Abstract:
Disclosed is a motorized machine which includes an electrical system monitoring system which results in detecting arcing in the electrical distribution system of the machine and the ability to provide notification and protection for such arcing. The system functions to monitor the electrical distribution system of the machine to sense the frequencies of signals in the system using appropriate filtering. One type of filtering which may be used is based upon a heterodyning circuit which provides variable frequency filtering for filtering a signal representative of the current in at least one electrical circuit of the machine. The heterodyning circuit output is configured to produce a signal which may be logarithmically related to the filtered signal. If the output signal exceeds a predetermined limit (representative of noise) for a predetermined period (representative of a typical arc duration), the system generates an arc signal. The arc signal may then be used to operate a circuit interrupter or an indicator in a circuit protection system or both.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates, in general, to arc fault detection and, more specifically, to arc fault detection in an electrical distribution system of a motorized machine.  
         BACKGROUND OF THE INVENTION  
         [0002]    There are various conditions that may cause an arc fault. Corroded, worn or aged wiring or insulation, insufficient contact pressure, electrical stress from repeated overloading, etc., may result in an arc fault. These conditions may damage the insulation of the wiring and create excessive heating temperatures. In general, these conditions have been found to occur in applications where vibrations and relatively high temperatures are normally present. More specifically, vehicles (e.g. automobiles, airplanes, trucks, off-road equipment, etc.) and other moving or vibrating equipment provide a harsh environment for electronics and electrical systems (direct current (D.C.) or alternating current (A.C.)).  
           [0003]    The development of electronics and electrically powered accessories has resulted in an increase in the use of electronics and electrical power in vehicles. Examples of electronics and electrically powered accessories used in vehicles include:  
           [0004]    electronic fuel injection or fuel control;  
           [0005]    electronic timing control;  
           [0006]    electronic transmission shift control;  
           [0007]    electronic HVAC control;  
           [0008]    electronic lighting control;  
           [0009]    electronic braking control (e.g. anti-lock braking, traction control, slip control, etc.);  
           [0010]    power convenience accessories (e.g. power seats, power windows, heated seats, personal lighting, heated steering wheels, power sun roof, power steering wheel tilt, power mirrors, tire inflation control, etc.);  
           [0011]    electronic cruise control;  
           [0012]    on-aboard navigation systems; and  
           [0013]    air bags.  
           [0014]    Many of the electronics and power accessories listed above are also used in aircraft and off-road vehicles (e.g. tractors, tracked vehicles, excavators, etc.). With hybrid and pure electric vehicles, the use and transmission of electrical power is multiples greater than with conventional vehicles due to the use of electricity to power the motors which propel the vehicles.  
           [0015]    As a result of the substantial increase in use of electronics and electrical power accessories in vehicles, and the use of electric motors to propel vehicles, the potential for arc faults in the electrical systems of vehicles has also increased. As discussed above, such arcing can damage wiring and electronics or, cause unwanted heating. Thus, it would be desirable to provide a system for detecting and controlling arc faults in vehicle electrical systems.  
           [0016]    Detection and control of arc faults is relatively complicated. For example, the occurrence of an arc fault in one branch circuit of a power distribution system of a vehicle may generate a false arc detection signal in another branch circuit. As a result, circuit breakers or interrupters in more than one branch circuit may erroneously trip. Relatively noisy loads within the vehicle, such as electric motors (engine fan, heater fan, power seat motors, etc.) can create high frequency disturbances, which may appear to be arc faults and cause unwanted circuit breaker tripping. Similarly, external high frequency disturbances within the machines&#39; operative environment also may appear to be arc faults and cause unwanted circuit tripping.  
           [0017]    There are two types of arc faults that may occur in a vehicle. A first type is a high-energy arc that may be related to high current faults; a second type is a low current arc that may be related to the formation of a carbonized path between conductors. The first type may result from an inadvertent connection between a line conductor and neutral conductor or a line conductor and ground. The first type may draw current that is above the rated capacity of the circuit, arcing as the conductors are physically joined.  
           [0018]    The other type of arc fault, the carbonization between electrical conductors, may be considered more problematic. Since the current in the arc may be limited to less than the trip rating of an associated circuit breaker or interrupter, such arcs may become persistent without observation and may result in certain conditions. Contact arcs may be caused by springs in switches that become worn which, in turn, may reduce the forces that hold electrical contacts together. As the electrical contacts heat and cool down, the conductors may touch and separate repeatedly, thereby possibly creating arcs known as “sputtering arcs.” Such sputtering arcs can create carbonized paths resulting in persistent low current arcs in the electrical system.  
           [0019]    Contact arcs or sputtering arcs may also be observed in contacts which are made from different materials. For example, aluminum wiring which contacts copper wiring may oxidize at the contact points. In this case a non-conductive layer may build up over time between the contact points and arcing may result.  
           [0020]    In view of the potential for arc faults in vehicles, it would be desirable to provide vehicles with arc fault detection.  
         SUMMARY OF THE INVENTION  
         [0021]    The present invention provides a motorized machine which generates vibration during operation. The machine includes a motor configured to generate mechanical energy, a source of electrical energy, at least one electrical load having a function, an electrical distribution system configured to couple the electrical load to the source of electrical energy, and a circuit protection system coupled to the electrical distribution system. The circuit protection system is configured to interrupt application of electrical energy from the source of electrical energy or to indicate an arc event in response to an arc signal. An electrical arc detection circuit is coupled to the circuit protection system and is configured to monitor the electrical energy and generate the arc signal when the electrical energy generates a signal representative of an electrical arc.  
           [0022]    Another embodiment of the invention provides a method for detecting an arcing fault in a motorized machine that generates vibration, with the motorized machine having an electrical distribution system including a circuit protection system, a source of electric energy, and at least one electrical load having a function. The method of arc detection comprises the steps of monitoring the electrical distribution system with a superheterodyne circuit, generating an oscillator frequency which cycles between a low frequency and a high frequency. The oscillator circuit is coupled to the superheterodyne circuit. Eliminating background and spurious noise with a comparator circuit coupled to the superheterodyne circuit in a reference voltage terminal. Monitoring time of the arcing fault based on a signal from the comparator circuit with an arc timing monitor circuit. Compensating for arcing drop-outs based on signal from the arc timing monitor circuit with a compensating circuit. Generating a further signal indicative of the arc fault if the predetermined time period if exceeded with an accumulating circuit based on the signal from the compensating circuit and, generating an arc signal to operate the circuit protection system, with the trip signal generation circuit based on further signal from the accumulating circuit. Another embodiment of the method of arc detection includes the step of activating one of a circuit interrupter and an indicator. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0023]    [0023]FIG. 1 is a block diagram representation of a vehicle including an embodiment of an arc detection circuit.  
         [0024]    [0024]FIG. 2 is a detailed circuit diagram of an exemplary embodiment of an arc detection circuit.  
         [0025]    [0025]FIG. 3 is a detailed circuit diagram of a simulated arc generation circuit.  
         [0026]    [0026]FIG. 4 is a detailed circuit diagram of an exemplary embodiment of a DC arc detection circuit. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0027]    [0027]FIG. 1 is a block diagram representation of a vehicle or a machine  10  whether land, air or sea based. Vehicle  10  includes a D.C. energy storage power source  12  (e.g., a battery), an A.C. or D.C. power source  14  (e.g. a generator or alternator driven by engine  16 , a fuel cell, or a photovoltaic device such as a solar cell array), a motor engine  16 , engine controls  18 , heating, ventilating and air conditioning system  20  (HVAC), lighting  22 , traction and braking system controls  24 , a braking system  26 , an application function control A  28 , and an application specific function control B  30 . If the vehicle is a land based vehicle such as an automobile, truck or off-road machine equipment (e.g. tractor, excavator, tracked vehicle or construction equipment), the vehicle could also include electronic transmission controls  32 , a transmission  34 , and typically at least one driven wheel  36  and may include an implement  37 . The implement  37  can be, for example, a spindle coupled to the motor  16  for spinning a material against a tool for shaping the material, or a movable arm coupled to the motor  16  to move materials in a predetermined manner such as a crane or a backhoe.  
         [0028]    In general, in land based vehicle  10 , motor engine  16  is mechanically coupled to transmission  34  which is mechanically coupled to at least one drive wheel  36 . In operation the mechanical energy from engine  16  is transmitted through transmission  34  which controls the direction and speed of wheel  36  relative to engine speed  16 . In most modern vehicles such as automobiles, engine  16  is controlled by electronic engine controls  18 . Such controls  18  typically control electronic fuel injection, electronic timing and, in some cases, electronic engine valves. In most modern vehicles such as automobiles, high powered tractors and off-road equipment, electronic transmission controls  32  control the shifting of transmission  34  based upon parameters such as engine speed signals from electronic engine control  18 , and signals from the electronic braking and traction control systems  24 .  
         [0029]    The HVAC system  20  typically includes temperature controls and air movement fans. Lighting system  22  typically includes the vehicle lighting and the appropriate lighting controls which vary substantially from vehicle to vehicle. More specifically, in addition to the primary vehicle lighting provided to permit vehicle operation in the dark, many vehicles include interior lighting systems for instruments and compartment lighting.  
         [0030]    Referring to traction and braking system controls  24 , these controls are coupled to the braking system  26  and, as discussed briefly above, to transmission control  32 . Traction control systems are generally known and operate to pulse the brakes on various wheels of a vehicle to redirect power flow through the vehicle differentials to limit the application of power to a wheel spinning at a rate high relative to the other powered wheel(s) of the vehicle. The braking system control in most modern vehicles is commonly referred to as an antilock braking system and operates to relieve pressure on the brakes when the system determines that the wheel associated with a particular brake is sliding relative to the surface upon which the vehicle is traveling.  
         [0031]    [0031]FIG. 1 includes two application function controls  28  and  30 . However, depending upon on the vehicle or machine, this number may vary. One example of an application specific function control would be the electronics and control system for an onboard navigation system  38 . Another example of an application specific function control would be the control for the vehicle air bags  40 . Other examples of systems which may require applications specific function controls include power seats, power windows, heated seats, personal lighting, heated steering wheels, power sun roofs, power steering wheel tilt, power mirrors, tire inflation control, off-road vehicle slip control, electronic cruise control, etc.  
         [0032]    In vehicles and machines, including substantial numbers of the electronic controls and electrically powered accessories such as those discussed above, all of these controls require power from a power source such as D.C. power source  12  which in most vehicles and machines is a storage battery which in turn today is charged by A.C. power source  14 , that is typically an alternator and appropriate voltage regulator and rectification system. Alternatively, a D.C. generator can be used to charge the battery. As vehicle electronics and wiring systems become more complicated, a range of circuit protection  42  is provided. Many circuits in vehicles are currently protected by passive circuit protection such as fuses which are responsive to a very limited type of circuit fault. These limited types of circuit fault are short circuit and overload.  
         [0033]    One of the problems with having a limited range of circuit protection is the absence of protection for circuits when arcing is occurring within the electrical system. Such arcing can create noise within the system which can interfere with sensitive electronics and, more dangerously, can create fire within the vehicle. Accordingly, circuit protection  42  includes a circuit interrupter  48 , such as for example, controllable mechanical or semiconductor circuit interrupters and fuses for interrupting the application of D.C. power to the vehicle electronics. In particular, power source  12  is coupled to engine controls  18 , transmission control  32 , HVAC system  20 , lighting  22 , traction control and braking system controls  24 , application specific function control A  28  and application specific function control B  30  with circuit protection system  42 . In operation, circuit protection system  42  can interrupt power supplied to the various electronics via electrical distribution system  41  power conductors  18 A,  32 A,  20 A,  22 A,  24 A,  28 A and  30 A.  
         [0034]    In some applications, the circuit protection system  42  includes an indicator  49  that enunciates an arcing event in the one or more specific functions in the vehicle electronic system. Specific functions, such as electronic braking or window motors, should not have power cut-off, notwithstanding arcing. In such instances when the arc detection circuit  44  detects an arcing event, an arc signal is sent to the circuit protection system  42  which in turn activates the indicator  49 . The indicator  49  can be a visual display that may comprise a warning light, an audible signal, including a message, tone or noise or a tactile indicator such as a vibrating surface in contact with the system operator. The indicator  49  can be located within the vicinity of the operator of the vehicle  10  or machine having the arc detection circuit  44  to alert the operator to the arcing event with the operator then taking appropriate action. Thus, at the option of the arc detection system designer, the circuit protection system  42  can be configured to enunciate an arcing event, interrupt electrical power-supply or both.  
         [0035]    To protect against arcing within the vehicle electronic system an arc detection circuit  44  is provided. In particular, an arc detection circuit  44  is configured to detect signals generated within one or more conductors  18 A,  32 A,  20 A,  22 A,  24 A,  28 A or  30 A which are representative of arcing within the electrical circuits, electronics and electrical equipment associated with these circuits. In simpler systems, arc detection circuit  44  may only monitor the power conductor from source  12 . Of course, the specific monitoring scheme can be varied depending upon cost constraints, detection accuracy requirements, reliability requirements, etc.  
         [0036]    In operation, arc detection circuit  44  monitors the conductors to determine if arcing is present. If an arcing event is present, circuit  44  provides an arc signal to the circuit protection system  42  along signal conductor  46  to activate an indicator  49  to notify the system operator, or the circuit interrupter  48 , which then will trip one or more of the circuit breakers or circuit interrupters associated with the conductors to provide power from power source  12  to the respective controls and electrical equipment or both. Signal conductor  46  may include one or more signal conductors depending upon a number of conductors being monitored for arcing.  
         [0037]    Depending upon the vehicle and electronics being provided power, circuit protection system  42  may include indicators  49  and circuit interrupters  48  such as electronically controlled circuit breakers or appropriate semiconductor switches which can be controlled (opened or closed) based upon a signal from arc detection circuit  44 .  
         [0038]    Vehicle  10  was described above as a land based vehicle. However, vehicle  10  could be any other type of vehicle including an airplane, jet, boat, etc. Depending upon the type of vehicle, the engine may be a piston engine or turbine engine and may be fueled by gasoline, diesel fuel, natural gas, etc. In the case of an airplane or jet, vehicle  10  would not include a transmission  34  or transmission controls  32 . Rather, propulsion of the vehicle would be generated directly from turbine(s) or propeller(s) coupled to the engine(s)  16 .  
         [0039]    The use of vehicle electronics and electrically powered components has increased and continues to increase in vehicles. These increases in vehicle electronics has resulted in substantial rises in currents in conventional automotive powered systems which have typically a range of 12-14 volts. As a result, it is likely that battery voltages will be increased to voltages above 12 volts (e.g. range of 36 volts to 42 volts nominal). Currently, most over-the-road semi-trucks include 24 volt systems and aircraft include AC voltage systems for example nominal 24 volts AC. These increased voltages will also increase the potential for arcing due to the fact that increased voltages permit arcing to occur over larger air gaps.  
         [0040]    Notwithstanding the range of voltages mentioned, the detection techniques described herein are not voltage sensitive. The technique for AC circuits applies for all AC voltages and likewise, the technique for DC circuits applies to all DC voltages.  
         [0041]    Referring now to FIG. 2, FIG. 2 is a detailed circuit diagram of arc detection circuit  44 . In general, arc detection circuit  44  includes an oscillator  50 , a heterodyning chip  52  such as chip number SA626 manufactured by Phillips Semiconductor, a power source  54 , a level comparator circuit  56 , and arc time monitoring circuit  58 , one shot circuit  60 , a time accumulating circuit  62 , and a trip signal generation circuit  64 . Oscillator  50  is coupled to the oscillator inputs OSE-E and OSC-B of heterodyning chip  52 . In general, oscillator  50  is configured to generate an oscillator frequency which cycles between a low frequency and a high frequency. Ideally, this frequency range would be as broad as possible if it were not cost and component restrained. Some applications may permit costs which would support a range of 20.0 to 40.0 megahertz, and the circuitry shown in FIG. 2 provides an oscillator which generates oscillator frequencies which cycle from 30.0 to 35.0 megahertz wherein the oscillator cycles from the low to the high oscillator frequency in less than one millisecond.  
         [0042]    Power supply  54  is a D.C. power supply which supplies three (3) volts to circuit  52  as shown in FIG. 2. This power supply is connected to the D.C. power source  12 , but could be configured for connection to A.C. power source  14 .  
         [0043]    Circuit  52  monitors an electrical circuit (i.e. voltage or current) at the RF in  and RF out  pins. Depending upon the application these pins are coupled to the positive and/or negative conductors in the circuit. The particular configuration shown in FIG. 2 is for connection to an A.C. system with the conductors of the system being connected at RF in  and RF out  of chip  52 . Chip  52  is also coupled as shown to two 10.7 megahertz filters  80  and  82 . These filters were selected based upon the frequencies which are permitted for RF circuit use by the U.S. Government. However, depending upon future availability or uses for the circuit, these filters may be changed to filter at other center frequencies. Chip  52  is wired as shown in FIG. 2 so that chip  52  operates to subtract the frequency of the signal input at RF in  and RF out  from the frequency of oscillator  50 , and filter the difference in these frequencies at 10.7 megahertz. The result is that circuit  52  provides a variable frequency filter.  
         [0044]    An analysis of arcing in both A.C. and D.C. circuits shows that arcing generates relatively high amplitude signals across a very large range of frequencies including at least 20.0 through 40.0 megahertz. Accordingly, since oscillator  50  oscillates between 30.0 and 35.0 megahertz, chip  52  will generate a continuously high signal at the RSSI output throughout the oscillation of oscillator  50  when arcing is occurring in the system coupled to the RF input  51  of chip  52 . However, when chip  52  merely detects signals which exist at selected frequencies between 30.0 and 35.0 megahertz, chip  52  will only generate spikes or pulses at the RSSI outputs.  
         [0045]    Circuit  52  provides logarithymic amplification to the filtered difference between the oscillator  50  signal and the signal applied to RF in  and RF out .By way of example, this signal generated at RSSI is set to be within a range of 0 to 1 volts wherein that voltage is an indication of the decibel level of the input signal RF in .  
         [0046]    The signal at RSSI is applied to comparator circuit  56 . Circuit  56  includes a comparator  66  and reference voltage terminals  68 . In operation, comparator circuit  56  changes output state (e.g. goes high) only if a voltage generated by circuit  52  exceeds the predetermined voltage reference set at terminal  68 . The purpose of comparator circuit  56  is to eliminate the effects of background and spurious noise on arc detection. If the signal generated at the RSSI output is greater than the reference signal  68  the output of comparator  66  is set high (i.e. changes state from the normal state representative of no arcing to a state representative of arcing). The signal at the output of comparator  66  is applied to time monitoring circuit  58 .  
         [0047]    Time monitoring circuit  58  operates to determine if the time the output of comparator  66  is high is indicative of the time period (e.g. milliseconds or more) of a typical arcing event. If the time period is sufficient, then time monitoring circuit  58  applies a signal to one shot circuit  60  which compensates for the extinguishing of an arc when the voltage of the monitored A.C. power goes through the zero crossing. The purpose of the mono-stable multi-vibrator circuit ( 60 ) also generally known as a one-shot circuit, is to count the number of arcing half-cycles in an AC wave form.  
         [0048]    The signal from one shot circuit  60  is applied to accumulating circuit  62  which determines if there has been arcing for at least a predetermined number of half cycles (e.g. three) of the A.C. system being monitored for arcing. If arcing exists for a predetermined number of half cycles, a signal is applied by circuit  62  to trip circuit  64  which outputs a trip signal on conductor  46  to operate a circuit interrupter such as a circuit breaker or provide a signal to operate an indicator  49 .  
         [0049]    The components of the vehicle described in reference to FIG. 1 would normally require D.C. electrical power. The detection circuit of FIG. 2 is configured for an A.C. system and is readily converted into arc detection circuit for a D.C. electrical system. In particular, to convert the circuit of FIG. 2 to an arc detection circuit for a D.C. electrical system, a 1.0 k resistor  141  is inserted at the output of comparator  66 , and capacitor  150  and diode  156  of one-shot circuit  60  are removed and replaced by a direct connection between the output of comparator  146  and the negative input of comparator  164 . The three associated resistors  152 ,  154 , and  158  of one shot circuit  60  are removed as well as resistor  148 . It should be understood that “removed” as used herein may mean simply disconnecting the appropriate lead in the circuit. An exemplary embodiment of a DC circuit is illustrated in FIG. 4. The purpose of this change is to compensate the lack of zero crossings in D.C. circuits. Arcing drop outs compensated for typically have variable durations, for example 0.5 millisecond or 1.0 millisecond.  
         [0050]    To monitor the desired electrical circuit either current transformers (CT) or shunts can be used as appropriate to couple the RF inputs of chip  52  to the circuit to be monitored. Depending upon the application and type of loads on electrical circuits either a CT or shunt and the respective configuration thereof would be chosen. For example, for A.C. and D.C. applications it is desirable to eliminate fundamental A.C. or D.C. current signals. Since the frequency range of interest for the circuit shown in FIG. 2 is between 30.0 and 35.0 megahertz, the core of a CT would be a low permeability core. Such low permeability core provides relatively good immunity from noise signals in the kilohertz range.  
         [0051]    Referring to FIG. 3, FIG. 3 illustrates a test circuit  70  including a contact switch having contacts  72  and an output terminal  74  which is coupled to ground wherein the conductor  76  from transistor  78  passes through the system CT. In operation, when contacts  72  are brought into contact, circuit  70  generates a signal which simulates arcing through conductor  76  which is then monitored by the current transformer associated with the A.C. arc detection circuit of FIG. 2 or the D.C. arc detection circuit of FIG. 4 discussed above.  
         [0052]    The following is a table listing all of the components set out in FIGS. 2, 3 and  4  and their associated reference numbers, component types and values or part references as applicable.  
                                                             Component Value or       Reference No.   Component Type   Part Reference                                52   Heterodyning   SA626           Circuit       66   Comparator   LM2901       78   Transistor   2N3904       80   10.7 MH z  Filter   SFECA10.7MAS       82   10.7 MH z  Filter   SFECA10.7MAS       84   Capacitor   0.1 μF       86   Resistor   5.49 k ohms       88   Resistor   3.74 k ohms       90   Comparator   LM 2904       92   Resistor   66.5 k ohms       94   Resistor   22.1 k ohms       96   Resistor   33.2 k ohms       98   Capacitor   0.074 μF       100   Operational   LM2904           Amplifier       102   Resistor   51 k ohms       104   Diode   MV 7005       106   Capacitor   68 pF       108   Capacitor   39 pF       110   Inductor   33 nH       112   Capacitor   39 pF       114   Resistor   22.1 k ohms       116   Capacitor   39 pF       118   Capacitor   1000 pF       120   Capacitor   1000 pF       122   Capacitor   1000 pF       124   Capacitor   1000 pF       126   Capacitor   1000 pF       128   Capacitor   0.1 μF       130   Resistor   4.99 k ohms       132   Resistor   4.02 k ohms       136   Resistor   2.3 k ohms       138   Resistor   86.6 k ohms       140   Capacitor   0.033 μF       141   Resistor   1.0 k ohms       142   Resistor   11.3 k ohms       144   Resistor   33.2 k ohms       146   Operational   LM2901           Amplifier       148   Resistor   20 k ohms       150   Capacitor   .01 μF       152   Resistor   60 k ohms       154   Resistor   60 k ohms       156   Diode   1N4148       158   Resistor   60 k ohms       160   Resistor   5 k ohms       162   Resistor   20 k ohms       164   Operational   LM2901           Amplifier       166   Resistor   20 k ohms       168   Transistor   2N3904       170   Resistor   42 k ohms       172   Resistor   9 k ohms       174   Capacitor   0.1 μF       176   Resistor   150k ohms       178   Resistor   150k ohms       180   Resistor   20 k ohms       182   Transistor   2N3904       184   Resistor   10 k ohms       186   Operational   LM2901           Amplifier       188   Resistor   20 k ohms       190   Capacitor   0.01 μF       192   Resistor   10 k ohms       194   Transistor   2N3904       196   Resistor   8 k ohms       198   Resistor   10 k ohms       200   Capacitor   0.01 μF       202   SCR   EC103D       204   Capacitor   0.1 μF       206   Voltage Regulator   LM317       208   Resistor   20 k ohms       210   Resistor   150 k ohms       212   Resistor   48 k ohms       214   Resistor   10 k ohms       216   Transistor   2N3904       218   Resistor   1 k ohms       219   Capacitor   0.1 μF       220   Capacitor   0.01 μF       222   Transistor   2N3904       224   Transistor   2N3904       226   Resistor   68 k ohms       228   Resistor   510 k ohms       230   Capacitor   1.2 nF       232   Transistor   2N3904                  
 
         [0053]    While two embodiments and multiple applications for the arc detection system have been disclosed and described in detail, various other modifications could be considered within the scope of the invention. For example, it is contemplated that the A.C. or D.C. arc detection would be usable in vibrating equipment such as machine tools, robots, and other manufacturing equipment. By way of another example, the center filter frequency of 10.7 megahertz may be modified depending upon frequencies made available by the Government in the future and the particular application for the arc detection. Furthermore, depending upon component availability and cost the frequency range and cycling frequency of oscillator circuit  50  may be modified to suit particular applications, cost constraints and component availability. Still furthermore, it is contemplated that all or a portion of the circuitry disclosed may be embodied on a single chip, and further modifications may include multiple channels of arc detection. These modifications and other applications are intended to be covered in the scope of the appended claims.