Abstract:
A blown fuse detector according to an exemplary aspect of the present disclosure includes, among other things a fuse and a resistor in series with a circuit breaker. The circuit breaker and the resistor are in parallel with the fuse and the circuit breaker is configured to trip when the fuse blows.

Description:
BACKGROUND 
       [0001]    Generally, this disclosure relates to the field of electrical fuses. More particularly, this disclosure relates to a method and apparatus for detecting a blown fuse in an electrical system. 
         [0002]    Various types of equipment include complicated electrical systems that incorporate fuses to protect the power source, the system load, or the system wiring from an overload or a short circuit. In the case of an overload or a short circuit to the electrical system, the fuse will fail or blow and interrupt the flow of current in the system to prevent damage to the power source, the system load, or the system wiring. Determining the status of these fuses is often difficult, especially during the maintenance and operation of the piece of equipment. 
       SUMMARY 
       [0003]    A blown fuse detector according to an exemplary aspect of the present disclosure includes, among other things, a fuse and a resistor in series with a circuit breaker. The circuit breaker and the resistor are in parallel with the fuse and the circuit breaker is configured to trip when the fuse blows. 
         [0004]    A blown fuse detector assembly according to an exemplary aspect of the present disclosure includes, among other things, a power panel and at least one detection circuit in the power panel. The detection circuit includes a fuse and a resistor in series with a circuit breaker. The circuit breaker and the resistor are in parallel with the fuse and the circuit breaker is configured to trip when the fuse blows. The circuit breaker may contain an isolated auxiliary contact that indicates the state of the circuit breaker. 
         [0005]    A method of assembling a blown fuse detector according to an exemplary aspect of the present disclosure includes, among other things, positioning a circuit breaker in series with a resistor and positioning a fuse in parallel with the circuit breaker and the resistor. 
         [0006]    These and other features of the disclosed examples can be understood from the following description and the accompanying drawings, which can be briefly described as follows. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  schematically illustrates an example power system. 
           [0008]      FIG. 2  schematically illustrates an example blown fuse detection circuit in the example power system of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0009]      FIG. 1  schematically illustrates an example power system  10  including a power source  12 , a power panel  14 , and a load  16 . In this example, power source  12  includes a source bus bar and the load  16  includes a resistive component, such as an aircraft component or system wiring that receives power from the power source  12 . The example power panel  14  includes circuit breakers  18  arranged in rows and columns that communicate with a circuit breaker position sensor  20  via an electrical connection  22 . The circuit breakers  18  each move between an active position and a tripped position (i.e., an off position) in response to a load current. Each circuit breaker  18  includes an isolated auxiliary contact  19  that indicates the position of the circuit breaker  18  (shown in  FIG. 2 ). The circuit breaker position sensor  20  determines if the circuit breaker  18  is in an active position or a tripped position by monitoring the isolated auxiliary contact  19  and relays the circuit breaker position information to a remote location  30 , such as an aircraft cockpit, a maintenance facility, or a mobile device. The circuit breaker position sensor  20  may communicate with the remote location  30  via a wireless connection or a hard wired connection, such as an airplane data bus. 
         [0010]    In some cases, fuses are used in place of circuit breakers for protection. Some fuses do not have a means to remotely indicate fuse failure. Each circuit breaker  18  forms a portion of a detection circuit  24  as illustrated in  FIG. 2 . The detection circuit  24  includes a power source  12  and the circuit breaker  18  connected in series with a resistor  26 , and a fuse  28  connected in parallel with the circuit breaker  18  and the resistor  26 . Due to the finite impedance of the fuse  28 , load current is shared between the fuse  28  and the parallel resistor  26  and circuit breaker  18  in combination. The resistor  26  impedance is selected so that the series impedance of the resistor  26  and circuit breaker  18  in combination limits the circuit breaker current to an amount less than the trip limit of the circuit breaker  18  at the fuse  28  failure current. The resistor  26  is sized to prevent excessive current from flowing through the circuit breaker  18  during normal operation that would trip the circuit breaker  18 . In this example, the fuse  28  amperage rating is greater than the circuit breaker  18  amperage rating by a factor of approximately ten. In another example, the fuse  28  amperage rating is greater than the circuit breaker  18  rating by a factor of approximately one hundred. 
         [0011]    When the detection circuit  24  experiences an overload or short circuit, the resistor  26  initially forces the overload current through the fuse  28 , causing it to fail and subsequently, the overload current will flow through the circuit breaker  18 . Because the circuit breaker  18  amperage rating is much lower than the amperage rating of the fuse  28 , the circuit breaker  18  will trip when the full load current travels through the circuit breaker  18 . When the circuit breaker  18  trips, the circuit breaker position sensor  20  (shown in  FIG. 1 ) detects the tripped circuit breaker  18  and communicates the row and column location of the tripped circuit breaker  18  to the remote location  30 . Remotely communicating the tripped breaker  18  is particularly beneficial when the power panel  14  is not easily accessible and the status of the fuse  28  could determine how to operate the piece of equipment with which the power system  10  is associated. Additionally, locating the circuit breaker  18  and the resistor  26  in parallel with the fuse  28  allows for simulation of a blown fuse  28  by manually tripping the circuit breaker  18 . 
         [0012]    The preceding description is exemplary rather than limiting in nature. Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from the essence of this disclosure. The scope of legal protection given to this disclosure can only be determined by studying the following claims.