WO2017034444A1 - Method for preventing arcing between contacts of switching equipment - Google Patents

Abstract

A method for preventing arcing between contacts of switching equipment requires the use of an additional switching device. The additional switching device has switching contacts and switches a protective circuit. The protective circuit consists of, connected in-parallel, a capacitor, a voltage protection device and a discharge circuit to be switched. The connection and disconnection of the protection circuit, in-parallel to the switching equipment contacts to be protected, is carried out in a strict sequence. In order to enhance protection effectiveness, an inductance is introduced into load circuits.

Description

A method of preventing arcing between             switching equipment contacts

The invention relates to the fields                 electrical engineering, electroautomatics, telemechanics and                 designed to protect the switching contacts                 equipment from arc discharges during short circuit and                 opening electrical circuits. Technical result from                 application of the invention is to reduce                 dimensions of switching equipment, in use                 faster devices in increasing                 reliability and longer contact life                 switching equipment up to the maximum                 mechanical wear of switching mechanisms                 devices.

 To increase the switching life                 equipment used:

 1. Switching equipment special                 designs, for example, with reinforced contacts;

 2. Magnetic blowing of contacts of switching equipment;

 3. The inclusion of semiconductor devices in                 circuit of contacts;

 4. Spark suppression chains installed                 parallel to relay contacts or parallel to load.

 The first two methods guarantee high                 reliability through design measures during development                 switching equipment, but quite exotic,                 roads are characterized by increased dimensions and increased                 power coil control.

 The third method is inferior in reliability due to                 application of semiconductor devices in switching circuits.

Industrial electrical engineering focuses on                 not expensive, standard switching equipment,                 therefore the use of spark suppression chains is the most                 A common way to suppress arc discharges at contacts.

 Effective protection extends significantly                 life switching equipment.

 In practice, the following                 effective and economical schemes:

 1. C-chains.

  2. RC circuit.

 3. Reverse diodes.

 4. Varistors.

 5. Combined circuits, for example, a varistor                 plus an RC circuit.

 Protective circuits may include:

 1. Parallel to the load.

 2. Parallel to relay contacts.

 3. Parallel to contacts and load at the same time.

 Most known switching schemes                 spark suppression chains has the following disadvantages.                 Spark protection circuits are under continuous operation.                 operating voltage, resulting in circuit reliability                 protection falls over time. Short circuit in                 spark chain protection likely to disrupt                 protected circuit. Application of protection circuit with diode                 involves the inclusion of a certain polarity in the circuit, and                 the reliability of such a scheme will depend on the reliability                 semiconductor element, that is, a diode.

 It is generally accepted that adverse                 contact mode is switching (breaking)                 DC circuits especially with inductive                 load, as this creates conditions for                 occurrence and maintenance of the arc (Dmitriev B.C.,                 Serganov I.G. The basics of railway automation and                 telemechanics. The textbook for technical schools. transport. -                 M .: Transport, 1988, p. 43.) / 1 /.

 At the same time, it is believed that with                 short circuit with inductive load erosion                 insignificant (Author: Mitsun V.V., Lenskaya L.N., Golub                 V. I. Edition: Radio Electronics Issues, TPN Series,                 1973, no. 4. UDC 621.316.015.4 with 61.) / 2 /.

 In the protection circuit, where the contact is bridged                 capacitor, (Dmitriev B.C., Serganov I.G. Basics                 railway automation and telemechanics. Tutorial for                 technical schools transport. - M.: Transport, 1988, s                 45.) / 1 / when opening the circuit, energy, instead of breakdown                 air gap spent on charge                 capacitor. However, at the next contact closure,                 capacitor discharges through low resistance                 contact, which worsens the working conditions of the latter, then                 there is significantly increased erosion of contact.

Closest in technical essence to                 the claimed invention is selected as                 prototype DC circuit breaking spark                 suppressor device. Patent No. US 5764459) / 3 /, containing                 two consecutive contact groups. Parallel                 the first group of contacts includes a spark chain                 consisting of a series capacitor and                 circuit consisting of resistor and inductor included                 parallel to the diode. In this case, the second pair of contacts                 provides circuit opening. First opens                 a pair of contacts, while the discharge current closes through                 sparkling chain. The second group of contacts opens                 load circuit after everything has stopped in the circuit                 currents. This eliminates spark discharge between                 contacts. At the same time, the first group of contacts                 closes the capacitor through the resistor and inductor,                 thereby discharging the capacitor.

The prototype and the claimed invention have                 following similar salient features, two groups                 pins, a capacitor that is used as                 spark chain, the circuit that connects to                 capacitor to discharge before the next cycle                 switching load.

The prototype has the following disadvantages:

 1. Contacts of the first and second groups should                 be equivalent in current load and breakdown voltage.

 2. The inclusion of the scheme requires compliance                 polarity.

 3. Inductive load circuits required                 the use of a large capacitor rated                 high voltage.

 4. The reduced speed of the circuit.

 5. When switching (when closing the contacts) in                 resistive loads will erode contact.

 6. When switching (when closing the contacts) in                 resistive load circuits arcing worsens EMC.

 7. Limited reliability of the circuit.

 These disadvantages are due to the fact that in                 the circuit contacts of the first and second groups are included                 sequentially, applied diode and polar                 capacitor, no protection element                 voltage, and therefore the capacitor in the circuit is chosen                 the value capable of storing all the inductance energy                 load, otherwise the voltage across the capacitor                 may exceed the capacitor breakdown voltage due to                 high capacitance decreases performance                 circuit, when switching (when closing the contacts) in the circuit with                 resistive load means are not provided for                 prevent arcing, which                 occurs when contacts are brought together when punching                 the voltage for the gap between the contacts will be less                 supply voltage in the circuit, and the arc discharge will                 maintained during bounce of contacts. In chain                 A semiconductor element is used.

The purpose of the invention to reduce or eliminate                 destructive arc discharge (spark) between contacts                 switching device switching active or                 inductive loads in the DC circuit and so                 way to significantly increase the service life                 switching device, improve EMC, increase                 reliability of the protection circuit due to exclusion                 semiconductor elements in contact circuits, increase                 reliability due to the fact that protection circuits are under                 voltage only during transients during                 switching time, ensure non-polar inclusion of the circuit                 protection, reduce the size of the protection elements.

To achieve the goal in                 in accordance with the claimed invention, the method                 prevent arcing between contacts                 switching equipment, proceed as follows.                 In the load circuit include inductance (inductor), if                 the load is not inductive or inductance                 not enough to fulfill the goal, this                 circuit element is required in order to prevent                 damage to contacts of switching equipment during their                 short circuit. Inductance in the load circuit delays                 development of an arc discharge when conditions for                 breakdown of the gap between contacts when they approach each other and                 bounce. Use an additional device,                 changeover contact which connects the protective circuit                 parallel to the main contacts of the switching                 hardware after switching contacts                 equipment reliably closed. Use a protective circuit,                 consisting of a parallel capacitor and                 voltage protection element. The protective circuit is connected                 parallel to the main contacts of the switching                 devices after the contacts of the main device                 have already been reliably closed so that the protective capacity                 circuit did not work on the destruction of contacts at the time of their                 short circuits, for the same reason, at the time of connection                 contacts of the additional device, protective capacity                 The circuit must be discharged. Protective circuit capacitor                 starts to fulfill its function at the moment of opening                 contacts of protected switching equipment, such                 so that the voltage across the capacitor of the protection circuit                 grows slower than the voltage value, which                 required for the breakdown of the increasing gap between                 breakable contacts. Slew rate                 on the capacitor depends on the current in the circuit and the capacitance                 capacitor and does not depend on the magnitude of the inductance in                 load circuit. Capacitor Resistance                 worsens its work, which is taken into account when choosing the type                 capacitor in the protection circuit. Increase rate                 breakdown gap when opening contacts                 switching device depends only on its                 designs. In the protection circuit, a protection element is used according to                 voltage that limits the voltage to                 capacitor and on the contacts of the switching equipment in                 permissible working limits. Security Feature                 voltage absorbs all remaining energy                 inductance after part of the energy                 the inductance is expended on the charge capacitor circuit                 protection and dissipation in the core inductance. Than                 higher voltage at which the limitation occurs in                 protection chains, the faster transients end                 at the stage of disconnecting the load. From protection element to                 voltage does not require high speed                 thanks to a parallel capacitor. After                 completion of transients in the power circuit,                 disconnect (open) the changeover contact of the additional                 devices from the power circuit, to do this                 sufficient delay between opening contacts                 switching equipment and opening of cross over                 contacts of the additional device. Changeover contact                 additional devices disconnect (open) from the circuit                 power supply at zero or low current in the circuit                 load and at zero or low voltage on                 contacts of the additional device. After shutdown                 (open) from the power circuit of the changeover contact                 option device, changeover contact                 option device closes the capacitor circuit                 protection through the discharge circuit. Discharge Circuit Parameters                 chosen so that the capacitor protection circuit                 completely discharged until the next connection                 protection to the contacts of switching equipment.                 An additional device is chosen so that                 his contacts were transient current resistant                 in the protection circuit.

Brief Description of the Drawings

 The following notation is used on [Fig.1], [Fig.2]:

K1 - contacts of switching equipment;

 K2 - contacts of an additional device,                 protection circuits intended for switching;

 C1 - capacitor of the protection circuit;

 FV1 - voltage protection element,                 preferably a varistor;

 R1 is a bit chain, preferably                 resistor or series resistor and inductor;

 L1 is the inductance for the load circuit.

In series with the circuit, they do not turn on                 shown in the drawing in series                 power source and load. The load may include                 a combination of resistive, inductive loads and                 engines. Circuit elements are switched in                 sequences as described.

Fig. 1

 is part of the functional                     diagram illustrating the principle of the first                     preferred embodiment of the invention.

Fig. 2

 is part of the functional                     diagram illustrating the principle of the second                     preferred embodiment of the invention.

 In the load circuit include inductance                 (choke) with steel core if load is not                 is inductive or its inductance is not enough                 to achieve the goal.

 To control an optional device                 additional contacts may be used                 switching equipment and RC chains, type devices                 timers installed on contactors, software                 control through controllers.

 As a voltage protection element                 suppressors, varistors, arresters can be used.

Industrial applicability

 In emergency equipment                 small-sized high-speed relays are used.                 Relay contacts cannot be bridged. In equipment                 relays are placed on blocks in an amount of up to 32 pieces,                 maybe more. Relay performance affects                 hardware parameter as channel delay                 command transfers. Relay contacts are used in circuits.                 DC 220V. The load may be                 the control coil of a powerful switch is used,                 steel core coil inductance can                 reach values of 50H. The current in the coil can be up to                 0.25A. Without protection, with a steady current of 0.125A through                 load with inductance 50H, relay contacts fully                 fail after 700 shifts. Without protection, when                 steady current 0.25A through load inductance                 50H, relay contacts completely fail after 10                 switchings. A protection circuit consisting of                 from a capacitor with a capacity of 0.2 μF, a varistor with a working                 voltage for direct current 350V, discharge circuit                 in the form of a 0.25W resistor and a nominal value of 200kOhm.                 The protection circuits are respectively switched by                 contacts of the second similar relay, delays on                 switching off which formed by                 RC chains. With protection circuit, with steady current 1.0A                 through a load of inductance 50H, after 4000                 switching, on the contacts of both relays damage is not                 observed. Contact damage was evaluated                 electrically, i.e. resistance was measured                 contacts with an ohmmeter, as well as a visual way through                 microscope after complete disassembly of the tested relays.

 1. Dmitriev B.C., Serganov I.G. The basics                 railway automation and telemechanics. Textbook                 for technical schools transport. - M .: Transport, 1988,                 p. 43 and 45.

 2. Author: Mitsun V. V., Lenskaya L. N.,                 Golub V. I. Edition: Issues of Radio Electronics, Series                 TPN, 1973, no. 4. UDC 621.316.015.4 p.61.

 3. DC circuit breaking spark suppressor                 device. Patent No. US 5764459.

Claims (2)

A method of preventing arcing between                 contacts of switching equipment in which in the circuit                 direct current with inductive load, except                 protected contacts of switching equipment                 use the contacts of the additional device, and on                 the moment of opening the contacts of switching equipment,                 parallel to the contacts of the switching equipment is on                 capacitor, and after the capacitor protection circuit                 disconnected from the power circuit, it is discharged through the circuit                 discharge, characterized in that the protection circuit consisting of                 parallel connected capacitor and protection element according                 voltage is connected parallel to the contacts                 switching equipment via changeover contact                 additional device, and when shorted open                 contacts of switching equipment and contacts                 optional device observe the following                 sequence when switching contacts                 the equipment commutes (closes) the power circuit, only                 then parallel to the switching contacts                 equipment through the contacts of an additional device                 connect the protection circuit with a fully discharged                 capacitor when switching equipment contacts                 open, the power circuit is closed through                 series contacts of additional                 devices and protective circuit consisting of parallel                 included capacitor and voltage protection element,                 while the condition that increasing                 voltage across the capacitor in the protection circuit at every moment                 time less breakdown voltage in increasing                 the gap between the contacts of the switching equipment,                 a voltage protection element limits the voltage to                 capacitor and on the contacts of the switching equipment in                 operating limits and extinguishes the energy stored in                 inductance after transient loads in the circuit                 processes will end to acceptable values, i.e. current                 drops to zero or to an acceptable value, turn off                 protection circuit (open) from the supply circuit, and by                 changeover contact of an additional device                 connect the discharge circuit parallel to the circuit capacitor                 protection, while up to the next switching cycle                 disconnection of switching equipment withstand time,                 so that the capacitor of the protection circuit is discharged                 to zero or to an acceptable value, when choosing                 protection circuit capacitors take into account that                 the voltage rise rate across the capacitor depends                 from capacitor capacitance and current in the load circuit, speed                 increase the clearance between switching contacts                 equipment depends only on the design of switching equipment.  The method according to claim 1, characterized in that in the chain                 loads include inductance sufficient for                 effectively preventing arcing between                 contacts of switching equipment at the time of their closure.