SU922941A1 - Device for protecting three-phase electric equipment from breaking one of phase wires - Google Patents

Description

The invention relates to electrical engineering, in particular to relay protection of three-phase electrical installations, such as electric motors, against breakage of one of the phases.

Known devices for protection ⁵

electric motors from the interruption of one of the phases that react to overcurrent in this mode [1].

However, such devices have bol- ¹⁰ Choe response time.

The closest in technical essence to the proposed device is! to protect a three-phase electrical installation from the interruption of one of the phases, containing three current transformers included in the phase circuits, the magnetic system of which is fast dissolving, the main secondary windings' _{n are} connected in an open triangle and connected via a rectifier to the reacting organ, and the auxiliary secondary windings are connected sequentially 2

and closed to a capacitor to create ferromagnetic resonance (2) ...

A disadvantage of the known device is low efficiency, due to the consumption of electricity in full-phase mode of operation and inconvenience in operation, caused by the need to install current transformers with additional secondary winding and setting the circuit of ferromagnetic resonance.

The purpose of the invention is to increase the efficiency, reliability and ease of operation of the device.

This goal is achieved by the fact that in the device for protection of a three-phase electrical installation from the interruption of one of the phases containing three current transformers connected to the phase supply wires, the secondary windings of which are connected to an open triangle and connected to the reacting element through a rectifier as a current transformer of the first phase trans3 922941 4 is applied

current characteristic with linear characteristic; current transformers of the second and third phases used branched magnetic current transformers, having two rods with 5 linear magnetization characteristics and one fast unlocking rod, while the secondary winding of the current transformer of the second phase is located on the second rod with linear characteristics - By magnetization, and the secondary winding of the current transformer of the third phase is located on the fast-saturating rod, and their primary windings are located on the first x rods with linear 5 magnetization characteristic.

FIG. 1 depicts a fundamental. the electrical circuit of the device to protect the three-phase electrical installation from the break of one of the phases in fig. 2 - currents of the secondary windings of current transformers of individual phases in full-phase mode of operation ( _{ί Λι} 1 ^, I ^); in fig. 3 '”harmonic components of the currents of the secondary windings of current transformers ^{25 of the} second and third phases.

The device contains three transformers 1, 2 and 3 of current, included in the circuits of phases A, B and C, a rectifier 4, a reacting organ 5, a normally-closed 30 pin 6 of which is installed in series with the coil supply circuit of the electromagnetic switch 7 with the power contacts 8, 9 and 10 for connecting electrical installations. 11 to the power sources ₃₅ and nick with a contact 12 for creating samopodpitki chain, as well as buttons 13, the "Start" and 14 "stop" control.

40

In the initial position responsive element 5 is de-energized and its normally-closed contact 6 gives permission for the supply to the coil of the electromagnetic switch 7. Pressing knop- ⁴⁵ ki control coil 13 of the electromagnetic switch 7 are fed along the chain: In phase - control button 14 - the button control 13 - the switch coil 7 "track 6 rea- ⁵⁰ tiruyuschego body 5 - phase C. Contact switch 12 shunts the control button 13 and the power contacts 8, 9 and 10 commute phase circuit connecting electrical installation 11 to the source of * ⁵ niku power.

The transformer 1 of the current of the first phase has a linear magnetization characteristic and the current 1 of the secondary winding is sinusoidal with a sinusoidal primary current (Fig 2). The magnetic system of transformers 2 and 3 of the current of the second and third phases is branched and has two rods with a linear characteristic, magnetization and one fast-saturating rod, and their secondary windings are located on the rod with a linear magnetization characteristic (current transformer 2) on the fast-saturating rod (transformer 3 currents). With a sinusoidal primary current on the secondary windings of current transformers of the second and third phases, in addition to the main, there are odd harmonic components. The material of the rods of the branched magnetic system of current transformers of the second and third phases, a. also their section is chosen so that the current of the secondary winding of the transformer! The second phase current 3 ^ represents the sum, and the secondary current of the third phase current transformer is For the difference between the currents of the main and third harmonic components, and the currents of the higher harmonic components are absent or very small (Fig. 3).

In single-phase operation, the total current flowing in the secondary winding circuit will be zero and the reacting organ continues to be in a de-energized state.

_> If one of the phases is cut off, the currents of the secondary windings of the current transformers of the remaining two phases will be shifted by 180® ³ , and the resulting current will be 'equal to the amplitude doubled current of the third harmonic component (break of the first phase) or current of the third harmonic component (break of the third or second phase ). This current is rectified by the rectifier 4 and triggers the reacting organ 5 · The reacting organ triggers and with its normally closed contact 6 breaks the power supply circuit of the coil of the electromagnetic switch 7, removes it from the self-energizer, and by its contacts 8, 9 'and 10 it disconnects the electrical installation 11 from power source.

The proposed device for the protection of three-phase electrical installation from the break of one of the phases is economical, reliable and convenient in operation and can find

5,922,941 6

widely used to protect three-phase electrical installations.

Claims (1)

Claim A device for protection of a three-phase electrical installation from the interruption of one of the phases, containing three current transformers included in the phase ¹ power supply wires, the secondary windings of which are connected to an open triangle and connected to the reacting element through a rectifier, distinguishing ** me in that economical, reliable and easy to use, a current transformer with linear characteristics was used as a current transformer of the first phase. Which, as current transformers of the second and third phases, used current transformers with a branched magnetic system, having two rods with a linear magnetization characteristic and one fast-dissolving ster? 5, the secondary winding of the current transformer of the second phase is located on the second rod with a linear magnetization characteristic, and the secondary winding of the current transformer of the third phase is located on the rapidly saturating rod, and their primary windings are located on the first rods with a linear magnetization characteristic.