Abstract:
Electrical arc suppression when terminals under load are connected/unconnected is provided via an applied magnetic field causing the arc path to be lengthened, with the consequences that the voltage necessary for the arc to be sustained is increased and the arc energy is decreased. In a preferred form, at least one magnet with a high permeability flux return path is placed adjacent the terminal proximity zone of initial/final touching of mating terminals. The magnetic field increases the arc length, and thereby suppresses the arc by increasing the voltage necessary to sustain the arc and decreasing the energy of the arc.

Description:
TECHNICAL FIELD 
     The present invention relates to electrical connectors, and more particularly to electrical arc suppression when the electrical connectors are separated from each other under load. 
     BACKGROUND OF THE INVENTION 
     Power and signal distribution connectors mechanically and electrically connect at least two conductors at, ideally, the lowest possible power loss. Connectors are not designed to make and break an electrical circuit. Devices such as switches, relays and contactors are designed to switch current/voltage circuits. Nevertheless, during their service life, connectors can be plugged/unplugged under load many times (i.e. “hot plugged”). Very often this disconnection under load occurs when physically switching off the power in advance would be considered time-consuming and inconvenient. Also, connectors in automotive power networks are plugged and unplugged under load during diagnostic procedures, fuses are plugged at short circuit conditions, and so forth. Under some circumstances in the above situations, the connector suffers no significant damage with multiple engages/disengages. Other times, just one disconnect will damage the terminals beyond repair. In other words, under specific conditions, a long arc may be generated at engage/disengage, which may cause extensive terminal erosion. This erosion may damage the physical shape of the terminal, preventing re-engagement or proper terminal contact forces after assembly. Additionally, the electrical arc may have serious consequences for the environment or nearby personnel. 
     FIGS. 1A and 1B depict a pair of matable electrical connectors  10 , wherein the male terminal  12  thereof has just been separated from the female terminal  14  thereof, and the tips of the terminals are presently within the terminal proximity zone Z. By “terminal proximity zone” is meant a zone length over which an electrical arc is most prone to arise when the terminals are subjected to an applied voltage (that is, when under load), which length may vary depending, for example, upon circuit load and atmospheric conditions. An electrical arc  16  leaps between the closest tips  12   t ,  14   t  of the terminals  12 ,  14 , taking a most direct path therebetween. Because a most direct path is taken, the arc energy is maximal, resulting in potential for terminal erosion and for possible personnel injury. 
     Accordingly, it would be highly desirable if such arcs could be suppressed (quenched). 
     As shown at FIGS. 2A and 2B, it is well known that if a wire  20  is located between attracting magnets  22 ,  24  so as to be inside the magnetic field B, and if a current I is flowing along the wire, then a force is applied to the moving electrons by the magnets, referred to as the “Lorentz Force”. The direction of the force depends upon the direction of the magnetic field B and the direction of the current I, as shown. The resulting force F applied to the wire depends upon the magnitude of both the current I and the magnetic field B, the length of the wire exposed to the magnetic field, and the relative orientation between the wire and the magnetic field, given by: 
     
       
           F=IlB  sin θ, 
       
     
     where l is the length of wire exposed to the magnetic field B and θ is the angle between B and I, as shown by FIG.  2 . When the angle θ is ninety degrees (that is, I is perpendicular to B), sin θ equals one and the force F is a maximum. When the angle θ is zero degrees (that is, I is parallel to B) sin θ equals zero and the force F is a minimum (equal to zero). 
     It would be desirable if somehow the above discussed Lorentz Force could be adapted to suppress electrical arcing when connectors are connected/unconnected under load. 
     SUMMARY OF THE INVENTION 
     The present invention provides electrical arc suppression when terminals under load are connected/unconnected via an applied magnetic field causing the arc path to be lengthened, with the consequences that the voltage necessary for the arc to be sustained is increased and the arc energy is decreased. 
     An electrical arc may be generated between terminals (including electrodes, contacts, etc.) when both the voltage and the current exceed certain minimum values. These minimum values are determined by the electrode material (e.g. silver 12V/0.4A, and carbon 20V/0.01A). In this regard, a magnetic field electrical arc suppression assembly according to the present invention includes at least one magnet placed adjacent the location (terminal proximity zone) of initial/final touching of mating connector terminals. The magnetic field produced the at least one magnet pervades the space occupied by the air gap between the terminals (the terminal proximity zone) such that as the terminals are brought into contact or separated from contact and the circuit is live, the tendency of an electrical arc to arise and be sustained is suppressed (quenched) by the magnetic field applying a force on the moving electrons as the arc commences. This force causes the electrons to take a curved (or otherwise longer) path across the air gap rather than take a straight-line path. Because a curved path is longer than a direct (straight line) path, a higher arc voltage is required to sustain the arc and the arc energy is diminished, thus suppressing (quenching) the arc, and thus greatly reducing the energy of the arc. 
     The at least one magnet may, for example, be in the form of a single magnet or a pair of diametrically opposed, attracting magnets. The at least one magnet may be of the permanent type, or may be of the electromagnet type. A magnetic circuit is provided via a yoke, as for example composed of a ferromagnetic material, to minimize reluctance of the magnetic circuit and thereby optimize the magnetic field conditions in the air gap of the terminal proximity zone during engage/disengage of the terminals. 
     The arc suppression (quenching) effect of the magnetic field according to the present invention is not limited by choice of the location of the at least one magnet. For example, it is possible to have the at least one magnet either integral with, or unconnected with, the connector. In other words, the at least one magnet may be integrated into the structure of the connector, be attached to a stationary part of the connector (e.g., fuse box), or be connected to a movable part of the connector or another component (e.g., a wiring harness) or some combination thereof. It is important that the magnetic field in the terminal proximity zone be oriented as close as possible to perpendicular in relation to the direction of the electrical current. Also, since the arc suppression performance of the magnetic field is dependent upon the strength of the magnetic field, a stronger magnet gives a better arc suppression (quenching) performance. 
     The present invention includes all possible methods of packaging the at least one magnet, as for example by molding, spraying, assembling, etc. Further, where the electromagnet type is used, the current therefore may be from a circuit carrying current through the connectors, or may be from a circuit external to the connectors. Additionally, the aforedescribed magnetic field suppression of connector separation arcing may also be applied at component terminals used to connect relays, fuses, electronic modules, motors, resistors, capacitors, inductances, lamps, etc. 
     Accordingly, it is an object of the present invention to provide suppression of electrical arcing between separating/connecting terminals under load via an applied magnetic field in the air gap between the terminals. 
     This and additional objects, features and advantages of the present invention will become clearer from the following specification of a preferred embodiment. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1A is a side view of a prior art pair of electrical connectors, shown being separated under load. 
     FIG. 1B is a bottom plan view of the pair of prior art electrical connectors, seen along line  1 B— 1 B of FIG.  1 A. 
     FIG. 2A is a perspective view of a current carrying wire exposed to a magnetic field being subjected to a force by the magnetic field. 
     FIG. 2B is a top plan view, seen along line  2 B— 2 B of FIG.  2 A. 
     FIG. 3A is a side view of a pair of electrical connectors equipped with magnetic field electrical arc suppression according to the present invention, shown being separated under load. 
     FIG. 3B is a bottom plan view of the pair of electrical connectors, seen along line  3 B— 3 B of FIG.  3 A. 
     FIG. 4 is a graphical depiction of electrical arc energy as a function of separation speed for a pair of terminals with and without magnetic field electrical arc suppression. 
     FIG. 5 is a front end view of an electrical connector equipped with a magnetic field electrical arc suppression assembly according to the present invention. 
     FIG. 6 is a partly sectional top view of a mated pair of connectors, wherein one of the connectors is equipped with the magnetic field electrical arc suppression assembly as depicted at FIG.  5 . 
     FIG. 7 is a front end view of an electrical connector equipped with an alternative magnetic field electrical arc suppression assembly according to the present invention. 
     FIG. 8 is a partly sectional top view of a mated pair of connectors, wherein one of the connectors is equipped with the alternative magnetic field electrical arc suppression assembly as depicted at FIG.  7 . 
     FIG. 9 is a circuit diagram for the pair of connectors depicted at FIGS. 7 and 8. 
     FIG. 10 is an alternative circuit diagram, wherein the current to power the magnets is provided by the terminal current, itself. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the Drawing, FIGS. 3 through 9 depict the present invention, wherein FIGS. 3A through 4 depict the operative principles, FIGS. 5 and 6 depict a preferred embodiment of the present invention, and FIGS. 7 through 9 depict an alternative preferred embodiment of the present invention. 
     At FIGS. 3A and 3B, a pair of electrical connectors  100  are shown in the form of single terminal mating male and female connectors  102 ,  104 . The mutually closest tips  102   t ,  104   t  of the terminals  102 ,  104  are separated by an air gap G which is within the terminal proximity zone Z, the length of the zone being that which is most prone to involve electrical arcing and may vary depending, for example, upon circuit load and atmospheric conditions. An electrical arc  106  leaps between the terminals  102 ,  104 . However, because a magnet  108  provides a magnetic field B in the terminal proximity zone Z, as the electrons span the air gap G between the tips, the magnetic field subjects them to a force F which is perpendicular to their direction of movement. Accordingly, the electrons cannot take a most direct path (straight line) between the tips  102   t ,  104   t , but rather must take a curved path (see FIG.  3 B). Because a curved path is longer than a direct (straight line) path, a higher arc voltage is required to sustain the arc and the arc energy is diminished, thus suppressing (quenching) the arc  106 . 
     FIG. 4 is a graph of arc energy versus opening (separation) speed for two pairs of terminals, one pair of terminals, identified by Curve A has magnetic field electrical arc suppression, while the other pair of terminals, identified by Curve B, does not. Curve A clearly indicates electrical arc suppression as compared to Curve B, wherein the magnetic field has a value of 0.215T in the terminal proximity zone. The pair of terminals of Curve A benefits from the magnetic field lengthening the arc and therefore increasing the necessary voltage to sustain the arc. This, in turn, shortens both arc duration and arc energy which reduces erosion of the terminals of Curve A. 
     FIGS. 5 and 6 depict a preferred example of a magnetic field electrical arc suppression assembly  110  integrated into an electrical connector  112 , collectively providing an arc suppressed connector  114  . 
     FIG. 5 shows merely by way of example two male terminals  116 ,  118  located in the electrical connector  112 , which is female as defined by a shroud  120 . The shroud  120 , in turn, defines an interior space  122 . The terminal proximity zone Z (see FIG. 6) is located generally at a mid-section of the interior space  122 . The terminals  116 ,  118  are isolated by outer arc walls  124  and an inner arc wall  126 . 
     The magnetic field arc suppression assembly  110  has a counterpart at each terminal  116 ,  118 , each counterpart including a magnet  128  and a yoke  130 . The magnet  128  is of the permanent type and is located by the shroud  120  so as to laterally overlie the respective terminal across the terminal proximity zone Z. The yoke  130  is composed of a high permeability (ferromagnetic) material, as for example iron, and includes a pole piece  132  which is positioned via the shroud diametrically opposite the magnet  128 . The facing pole  134  of the magnet  128  provides a magnetic field B across an air gap G to the pole piece  132 . The yoke  130  provides a U-shaped return flux path to the opposing pole  136  of the magnet so that a majority of reluctance the magnetic circuit is located at the terminal proximity zone. 
     FIG. 6 depicts a male mating connector  140  having female terminals  142 ,  144 , shown mated with the arc suppressed connector  114  and its respective terminals  116 ,  118 . In operation, should the mating connector  140  be separated from, or joined to, the arc suppressed connector  114  and the circuit connected with the terminals have a voltage applied across the terminals, an arc would tend to form across the terminal proximity zone, except that the magnetic field will suppress (quench) the arc because the path taken by the electrons between the terminals must be curved, as opposed to straight, as detailed and explained hereinabove. 
     It will be understood that two permanent magnets could alternatively be utilized, wherein the second magnet is located where the pole piece is shown in FIG. 5 (that is, it replaces the pole piece), and wherein the yoke would be U-shaped so as to provide a return flux path between the opposing poles of each of the magnets. Further, the magnetic circuit can be designed to suit size, weight, cost and other criteria, in which, for example, a single magnet may provide a magnetic field for a number of terminal proximity zones. 
     Turning attention now to FIGS. 7 though  9 , an alternative example of a magnetic field electrical arc suppression assembly  210  integrated into an electrical connector  212 , collectively providing an arc suppressed connector  214 . 
     FIG. 7 shows merely by way of example two male terminals  216 ,  218  located in the electrical connector  212 , which is female as defined by a shroud  220 . The shroud  220 , in turn, defines an interior space  222 . The terminal proximity zone (see FIG. 8) is located generally at a mid-section of the interior space  222 . The terminals  216 ,  218  are isolated by outer arc walls  224  and an inner arc wall  226 . 
     The magnetic field arc suppression assembly  210  has a counterpart at each terminal  216 ,  218 , each counterpart including a magnet  228  and a yoke  230 . The magnet  228  is of the electromagnet type, which may advantageously include a ferromagnetic core, and is positioned via the shroud  220  so as to laterally overlie the respective terminal across the terminal proximity zone Z. The yoke  230  is composed of a high permeability (ferromagnetic) material, as for example iron, and includes a pole piece  232  which is located in the shroud diametrically opposite the magnet  228 . The facing pole  234  of the magnet  228  provides a magnetic field B across an air gap G to the pole piece  232 . The yoke  230  provides a U-shaped return flux path to the opposing pole  236  of the magnet so that a majority of reluctance the magnetic circuit is located at the terminal proximity zone. Current to energize the windings  238  of each of the magnets  228  is provided by a separate circuit  246  (see the wiring diagram of FIG.  9 ). 
     FIG. 8 depicts a male mating connector  240  having female terminals  242 ,  244 , shown mated with the arc suppressed connector  214  and its respective terminals  216 ,  218 . 
     In operation, should the mating connector  240  be separated from, or joined to, the arc suppressed connector  214  and the circuit connected with the terminals have a voltage applied across the terminals, an arc would tend to form across the terminal proximity zone, except that the magnetic field will suppress (quench) the arc because the path taken by the electrons between the terminals must be curved, as opposed to straight, as detailed and explained hereinabove. 
     The current to power the magnet  228  may alternatively be provided by the terminal circuit  248 , itself, as depicted by the wiring diagram of FIG.  10 . It is believed in this regard, that when the terminals separate, the magnetic field collapse is momentarily postponed by electrical arcing. Accordingly, the magnetic field will serve to suppress (quench) the arc before and during its collapse. On the other hand, it is believed that when the terminals approach contact, in order for an arc to be present, a current must be flowing in the windings, whereupon the magnetic field will serve to quench the arc. Of course, in either case, any electromotive force due to inductance of the windings should be considered in designing the magnets  228 . 
     It will be understood that two electromagnets could alternatively be utilized, wherein the second magnet is located where the pole piece is shown in FIG. 7 (that is, it replaces the pole piece), and wherein the yoke would be U-shaped so as to provide a return flux path between the opposing poles of each of the magnets. Further, the magnetic circuit can be designed to suit size, weight, cost and other criteria, in which, for example a single magnet may provide a magnetic field for a number of terminal proximity zones. 
     To those skilled in the art to which this invention appertains, the above described preferred embodiment may be subject to change or modification. Such change or modification can be carried out without departing from the scope of the invention, which is intended to be limited only by the scope of the appended claims.