RU119544U1 - STATIC FREQUENCY CONVERTER FOR TESTING TRANSFORMER AND REACTOR EQUIPMENT - Google Patents

Abstract

Static frequency converter (FFC) for testing transformer-reactor equipment, containing three single-phase units for converting three-phase mains voltage into single-phase voltage, adjustable in frequency and amplitude, each of which is connected by the output to the primary winding of its separate single-phase transformer, and the input is connected to the first output control unit, while the ends of the secondary windings of single-phase transformers are connected together at a common point, and the beginnings of the secondary windings of the first and third transformers are connected respectively to the first and third output terminals, a switch with closing contacts and a drive, connected by its input to the second output of the control unit, and two closing contacts of the switch connect the beginning of the secondary winding of the first transformer with the beginning of the secondary windings of the second and third transformers, in addition, the first output terminal is connected to the beginning of the secondary winding of the second transformer through the first closure an opening contact of the switch, characterized in that the switch is additionally equipped with a third make contact connected between the common point and the second output terminal, and a fourth contact - open contact connected between the second output terminal and the beginning of the secondary winding of the second transformer.

Description

The proposal relates to electrical engineering, to static frequency converters for providing power supply during testing and is used in testing transformers and high power reactors.

The well-known circuit / 1 / for testing transformer-reactor equipment uses a single-phase regulated network in the form of an autonomous generator, alternately connected to two terminals of the tested device. The disadvantage of this scheme is the complexity of the transition from one measurement scheme to another, as this is done manually.

The closest in technical essence and the achieved results is a static converter / 2 / frequency (HFC) for testing transformer and reactor equipment, containing three single-phase units for converting three-phase mains voltage to a single-phase voltage, adjustable in frequency and amplitude, each of which is connected to the primary output the winding of its separate single-phase transformer, and the input is connected to the first output of the control unit, while the ends of the secondary windings of single-phase transformers are connected together at the common point, and the beginnings of the secondary windings of the first and third transformers are connected, respectively, to the first and third output terminals, a switch with make contacts and a drive connected to the second output of the control unit by its input, and two make contacts of the switch connect the start of the secondary windings of the first transformer with the beginnings of the secondary windings of the second and third transformers, in addition, the first output terminal is connected to the beginning of the secondary winding of the second transformer through the first circuit breaker contact.

This "phase switch / 2 / connects the output windings of the transformers in parallel in single-phase mode and in a three-phase circuit in three-phase mode." The disadvantage of the prototype is the relatively low coefficient of use of HF equipment when tested in single-phase mode.

The technical result is the best use of the available power of the HRC, simplification of the test process, increasing its reliability,

The technical result is achieved due to the fact that the circuit breaker is additionally equipped with a third make contact connected between the common point and the second output terminal and a fourth make contact, also connected between the second output terminal and the beginning of the secondary winding of the second transformer.

Thanks to these contacts, an automatic change of the operating mode of the HRC is made, which simplifies the test process.

Figure 1 shows the load power circuit in a three-phase test mode.

Figure 2 shows the equivalent circuit load power in a single-phase test mode.

Figure 3 shows the equivalent circuit of the load power in a single-phase test mode for the known circuit / 3 /.

A static frequency converter for testing transformer and reactor equipment, contains three single-phase units 1, 2, 3 converting a three-phase mains voltage to a single-phase voltage, adjustable in frequency and amplitude. Each conversion unit is connected by an output to the primary winding of its single-phase transformer 4, 5, 6, and by an input connected to the first output of the control unit 7. The ends of the secondary windings of single-phase transformers are connected together to a common point N.

There is a switch 8 with make contacts 9, 10, 11 and a make contact 12 with the drive (coil) 13. Moreover, the contacts 11 and 12 are additionally introduced. The drive with its input is connected to the second output of the control unit. The output terminals of the HFC are designated 14, 15, 16. The beginning of the secondary windings of the first 4 and third 6 transformers are connected to the first 14 and third 16 output terminals.

The first output terminal 14 is also connected to the beginning of the secondary winding of the second transformer 5 through the first make contact 9 of the switch 8.

The beginning of the secondary winding of the first transformer 4 through the make contacts 9 and 10 of the switch is connected to the beginnings of the secondary windings of the second 5 and third 6 transformers.

An additional make contact 11 on one side is connected to a common point N of all transformers, and on the other hand, with a second output terminal 15. An additional make contact 12 is connected between the beginning of the secondary winding of the second transformer 5 and the second output terminal 15. The control unit 7 sets the modes and operating parameters for blocks 1 ÷ 3 and drive 13. The test load 17 (three-phase transformer or reactor) is also shown, connected to the output terminals 14 ÷ 16.

HRC works as follows. Blocks 1, 2, 3 receive the mains voltage and in a known manner (through the rectification-filtering-inverting cycle) convert it into a single-phase sinusoidal voltage of adjustable frequency and amplitude. The control unit 7 sets the operation modes and parameters. Two operating modes are possible: three-phase and single-phase.

In the three-phase operation shown in FIG. 1, transformers 4 ÷ 6 form a star circuit. In this case, each of blocks 1–3 generates a voltage that is shifted in phase with respect to the voltage of other blocks. These three voltages are applied to the output terminals 14, 15, 16 to which the test load 17 (transformer) is connected. Contact 12 is in the closed state, and contacts 9, 10, 11 are in the open state. The measurement scheme for the load in figure 1 is not shown, since it is optional, and its configuration depends on the type of test (measurement), type of instrument, etc.

In single-phase mode, at the command of the control unit, the drive 13 automatically switches contacts 9 ÷ 12. In this case, the contact 12 is opened, and the remaining contacts are closed. Moreover, all the beginnings of transformer windings 4–6 are connected to the output terminal 14, and their ends (common point N) are connected to the output terminal 15. Blocks 1–3 work in parallel and generate in-phase voltages by the signal from the control unit 7. The resulting load power equivalent circuit is shown in FIG. 2. It can be seen from it that the load phase 17 connected to the output terminals 14, 16 is shorted, so that its two other phases can consume more current (power) from the frequency converter. A “normal” switching circuit (without shorting one load phase, see, for example, / 3 /, where a circuit with alternating switching of phase pairs is shown) is shown in Fig. 3. In such a switching circuit (Fig. 3), in contrast to the circuit shown in Fig. 2, an uneven and, most importantly, undetectable distribution of currents over the phases of the load occurs, since the current in one phase is between contacts 14, 15, approximately two times more than in the other two phases - between contacts 14, 16 and 15, 16. In figure 2, the distribution of currents along the windings of two different phases of the load is the same. Measurements of currents directly in the phase windings are not always possible, since only three leads are output from the triangle of the transformer windings 17 (load) - the vertices of the triangle, and the leads (the beginnings and ends of the individual windings) are not output. In addition, in two windings of different phases of the transformer (reactor), an identical and larger magnetic flux than in FIG. 3 is created, which ensures the symmetry of this flux in these windings.

Thus, the proposed inclusion allows a more rational use of power at the output of the HF and, therefore, expands the load capabilities. Technological operations are accelerated, since manual switching is not required when switching from the three-phase test mode to the single-phase mode and, conversely, due to the automatic switching of the switch contacts.

Information sources:

1. Aleksenko G.V. etc. Testing of high-voltage and powerful transformers and autotransformers. M., SEI, 1962, p. 579, Fig. 7-6.

2. lme.org.ru> products / sfc.htm (prototype)

3. Patent RU No. 2282862, IPC class: G01R 31/06, 2006, bull. 24.

Claims (1)

A static frequency converter (HFC) for testing transformer and reactor equipment, containing three single-phase units for converting a three-phase mains voltage to a single-phase voltage, adjustable in frequency and amplitude, each of which is connected by an output to the primary winding of its own single-phase transformer, and the input is connected to the first output control unit, while the ends of the secondary windings of single-phase transformers are connected together to a common point, and the beginning of the secondary windings of the first and third trans the transformers are connected respectively to the first and third output terminals, a switch with make contacts and a drive connected to the second output of the control unit by its input, and two make contacts of the switch connect the beginning of the secondary winding of the first transformer with the beginnings of the secondary windings of the second and third transformers, in addition, the first the output terminal is connected to the beginning of the secondary winding of the second transformer through the first closing contact of the switch, characterized in that the switch is an additional but it is equipped with a third make contact connected between the common point and the second output terminal, and a fourth make contact, connected between the second output terminal and the start of the secondary winding of the second transformer.