SU1259397A1 - Device for protection of three-phase electric installation against incomplete phase operation - Google Patents

Abstract

The invention relates to the field of electrical engineering - relay protection of a three-phase electric motor against an incomplete-phase mode. The purpose of the invention is to increase the operational reliability by monitoring the integrity of the phases of the network before switching on. The device contains a magnetic contactor, the clocks 4 of which are included in the supply phases of the electric motor 20, and the coil 3 of the contactor through contact I and pin 19 of the actuating element 14 is connected to two phases of the supply network, the Three-phase semi-period rectifiers 1 and 2 are connected to the supply phases before and after power contacts 4 magnetic contactor. Between the outputs of the rectifiers 1 and 2, through the button 5 Start and the deputy 1а10Б | НЮ contact of the toggle switch 18, diode 7 is turned on. To the output of the rectifier 2, the thyristor 8 is connected, the control to the circuit of which is connected through the glow discharge indicator II and the resistor 10 to The rectifier is connected to the device. 1. Control of the integrity of the phases of the network before switching on is ensured by the introduction of two additional capacitors 12 and 13, a current limiting resistor 15, a light indicator 11 and a switch 18 with a short-circuit contact. 2 Il. - -; . JP Yu SP "m

Description

The invention relates to electrical engineering and can be used to protect three-phase electric motors from operating on two phases.

The purpose of the invention is to increase the operational reliability by monitoring the integrity of the phases of the network before turning on the electric motor.

Fig, 1 shows a functional diagram of the proposed device; FIG. 2 shows the diagrams of the rectified voltage.

The device contains two three-phase single-wavelength phase switches 1 and 2, coil 3 contactor ,,. Contacts 4 last, button 5 Start, button b

Stop, diode 7, thyristor 8, resistor 9, first current limiting resistor 10, glow indicator 11, second 12 and third 13 capacitors, actuator coil (relay) 14, second current limiting resistor 15, resistor 16, first capacitor 17, toggle switch 8 with closing contacts, closing contact 19 of the coil of the actuator (relay) 14, electric motor 20, terminals A, B and C of a three-phase sinusoidal alternating voltage, terminal Y of the neutral point of the network.

Fig. 2 shows diagrams of rectified voltage supplied to the thyristor anode 8, which correspond to the normal mode of operation of a three-phase electric motor when three-phase symmetric voltage (a) is applied to it and the case of disappearance of one of the phases (for example, phase B) voltage supply (b)

The device works as follows.

In the presence of a symmetric star of the supply voltage, the waveform at the output of the three-phase half-wave rectifiers 1 and 2 has the form shown in Fig. 2a. When a three-phase sinusoidal, alternating voltage is applied to terminals A, B and C in manual start mode, button 5 is pressed. Start and voltage is applied to resistor 9. Through diode 7 to anode, thyristor 8 through resistor 9, the second capacitor 12 begins to charge. the voltage on the second capacitor 12 reaches the ignition value of the glow discharge indicator 11, the latter ignites and the second capacitor 12 is discharged along the circuit

the first current boundary resistor 10 is a glow discharge indicator II — the control electrode of the thyristor 8. At the same time, the thyristor is turned on. Current flows from pushbutton 5 to start through diode 7, thyristor 8, current limiting resistor 15, third capacitor 13 and coils of the actuator (relay) 14. When charging the third capacitor 13, the coil of the actuator (relay) 14 and its is turned on. With their contact 19, it supplies voltage to the contactor roller 3. In this case, contacts 4 of the coil 3 of the contactor supply 5 voltage to the electric motor 20 and three-phase half-wave rectifier 2, from the output of which to the anode of the thyristor 8. When the start button 5 is released and all three phases are present, the thyristor remains on.

With the disappearance of one phase, for example phase B, at the output of three-phase half-wave rectifiers 1 and 2, the voltage diagram looks like that shown in Fig. 2b. On this diagram there are areas x in which there is no voltage, and therefore.

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the current flowing through the thyristor 8 at this time is zero, the thyristor 8 is closed and after the discharge time of the third capacitor 13 the coil of the actuator (relay) 14 is de-energized, the contact 19 is opened, the coil 3 of the contactor is turned off, which by its contacts 4 turns off the spectromotor 20.

When one of the phases disappears on the high side of the power line on a wire with a missing phase, the voltage of the two remaining phases is induced, so section x can have a very short duration. An artificial switching circuit consisting of a resistor 16 and a first capacitor 17 is designed to turn off the thyristor 8 in such a ditiya.

In the automatic start mode, the toggle switch 18 with normally open contacts is turned on. In this mode, all three phases are monitored only at the input of the device. With the inclusion of the toggle switch 18 start thyristor 8 is the same as in the manual start mode.

When one or two phases disappear, the first capacitor is constantly frozen and discharged through the indicator.

glow glow torch and thyristor 8. At the same time glow glow indicator 11 lights up and goes out. The on-off frequency of the glow discharge indicator 11 and, therefore, the thyristor 8 is selected by the value of the resistor 8 and the first capacitor 12 and is approximately 2 Hz. A blinking glow indicator indicates that there is no phase.

With each bit of the first capacitor 12, the thyristor 8 is switched on with a frequency f of 2 Hz, and is turned off with a frequency of following the henna-diagram (Fig. 26) equal to f 50 Hz.

When the thyristor 8 is turned on and off, the main current passes through the third capacitor 13 and not through the actuator (relay) 14, so the relay does not turn on. When the missing phase is restored, the next discharge of the first capacitor 12 turns on the thyristor 8, a high voltage level is applied at the cathode and the control electrode, therefore the charge discharge of the second capacitor 12 stops and the glow discharge indicator 11 stops flashing. indicates the presence of all phases. When the third capacitor 13 is charged, the coil of the actuator (relay) 14 and, consequently, the electric motor 20 are turned on.

When one or two phases disappear for a time less than 2 seconds (this time is regulated by changing the capacitance value of the second capacitor 13), the thyristor 8 may close, but the coil of the actuating element (relay) 14 is held by the discharge current of the third capacitor 13. Fast recovery of the missing phase again turns on the thyristor 8 for a constant time, i.e. the actuator coil (rail) 14 does not have time to turn off and on, and therefore, short-term switching off and on of the electric motor 20 occurs.

The motor is stopped by the button 6 breaking the current in the thyristor 8 circuit. In this case, the thyristor is closed, the coil of the actuating element (relay) 14 is de-energized, and with its contacts it opens the circuit of the coil 3 of the contactor, which is switched off by contacts 4 and turns off the electric motor. Button 6 Stop at 10

15

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the jam is locked and released from the lock when you press 5 Start.

An artificial switching circuit of the thyristor 8, consisting of a series-connected resistor 16 and the first capacitor 17, is provided in the circuit for increasing the sensitivity of protection.

The application of the proposed device for protection of a three-phase electric motor against an unfinished phase mode favorably distinguishes it from a base object (thermal relay of the type TRI-10). The technical and economic effect is to improve performance.

Claims (1)

Invention Formula A device for protection of a three-phase electric motor against an incomplete-phase mode, containing a switching device, the power contacts of which are connected to the mains phases and the electric motor, and the control coil through the closing contacts of the actuator is connected to two phases of the mains The first current-limiting resistor TK to the first output of the coil of the actuating element, an artificial switching circuit, consists of 1 Y of series-connected ne capacitor and the first resistor and connected by one output to the common point of the Stop button and the first current-limiting resistor, and the other to the second output of the actuator coil connected to the neutral wire of the network, the first and second three-phase single-field rectifiers, the first of which is directly connected An electric button is connected to the terminals of the electric motor, and the second to the three-phase network, and the Start button connected to the diode anode and the first terminal of the second is connected to the output of the second three-phase half-wave rectifier. The cathode of the diode is connected to the thyristor anode and the output of the first one-half-period rectifier, characterized in that, in order to increase the operational reliability by monitoring the integrity of the mains phases before turning on the electric motor, it is equipped with the second and third the capacitor is the second current-limiting resistor, the low-voltage indicator and the switch, the closing contacts of which are included parallel to the Start button, the second terminal of the second resistor is connected to the same terminals of the second capacitor and the second current-limiting resistive A 8 C B C A B C L ./ШШШ1Ш 1259397 - a torus, another (the OUTPUT of which is connected to the control electrode of the thyristor through a glowing indicator, another output of the second capacitor is connected to the neutral point of the network, and the third capacitor is connected parallel to the coil of the actuating element. Editor Y. Derbak Order 5132/53 Draw 612 Subscription VNIIPI USSR State Committee for inventions and discoveries U3035, Moscow, Zh-35, Raushsk nab., 4/3 Production and printing company, Uzhgorod, Projecto st., 4 Ф14г.2 Compiled by V. Orlov Tehred M. Khodanich Proofreader V. But ha