RU2109364C1 - Switching device contact system - Google Patents

Abstract

FIELD: electrical engineering. SUBSTANCE: contact system has group of movable contact members in the form of alternating conducting and insulating plates 2 and 3, respectively, joined together to from smooth solid surface 4 with fixed brushes 5 sliding over it. Nonlinear resistance units 6 cut in between adjacent brushes possess breakdown voltage insufficient to build up arcing process across each auxiliary contact during its opening. With power and auxiliary contacts normally closed, the former is first to open and load current starts flowing over auxiliary-contact circuit and upon breaking of auxiliary contacts with certain time delay, current starts flowing over circuit set up of members 6 (in case member 7 is not inserted in circuit) or over circuit using member 7. EFFECT: improved design. 2 cl, 1 dwg

Description

 The invention relates to electrical apparatus and is intended to provide arc-free switching of direct current circuits.

 A device [1] is known in which, to facilitate switching conditions of an active-inductive load, the main contact is equipped with a bridge-type contact part in the form of a package of contact plates with different conductivities. These plates, alternately opening, provide a stepwise increase in resistance and a gradual decrease in current in the circuit to be opened. This device allows you to increase the life of the contact system, however, here, too, arc-free opening can be achieved only at sufficiently low levels of supply voltage.

 The closest in technical essence to the invention is a device [2], which has a main contact, shunted by a chain of series-connected auxiliary contacts, each of which is shunted by a power resistor. The specified contact system does not provide a fixation of the breaking voltage at the auxiliary contact, which contributes to the formation of an arc.

 The aim of the invention is to provide arc-free switching of an electric circuit with an active-inductive load, for which it is proposed that the switching device be equipped with a more perfect contact system.

 In a contact system containing a main contact common with the prototype [2] and a circuit shunting it made up of auxiliary contacts, the above goal is achieved by the fact that the auxiliary contact system contains groups of movable and fixed contact parts that make a fixed contact with each switching sliding stepping movement, a group of moving contact parts is made in the form of a sequence of alternating conductive and insulating plates, fastened together so that they form a smooth monolithic working surface designed for sliding stationary contact parts along it, while the conductive plates are completely isolated from each other, a group of fixed contact parts made in the form of a sequence of brushes isolated from each other and adjacent to the sliding surface, adjacent brushes in of the indicated sequence are displaced to each other by equal distances equal to the distances between adjacent conductive plates, non-linear resistive electrodes are connected between adjacent brushes components forming a serial circuit, one output of which is connected to the first output of the main contact, and the other to the second output of the main contact.

 According to paragraph 2 of the claims, the contact system is characterized in that it is additionally equipped with a powerful non-linear resistive element, which shunts the main contact.

 The drawing shows a contact system containing the main contact 1 and the auxiliary contact system, which consists of a group of movable contact parts made in the form of alternating conductive 2 and insulating 3 plates, bonded together and forming a smooth monolithic surface 4, on which a group of fixed contact brushes 5. Between adjacent brushes are connected non-linear resistive elements 6 of a potentially limiting type (for example, a varistor, a zener diode, etc.). The main contact 1 is additionally shunted by a powerful non-linear resistive element 7.

 The movable part composed of elements 2 and 3 is shown schematically. It can have a different design depending on the drive used in the switching device.

 If a rotating stepper motor is used as the drive, then the moving part of the auxiliary contact system will perform unidirectional stepping (shown in the drawing by a unidirectional arrow). In this case, the movable part will be a body of revolution and mechanically connected with the shaft of the stepper motor.

 The movable part can also perform a step-by-step movement: rotary or linear (shown in the drawing by a bidirectional arrow), which requires an appropriate electric motor as a drive.

 The contact system shown in the drawing, operates as follows. In the initial (on) state, the main contact 1 is closed, the conductive plates 2 bridge the brushes 5, which leads to the bypassing of the non-linear resistive elements 6. The current from the power source flows mainly through the main contact 1, and insignificant leakage currents flow through the shunt circuits.

 upon shutdown, the main contact 1 opens first and the load current passes to the shunt circuit, which consists of auxiliary contacts formed by elements 2 and 5. The voltage drop in this circuit is insignificant (3 - 5 V), so opening of contact 1 will be arcless. After the contact parts of the main contact 1 are fully extended, the movable part of the auxiliary contact system starts moving by the maximum gap and moves one step α, after which it occupies the position when the axis of symmetry of the plates 2 and brushes 5 coincide, which corresponds to the open state of the auxiliary contact chain . The breakdown voltage of the nonlinear resistive elements 6 is selected to be smaller in magnitude than the voltage of the formation of a short arc, so the opening of each individual auxiliary contact will be arcless. The total breakdown voltage of the entire circuit from the elements 6 is chosen significantly greater than the voltage of the power source, and the breakdown voltage of the element 7 has an intermediate value between the indicated voltages. Since the opening of the chain of auxiliary contacts cannot occur strictly simultaneously, then as they open, the elements 6 will be introduced into the shunt circuit gradually and only with the connection of the last element 6 the whole circuit will be activated; the breakdown voltage of this circuit will exceed the voltage of the power source and the load current will go into this circuit if there is no element 7 in the circuit. The dissipative energy accumulated in the load will be dissipated by a circuit of non-linear resistive elements 6, so the latter must be sufficiently powerful and equipped with coolers. If there is an element 7 in the circuit, the elements 6 pass the current only during the opening time of the auxiliary contacts, therefore they can be selected as low-power, but then the element 7 will have to dissipate almost all the energy stored in the load. With the completion of the quenching of the load current, the shutdown process ends.

 The contact system, despite the apparent complexity, can be made quite compact and, most importantly, safe, especially in comparison with currently used arc extinguishing devices.

Claims (2)

 1. The contact system of the switching device containing the main contact and the circuit shunting it, composed of an auxiliary contact system, characterized in that the auxiliary contact system contains a group of movable and fixed contact parts, making a fixed sliding step movement with each switching relative to each other, group movable contact parts made in the form of a sequence of alternating conductive and insulating plates bonded together so that they form smoothly a monolithic work surface designed to slide stationary contact parts along it, while the conductive plates are completely isolated from one another, the group of fixed contact parts is made in the form of a sequence of brushes isolated from one another and adjacent to the sliding surface, adjacent brushes in the specified the sequences are offset by equal distances equal to the distances between adjacent conductive plates, non-linear resistive elements are connected between adjacent brushes, the image a series circuit, one terminal of which is connected to the first terminal of the main contact, and the other to the second terminal of the main contact, while the design of the contact surface of the brushes provides, when the group of movable contact parts corresponds to the included state of the main contact, the conductive plates of the group of fixed contacts -details, and when the position of the group of movable contact parts, occupied after its movement by one step relative to the position corresponding to the included state g avnogo contact open state conductive plates with respect to one another.  2. The system according to claim 1, characterized in that it is additionally equipped with a powerful non-linear resistive element, shunting the main contact.