Leakage current detection and interruption circuit

Abstract

A circuit is disclosed for disconnecting a power source upon the detection of a leakage. The circuit comprises a disconnect switch for disconnecting the power source. A primary circuit controls the disconnect switch. A secondary circuit senses a leakage current. An optical switch interconnects the primary circuit and the secondary circuit for opening the disconnect switch upon the secondary circuit sensing a leakage current. The circuit is suitable for use as a leakage current detection and interruption circuit for completely electrically disconnecting and isolating the power source and the primary circuit from the secondary circuit.

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       49 . A power plug comprising: 
 a body;    neutral and phase conductor prongs partially disposed within the body and extending therefrom;    output neutral and phase wires;    a reset button partially exposed from the body;    a reset shaft disposed within the body and coupled to the reset button;    a changeover mechanism disposed within the body for making or breaking electrical connections between the neutral and phase conductor prongs and the output neutral and phase wires, respectively, the changeover mechanism including a disconnect mechanism, a pair of moveable members electrically connected respectively to the output neutral and phase wires and moveable by the disconnect mechanism, and a coil having a core coupled to the disconnect mechanism; and    a circuit board disposed within the body and having a leakage current and short circuit detection circuit, the leakage current and short circuit detection circuit being connected to the coil to energize the coil in response to detecting a leakage current or a short circuit on an output side of the plug;    wherein the disconnect mechanism has a first position in which the pair of moveable members are electrically disconnected respectively from the neutral and phase conductor prongs, and a second position in which the pair of moveable members are electrically connected respectively to the neutral and phase conductor prongs, and wherein the reset shaft and the core cooperate with the disconnect mechanism to move it from the first position to the second position when the reset button is pressed and to move it from the second position to the first position when the coil is energized.    
   
   
       50 . The power plug of  claim 49 , wherein the neutral and phase conductor prongs each includes a stationary contact terminal, 
 wherein the two moveable members are contact levers and each include a moveable contact terminal corresponding to the respective stationary contact terminal,    wherein the disconnect mechanism includes a slidable lock member coupled to the core and capable of being engaged with or released from the reset shaft, and two side arms each disposed adjacent one of the moveable contact levers to move the moveable contact levers, and    wherein when the reset button is pressed, the disconnect mechanism is engaged with the reset shaft and locked in the second position so that the moveable terminals contact the stationary terminals, and when the coil is energized, the disconnect mechanism is released from the engagement with the reset shaft so that the moveable terminals are separated from the stationary terminals.    
   
   
       51 . The power plug of  claim 49 , further comprising a shield line of the output neutral and phase wires, the shield line being connected to the leakage current and short circuit detection circuit, wherein the leakage current and short circuit detection circuit includes a photo coupler IC and a silicon-controlled rectifier (SCR), an input of the photo coupler IC being connected to the shield line and an output of the photo coupler IC being connected to a gate of the SCR, the SCR supplying a current to the coil when the SCR is conductive.  
   
   
       52 . The power plug of  claim 51 , further comprising a test button partially exposed from the body, 
 wherein the leakage current and short circuit detection circuit further includes a test switch operable by the test button, the test switch being connected to the input of the photo coupler IC.    
   
   
       53 . The power plug of  claim 49 , further comprising a ground conductor prong extending from the body for electrically connecting to the ground.  
   
   
       54 . A power plug comprising: 
 neutral and phase conductor prongs;    output neutral and phase wires;    a changeover mechanism for making or breaking electrical connections between the neutral and phase conductor prongs and the output neutral and phase wires;    a shield line disposed around the output neutral and phase wires; and    a leakage current and short circuit detection circuit electrically connected to the shield line and the changeover mechanism for generating a signal to cause the changeover mechanism to break the electrical connections between the neutral and phase conductor prongs and the output neutral and phase wires in response to detecting a leakage current or a short circuit condition on the shield line,    wherein the leakage current and short circuit detection circuit includes a photo coupler IC and a silicon-controlled rectifier (SCR), an input of the photo coupler IC being connected to the shield line and an output of the photo coupler IC being connected to a gate of the SCR, the SCR supplying a current to the changeover mechanism when the SCR is conductive.    
   
   
       55 . An electric plug comprising: 
 a housing;    first and second electrical lugs partially supported within the housing and extending therefrom;    first and second wires;    a reset button partially extending from the housing;    a return spring disposed within the housing and coupled to the reset button;    a disconnect switch disposed within the housing for making or breaking electrical connections between the first and second electrical lugs and the first and second wires, respectively, the disconnect switch including a latch bar, first and second switches electrically connected respectively to the first and second wires and moveable by the latch bar, and a coil having a plunger which activates the latch bar; and    a circuit disposed within the housing and having a leakage current and short circuit detection circuit, comprising a primary circuit and a secondary circuit, the leakage current and short circuit detection circuit being connected to the coil to energize the coil in response to detecting a leakage current or a short circuit on an output side of the plug; wherein the latch bar has a first position in which the first and second switches are electrically disconnected respectively from the first and second electrical lugs, and a second position in which the pair of moveable members are electrically connected respectively to the first and second electrical lugs, and wherein the return spring and the plunger cooperate with the latch bar to move it from the first position to the second position when the reset button is pressed and to move it from the second position to the first position when the coil is energized.    
   
   
       56 . The electric plug of  claim 55 , wherein the first and second electrical lugs each includes a terminal, 
 wherein the first and second switches are resilient metallic conductors and each includes a resilient contact terminal corresponding to the respective terminal, wherein the latch bar includes a latch shoulder activated by the plunger and capable of being engaged with or released by the return spring, and the latch shoulder engages a shoulder of a switch operator to move the resilient metallic conductors, and    wherein when the reset button is pressed, the latch bar is engaged against the urging of the return spring and the latch shoulder is engaged with the shoulder of the switch operator so that the resilient contact terminals electrically couple to the terminals, and when the coil is energized, the latch bar is released from the engagement with the shoulder so that the resilient contact terminals are separated from the stationary terminals.    
   
   
       57 . The electric plug of  claim 55 , further comprising a shield of first and second wires, the shield being connected to the leakage current and short circuit detection circuit, wherein the leakage current and short circuit detection circuit further comprises a photo an optocoupler and a silicon-controlled rectifier (SCR), an input of the optocoupler being connected to the shield and an output of the optocoupler being connected to a gate of the SCR, the SCR supplying a current to the coil when the SCR is conductive.  
   
   
       58 . The electric plug of  claim 57 , further comprising a test button partially exposed from the housing, wherein the leakage current and short circuit detection circuit further includes a switch operable by the test button, the switch being coupled to the input of the optocoupler.  
   
   
       59 . The power plug of  claim 55 , further comprising a grounding lug extending from the housing for electrically connecting to the ground.  
   
   
       60 . An electric plug comprising: 
 first and second electrical lugs;    first and second wires;    a disconnect switch for making or breaking electrical connections between the first and second electrical lugs and the first and second wires;    a shield disposed around the first and second wires; and    a leakage current and short circuit detection circuit, comprising a primary circuit and a secondary circuit, the leakage current and short circuit detection circuit being electrically connected to the shield and the disconnect switch for generating a signal to cause the disconnect switch to break the electrical connections between the first and second electrical lugs and the first and second wires in response to sensing a leakage current or a short circuit condition on the shield,    wherein the leakage current and short circuit detection circuit further includes an optocoupler and a silicon-controlled rectifier (SCR), an input of the optocoupler being coupled to the shield and an output of the optocoupler being coupled to a gate of the SCR, the SCR supplying a current to the disconnect switch when the SCR is conductive.    
   
   
       61 . A power plug comprising: 
 a body;    neutral and phase conductor prongs partially disposed within the body and extending therefrom;    output neutral and phase wires;    a reset button partially exposed from the body;    a reset shaft disposed within the body and coupled to the reset button;    a changeover mechanism disposed within the body for making or breaking electrical connections between the neutral and phase conductor prongs and the output neutral and phase wires, respectively, the changeover mechanism including a disconnect mechanism, a pair of moveable members electrically connected respectively to the output neutral and phase wires and moveable by the disconnect mechanism, and a coil having a core coupled to the disconnect mechanism;    a circuit board disposed within the body and having a leakage current and short circuit detection circuit, the leakage current and short circuit detection circuit being connected to the coil to energize the coil in response to detecting a leakage current or a short circuit on an output side of the plug;    wherein the disconnect mechanism has a first position in which the pair of moveable members are electrically disconnected respectively from the neutral and phase conductor prongs, and a second position in which the pair of moveable members are electrically connected respectively to the neutral and phase conductor prongs, and wherein the reset shaft and the core cooperate with the disconnect mechanism to move it from the first position to the second position when the reset button is pressed and to move it from the second position to the first position when the coil is energized; and    a shield line of the output neutral and phase wires, the shield line being connected to the leakage current and short circuit detection circuit,    wherein the leakage current and short circuit detection circuit includes a photo coupler IC and a silicon-controlled rectifier (SCR), an input of the photo coupler IC being electrically connected to the shield line and an output of the photo coupler IC being electrically connected to a gate of the SCR, the SCR supplying a current to the coil when the SCR is conductive.    
   
   
       62 . The power plug of  claim 61 , wherein the neutral and phase conductor prongs each includes a stationary contact terminal, 
 wherein the two moveable members are contact levers and each include a moveable contact terminal corresponding to the respective stationary contact terminal,    wherein the disconnect mechanism includes a slidable lock member coupled to the core and capable of being engaged with or released from the reset shaft, and two side arms each disposed adjacent one of the moveable contact levers to move the moveable contact levers, and    wherein when the reset button is pressed, the disconnect mechanism is engaged with the reset shaft and locked in the second position so that the moveable terminals contact the stationary terminals, and when the coil is energized, the disconnect mechanism is released from the engagement with the reset shaft so that the moveable terminals are separated from the stationary terminals.    
   
   
       63 . The power plug of  claim 61 , further comprising a test button partially exposed from the body, 
 wherein the leakage current and short circuit detection circuit further includes a test switch operable by the test button, the test switch being connected to the input of the photo coupler IC.    
   
   
       64 . The power plug of  claim 61 , further comprising a ground conductor prong extending from the body for electrically connecting to the ground.  
   
   
       65 . A power plug comprising: neutral and phase conductor prongs; output neutral and phase wires; 
 a changeover mechanism for making or breaking electrical connections between the neutral and phase conductor prongs and the output neutral and phase wires;    a shield line disposed around the output neutral and phase wires; and    a leakage current and short circuit detection circuit electrically connected to the shield line and the changeover mechanism for generating a signal to cause the changeover mechanism to break the electrical connections between the neutral and phase conductor prongs and the output neutral and phase wires in response to detecting a leakage current or a short circuit condition on the shield line,    wherein the leakage current and short circuit detection circuit includes a photo coupler IC and a silicon-controlled rectifier (SCR), an input of the photo coupler IC being electrically connected to the shield line and an output of the photo coupler IC being electrically connected to a gate of the SCR, the SCR supplying a current to the changeover mechanism when the SCR is conductive.    
   
   
       66 . The power plug of  claim 61 , wherein the gate of the SCR is electrically de-coupled from the shield line.  
   
   
       67 . The power plug of  claim 65 , wherein the gate of the SCR is electrically de-coupled from the shield line.  
   
   
       68 . A power supply device comprising: 
 input neutral and phase conductors;    output neutral and phase conductors;    a changeover mechanism for making or breaking electrical connections between the input neutral and phase conductors and the output neutral and phase conductors; a sensing lead for sensing an abnormal condition; and    a leakage current and short circuit detection circuit electrically connected to the sensing lead and the changeover mechanism for generating a signal to cause the changeover mechanism to break the electrical connections between the input neutral and phase conductors and the output neutral and phase conductors in response to detecting an abnormal condition on the sensing lead,    wherein the leakage current and short circuit detection circuit includes a photo coupler IC and a silicon-controlled rectifier (SCR), an input of the photo coupler IC being electrically connected to the sensing lead and an output of the photo coupler IC being electrically connected to a gate of the SCR, the SCR supplying a current to the changeover mechanism when the SCR is conductive.