the three load currents differ by more than a predetermined amount; and

comparing the generated signal to a signal indicative of the predetermined duration.