CN110620001A

CN110620001A - Test transformer

Info

Publication number: CN110620001A
Application number: CN201810635056.2A
Authority: CN
Inventors: 熊锋; 刘国训; 欧小平; 何海江
Original assignee: TBEA Hengyang Transformer Co. Ltd
Current assignee: TBEA Hengyang Transformer Co. Ltd
Priority date: 2018-06-20
Filing date: 2018-06-20
Publication date: 2019-12-27

Abstract

The invention provides a test transformer which comprises at least one of a first shunting switch, a second shunting switch, a third shunting switch, a fourth shunting switch and a fifth shunting switch, wherein the first shunting switch is used for realizing the conversion between a direct connection state and an excitation state of a three-phase primary side winding and a secondary side winding, the second shunting switch is used for realizing the conversion between an internal tap and a full turn of the primary side winding of each phase, the third shunting switch is used for realizing the conversion between a star connection and an angular connection of the three-phase primary side winding, the fourth shunting switch is used for realizing the conversion between a star connection and an angular connection of the three-phase secondary side winding, and the fifth shunting switch is used for realizing the conversion between a serial connection and a parallel. In the invention, any one or more of various changes such as direct connection of the primary winding and the secondary winding, tapping of the primary winding, serial/parallel connection of the secondary winding, star/angular connection of the primary winding and star/angular connection of the secondary winding can be realized by only adopting one testing transformer, so that expected partial or even all test projects can be finished by utilizing one testing transformer, the cost is low, and the occupied area is small.

Description

Test transformer

Technical Field

The invention relates to the technical field of transformer production, in particular to a test transformer, and particularly relates to a test transformer capable of realizing multiple changes of primary and secondary winding direct connection, primary winding tap, secondary winding serial/parallel connection, primary winding star/angle connection, secondary winding star/angle connection and the like.

Background

At present, the connection groups of the conventional transformer are relatively fixed, namely: the wiring method of the original secondary side three-phase winding is either star connection or delta connection, and mutual conversion cannot be realized; the primary and secondary windings of the conventional transformer cannot be directly connected; the secondary three-phase winding of the conventional transformer can not realize series-parallel connection change.

Therefore, if the conventional transformer is directly used as a test transformer, all the expected test items are completed, and the conventional transformers with different primary and secondary winding structures need to be configured, so that the cost is high, and the occupied area is large.

Disclosure of Invention

The present invention has been made to solve, at least in part, the technical problems occurring in the prior art.

The technical scheme adopted for solving the technical problem of the invention is as follows:

the invention provides a test transformer which comprises a three-phase iron core, and a three-phase primary winding and a three-phase secondary winding which are respectively wound on the three-phase iron core, and also comprises at least one of a first tapping switch, a second tapping switch, a third tapping switch, a fourth tapping switch and a fifth tapping switch, wherein the first tapping switch is used for realizing the conversion between the direct connection state and the excitation state of the three-phase primary winding and the secondary winding, the second tapping switch is used for realizing the conversion between the internal tapping of each phase primary winding and the full turn, the third tapping switch is used for realizing the conversion between the star connection and the angular connection of the three-phase primary winding, the fourth tapping switch is used for realizing the conversion between the star connection and the angular connection of the three-phase secondary winding, and the fifth tapping switch is used for realizing the conversion between the internal series connection and the parallel connection of each phase secondary winding.

Optionally, each phase of the primary winding is divided into a first primary winding and a second primary winding, and each phase of the secondary winding is divided into a first secondary winding and a second secondary winding.

Optionally, the head outgoing lines of the first primary winding of each phase and the first secondary winding of each phase, or the head outgoing lines of the second primary winding of each phase and the second secondary winding of each phase are connected to the first tapping switch; the first tapping switch is specifically used for enabling the three-phase primary and secondary windings to be in a through state when a through gear is adjusted, and enabling the three-phase primary and secondary windings to be in an excitation state when an excitation gear is adjusted.

Optionally, the respective head and tail outgoing lines of the first primary winding and the second primary winding of each phase are connected to the second tapping switch; the second tap switch is specifically configured to, when a tap gear is adjusted, enable the first primary winding of each phase not to operate and only enable the second primary winding of each phase to operate, or enable the second primary winding of each phase not to operate and only enable the first primary winding of each phase to operate; and when the full-turn gear is adjusted, the first primary winding and the second primary winding of each phase are connected in series and then work together.

Optionally, a tail outgoing line of the second primary winding of each phase or a tail outgoing line of the first primary winding of each phase is connected to the third tapping switch; the third tapping switch is specifically used for enabling the three-phase primary winding to be in angular connection when the angular connection gear is adjusted, and enabling the three-phase primary winding to be in star connection when the star connection gear is adjusted.

Optionally, a tail outgoing line of the second secondary winding of each phase or a tail outgoing line of the first secondary winding of each phase is connected to the fourth tap switch; the fourth tapping switch is specifically used for enabling the three-phase auxiliary winding to be in angular connection when the angular connection gear is adjusted, and enabling the three-phase auxiliary winding to be in star connection when the star connection gear is adjusted.

Optionally, leading-out wires at the head and the tail of each of the first secondary winding and the second secondary winding of each phase are connected to the fifth tapping switch; the fifth tapping switch is specifically used for enabling each phase of the first secondary winding to be connected with the second secondary winding in parallel when the parallel gear is adjusted, and enabling each phase of the first secondary winding to be connected with the second secondary winding in series when the series gear is adjusted.

Optionally, the first primary winding is divided into a first primary inner winding and a first primary outer winding which are connected in series, and the second primary winding is divided into a second primary inner winding and a second primary outer winding which are connected in series;

the first secondary winding is divided into a first secondary inner winding, a first secondary middle winding and a first secondary outer winding which are connected in series, and the second secondary winding is divided into a second secondary inner winding, a second secondary middle winding and a second secondary outer winding which are connected in series;

the first secondary inner winding, the second secondary inner winding, the first primary inner winding, the second primary inner winding, the first secondary inner winding, the second secondary inner winding, the first primary outer winding, the second primary outer winding, the first secondary outer winding and the second secondary outer winding are sequentially sleeved on the iron core from inside to outside.

Optionally, the first primary winding and the second primary winding have the same structure and the same number of turns, the first primary inner winding and the first primary outer winding have the same number of turns, and the second primary inner winding and the second primary outer winding have the same number of turns;

the first secondary winding with the structure and the number of turns of the second secondary winding are the same respectively, the first secondary inner winding with the number of turns of the first secondary outer winding are the same, the second secondary inner winding with the number of turns of the second secondary outer winding are the same.

Optionally, each tap changer is an off-circuit tap changer.

Optionally, the test transformer further comprises a control unit, configured to control actions of the tap changers and read current state information of the test transformer.

Has the advantages that:

in the invention, any one or more of various changes such as direct connection of the primary winding and the secondary winding, tapping of the primary winding, serial/parallel connection of the secondary winding, star/angular connection of the primary winding and star/angular connection of the secondary winding can be realized by only adopting one testing transformer, so that expected partial or even all test projects can be finished by utilizing one testing transformer, the cost is low, and the occupied area is small.

Drawings

Fig. 1 is a schematic diagram of a tap changer wiring provided by an embodiment of the present invention;

fig. 2 is a tap changer gear table provided in an embodiment of the present invention;

fig. 3 is a schematic plan view of a test transformer according to an embodiment of the present invention;

FIG. 4 is a schematic diagram of an arrangement of single-phase primary and secondary windings according to an embodiment of the present invention;

fig. 5 is a schematic diagram of a tap angle connection of a three-phase primary winding according to an embodiment of the present invention;

fig. 6 is a schematic diagram of a full-turn angle connection of a three-phase primary winding according to an embodiment of the present invention;

fig. 7 is a schematic diagram of a three-phase primary winding tap star connection provided in the embodiment of the present invention;

fig. 8 is a schematic diagram of a full-turn star connection of a three-phase primary winding according to an embodiment of the present invention;

FIG. 9 is a schematic diagram of a three-phase secondary winding series connection angle connection provided by an embodiment of the invention;

fig. 10 is a schematic diagram of a series star connection of three-phase secondary windings according to an embodiment of the present invention;

FIG. 11 is a schematic diagram of a parallel connection of three-phase secondary windings according to an embodiment of the present invention;

fig. 12 is a schematic diagram of a three-phase secondary winding parallel star connection provided in the embodiment of the present invention.

In the figure: 1-a first tap switch; 2-a second tap switch; 3-a third tapping switch; 4-a fourth tap switch; 5-a fifth tap switch; LV-low voltage winding; MV — medium voltage winding; HV-high voltage winding; tap-voltage regulating winding; LV inner 1-first secondary side inner winding; LV inner 2-second secondary side inner winding; HV1 inner-first primary side inner winding; HV2 inner-second primary side inner winding; 1 in LV-first secondary winding; 2-second secondary side winding in LV; HV1 outer-first primary side outer winding; HV2 outer-second primary side outer winding; LV outer 1-first secondary outer winding; LV outer 2-second secondary outer winding.

Detailed Description

In order to make the technical solutions of the present invention better understood, the present invention is further described in detail below with reference to the accompanying drawings and examples.

The embodiment provides a test transformer, which comprises a three-phase iron core, and a three-phase primary winding and a three-phase secondary winding which are respectively wound on the three-phase iron core.

As shown in fig. 1 to 3, the test transformer further includes at least one of a first tap switch 1, a second tap switch 2, a third tap switch 3, a fourth tap switch 4, and a fifth tap switch 5. The first tapping switch 1 is used for realizing the conversion between the direct connection and the excitation state of the three-phase primary and secondary windings, the second tapping switch 2 is used for realizing the conversion between the internal tapping of each phase primary winding and the full turn, the third tapping switch 3 is used for realizing the conversion between the star connection and the angular connection of the three-phase primary winding, the fourth tapping switch 4 is used for realizing the conversion between the star connection and the angular connection of the three-phase secondary winding, and the fifth tapping switch 5 is used for realizing the conversion between the serial connection and the parallel connection inside each phase secondary winding. Wherein star connection refers to star connection, and angle connection refers to triangle connection.

In the embodiment, any one or more of various changes such as direct connection of the primary winding and the secondary winding, tapping of the primary winding, serial/parallel connection of the secondary winding, star/angular connection of the primary winding and star/angular connection of the secondary winding can be realized by only one testing transformer, so that expected partial or even all test items can be completed by one testing transformer, the cost is low, and the occupied area is small.

Preferably, each tap changer is an off-circuit tap changer.

In the embodiment, each phase of primary winding is divided into a first primary winding and a second primary winding, the number of turns of the second primary winding is the number of turns at a tap, and the number of turns of the first primary winding is the number of full turns minus the number of turns at the tap; each phase of secondary windings is divided into a first secondary winding and a second secondary winding.

The specific operation of the first to fifth tap switches will be described in detail based on the structures of the split primary and secondary windings with reference to fig. 1 and 2.

As shown in fig. 1, in the wire frame where the second tap switch 2 is located, the winding between a1 and a2 is an a-phase first primary winding, and the winding between A3 and a4 is an a-phase second primary winding; the winding between B1 and B2 is a first primary winding of a B phase, and the winding between B3 and B4 is a second primary winding of the B phase; the winding between C1 and C2 is a C-phase first primary winding, and the winding between C3 and C4 is a C-phase second primary winding.

In the wire frame where the fifth tap switch 5 is located, the winding between a1 and a2 is a-phase first secondary winding, and the winding between a3 and a4 is a-phase second secondary winding; the winding between b1 and b2 is a b-phase first secondary winding, and the winding between b3 and b4 is a b-phase second secondary winding; the winding between c1 and c2 is a c-phase first secondary winding, and the winding between c3 and c4 is a c-phase second secondary winding.

As shown in fig. 1, the head outgoing lines of the first primary winding of each phase and the first secondary winding of each phase (or the head outgoing lines of the second primary winding of each phase and the second secondary winding of each phase) are connected to the first tap switch 1. As shown in fig. 2, the first tap switch 1 is specifically configured to, when a through gear (i.e., a gear "1" in the gear table of the first tap switch in fig. 2) is adjusted, make the three-phase primary and secondary windings through, that is, the a-phase primary winding is connected to the a-phase secondary winding, the B-phase primary winding is connected to the B-phase secondary winding, and the C-phase primary winding is connected to the C-phase secondary winding; and when the excitation gear is adjusted (namely, the gear position is '2' in the gear position table of the first tapping switch in the figure 2), the three-phase primary and secondary windings are in an excitation state, namely A, B and the C-phase primary winding are disconnected with the a-phase secondary winding, the b-phase secondary winding and the C-phase secondary winding respectively.

In this embodiment, the test transformer adopts the first tap switch 1 to realize the direct connection of the primary side and the secondary side, that is, the direct connection of the primary side input and the secondary side output, when the first tap switch 1 is adjusted to the gear "1", the primary side and the secondary side are in the direct connection, and when the first tap switch 1 is adjusted to the gear "2", the primary side and the secondary side are in the excitation state. After the primary and secondary windings are directly connected, the input voltage and current of the primary winding are directly connected to the secondary winding, the voltage and current supplied to the load by the secondary winding are the voltage and current of the primary winding, and meanwhile, the primary and secondary windings of the test transformer are not excited and do not work.

As shown in fig. 1, the respective head and tail outgoing lines of the first primary winding and the second primary winding of each phase are connected to the second tapping switch 2. As shown in fig. 2, the second tap changer 2 is specifically configured to, when a tap shift is adjusted (i.e. a shift position "1" in the shift table of the second tap changer in fig. 2), make the first primary winding of each phase not work and only make the second primary winding of each phase work (or make the second primary winding not work and only make the first primary winding work), and when a full-turn shift is adjusted (i.e. a shift position "2" in the shift table of the second tap changer in fig. 2), make the first primary winding and the second primary winding of each phase work together after being connected in series, so as to realize a change between an internal tap and a full turn of the primary winding of each phase through different shift positions of the second tap changer 2.

As shown in fig. 1, the tail outgoing line of the second primary winding of each phase (which may also be the tail outgoing line of the first primary winding) is connected to the third tapping switch 3. As shown in fig. 2, the third tap changer 3 is used in particular to angle-connect the three-phase primary windings when adjusting to an angular gear (i.e. gear "1" in the third tap changer gear table in fig. 2) and to star-connect the three-phase primary windings when adjusting to a star gear (i.e. gear "2" in the third tap changer gear table in fig. 2).

As shown in fig. 1, the tail outgoing line of the second secondary winding (which may also be the tail outgoing line of the first secondary winding) of each phase is connected to the fourth tap switch 4. As shown in fig. 2, the fourth tap changer 4 is used in particular to angle-connect the three-phase secondary windings when adjusting to an angular gear (i.e. gear "1" in the fourth tap changer gear table in fig. 2) and to star-connect the three-phase secondary windings when adjusting to a star gear (i.e. gear "2" in the fourth tap changer gear table in fig. 2).

As shown in fig. 1, the respective head and tail outgoing lines of the first secondary winding and the second secondary winding of each phase are connected to the fifth tap switch 5. As shown in fig. 2, the fifth tap changer 5 is specifically configured to connect the first and second secondary windings of each phase in parallel when a parallel shift (i.e., shift position "1" in the fifth tap shift table in fig. 2) is adjusted, and to connect the first and second secondary windings of each phase in series when a series shift (i.e., shift position "2" in the fifth tap shift table in fig. 2) is adjusted.

As shown in fig. 4, the first primary winding is divided into a series connection of a first primary inner winding HV1 and a first primary outer winding HV1, and the second primary winding is divided into a series connection of a second primary inner winding HV2 and a second primary outer winding HV 2. In other words, each phase primary winding is divided into 4 windings inside HV1, inside HV2, outside HV1 and outside HV2, so that the three-phase primary windings comprise 12 windings and two separate second and third tap switches 2 and 3 are respectively used to realize tap/full turn, star/angle connection changes: when the second tapping switch 2 is adjusted to the gear position 1, the primary side is a tap, and when the gear position 2 is adjusted, the primary side is full turns; when the third tapping switch 3 is adjusted to the gear 1, the primary side is in angular connection, and when the third tapping switch is adjusted to the gear 2, the primary side is in star connection. In addition, the primary winding of the test transformer can input different voltages at tapping and full turn by using a second tapping switch to normally work; when the test transformer works under full voltage and full capacity and is suitable for primary side tapping, full turn tapping, the primary side three-phase winding can be subjected to end-to-end connection change through the third tapping switch 3, and star/angle connection change is achieved.

The first secondary winding is divided into a first secondary inner winding LV inner 1, a first secondary inner winding LV middle 1 and a first secondary outer winding LV outer 1 which are connected in series, and the second secondary winding is divided into a second secondary inner winding LV inner 2, a second secondary inner winding LV middle 2 and a second secondary outer winding LV outer 2 which are connected in series. In other words, each phase of secondary side winding is divided into 6 windings including LV inner 1, LV inner 2, LV middle 1, LV middle 2, LV outer 1 and LV outer 2, so that the three-phase secondary side winding includes 18 windings, and two separate fourth tapping switches 4 and fifth tapping switches 5 are respectively adopted to realize series/parallel connection and star/angular connection changes: when the fifth tapping switch 5 is adjusted to the gear 1, the secondary sides are connected in parallel, and when the fifth tapping switch is adjusted to the gear 2, the secondary sides are connected in series, so that the internal serial/parallel change of each phase of secondary side winding is realized; when the fourth switch 4 is switched to the gear 1, the secondary side is in angular connection, and when the fourth switch is switched to the gear 2, the secondary side is in star connection, so that star/angular connection conversion of the three-phase secondary side winding is realized.

The inner side 1 of the first secondary side inner winding LV, the inner side 2 of the second secondary side inner winding LV, the inner side of the first primary side inner winding HV1, the inner side of the second primary side inner winding HV2, the middle 1 of the first secondary side winding LV, the middle 2 of the second secondary side winding LV, the outer side of the first primary side outer winding HV1, the outer side of the second primary side outer winding HV2, the outer side 1 of the first secondary side outer winding LV and the outer side 2 of the second secondary side outer winding LV are sequentially sleeved on the iron core from inside to outside.

The following describes in detail the implementation manners of the tap, full turn, star connection and angular connection of the three-phase primary winding and the serial connection, parallel connection, star connection and angular connection of the three-phase secondary winding based on the specific structures of the primary winding and the secondary winding in combination with fig. 1, fig. 2 and fig. 5 to fig. 12.

As shown in fig. 1, 2 and 5, when the second tap switch is adjusted to the gear position "1" and the third tap switch is adjusted to the gear position "1", both the inside of the first primary side inner winding HV1 and the outside of the first primary side outer winding HV1 of each phase do not work, only the inside of the second primary side inner winding HV2 and the outside of the second primary side outer winding HV2 of each phase work, that is, three-phase primary side winding taps, and the inside of the second primary side inner winding HV2 and the second primary side outer winding HV2 of each phase are connected in series and then are connected in an angle mode, so that a three-phase primary side winding tap angle joint structure is formed.

As shown in fig. 1, 2 and 6, when the second tap switch is adjusted to gear position "2" and the third tap switch is adjusted to gear position "1", the inner part of the first primary side inner winding HV1 and the outer part of the first primary side outer winding HV1 of each phase, and the inner part of the second primary side inner winding HV2 and the second primary side outer winding HV2 of each phase are all operated, that is, the three-phase primary side windings are fully connected, and the inner part of the first primary side inner winding HV1, the outer part of the first primary side outer winding HV1, the inner part of the second primary side inner winding HV2 and the second primary side outer winding HV2 of each phase are sequentially connected in series and then are connected in an angular mode, so that a full-turn angular mode structure of the three-phase primary side windings.

As shown in fig. 1, 2 and 7, when the second tap changer is adjusted to the gear position "1" and the third tap changer is adjusted to the gear position "2", both the inside of the first primary side inner winding HV1 and the outside of the first primary side outer winding HV1 of each phase do not work, only the inside of the second primary side inner winding HV2 and the outside of the second primary side outer winding HV2 of each phase work, that is, three-phase primary side winding taps, and the inside of the second primary side inner winding HV2 and the second primary side outer winding HV2 of each phase are connected in series and then are star-connected, so that a three-phase primary side winding tap star-connected structure is formed.

As shown in fig. 1, 2 and 8, when the second tap switch is adjusted to gear "2" and the third tap switch is adjusted to gear "2", the inner of the first primary side inner winding HV1 and the outer of the first primary side outer winding HV1 of each phase, and the inner of the second primary side inner winding HV2 and the second primary side outer winding HV2 of each phase are all operated, that is, the three-phase primary side windings are fully wound, and the inner of the first primary side inner winding HV1, the outer of the first primary side outer winding HV1, the inner of the second primary side inner winding HV2 and the second primary side outer winding HV2 of each phase are sequentially connected in series and then are star-connected, so that a full-turn star-connected structure of the three-phase primary side windings is formed.

As shown in fig. 1, 2 and 9, when the fourth tapping switch is adjusted to the gear position "1" and the fifth tapping switch is adjusted to the gear position "2", the first secondary inner winding LV inner 1, the first secondary middle winding LV middle 1, the first secondary outer winding LV outer 1, the second secondary inner winding LV inner 2, the second secondary middle winding LV middle 2 and the second secondary outer winding LV outer 2 of each phase are sequentially connected in series and then are connected in an angle manner, so that a three-phase secondary side winding series angular connection structure is formed.

As shown in fig. 1, 2 and 10, when the fourth tapping switch is adjusted to the gear position "2" and the fifth tapping switch is adjusted to the gear position "2", the first secondary inner winding LV inner 1, the first secondary middle winding LV middle 1, the first secondary outer winding LV outer 1, the second secondary inner winding LV inner 2, the second secondary middle winding LV middle 2 and the second secondary outer winding LV outer 2 of each phase are sequentially connected in series and then star-connected, so as to form a three-phase secondary side winding series star-connected structure.

As shown in fig. 1, 2 and 11, when the fourth tapping switch is adjusted to the gear position "1" and the fifth tapping switch is adjusted to the gear position "1", the first secondary inner winding LV inner 1, the first secondary middle winding LV middle 1 and the first secondary outer winding LV outer 1 of each phase are sequentially connected in series, the second secondary inner winding LV inner 2, the second secondary middle winding LV middle 2 and the second secondary outer winding LV outer 2 of each phase are sequentially connected in series, and the first secondary winding and the second secondary winding of each phase are connected in parallel and then are connected angularly, so that a three-phase secondary winding parallel angular connection structure is formed.

As shown in fig. 1, 2 and 12, when the fourth tapping switch is adjusted to the gear position "2" and the fifth tapping switch is adjusted to the gear position "1", the first secondary inner winding LV inner 1, the first secondary middle winding LV middle 1 and the first secondary outer winding LV outer 1 of each phase are sequentially connected in series, the second secondary inner winding LV inner 2, the second secondary middle winding LV middle 2 and the second secondary outer winding LV outer 2 of each phase are sequentially connected in series, and the first secondary winding and the second secondary winding of each phase are connected in parallel and then star-connected, so that a three-phase secondary winding parallel star-connected structure is formed.

Furthermore, the first primary winding and the second primary winding are respectively the same in structure and number of turns, the number of turns in the first primary inner winding HV1 is the same as that of turns outside the first primary outer winding HV1, the number of turns in the second primary inner winding HV2 is the same as that of turns outside the second primary outer winding HV2, namely the first primary winding and the second primary winding are respectively divided into an inner part and an outer part, the inner part and the outer part respectively account for half of the number of turns, and the inner part and the outer part of the first primary winding are connected in series and then connected in series with the inner part and the outer part of the second primary winding;

the structure and the number of turns of the first secondary winding and the second secondary winding are respectively the same, the number of turns of the first secondary inner winding LV inner 1, the first secondary inner winding LV middle 1 and the first secondary outer winding LV outer 1 is the same, and the number of turns of the second secondary inner winding LV inner 2, the second secondary inner winding LV middle 2 and the second secondary outer winding LV outer 2 is the same.

In this embodiment, the test transformer may further include a control unit, configured to control actions of the tap changers and read current state information of the test transformer. The control unit can adopt a PLC inside the existing transformer control device.

Specifically, the central control system can control all tap switches to act through a PLC (programmable logic controller) in the transformer control device so as to realize the shifting of the transformer and read the current state information of the transformer.

In summary, the test transformer includes 30 windings and 5 tap changers on the primary and secondary sides. Specifically, the primary winding of the test transformer is designed into HV1 and HV2 according to the requirements of voltage at tapping and full turn and star/angle connection change, HV1 and HV2 are respectively divided into an inner winding part and an outer winding part on the physical position of winding arrangement, and the inner winding part and the outer winding part of HV1 and HV2 are respectively connected in series; when the second tapping switch 2 is adjusted to the tapping range, the winding HV2 works, and the winding HV1 does not work; the HV1 and HV2 windings are coupled in series to work together when the second tap switch 2 is adjusted to full turn. The secondary winding of the test transformer is designed into two parts of LV1 and LV2 according to the requirements of series/parallel connection and star/angle connection change, each part is divided into three parts with the same number of turns, the three parts are arranged inside, inside and outside the physical position of winding arrangement, the series and parallel connection change of each phase of secondary windings LV1 and LV2 can be realized through a fifth tap switch 5, and the star and angle connection change of the three-phase secondary windings can be realized through a fourth tap switch 4.

The inventors found that the test transformer of the above-described structure can achieve a variety of changes as in tables 1 and 2 below.

Table 1: test transformer primary winding connection method and input voltage

Table 2: test transformer secondary winding connection method and output voltage

It will be understood that the above embodiments are merely exemplary embodiments taken to illustrate the principles of the present invention, which is not limited thereto. It will be apparent to those skilled in the art that various modifications and improvements can be made without departing from the spirit and substance of the invention, and these modifications and improvements are also considered to be within the scope of the invention.

Claims

1. A test transformer comprises a three-phase iron core, and a three-phase primary winding and a three-phase secondary winding which are respectively wound on the three-phase iron core, characterized in that the test transformer further comprises at least one of a first tapping switch, a second tapping switch, a third tapping switch, a fourth tapping switch and a fifth tapping switch, wherein the first tapping switch is used for realizing the conversion between the through state and the excitation state of the three-phase primary and secondary windings, the second tapping switch is used for realizing the conversion between the internal tap of the primary winding of each phase and the full turn, the third tapping switch is used for realizing the conversion between star connection and angle connection of the three-phase primary winding, the fourth tapping switch is used for realizing the conversion between the star connection and the angle connection of the three-phase secondary winding, and the fifth tapping switch is used for realizing the conversion between the series connection and the parallel connection inside each phase of secondary side winding.

2. The test transformer of claim 1, wherein each phase of the primary winding is divided into a first primary winding and a second primary winding, and each phase of the secondary winding is divided into a first secondary winding and a second secondary winding.

3. The test transformer of claim 2, wherein the head lead-out wires of the first primary winding of each phase and the first secondary winding of each phase, or the head lead-out wires of the second primary winding of each phase and the second secondary winding of each phase are connected to the first tapping switch; the first tapping switch is specifically used for enabling the three-phase primary and secondary windings to be in a through state when a through gear is adjusted, and enabling the three-phase primary and secondary windings to be in an excitation state when an excitation gear is adjusted.

4. The test transformer of claim 2, wherein the respective head and tail outgoing lines of the first primary winding and the second primary winding of each phase are connected to the second tapping switch; the second tap switch is specifically configured to, when a tap gear is adjusted, enable the first primary winding of each phase not to operate and only enable the second primary winding of each phase to operate, or enable the second primary winding of each phase not to operate and only enable the first primary winding of each phase to operate; and when the full-turn gear is adjusted, the first primary winding and the second primary winding of each phase are connected in series and then work together.

5. The test transformer of claim 2, wherein a tail outgoing line of the second primary winding of each phase or a tail outgoing line of the first primary winding of each phase is connected to the third tapping switch; the third tapping switch is specifically used for enabling the three-phase primary winding to be in angular connection when the angular connection gear is adjusted, and enabling the three-phase primary winding to be in star connection when the star connection gear is adjusted.

6. The test transformer of claim 2, wherein a tail outgoing line of the second secondary winding of each phase or a tail outgoing line of the first secondary winding of each phase is connected to the fourth tap switch; the fourth tapping switch is specifically used for enabling the three-phase auxiliary winding to be in angular connection when the angular connection gear is adjusted, and enabling the three-phase auxiliary winding to be in star connection when the star connection gear is adjusted.

7. The test transformer of claim 2, wherein the head and tail outgoing lines of the first secondary winding and the second secondary winding of each phase are connected to the fifth tapping switch; the fifth tapping switch is specifically used for enabling each phase of the first secondary winding to be connected with the second secondary winding in parallel when the parallel gear is adjusted, and enabling each phase of the first secondary winding to be connected with the second secondary winding in series when the series gear is adjusted.

8. Test transformer according to any of claims 2-7,

the first primary winding is divided into a first primary inner winding and a first primary outer winding which are connected in series, and the second primary winding is divided into a second primary inner winding and a second primary outer winding which are connected in series;

9. Test transformer according to claim 8,

the first primary winding and the second primary winding are respectively identical in structure and number of turns, the first primary inner winding and the first primary outer winding are identical in number of turns, and the second primary inner winding and the second primary outer winding are identical in number of turns;

10. Test transformer according to any of claims 1-7, characterized in that each tap changer is an off-circuit tap changer.

11. Test transformer according to any of claims 1-7, characterized in that it further comprises a control unit for controlling the action of each tap changer and reading the current status information of the test transformer.