SU1064367A1 - Device for inspecting phase alternation in three-phase four-wire a.c. network - Google Patents

Abstract

A device for controlling the alternation of the phases of a three-phase four-wire alternating current network, containing a phase-shifting chain of a phase-shifting capacitor and two forward and reverse phase alternation signaling lamps, characterized in that, in order to improve the efficiency, the direction of the circuit will decrease, as before, the de- phasing of the phase will decrease, as-circuits will decrease in the same way as before. violation of phase rotation, in one of the phases the primary winding of the phase-changing transformer, made with a transformation ratio of 0.5, is additionally included, and in two d Other phase-shifting chains of series-connected capacitor and resistor with parameters that satisfy the ratio W i, while the end of the primary winding of the phase-shifting transformer is combined with the end of the secondary and capacitors of the phase-shifting chains and connected to the neutral of the network, and the beginning of the secondary winding of the phase-shifting transformer is connected through lamps signaling of direct and reverse phase alternation to the connection points of a capacitor and a phase-shifting resistor.

Description

The device relates to electrical engineering and can be used in electric drive systems, as well as in other systems where control of the correctness of the alternation of the phases of a three-phase network is necessary. Devices are known for controlling the alternation of phases in a three-phase network, containing threshold elements, pulse expanders, logic elements, and an output amplifier with an actuating element. If there is a three-phase voltage at the input of a direct sequence of phase alternation, a sequence of pulses appears at the output of the trigger, which through the output amplifier acts on the actuator. The presence of a three-phase voltage reverse phase sequence device at the input leads to a mismatch of the pulses at the input of the logic element I and, as a result, the sequence of the pulses at the output of the trigger 1 disappears. The disadvantage of such devices is their complexity and the need to use a separate power source microchips Closest to the proposed technical entity is a device for controlling phase alternation, which consists of two signal lamps, included in the first and second phases and a phase-shifting capacitor, included in the third phase. These three elements are connected by a star, and the neutral of the network is not connected to the circuit. With direct phase rotation, the lamp is turned on, turned on in the first phase, and the lamp, turned on in the second phase, is dim. When the phases are reversed, the lamp is turned on in the second phase and the lamp turned on in the first phase is dim (2. The device’s deficiency is low, the accuracy of the information, i.e., the lamp is hot or bright or dim. under external lighting conditions and asymmetry of phase voltages. Under such conditions, it is difficult to determine which lamp is burning and how dim it is very difficult. The purpose of the invention is to increase the efficiency of controlling the phase sequence correctness by reducing the voltage of the phase voltage. accuracy of the information. The goal is achieved by the fact that in the device for controlling the phase alternation of a three-phase four-wire AC network containing a phase-shifting circuit of a phase-shifting capacitor and two signaling lamps for forward and reverse phase alternation, the primary winding is connected in one NC phase shifting transformer., made with a transformation coefficient of 0.5, and into the other two - phase-shifting chains of series-connected Capacitor and a resistor with parameters and satisfying the relation, with the end of the primary winding of the phase-shifting t-ranformator combined with the end of the secondary and capacitors of the phase-shifting chains and connected to the mains neutral, and the beginning of the secondary winding of the specified phase-shifting transformer is connected via signal lamps for forward and reverse phase alternation the capacitor and the resistor of the phase-shifting chains. On fng. shows a diagram of the proposed device; in fig. 2 - vector diagrams, which describe the operation of the device. The device contains a phase-shifting transformer 1, the primary winding of which is connected between one phase conductor and neutral. A chain consisting of a series-connected phase-shifting capacitor 2 and a resistor 3 is connected between the second phase conductor and a neutral, and a similar chain consisting of the phase-shifting capacitor 4 and a resistor 5 is located between the third phase conductor and the neutral. One end of the secondary winding of the phase-shifting transformer I connected to neutral. Between the second end of the secondary winding of the transformer and the junction point of the capacitor 2 and the resistor 3, as well as between the same end of the secondary winding and the point; The connections of capacitor 4 and resistor 5 include two similar chains consisting of series-connected extinguishing resistor 6 and lamp 7 and respectively extinguishing resistor 8 and lamp Q. The principle of operation of the device for controlling the phase rotation of a three-phase network is explained by a vector diagram (FIG. 2), depicted for the case when the phases are connected in direct sequence (Fig. 2a), i.e. phase A to point A, phase B to point B and phase C to point C. The chain consisting of capacitor 2 and resistor 3 creates a leading current shift Jig in phase B by 30 ° with respect to Uj. Identical chain in phase C (capacitor 4 and resistor 5) creates a leading shift toka IB by 30 ° with respect to Uc, i.e. ty ir The Up voltage on the secondary winding of the phase-shifting transformer 1 is shifted relative to Od by 180 ° and is 0.5 UA in magnitude. . When the symmetry of the phase voltages i. UA UB Uc The voltages U and Ua are equal in magnitude and coincide in phase, therefore, the voltage Uj, on the chain consisting of the damping resistor B and lamp 7, is zero and lamp 7 is off. The lamp 9 is thorny and has a negative phase sequence (ABC), since

Voltage 1/44 U | - U 2U | COs30

If the phase rotation order is changed, for example, to connect point C to phase C, and phase C to phase B, it is possible to determine from the vector diagram (Fig. 26) that lamp 7 lights up and lamp 9 goes out. alternating phases (ACE).

The proposed device provides a higher accuracy of information on the order of phase alternation as compared with the prototype, since there is no need to determine the degree of brightness of candlesticks, i.e. Sigial lamp is on or off.

This increase in the accuracy of information is ensured by introducing a phase-shifting transformer with a transformation ratio of 0.5, included in one of the phases of the three-phase circuit, and two phase-shifting chains, included in two other phases of the network. Moreover, n; the arrammeters of each phase-shifting chain provide in them an advance shift of 30 ° compared with the voltage in this phase. Thanks to this in the case of the right; The alternation of phases and under the condition of symmetric NC voltage, the voltage Ue, 7 applied to the signal lamp 7 (wrong phase rotation) is equal to the voltage difference across the second-phase winding transformer n on the capacitor 2, and since | U | I lUi) and coincide in the direction (Fig. 2), this difference is equal to a scale and the lamp 7 does not light up; Lamp voltage 9 (correct phase rotation) equal to the difference

the voltage Oi on the secondary plug of the inverting transformer and 0 on the capacitor 4 (Fig. 2) is different from zero and equal to 2 U (cos 30 °. Consequently, the lamp 9 is on, and the right phase 5 is symmetrical and the phase voltages are symmetric, for example The life on lamp 9 is zero (Fig. 2 $) and is different from zero on lamp 7. The latter is lit, with a warning about the wrong phase rotation.

Q The asymmetry occurring in real networks is 15–20 / o nominal voltage level, therefore, under the condition of voltage inequality, the voltage on the signal lamp that does not burn is different from zero, but not enough to cause a glow its filament, in contrast to the prototype, where the signal lamps are constantly present on: a voltage different from zero sufficient to cause a glow of the filament.

In addition, the asymmetry of phase voltages in a real three-phase network also reduces the accuracy of the information in the prototype circuit, since the more intense luminescence of the corresponding signal lamp can signal not the correct (wrong) phase alternation. that the asymmetry in this phase exceeds the permissible rate.

Therefore, the proposed device

improves the conditions of operation of systems where

It is necessary to control the correctness of the alternation of phases, by eliminating the influence and asymmetry of the phases on the accuracy of controlling the alternation of phases. As a result, the time is reduced.

find and fix the problem.

Claims (1)

DEVICE FOR CONTROL OF PHASES OF ALTERNATING PHASES OF A THREE-PHASE FOUR-WIRING AC NETWORK, containing a phase-shifting chain of a phase-shifting capacitor and two signaling lamps for forward and reverse phase rotation, characterized in that, in order to increase the efficiency of monitoring ways to reduce the influence of voltage asymmetry on phase accuracy information , one of the phases additionally includes the primary winding of the phase-reversing transformer, made with a transformation coefficient of 0.5, and in the other two - phase-shifting chains of a series-connected capacitor and resistor with parameters satisfying the relation, while the end of the primary winding of the phase-shifting transformer is combined with the end of the secondary and capacitors of the phase-shifting chains and connected to the neutral of the network, and the beginning of the secondary winding of the phase-shifting transformer is connected through the signal lamps of the forward and reverse phase rotation to the connection points of the capacitor and the resistor of the phase-shifting chains.