SU1700675A1 - Device for protection of three-phase electric installation against two-phase operation - Google Patents

Abstract

The invention relates to electrical engineering, in particular to devices protecting three-phase electrical installations from operating on two phases. The purpose of the invention is to simplify and increase the reliability of the device. In the event of a phase failure that does not have a current transformer, the electrical installation is powered by a linear voltage. As a result, in one of the current transformers, the current in the secondary winding changes the phase by 180 ° C. in comparison with another current transformer, which leads to the locking of transistor switches 31, 32. In this case, the photo thyristors of the optocouplers 26, 27 are also locked. The power circuit of the winding 21 of the electromagnetic contactor is broken and the electrical installation 23 is disconnected from the mains. 1 sludge.

Description

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The invention relates to electrical engineering, in particular, to protection devices from operation on two phases of three-phase electrical installations, in particular asynchronous and synchronous electric motors, electromagnets, converters, and the like.

The purpose of the invention is to simplify and increase the reliability of the device.

The drawing shows a schematic diagram of the proposed device to protect a three-phase electrical installation from working on two phases.

The device contains phase transformers 1, 2 currents, the ends of the secondary windings of which are interconnected and grounded, the windings are connected to the inputs of the measuring transducers 3, 4, each made in the form of two oppositely connected circuits of the series-connected diode 5, 6 (7, 8 ), a resistor 9,10 (11, 12) and a light emitting diode of a transistor optocoupler 13, 14 (15, 16), shunt by a zener diode 17, 18 (19,20), an electromagnetic contactor 21, the power contacts 22 of which are included in the phase conductors of a three-phase electrical installation 23, chain ku connected to the mains and consisting of a button 24 Stop connected in series with the button Start 25 and the winding of the electromagnetic contactor 21, two oppositely connected photo thyristor optocouplers 26, 27 connected by one of the terminals with a common point of the buttons Start and Stop, and the other - with the closing block contact 28 of the electric contact contactor connected to the common point of the Start button 25 and the winding of the electromagnetic contactor 21, the source

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29 operating current, the input of which is connected in parallel to the winding of the electromagnetic contactor,

The LEDs of the thyristor optocouplers 26, 27 are connected through a resistor 30 in series unidirectionally with two optotransistor switches 31, 32 consisting of sequentially connected phototransistors of optocouplers 13, 15 (14, 16), while the cathode of the LED of the thyristor optocoupler 26 is connected to the negative terminal. the source of the source 29 operating current, and the emitters of phototransistors opto.nov 15, 16 - to the positive terminal of the source 29 of the operating current. A capacitor 33 is connected between the negative terminal of the operating current source 29 and the collectors of the phototransistor of the optocouplers 13, 14.

The device works as follows.

When the Start button is pressed, the electromagnetic contactor 21 is triggered and the electrical installation 23 is connected to the three-phase network. Phase wires carry load currents that are phase shifted relative to the voltage by an angle (pH at I 1H, which induce an emf proportional to them in the secondary windings of the current phase transformers 1, 2. The voltage of the secondary windings of the phase transformers 1, 2 current straightens at the same time, during the positive half-period, the current passes through a series-connected diode 5 (7), resistor 9 (11) and light-emitting diode of the transistor optocoupler 13 (15). In the negative half-period, the current flows in the opposite direction along The following circuits are diode 6 (8), resistor 10 (12) and light-emitting diode of transistor optocoupler 14 (16). Thus, in each half-period, measuring transducers 3, 4 form light pulses in the respective optocouplers 13, 15 (14, 16 a) half-period (-y or 180 °) of the supply voltage. The voltage amplitude on the light-emitting diodes of the optocouplers 13-16 is limited to 17-20 zener diodes. As a result, for each phase, the signals of a rectangular shape, the polarity of which corresponds to the polarity of the corresponding current.

Due to the alternation of current in the phases in each half-period of the supply voltage

neither for -g period (- & or 60 °)

coincidence of signals of the same polarity in two phases occurs. As a result

for this time (or 60 °)

one of the parallel-connected optotransistor switches 31 (32) opens, and the phototransistors of the optocouplers 14, 16 (13, 15) pass current from the source 29 of the operating current and the capacitor 33 is charged. As a result, the light emitting diodes of the thyristor optocouplers 26, 27 continuously flow current, which ensures reliable connection of photo thyristors with any method of connecting the winding of the electromagnetic contactor 21 to the phase conductors of the supply network, i.e. not strictly required

Phasing the supply voltage winding of the electromagnetic contactor with the control pulses of the photothyristors 26, 27. The photo thyristors of the optocouplers 26, 27 are opened and, together with the series-connected auxiliary contact 28 of the electromagnetic contactor 21, shunt the Start button 25. When the transformer is cut off current, the current disappears in the circuit x corresponding

transmitter 3 (4), the light emitting diodes of transistor optocouplers 14, 16 (13, 15) do not work, and both optotransistor switches 31, 32 are closed, which causes the photothyristors of optocouplers 26, 27 to lock. The power supply of the winding of the electromagnetic contactor 21 is broken and the electrical installation 23 is disconnected from the network.

In the event of a phase failure that does not have a current transformer, the electrical installation is powered by a linear voltage. As a result, in one of the transformers, the current in the secondary winding changes the phase by 180 ° compared to another current transformer, which

leads to locking of the optotransistor switches 31, 32. In this case, the photo thyristors of the optocouplers 26, 27 are also locked. The supply circuit of the winding of the electromagnetic contactor 21 is broken and the electrical installation 23 is disconnected from the network.

The advantage of the proposed device in comparison with the prototype is the simplification of the scheme, the third

current transformer and associated measuring transducer and transistor switch, as well as improving the electrical safety of its service, since the secondary windings of phase current transformers can be grounded, which does not affect the operation of the device and meets the requirements of electrical installation rules. In the prototype, the secondary windings of current transformers are not electrically interconnected and are not grounded. With

grounding the windings of the TT device known inoperable.

Formula of the Invention A device for protection of a three-phase electrical installation from two-phase operation, comprising two phase current transformers with leads for connection to the phase wires supplying the electrical installation, two phase measuring converters, two inputs of which are connected respectively to the beginnings and ends of the secondary windings of phase transformers current, an electromagnetic contactor, the power contacts of which are connected by one pins to the terminals for connection to the wires of the three-phase network, and others to the three-phase conductors hot electrical installation, operating current source, inputs connected in parallel to the winding of the electromagnetic contactor, a chain connected to the terminals for connection to the supply mains phases and made in the form of successively connected Stop, Start and winding buttons of the electromagnetic contactor, one output of the closing contact block of which is connected to the common point of the Start button and the windings of the electromagnetic contactor, two photo-thyristor counter-parallel-connected optocouplers interconnected by a common connection point the Start and Stop buttons and the second output of the closing contact of the electromagnetic contactor, the LED of one thyristor optocoupler is connected by a cathode to the minus one

the output of the operating current source, and the anode to the cathode of the LED of another thyristor optocoupler, two transistor switches, the inputs of which are connected to the outputs of the respective measuring transducers, and the collector circuits of the transistor switches are connected to the positive output of the operating current source, characterized by In order to simplify and increase the reliability of the device, each phase measuring transducer is made in the form of two anti-parallel-connected chains of series-connected x diode, resistor and zediodiode, shunting zener diode, transistor switches are connected in parallel with each other, each transistor switch contains two series-according to the connected phototransistor of the diode-transistor optocouplers, emitter pins of the phototransistors of the transistor switches are connected to the minus output of the operating current source through a capacitor the resistor - with the anode of the LED of another thyristor optocoupler, and to the ends of the secondary windings of current transformers connected between the cathodes of two LEDs of one transistor switch and the anodes of the LEDs of the other transistor switch are connected to the terminals for connection to the ground terminals of the device.

Claims (1)

Claim A device for protecting a three-phase electrical installation against two-phase operation, comprising two phase current transformers with leads for connection to the phase wires supplying the electrical installation, two phase measuring transducers, two inputs of which are connected respectively to the beginnings and ends of the secondary windings of the phase current transformers, an electromagnetic contactor, the power contacts of which are connected to the terminals with one terminal for connection with the wires of a three-phase network, and others with phase wires of a three-phase electrical installation, operating current source, inputs connected in parallel to the coil of the electromagnetic contactor, a chain connected to the terminals for connecting to the phases of the supply network and made in the form of sequentially connected Stop, Start, and electromagnetic contactor windings, one terminal of the closing block contact of which is connected to the common point of the Start button and the windings of the electromagnetic contactor, two counter-parallel connected photothyristor optocouplers connected to each other by a common connection point of the Start and Stop buttons and the second by the output of the closing block contact of the electromagnetic contactor, the LED of one thyristor optocoupler is connected by a cathode to the negative terminal of the operating current source, and the anode to the cathode of the LED of another thyristor optocoupler, two transistor switches, the inputs of which are connected to the outputs of the corresponding measuring transducers, and the collector circuit of the transistor keys connected by one clamp to the positive terminal of the operating current source, characterized in that, in order to simplify and improve the reliability of the device, Each phase measuring transducer is made in the form of two counter-parallel-connected chains of diode, resistor and szetodiode connected in series by a zener diode, transistor switches are connected in parallel with each other, each transistor switch contains two diode-transistor optocouplers phototransistors connected in series, emitter outputs of phototransistors transistor switches through a capacitor are connected to the negative terminal of the operating current source, and through a limiting re a resistor - with the anode of the LED of another thyristor optocoupler, and the cathodes of two LEDs of one transistor switch and the anodes of the LEDs of another transistor switch are connected to the ends of the secondary windings of the current transformers connected to each other and connected to the terminals for grounding with the common wire of the device. * 1 1 J R | 1 L L_j Compiled by V. Orlov Editor N. Tupitsa Tehred M. Morgenthal Corrector O. Kravtsova Order 4474 Circulation Subscription VNIIIPI of the State Committee for Inventions and Discoveries under the State Committee for Science and Technology of the USSR 113035, Moscow, Zh-35, Raushskaya nab., 4/5 Production and Publishing Combine Patent, Uzhgorod, 101 Gagarin St.