SU1617569A1 - Device for controlling power three -phase load - Google Patents

Abstract

The invention relates to devices for controlling three-phase power, for example, electric furnaces and various electric heaters with a two-piece heating element in each phase. The purpose of the invention is to expand the adjustment capabilities and improve the energy performance by increasing the number of stages of regulation without increasing the number of load sections. The device contains three AC thyristor switches on thyristors 28–33 and keys 7–27. Using three-phase switches, each phase contains two sections, it is connected via one of twelve symmetric circuits, each of which corresponds to the power consumed from the network. Between adjacent fixed stages of power consumption, it is smoothly controlled by phase voltage regulation. By increasing the number of power levels while smoothly controlling its consumption, the goal is achieved. 3 il.

Description

1

The invention relates to devices for controlling three-phase power, for example electric furnaces and various industrial electric heaters with two-section heating elements in each phase.

The purpose of the invention is to expand the adjustment capabilities and improve the energy performance by increasing the number of stages of regulation without increasing the number of load sections.

Figure 1 is a schematic diagram of the proposed device; Fig. 2 shows a table of states of alternating current switches and their corresponding power; in fig. 3 shows the wiring diagrams of the load sections, corresponding to different variants of the alternating current key states.

The device (FIG. 1) contains sections 1-6 of two-section phase loads, keys 7

27 alternating current and thyristors 28 33. The successively connected pairs of sections 1 and 2, 3 and 4, 5 and 6 of the phases of the load are interconnected in a triangle via keys 13-21, forming three three-switching groups, also connected in triangles. The beginnings and ends of the phase loads from the sections are connected with a pair of keys 7 and 10, 8 and 11.12 and 19, and met-parallel-connected thyrisor pairs

28 and 29. 32 and 33. 30 and 31 to the terminals for connecting the mains A, C, B and interconnected through pairs of keys 24 and 25, 26 and 27, and the connection points of the load sections are connected to the free vertices of the adjacent phase key triangles formed by key pairs 17 and 20,

18 and 21, 16 and 19, which are interconnected through another pair of keys 22 and 23.

The device works as follows.

Switching the keys 7-27 provides a change in the structure of the circuit with a step change in the loads and the voltages applied to them, and the phase control of the counter-parallel thyristor pairs 28 and 29, 32 and 33, 30 and 31 ensures smooth control of the voltage and the power released in the load. within each stage of regulation.

Step regulation is carried out in accordance with the state table of switches 7-27 in FIG. 2 for each of the 12 possible adjustment steps, each of which corresponds to one of the circuits 34-45 (FIG. 3) for connecting the loads. The total control range is determined by the maximum and minimum power released in the load. The maximum power released in the load corresponds to the case of parallel connection of common load sections 1 and 2, 3 and 4. 5 and 6 for full linear voltage (state of keys 1 -FIG.2, circuit 34). The minimum power stage corresponds to the connection of series-connected common-phase load sections for phase voltage.

The magnitude of the adjustment steps and their uniformity are determined by the choice of specific resistances of the common-load sections. When the power ratio of the Pi / P2 sections is 1.5, the ratio of the relative powers in the order of decreasing them is 5: 3.734: 3: 2.078: 2; 1.867: 1.67: 1. 38: 1.2: 1: 0.67: 0.4.

A large number of stages of regulation allows a more smooth control of power in a three-phase load with an increase in the power factor in the whole range, since the phase regulation will be provided with small angles of regulation of the counter-parallel thyristor pairs within each stage, and in general some cases can be dispensed with phase regulation.

There are various options for the proposed device. For example, if the CTynefi4aToro is sufficient, the control of the anti-parallel thyristor pairs 2833 may be absent, may be phase-controlled; ., based on the same counter-parallel thyristor pairs, keys. The keys themselves can be made as separate switching elements, or group ones: two-and three-pole simple and switching two-position switches (relays, contactors, etc.).

Claims (1)

Apparatus of the Invention A device for controlling the power of a three-phase load, each phase of which is made up of two sections in series, containing three alternating current keys and three pairs of thyristors, in each of which the anode of one thyristor is connected to the cathode of the other, and their connection point is connected to the corresponding output for connecting the power supply network, so that, with a chain of extending the adjustment capabilities and improving the energy performance by increasing the number of stages of regulation without increasing the number of load sections, eighteen AC switches were inserted, the free power terminals of each pair of thyristors were combined, and the first, second, and third switches of the alternating current were connected to the output to connect the beginning of the load of the corresponding phase, and the fourth, fifth, and fifth keys of the alternating current were connected With the output for connecting the end of the load of the corresponding phase, the seventh, eighth, ninth, tenth, eleventh, twelfth, thirteenth, fourteenth, and fifteenth keys of alternating current form tr triples of keys connected in delta, two of the vertices of which are connected to the output for connecting the end of the load of the corresponding phase and to the output for connecting the beginning load of the adjacent phase, and one third of the apex of the triangle is connected to the point of connection of the free-phase loading sections The load of the first phase is connected via the sixteenth AC key with the output house to connect the start of the load vtg; a phase swarm, which is connected to an output via the seventeenth AC switch to connect the beginning of the load of the third phase. the output for connecting the end of the coyur through the eighteenth AC key is connected to the output for connecting the end of the first phase load, which is connected to the output for connecting the end of the second phase load; the output for connecting the common point of the third phase load sections is connected to pins for connecting common points of the load sections of the second and third phases through the twentieth and twenty-first keys of alternating current, respectively. Fig.Z