Patent Publication Number: US-11037745-B2

Title: Contactor device for high current switching applications

Description:
CROSS REFERENCE AND PRIORITY CLAIM 
     This patent application is a U.S. National Phase of International Patent Application No. PCT/EP2017/072650, filed Sep. 8, 2017, which claims priority to European Patent Application No. 16188082.8, filed Sep. 9, 2016, the disclosure of which being incorporated herein by reference in their entireties. 
     FIELD 
     Disclosed embodiments relate to an improved contactor device for high current switching applications. More specifically, but not exclusively, the disclosed embodiments relate to a contactor device for industrial or railways applications wherein a high D.C. current must be switched on and off with high frequencies switching actions. 
     BACKGROUND 
     As it is well known in this specific technical field, contactors are remote control switches with an electromagnetic actuator. Generally speaking, a distinction is made between a control circuit for a contactor with a contactor coil and a load circuit for a contactor to be switched with the connected loads. In many cases, as soon as a sufficient starting current flows through the contactor coil, the contactor responds and turns on the loads connected in the load circuit. To maintain the contactor in this state, a holding current must flow through the contactor. After the holding current is switched off, the contactor drops out. The energy stored in the contactor coil is dissipated in a free-wheeling circuit. The contactors of this known structure normally include a fixed contact and a movable contact. Both contacts are linked to a branch of the power supply line to be connected and disconnected by bridge connectors or metal flexible connectors such as a copper braid. In particular, the movable contact is generally connected to the power supply terminal through a flexible connecting braid. 
     The relatively high operating frequency of the switching device solicits very much the flexible connecting braid that suffers for failures reducing the lifetime of the switching device. Moreover, the movable contact is subject to a relatively high excursion with respect to the fixed contact in order to provide an effective sufficient opening space when the current flow must be interrupted without raising an excessive electric arc. 
     In order to guarantee an efficient switching action the movable contact is mounted on a mechanical moving system that requires a complex structure and a delicate angular movement sufficient to create a predetermined space between the contacts. 
     The known moving mechanisms of the moving contact are generally complex, expensive and do not allow to realize a compact design of the contactor device. 
     SUMMARY 
     The technical problem underlying the disclosed embodiments is that of providing an improved contactor device for high current switching applications having structural and functional characteristics to allow improving the overall performances of the switching device while obtaining a more compact physical structure. Another aim of the disclosed embodiments is to provide a contactor device having a higher reliability and a longer lifetime. Additionally, disclosed embodiments provide a contactor device that does not require any specific maintenance action or mechanical adjustment during its working life. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  shows a schematic and perspective view of a contactor device realized according to disclosed embodiments. 
         FIG. 1A  shows a schematic and perspective view of a multipolar structure including three contactor devices of the disclosed embodiments forming a 3-poles modular combination. 
         FIG. 1B  shows a schematic and perspective view of a single pole contactor according the disclosed embodiments but including an upper extinguishing arc portion different from that shown in  FIG. 1 . 
         FIG. 2  shows a front internal view of a base portion of the contactor device of  FIG. 1 . 
         FIG. 3  shows a schematic and perspective view of an upper portion of the base portion of the contactor device of  FIG. 2 . 
         FIG. 4  shows a schematic and perspective view of a lower portion of the base portion of the contactor device of  FIG. 2 . 
         FIGS. 5 and 6  are schematic views of internal contact particulars of the contactor device of the disclosed embodiments in two different operating conditions. 
         FIGS. 7A and 7B  show schematic views of a particulars of the contactor device of the disclosed embodiments in two different operating conditions, respectively. 
         FIG. 8  shows a schematic and perspective view of the contactor device of the disclosed embodiments incorporated into a more complex power system or structure, for instance a system with two poles, pre-charge contactor and a pre-charge resistor. 
     
    
    
     DETAILED DESCRIPTION 
     The solution idea at the basis of the disclosed embodiments is that of removing the fixed contact from the contactor device while providing a couple of movable contacts driven towards and away from each other with respect to a mutual contact position. According to the above solution idea, the technical problem is solved by an improved contactor device for high current switching applications, in particular industrial or railways applications wherein a high D.C. current must be switched on and off, the contactor device including a switch base portion including electric switching mechanism of a high voltage portion and an arc extinguishing portion covering the switching mechanism, characterized by comprising a couple of moving contacts driven towards and away from each other with respect to a mutual contact and abutting position, the contacts being mounted at the respective contact ends of a toggle mechanism activated by a low voltage driving portion incorporated in the switch base portion and active on the toggle mechanism. 
     The mentioned moving contacts are symmetrical and are positioned at the respective contact end of a corresponding elongated arm of the toggle mechanism. 
     Optionally, the toggle mechanism includes a couple of rods having a corresponding end joined in a sliding hinge that may be moveable up and down along a vertical slot of a frame in the switch base portion; the rods being made by an insulating material and having respective opposite ends hingedly coupled to a corresponding end of the arms opposite to the contacts, respectively. 
     Optionally, each end of the arms opposite to the contacts are sustained by a corresponding elongated portion of an element made by the same insulating material of the rods and linked, optionally hingedly linked, to a respective of the opposite ends. 
     Furthermore, optionally, the elongated arm is pivotally supported in a frame of the switch base portion by a corresponding pivot electrically connected to fixed terminal power contacts projecting outside the switch base portion. 
     Optionally, each of the arms is supported by the corresponding pivot extended transversally at the end of a fork like arm each linked to one corresponding of the fixed terminal power contacts. 
     It should be further noted that the sliding hinge is optionally contacted by an active end of the low voltage driving portion. 
     Optionally, the low voltage driving portion includes a coil active on a stem having a free distal end linked to one end of a lever which is pivotally mounted on a fulcrum fixed or integral with an internal frame of the switch base portion; the lever having a second arm with a free end active on the toggle mechanism to activate the switching of the moving contacts. 
     Optionally, an element is interposed between each arm and the corresponding supporting fork like arm for compensating possible degradation or usury of the contacts. 
     Moreover, optionally, an arc runner is provided over each of the moving contacts and each of the arc runner is electrically connected to a respective dissipation coil provided at the shoulder of each contact end of each of the arm. 
     Optionally, a couple of lateral metal flanges are laterally associated to each moving contact; each metal flange having a projecting flag toward the corresponding arc runner. 
     Optionally, a polar metal plate expansion is provided on both sides of the moving contacts. 
     Finally, it must be noted that the disclosed embodiments may be implemented in a power electric system including at least a contactor device as disclosed in the following description. 
     Further features and advantages of the contactor device of the disclosed embodiments will appear from the following description given by way of non limiting example with reference to the enclosed drawings. 
     With reference to the drawings, reference numeral  1  denotes a globally and schematically shown contactor realized according to the disclosed embodiments. The contactor  1  is specifically provided for industrial or railways applications wherein a high D.C. current must be switched on and off for high frequencies switching actions. 
     Just to give an idea of the working conditions and the range of current values involved for these kind of contactors, it should be noted that these devices must be able to efficiently switch currents at least in the range between 400 A to 1800 A and under operating voltage ranges between 1000 V and 4000 V. 
     Those operating ranges may even be referred to a single pole of the contactor. In many applications it is, however, necessary to provide a double pole configuration and/or a three poles configuration. 
     In this respect, the contactor  1  of the disclosed embodiments has a modular structure concerning a single pole configuration that may be doubled or provided in a three poles configuration including three parallel modules according to the user&#39;s needs, for instance as shown in  FIG. 1A . 
     In the following lines we will disclose just the structure of a single pole module. The module presents an envelope or housing  10  including all the moving portions of the contactor device  1  that will be disclosed hereinafter. The envelope  10  is made by a synthetic plastic material having a predetermined isolation coefficient. Such an envelope  10  has a base flange  13  and includes an internal frame  20  supporting the various moving components of the contactor  1 . 
     It should be noted that fixed terminal power contacts  11  and  12  are provided for the contactor  1 . Those fixed contacts  11 ,  12  project on opposite lateral sides of the envelope  10 . Those terminal power contacts  11 ,  12  are each associated to a corresponding internal moving contact  21 ,  22  provided inside the contactor device  1 , as will be explained hereinafter. 
     The contactor  1  of the disclosed embodiments is structured to be used on electrical equipment working in presence of severe shocks and vibrations that normally occur on-board of traction vehicles. 
     However, nothing refrains from employing this kind of contactors  1  in all the applications wherein a high D.C. current must be switched on and off, for instance: line contactors, power switches or converters, traction motors, electromagnetic brakes and heating/air conditioning systems. 
     The contactor  1  comprises a switch base portion  2  and an upper arc extinguishing portion  3 . 
     The switch base portion  2  is common for each different modular contactor  1  and corresponds to the envelope  10  while the upper arc extinguishing portion  3  may be considered a top coverage of the envelope  10  that may have a different size according to the different power category and voltage ranges that the contactor shall provide. The switch base portion  2  includes electrical switching mechanism and the arc extinguishing portion  3  is provided to cover and/or protect the electrical switching mechanism. 
     Therefore, the upper arc extinguishing portion  3  may be structurally different according to the different voltage ranges that must be treated and the corresponding arc chute type and energy capacity that shall be extinguished in total security. 
     For instance, an arc extinguishing portion  3  for a voltage value of 1000 V may have the structure shown in  FIG. 1  while an arc extinguishing portion  3 ′ for a voltage value of 3000 V may require a greater or thicker portion  3 ′ including several discharge mechanism or larger polar expansions as shown for instance in the embodiment of contactor  1 ′ of  FIG. 1B . 
     The common switch base portion  2  is the core of the contactor  1  or V according to the disclosed embodiments. 
     The internal schematic structure of this switch base portion  2  including the electrical switching mechanism of the disclosed embodiments is shown in  FIG. 2 . The switch portion  2  may be considered separated in a lower low voltage portion  4  and a higher high voltage portion  5 . The low voltage portion  4  is provided for driving the switching of the upper high voltage portion  5 . 
     The contactor  1  of the disclosed embodiments may be considered a monostable element that may be provided with normally closed contacts or normally open contacts according to the user&#39;s needs. 
     In this respect, according to the disclosed embodiments, the switching portion  2  includes a couple of moving electric contacts  21  and  22  which shall be put in abutment one against the other for allowing the passage or flow of the high DC current. Advantageously, the electrical contacts  21 ,  22  are symmetrically moving towards and away from each other. 
     It must be noted that the contactor  1 ,  1 ′ of the disclosed embodiments, contrary to the known solutions, has no fixed contacts but a couple of reciprocally symmetrically moving contacts driven towards and away from each other with respect to a mutual contact and abutting position. 
     Each moving contact  21  or  22  is positioned at the contact end  23  or  24  of a corresponding elongated arm  25 ,  26  of a toggle mechanism  30 , as shown in  FIGS. 2 and 3  and disclosed hereinafter. The arms  25 ,  26  are manufactured by a conductive material, for instance a metal. 
     Over the contacts  21 ,  22 , but still in the switch base portion  2 , respective arc runners  53 ,  54  are provided. 
     Those arc runners  53 ,  54  help dissipating the electric arc formed during the opening phase of the moving contacts  21 ,  22 . More particularly, each of the arc runner is electrically connected to a respective dissipation coil  51 ,  52  provided at the shoulder of each contact end  23 ,  24  of each arm  25 ,  26 . To each moving contact  21  or  22  it is associated a couple of lateral metal flanges  55 ,  56  having a projecting flag toward the corresponding arc runner  53  or  54 . 
     Moreover, a polar expansion  50 , that is to say a metal plate or flange, is provided on both sides of the moving contacts  2 ,  22 . 
       FIG. 3  shows just one of these metal plates  50  but it should be considered also the presence of a corresponding plate situated in a parallel position on the other side of the contacts  21 ,  22 . 
     The toggle mechanism  30  includes a couple of rods  31  and  32  that have a corresponding end joined in a sliding hinge  33  that may be moveable up and down along a vertical slot  27  of the frame  20 , as shown in  FIGS. 7A and 7B . The rods  31  and  32  are made by an insulating material, for instance a thermosetting material. 
     The opposite ends  44 ,  45  of each of the rods  31 ,  32  are linked, optionally hingedly linked, to a corresponding end of the arms  25  and  26 , opposite to the contacts  21 ,  22 , respectively. More specifically, each end of the arms  25 ,  26  opposite to the contacts  21 ,  22  sustained by a corresponding elongated portion  41 ,  42  of an element made by the same insulating material of the rods  31 ,  32 . 
     Those elongated portions  41 ,  42  are linked, optionally hingedly linked, to the relative rod  31  or  32  but are also linked to the corresponding end of each arm  25 ,  26  so that the movement of the elongated portions  41 ,  42  reflects in a movement of the associated arm  25 ,  26 . 
     Each arm  25  or  26  is pivotally supported in the frame  20  by a corresponding pivot  28 ,  29 . Each of the arms  25 ,  26  is pivotally supported by the corresponding pivot  28  or  29  in a position that corresponds substantially to one third of the whole longitudinal length of the arm. 
     The rods  31 ,  32  and the arms  25 ,  26 , together with the corresponding hinge joint  33 , the pivots  28 ,  29  and the links between the rods  31 ,  32  with the elongated portions  41 ,  42 , and indirectly with the arms  25 ,  26 , form the toggle mechanism  30  that allows driving the moving electric contacts  21  and  22  one toward the other and vice versa. The toggle mechanism is activated by the low voltage driving portion  4  that will be disclosed later. 
     The rods  31 ,  32  as well as the arms  25 ,  26  are formed by a couple of identical parallel components that are linked together more or less like a truss beam. 
     As the before, each of the arms  25 ,  26  is supported by the corresponding pivot  28 ,  29  but those pivots are extended transversally at the end of a fork like arm  35  or  36  respectively. Those fork arms  35 ,  36  are made by a conductive material such as a metal. 
     Those fork arms  35 ,  36  are substantially linked to the fixed terminal power contacts  11  and  12 . Therefore, the electric continuity between the moving electric contacts  21 ,  22  and the fixed terminal contacts  11 ,  12  is guaranteed by the metal continuity between the components  11 ,  35 ,  25  and  21  at one side and  12 ,  36 ,  26 , and  22  on the other side. 
     It must be further noted that an elastic element  47  or  48 , for instance a compression spring, is interposed between each arm  25  or  26  and the corresponding supporting fork like arm  35 ,  36  with the purpose to compensate possible degradation or usury of the moving contacts  21 ,  22 . 
     The hinge joint  33  is provided with a central annular elastic element  43  that is contacted by an active end  19  of the low voltage driving portion  4  and may be considered a bumper between the active end  19  and the whole toggle mechanism  30 . This hinge joint  33  is forced to slide along the vertical slot  27  by a sliding guide  39  that is visible in the  FIGS. 7A and 7B  wherein it is shown in two different functioning positions corresponding to the open (down) and close (up) contacts. 
     Coming back just to the low voltage driving portion  4 , such a portion includes a coil  6  that is electrically supplied by a low voltage reference potential, non shown being of a conventional type and driven by a suitable switching actuator. 
     The coil  6  is active on a stem  7  that is extended horizontally and parallel to the base flange  13  of the contactor envelope  10  inside the switch base portion  2 . The stem  7  is moved against the contrast of an elastic element  8 , for instance an elongated spring to be compressed. 
     The free or distal end  14  of the stem  7  is linked to one end  17  of a lever  15  which is pivotally mounted on a fulcrum  16  fixed or integral with the internal frame  20  of switch base portion  2  of the contactor  1 . 
     The lever  15  has a first arm  38  linked to the free distal end  4  of the stem  7  and another or second arm  18  free to move around the fulcrum when the lever  15  is actuated by the coil  6  and the stem  7 . 
     The free end  19  of this second arm  18  is active on the hinge joint  33  of the toggle mechanism  30  through the annular elastic element  43 . 
     It should be finally noted that an electric circuit  49  is provided for the supplying the coil  6  with different voltage values according to the different driving actuators of the low voltage driving portion. This circuit  49  is substantially a voltage level shifter suitable to receive a plurality of different voltage values. Moreover, a chopper relay device  46  is also available in the low voltage driving portion  4  for connecting all possible intermediate circuits. 
     In view of the previous description it should be evident the functioning of the contactor device  1  of the disclosed embodiments. 
     According to the solution idea at the basis of the disclosed embodiments, in the contactor device  1  there is no fixed contact but, on the contrary, a couple of movable contacts driven towards and away from each other with respect to a mutual contact position. 
     As clearly shown in the example of the  FIGS. 5 and 6 , according to the user&#39;s needs, the contactor may have an initial open contacts configuration or a close contacts configuration. 
     In any case, according to the set initial conditions, the coil  6  of the low voltage driving portion  4  is biased to move the stem  7  that is joined to one end  17  of the two arms lever  15  pivotally hinged on the fulcrum  16 . 
     The movement of the stem  7 , in contrast with the elastic element  8 , and the linked lever  15  moves the free end  19  of the lever that acts on the sliding hinge  33  of the toggle mechanism  30 . 
     That sliding hinge  33  is free to move up and down or axially along a slot of the frame  20  so to push up or down and this movement forces the whole toggle mechanism  30  to provide a closure or an aperture of the moving contacts  21 ,  22  according to the desired needs. 
     The structure of the double symmetrically moving contacts  21 ,  22  of the disclosed embodiments allows obtaining a physical separation of the contacts of at least 73 mm that allows reducing the risk of electric arc and renders particularly reliable the switching of the contactor device of the disclosed embodiments. 
     The contactor according to the disclosed embodiments may be used also for switching in high AC current applications. 
     In the previous lines the directional terms like: “forward”, “rearward”, “front”, “rear”, “up”, “down”, “above”, “below”, “upward”, “downward”, “top”, “bottom”, “side”, “vertical”, “horizontal”, “perpendicular” and “transverse” as well as any other similar directional terms refer just to the device as shown in the drawings and do not relate to a possible use of the same device. Accordingly, these directional terms, as utilized to describe the contactor in its upright vertical position on a horizontal surface have just the meaning to identify a portion of the device with respect to another portion as shown in the figures. 
     The term “comprising” and its derivatives, as used herein, are intended to be open ended terms that specify the presence of the stated features, elements, components, groups, integers, and/or steps, but do not exclude the presence of other unstated features, elements, components, groups, integers and/or steps. This concept also applies to words of similar meaning, for example, the terms “have”, “include” and their derivatives. 
     Moreover, the terms “member”, “section”, “portion”, “part” and “element” when used in the singular can have the dual meaning of a single part or a plurality of parts.