Switching apparatus for electric circuit section mainly for explosion hazardous zones

FIELD: electricity.

SUBSTANCE: switching apparatus for an electric circuit section mainly for explosion hazardous zones with a power supply source consists of two switching elements capable of movement towards each other and complete with contact plates at opposite ends of the elements in the direction of their movement and output conductors. In one conductor in series of the current passage there is a variable resistor, a current meter and one contact plate of the above contact. At that the second conductor is connected to the second contact plate of the contact and the variable resistor is complete with a regulator and indicator indicating limit values. The variable resistor may be made as a rheostat or a gate-controlled thyristor and before switching it is brought to the maximum value of resistance up to 1015 Ohm.

EFFECT: increased operational safety in explosion hazardous zones due to prevented spark producing in the switching process.

5 cl, 1 dwg


The invention relates to electrical engineering, namely to devices for switching electrical circuit sections with in-line power source, mainly intended for use in explosive areas.

Open or short section of an electric circuit with in-line power source AC or DC power is mostly accompanied by the occurrence of sparks or electric arcs between the moving contact plates or converging towards each other or diverge from the state of the connection.

The occurrence of the arc leads to a sharp temperature rise, the heating of the contact plates, melting and welding among themselves, which obstructs the further implementation of the contact of its core functions: opening or closure of an electrical circuit for prophylactic purposes or in an emergency. Under the contact plates in this case will be understood as the contact surface of the monolithic contact parts and specially made items from more durable or arc resistance materials. For example: the silvering of the contacting surfaces or the fabrication of contact pads of conductive ceramics.

One of the ways of dealing with the resulting electrical arc is the use of interrupters in circuit breakers,reducing the hazardous effects of arcing as, for example, in the patent for invention RU №2087973, H01H 1/20, 3/12, 13/14, 13/52, "NC host for the switch.

Another method is the use of a special arc chamber gases having in comparison with air at elevated qualities, for example the use of insulating gas (sulfur hexafluoride), which has higher dielectric strength with cooling and arc suppression ability, as, for example, in the patent for invention RU №2168787, H01H 31/00, "Gas disconnector switchgear high voltage gas-insulated".

In the patent for invention RU №2374716, H01H 1/58, "Connecting the device with the cooler is provided a method of reducing the negative effects arc due to the lower thermal energy released in the contact when switching.

In the patent for invention RU №2455720, H01H 1/22, "Contact host high speed circuit breaker" a device in which the movable contact is in the process of switching is involved in the rotational-translational motion, providing a more dense grinding to a stationary contact has a contact, silver soldering and removable arcing horn, with a consistent opening of the main and arcing contacts with the protection of silver to exchange from electric arc arose�.

In the patent for invention RU №2402091, H01H 1/48, "the Contact system of the circuit breaker" in the movable contact element is provided l-shaped groove, so that in the case of welding of the movable and stationary contact elements under the influence of dilatory spring fracture occurs the movable element in the region of the l-shaped groove and the release of the contact.

In the patent for invention RU №2417474, H01H 1/48, a Contact node of a high-speed switch contact node comprises a first main contact element mounted on the first axle drive mechanisms with springs pressing contact, and between the main elements of the intermediate element is mounted on a thrust Prykhodko actions associated with the actuator and the spring off. All the contact plate elements made of silver tipped with refractory conductive material.

When signal on off when short circuit or operational shutdown of the intermediate contact element mounted on traction Prykhodko steps, moves vertically upwards under the action of the actuator and the force of spring off in the direction of the disconnected position. Thus there is a consistent transition with a silver contact plates on the refractory ceramic material. Thus, the arc off the image�is on refractory tipped, but the working surface silver contact protected from Amhara. The arc is extinguished in the arc extinguishing device of the circuit breaker.

The main disadvantage of all these inventions is that they are not aimed at preventing the arc, and the consequences of its occurrence.

Known solutions for preventing the formation of arcs, namely that one contact is broken into multiple contacts installed in several parallel branches.

Thus, in the invention according to the patent RU No. 2154321, H01H 33/00, "a Method for disconnecting an electrical circuit" discloses a method of disconnecting an electric circuit switching device, a conductor circuit which consists of two parallel branches with different breaking capacity, each of which contains at least one arc quenching device.

In the invention according to the patent RU No. 2308780, H01H 31/24, "high current switch" described switching device, in which input current is bred along several parallel conductors terminating in contact elements, which, in fact, the switching circuit.

The disadvantages of the inventions according to patent RU №2154321 and RU №2308780 is that theoretically equal branches of conductors in operation burn and become electrically unequal, which leads to p�raspredelenie currents flowing through them and the appearance probability of the arc.

Note the common property of the considered inventions: they are all designed for the flow on circuits operating currents, which are predominantly of a large value in power plants.

There is an area of technology in which it is unacceptable not only the formation of the arc, and spark formation. This production, in which long-term or short-term there is a gaseous explosive mixture, which, when occurrence of sparks with a specific energy can explode and lead to devastating and tragic consequences.

To prevent a possible explosion in the atmosphere the production of explosive mixtures developed several types of protection, such as "explosion-proof membrane d", "membrane at a pressure of p", "intrinsic safety i" and others. For electrical circuits with switching devices, the most appropriate type of protection is "intrinsic safety i".

By definition (GOST R IEC 60079-11-2010 "Explosive atmospheres. Part II. Intrinsic safety "i" intrinsic safety "i" - this type of protection based on the restriction of electrical energy in the electrical equipment and connection wirings that are exposed to potentially explosive atmospheres, to a value below the level of�I, causing the ignition sparking or heating.

Thus, the possibility of sparking individual elements of intrinsically safe circuits is fundamentally valid, provided that the released electrical energy does not lead to ignition of the explosive mixture formed in the atmosphere specific industrial production. Such contacts are called normal sparking. However, this implies that schemes with similar normal sparking of the contacts must undergo mandatory certification tests for intrinsic safety.

Tests for intrinsic safety are conducted applying sparkle-forming mechanism. According to GOST R IEC 60079-11-2010 chain level "ic" connecting sparkle-forming mechanism should be considered (among others) instead of the normal sparking of the contacts, such as connectors, switches, buttons, potentiometers, (p. 45 cited standard). But this requires considerable labor and is a flaw in the design of such schemes of protection.

Also known electric device, allowing you to apply the intensity of lighting systems: the dimmer or dimmer (speed rheostat - a variable resistor) and pin electronic regulator power lighting, which can operate alone, with peripheral device�in order or with a push button (T Gallate, D. Fedullo. "Encyclopedia of an electrician. A practical guide". M., "omega", 2009).

In each of these devices has a switch (on/off) or third-party (the button). And for each of them characterized by the fact that the switch is installed first towards the higher potential (the phase of the power source).

The disadvantage of such devices is that on one of the contact plates of the switch turns the potential of the source power phase is formed and the charge.

When moving the second contact plate (approaching when you turn on or remove when you turn it on it is formed a charge of opposite sign. At a certain distance and the velocity of the contact plate may cause the formation of sparks, a recharging current from the power source.

As a prototype we choose the dimmer.

The essence of the invention is to provide a device for switching the phase of the electric circuit mainly for hazardous areas, prevent the formation of sparks in the process of switching.

The technical result is achieved in that a device for switching the phase of the electric circuit mainly for explosive atmospheres consisting of two switching elements capable peremeschat�Xia towards each other, equipped with contact plates on opposite ends in the direction of their movement and lead conductors, with one conductor in series in the physical direction of current flow included a variable resistance, a device for measuring current and one contact plate, the second conductor connected to the second contact plate, and a variable resistor provided with a controller and an indicator indicating the boundary values. Moreover, prior to implementation of the switching variable resistance has a maximum value.

A calculation circuit is provided in series with the contact variable resistance in a state with the minimal value. Thus, the presence of resistance in the circuit will not affect the fulfilment of its primary function.

Before opening the circuit variable resistance gradually transferred to the state with maximum value. When this current reaches a value (e.g., 10 μa), the break contacts will not lead to the formation of sparks due to the smallness of the energy released when you break this chain. The sharp increase in the value of the current in the breeding of the contact plates can not occur, as in Windows Explorer, in the physical direction of current flow, is a very large resistance and the appearance of sparks between to�nachname plates impossible. After disconnection of the circuit variable resistance remains in the same state, so before closing of circuit it has, too, the maximum resistance value, and therefore, when the circuit we will get the same minimum current (10 μa) adjusted for the impact of the transition process. How and when opening the circuit, the sharp increase in current is impossible because of the presence of the conductor in the physical direction of current flow greater resistance. And therefore, when closing the circuit, the spark will not occur. So, there will be the achievement of the technical result. The power source may serve as a voltage source and a current source. This decision is mainly used for DC circuits.

In the switching apparatus requiring human intervention (e.g., button), the measuring device allows you to visually assess the result of removal of the regulator in one of the limit values and the indicator (e.g., light) is the boundary value. The regulator may be built into the design of the button. For example, before clicking to rotate the upper cylindrical portion of the button at a certain angle in a clockwise direction (otherwise it doesn't click), this will transfer the variable resistance to a desired limit value.

In switching devices that do not require �the participation of the person, the role of the regulator performs an automatic scheme, but the presence of the measuring device and indicators of boundary values allows maintenance staff to monitor the progress of processes.

It is known that in DC circuits with a relatively small operating voltages and currents arch can be achieved by the inclusion of parallel discontinuous contacts estrogenically chains (paths), usually consisting of a series capacitance, inductance and active resistance. (N. To. Myshkin, V. V. Konchits, M. Braunovic. "Electrical contacts". Dolgoprudny, Publishing house "Intellect", 2008 ). This scheme is the ease of operations requires additional contacts to break themselves of the chains and leads to the difficulties of switching: if you break the chain contacts should be included before the break contacts on and off after that, and when the connection is activated before connecting contacts, and then disconnect.

Both switched and lockable electrical circuit can be connected to tens of kilovolts, to prevent sparking advantageously, the variable resistance reached a value of 1015Ohm.

In the case of a necessary absence in the closing circuits and/or circuit switched reactance appropriate variable resistance back�you in the form of a rheostat.

To simplify the construction of schemes for automatic circuit and/or circuit breaking appropriate variable resistance is made in the form of a lockable thyristor.

To ensure the symmetry of the alternating current appropriate variable resistance is made in the form of two structurally independent elements included in the conductors from different sides of the contact.

The invention is illustrated by the exemplary embodiment in the form of the electrical circuit shown in Fig. Circuit the proposed circuit device with the included power source is depicted in the form of a dipole.

Shown in the drawing, the two-terminal 1 has two outputs (potential φ1and the potential φ2with the direction of current flow from φ1for φ2) connected in the desired order series circuit of a variable resistance 2, the measuring device 3 and the contact 4 (the contact is closed, the operating mode).

Manufacturing technology of the device for switching the phase of the electric circuit mainly for use in hazardous areas according to the present invention is the following.

Typically, a variable resistance mounted on the same Board with switching devices (buttons, switches). This used standard methods of circuit Board. Rheostats, lockable tiree�Torah, buttons, relays, indicator lights, potentiometers, ammeters selected from commercially available products.

After mounting the printed circuit Board is installed in a commercially available box, if necessary, is filled with compound. Subsequently, the box is installed on the mounting panel of the equipment.

To confirm the technical result was assembled diagram of the constant current circuit shown in the drawing, in which variable resistance 2 made in the form of a variable resistor with a maximum resistance of 1010Ohms, with button on/off with contact 4. In series with a variable resistor 2 in the branch included ammeter 3. At the output of the two-terminal 1 between the points φ1and φ2a potential difference of 100 V. the current flowing in the branch on closed contact, is approximately 10 A. the Minimum resistance of the rheostat is approximately 10 Ohms.

The experiment was conducted as follows. Controlling the value of current when the current status on closed contact. Making sure that it is approximately 10 A, brought in for one minute rheostat in maximum position and recorded the maximum current value.

After clicking the button razikale contact. After one minute by pressing the closed contact and again recorded the maximum current value. If for�ykanji and the contact opens visually observed the formation of a spark. This cycle was repeated fifty times.

During the test spark formation was not observed a single time. The maximum value of the current by opening and closing of the contact lies in the range from 5×10-7And to 3×10-8A. the Variation in current in current state was within ±1.7% of the rated value.

The test results confirm the achievement of the technical result.

1. The device for switching the phase of the electric circuit mainly for explosive atmospheres consisting of two switching elements capable of moving towards each other, equipped with contact plates on opposite ends of the elements in the direction of movement and lead conductors, characterized in that one conductor in series in the physical direction of current flow included a variable resistance, a device for measuring current and one contact plate, the second conductor connected to the second contact plate, and a variable resistor provided with a controller and an indicator indicating the boundary values, and the implementation of the switching variable resistance has a maximum value.

2. The device according to claim 1, characterized in that the maximum value of the variable resistance reaches 1015Ohm.

3. The device according to claim 1, differently�Xia, the variable resistance is made in the form of a rheostat.

4. The device according to claim 1, characterized in that the variable resistance is made in the form of lockable thyristor.

5. The device according to claim 1, characterized in that the variable resistance in the form of two structurally independent elements included in the conductors from different sides of the contact.


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