Patent Publication Number: US-2021166903-A1

Title: Elctrical contactor

Description:
RELATED APPLICATIONS 
     This is application is a continuation of U.S. application Ser. No. 16/157,667 filed Oct. 11, 2018, which in turn claims the benefit of priority of U.S. Provisional Application No. 62/573,286, filed on Oct. 17, 2017, the entire contents of which application(s) are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to electrical contactors, and more particularly, but not exclusively, to electrical contactors having improved noise performance. 
     BACKGROUND OF THE INVENTION 
     Traditional contactor design is composed of three main parts: control circuitry, main contacts, and the mechanical housing. Typically the control circuitry is designed to avoid creating and/or inducing “noise” or other unwanted disturbances on the main contacts which may occur due to the windings of the electro-magnet that move the main contacts. The contactor may for instance may include a plunger that is electrically isolated from a contact bridging bar. (Gigavac, Model/PN: HX21CCC.) The ferrous parts (i.e., housing) of the contactor are typically not isolated from the main contacts. While ferrous parts are not isolated, they are also not intentionally connected. This allows ferrous parts to float at some voltage that may or may not be the same as the main contacts. Typically this is not a problem; however, if the main contact voltage fluctuates, it can change by enough (while the housing does not change with it) that at a certain point the potential between the two will be great enough for a spark (capacitive discharge) to jump and cause the housing voltage to jump to a voltage closer to that of the main contacts. This in turn can induce an unwanted voltage in the control circuit. Accordingly, there is a need in the art for contactors which avoid such problems. 
     SUMMARY OF THE INVENTION 
     In one of its aspects, the present invention may provide an improved electrical contactor in which the control circuit is isolated from the main contacts/circuit and in which a ferrous housing and other related ferrous parts are shielded from one another. Such an arrangement may also help to keep the main circuit from interfering with the control circuit. In such a situation, the contactor housing may also be grounded. In another of its aspects the present invention may provide an electrical contactor in which the main contacts are absolutely isolated from the housing to keep the housing from changing voltage drastically and unpredictably with undesirable effects on the control circuit. Alternatively, a main contact bridging bar may be electrically connected to the housing. In yet a further of its aspects, the present invention may provide an electrical contactor in which the housing is electrically connected to one of the poles of the main contacts to ensure that the housing voltage is held at the voltage of the main contacts and does not change unpredictably. In so doing, the typical double break main contacts will only break on a single contact so it may be preferred that the connection between the selected contact pole and housing be made through a high resistance to regain the full functionality of the two breaking contacts. 
     In view of the above, in one of its aspects the present invention may provide an electrical contactor, comprising a housing and a pair of electrical contacts mounted thereto, each contact having an end extending into the housing. The contactor may include a contact bridging bar movably positioned relative to the pair of electrical contacts such that the contact bridging bar contacts and electrically connects the pair of electrical contacts in a first position of the contact bridging bar. The contact bridging bar may be disposed out of contact with the pair of electrical contacts in a second position of the contact bridging bar. A plunger may be attached to the bridging bar, and coil windings may be disposed about the plunger. The coil windings may be configured to generate a magnetic field operable to move the plunger between first and second positions corresponding to the first and second positions of the contact bridging bar. In addition, either i) the plunger and contact bridging bar may be electrically isolated from one another and the housing connected to ground or ii) the plunger or a selected one of the pair of electrical contacts may electrically communicate with the housing. The housing may include a lower compartment in which the coil windings are disposed, and the lower compartment may include a ferrous wall disposed between the coils and the pair of electrical contacts. The ferrous wall may have an aperture with the plunger disposed therein. A conductive spring or a flexible conductive member may be connected to the plunger and the housing to provide electrical communication therebetween. The plunger or a selected one of the pair of electrical contacts may electrically communicate with the housing which is connected to ground. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing summary and the following detailed description of exemplary embodiments of the present invention may be further understood when read in conjunction with the appended drawings, in which: 
         FIG. 1  schematically illustrates an exemplary configuration of an electrical contactor in accordance with the present invention having a contact bridging bar electrically isolated from a plunger with the housing grounded; 
         FIG. 2  schematically illustrates a further exemplary configuration of an electrical contactor in accordance with the present invention having a plunger electrically connected to the housing; and 
         FIG. 3  schematically illustrates yet a further exemplary configuration of an electrical contactor in accordance with the present invention having a main contact electrically connected to the housing. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the figures, wherein like elements are numbered alike throughout,  FIG. 1  schematically illustrates an exemplary configuration of an electrical contactor  100  in accordance with the present invention. The contactor  100  may include a ferrous housing  110  having a lower compartment  116  defined by a ferrous wall  112  having an aperture  114  disposed therein. Coil windings  120  may be provided in the lower compartment  116  with a plunger  130  disposed between the coil windings and located within the aperture  114 . The plunger  130  may be attached to a main contact bridging bar  150  via an electrically isolative material  135 . The contactor  100  may also include a pair of main contacts  140 . The plunger  130  may be configured to respond to a magnetic field created by the coil windings  120  to allow the plunger  130  to move between a first position and a second position within the housing  110 . In particular, at a first position of the plunger  130 , the main contact bridging bar  150  may be disposed in contact with the main contacts  140  to electrically connect the main contacts to one another. In a second position of the plunger  130 , the main contact bridging bar  150  may be disposed out of contact with the main contacts  140  so the main contacts  140  are not in electrical communication with one another. The housing  110  may be grounded  180  to help ensure that the housing  110  stays at a constant voltage. By maintaining the housing  110  at a constant voltage and electrically isolating the main contact bridging bar  150  from the plunger  130 , and thus the coil windings  120 , extraneous electrical signals may be prevented from reaching the main contacts  140 . 
     In a further exemplary configuration, the present invention may provide an electrical contactor  200  similar to that of the contactor  100  of  FIG. 1 , but having a conductive member  280  providing electrical communication between the plunger  130  and housing  110 ,  FIG. 2 . In such a configuration, it is not necessary to ground the housing  110  or to electrically isolate the main contact bridging bar  150  from the plunger  130 . By electrically connecting the plunger  130  and housing  110 , a voltage potential will not develop between the housing  110  in the plunger  130 , and thus will not develop between the housing  110  and main contacts  140 . Since the plunger  130  is movable, the conductive member  280  may be flexible and may include a spring, for example. 
     In a still further exemplary configuration, the present invention may provide an electrical contactor  300  also similar to that of the contactor  100  of  FIG. 1 , but having a conductive link  380  electrically connecting the main contacts  100  with the housing  110 , possibly through a resistor so that the housing  110  stays at the same potential as the main contact  140  to which is connected. When the main contacts  140  are electrically connected to one another via the main contact bridging bar  150 , both main contacts  140  will be at the same potential as the housing  110 . The plunger  130  and main contact bridging bar  150  may be electrically isolated via the isolative material  135 . 
     These and other advantages of the present invention will be apparent to those skilled in the art from the foregoing specification. Accordingly, it will be recognized by those skilled in the art that changes or modifications may be made to the above-described embodiments without departing from the broad inventive concepts of the invention. It should therefore be understood that this invention is not limited to the particular embodiments described herein, but is intended to include all changes and modifications that are within the scope and spirit of the invention as set forth in the claims.