A reactor for a reactance type on-load tap-changer

Abstract

The reactor for a reactive on-load tap-changer according to the present invention has a three-phase three-column core structure, and the core columns are axially arranged with core laminations and air gaps alternating. The core laminations are of a parallel structure stacked by silicon steel sheets with the same height and arranged with an arithmetic progression in length. This structure can reduce the loss caused to the core by the magnetic flux bypassing the air gap. Four windings per phase are coaxially arranged and are cross-connected in series in pairs to form two parallel branches, arranged in an "X" shape, that is, winding 2a and winding 2b are connected in series to form one branch P1-P2 of the reactor, and winding 3a and winding 3b are connected in series to form another branch P3-P4 of the reactor. When the switch operates in the bridging state, the reactor is used to limit the circulating current I caused by the voltage between two taps. C The reactor provided by the present invention has low losses, low noise, and a circuit magnetic coupling coefficient ≈1, greatly improving the voltage regulation accuracy of the reactive on-load tap-changer.

Description

Technical Field

[0001] The present invention relates to the fields of power transformers, reactors and reactive on-load tap-changers, and relates to a reactor for a reactive on-load switch, which is used to cooperate with the reactive on-load switch of a power transformer to adjust the voltage. Background Art

[0002] As more and more power transformers independently developed in China enter the international market, reactive on-load switches are widely used in power transformers in the American markets such as the United States and Canada for voltage regulation, while all power transformers in China use resistive on-load switches. Reactive on-load switches are generally used for voltage regulation on the low-voltage side or power transformers with a particularly large number of tap positions, and a special reactor must be used to meet the switch voltage regulation function.

[0003] The design of the reactor needs to meet the following requirements: one is to minimize the loss of the reactor to reduce the overall loss of the transformer. Another point is that the magnetic coupling coefficient of the two-branch windings of the reactor is as close to 1 as possible to reduce the choking effect of the load current and the influence of leakage magnetic flux on the transformer windings. In addition, the operating noise of the reactor is as low as possible to avoid increasing the transformer noise. Summary of the Invention

[0004] To solve the above technical problems, the present invention proposes a reactor for a reactive on-load switch to meet the needs of the switch function.

[0005] The design scheme adopted by the present invention is as follows:

[0006] A reactor for a reactive on-load switch includes a three-column iron core, windings, and low-magnetic screws; the iron core is a three-phase three-column structure, and the iron core is installed by vertical iron core columns and horizontal upper and lower yokes; windings are sleeved on the iron core; the iron core columns are axially arranged and installed by a plurality of juxtaposed iron core discs, and there is an air gap between adjacent two iron core discs, and the iron core columns are cylindrical; the upper and lower yokes are independently stacked, and the cross-section is rectangular; eight low-magnetic screws connect the upper and lower clamping parts to connect the upper and lower yokes, and firmly assemble the iron core columns and the yokes into a whole; the front and rear upper clamping parts clamp the upper yoke and are firmly fixed by bolts, and the front and rear lower clamping parts clamp the lower yoke and are firmly fixed by bolts.

[0007] The iron core discs of the reactor are fixedly composed of several groups of silicon steel sheets arranged side by side in a circumferentially uniform distribution, and their cross-sections are approximately circular; each group of silicon steel sheets is fixedly composed of silicon steel sheets with the same height and arranged in an arithmetic progression in length. This structure can reduce the loss caused by the magnetic flux bypassing the air gap to the iron core. The lamination thickness is calculated according to the central angle corresponding to each group of laminations. Since the magnetic flux direction in the iron core is the same as the rolling direction of the grain-oriented silicon steel sheet, the side-by-side iron core discs greatly reduce the loss caused by the magnetic flux bypassing the air gap to the iron core; there is a circular hole in the center of the iron core disc, and a through bolt is used to firmly clamp the iron core discs of each column through the center of the circular hole. The bolts are fastened to the upper and lower yoke end faces to reduce the vibration of the iron core discs; the iron core discs of each column are cured by resin casting, and the air gaps between the discs are composed of high-strength epoxy resin plates; the iron core structure composed of the side-by-side iron core discs has high mechanical strength, low noise, and small iron core loss.

[0008] Four concentric windings are sleeved on each phase iron core column. The four windings are cross-connected in series in pairs to form two parallel branches of the reactor with opposite polarities. The four windings of each phase are arranged coaxially, with two windings arranged at the upper and lower positions. The two axially arranged windings are cross-connected in series to form two parallel branches. The upper inner winding and the lower outer winding are connected in series, and the upper outer winding and the lower inner winding are connected in series, and are arranged in an "X" shape on the outside of the iron core, and form two branches P1-P2 and P3-P4 of the reactor in parallel form. (That is, winding 2a and winding 2b are connected in series to form a branch P1-P2 of the reactor, and winding 3a and winding 3b are connected in series to form another branch P3-P4 of the reactor.) The leading ends of the windings of the two branches are marked as P1 and P3, and are led out vertically upward from their respective windings. The trailing ends are marked as P2 and P4, and are led out vertically downward from their respective windings.

[0009] The reactor windings are wound on the insulating paper tube with self-adhesive transposed conductors in the same winding direction and the same number of turns, ensuring that the leading ends P1 and P3 of the two branch windings are the same-named ends. The load currents flowing through the two branches cancel each other out in the iron core, reducing the influence of leakage magnetic flux on the transformer windings.

[0010] The reactor winding terminals P1 and P4 are connected to the tap selector of the on-load tap-changer through cables for selecting the voltage grade. The winding terminals P2 and P3 are connected to the vacuum circuit breaker of the on-load tap-changer through cables for outputting the voltage.

[0011] Upper pressure plates and insulating pads are assembled on the upper part of the reactor winding, and lower support plates and insulating pads are assembled on the lower part. Insulating spacers are placed between the winding and the iron core and between adjacent windings; the winding is pre-pressed and vacuum-dried, and is sleeved on the core body without clearance; eight low-magnetic bolts are used to connect the upper and lower clamping parts to fix the iron core column and the yoke. The upper limb plate presses the pressure plate and the upper insulating pad, and the lower limb plate presses the support plate and the lower insulating pad, so as to uniformly clamp the winding of the core body, making the winding and the iron core form a firm overall structure and reducing the noise during the operation of the reactor.

[0012] Working principle: When the on-load tap-changer is operating in the bridging state, the reactor is used to limit the circulating current I caused by the voltage between two taps. C ; When the switch is operating in the non-bridging state, the polarities of the two branch windings of the reactor are opposite, and the magnetic fluxes generated by the two parallel circuits are almost completely coupled. The magnetic coupling coefficient between the two branches is approximately 1. When the load current I L flows through the two branches, the generated magnetic fluxes cancel each other out, minimizing the influence of leakage magnetic flux on the transformer windings. At the same time, the accuracy of the switch for regulating voltage is improved.

[0013] Advantages of the present invention:

[0014] (1) The core column of the reactor is composed of juxtaposed core discs. The juxtaposed core discs greatly reduce the loss of the core caused by the magnetic flux bypassing the air gap. The center of each column of core discs is penetrated and compressed by a through bolt, reducing the vibration of the core, having high mechanical strength and low operating noise.

[0015] (2) The four coaxially arranged windings of the reactor adopt a layout type of cross-connected series in pairs, forming two electrical branches with opposite polarities, enabling the magnetic fluxes generated by the load current to cancel each other out, without choking effect. At the same time, the influence of leakage magnetic flux on the transformer windings is reduced.

[0016] (3) The mutual inductance between the two branch windings of the reactor is approximately equal to 1, and the circulating current generated by the leakage magnetic flux in the other branch winding is approximately 0, greatly improving the accuracy of the reactance type on-load tap-changer for regulating voltage.

[0017] The reactor provided by the present invention has low loss, low noise, and a circuit magnetic coupling coefficient ≈ 1, greatly improving the accuracy of the reactance type on-load tap-changer for regulating voltage. The present invention helps to enhance the competitiveness of China's power transformers in the international market, especially in the American region. Description of the drawings

[0018] The drawings are schematic structural diagrams of the present invention.

[0019] Figure 1 is a sectional view of one phase of the reactor body of the present invention;

[0020] Figure 2 is the front view of the reactor core assembly of the present invention;

[0021] Figure 3 is the top view of the juxtaposed core discs of the reactor of the present invention;

[0022] Figure 4 is the simplified diagram of the winding arrangement of the reactor of the present invention;

[0023] Figure 5 is the working principle diagram of the reactor of the present invention;

[0024] Among them, 5A is the operating state of the reactor when the on-load tap-changer is in the non-bridging position;

[0025] Among them, 5B is the operating state of the reactor when the on-load tap-changer is in the bridging position.

[0026] The markings in the figure are explained as follows: 1. Iron core; 11. Iron core discs; 2a. Upper inner winding; 2b. Lower outer winding; 3a. Upper outer winding; 3b. Lower inner winding; 4. Low-magnetic screw; 5. Pressure plate; 6. Insulating paper tube; 7. Insulating spacer; 8. Clamping limb plate; 9. Support plate; 10. Through bolt; P1. Head of winding 2a; P2. Tail of winding 2b; P3. Head of winding 3a; P4. Tail of winding 3b; I L 、Load current of on-load tap-changer; I C 、Circulating current of reactor. 12. Clamping piece, 13. Yoke, 14. Core column, 15. Bolt. Specific embodiments

[0027] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0028] The reactor for the reactive on-load tap-changer of the present invention includes a three-column iron core 1, windings 2a, 2b, 3a, 3b, and low-magnetic screws 4; the iron core is a three-phase three-column structure, and the iron core is installed and composed through vertical core columns 14 and horizontal upper and lower yokes 13; windings are sleeved on the iron core; the core column is axially arranged and installed by a plurality of juxtaposed iron core discs 11, and there is an air gap between adjacent two iron core discs, and the core column is cylindrical; the upper and lower yokes 13 are independently stacked, and the cross-section is rectangular; eight low-magnetic screws 4 connect the upper and lower clamping pieces to connect the upper and lower yokes, and firmly assemble the core column and the yoke into a whole; the front and rear upper clamping pieces 12 clamp the upper yoke and are firmly fixed by bolts 15, and the front and rear lower clamping pieces clamp the lower yoke and are firmly fixed by bolts.

[0029] The iron core discs 11 of the reactor are fixedly composed of several groups of silicon steel sheets arranged in a circumferentially uniform manner, and its cross-section is approximately circular; each group of silicon steel sheets is fixedly composed of silicon steel sheets with the same height and arranged in an arithmetic progression in length. This structure can reduce the loss caused by the magnetic flux bypassing the air gap to the iron core, and the lamination thickness is calculated according to the central angle corresponding to each group of laminations. Since the magnetic flux direction in the iron core is the same as the rolling direction of the grain-oriented silicon steel sheet, the juxtaposed iron core discs greatly reduce the loss caused by the magnetic flux bypassing the air gap to the iron core; there is a circular hole (with a diameter of Φ30) in the center of the iron core disc, and the through bolt is used to firmly clamp the iron core discs of each column through the center of the circular hole, and the screw is fastened on the end faces of the upper and lower yokes to reduce the vibration of the iron core disc; the iron core discs of each column are cured by resin casting, and the air gap between the discs is composed of high-strength epoxy resin plates; the iron core structure composed of juxtaposed iron core discs has high mechanical strength, low noise, and small iron core loss.

[0030] Four concentric windings are sleeved on each phase of the iron core column. The four windings are cross-connected in series in pairs to form two parallel branches of the reactor with opposite polarities. The four windings of each phase are arranged coaxially, with two windings arranged at the upper and lower ends. The two axially arranged windings are cross-connected in series to form two parallel branches. The inner winding at the upper end and the outer winding at the lower end are connected in series, and the outer winding at the upper end and the inner winding at the lower end are connected in series, and are arranged in an "X" shape on the outside of the iron core, and the two branches of the reactor are formed in parallel as P1-P2 and P3-P4. (That is, winding 2a and winding 2b are connected in series to form a branch P1-P2 of the reactor, and winding 3a and winding 3b are connected in series to form another branch P3-P4 of the reactor.) The leading ends of the windings of the two branches are marked as P1 and P3, and are led out vertically upward from their respective windings. The trailing ends are marked as P2 and P4, and are led out vertically downward from their respective windings.

[0031] The windings of the reactor are wound on the insulating paper tube with self-adhesive transposed conductors in the same winding direction and the same number of turns, ensuring that the leading ends P1 and P3 of the windings of the two branches are the same-named ends. The load currents flowing through the two branches cancel each other out in the iron core, reducing the influence of leakage magnetic flux on the transformer windings.

[0032] The terminals P1 and P4 of the reactor windings are connected to the tap selector of the on-load tap-changer through cables for selecting the voltage grade. The terminals P2 and P3 of the windings are connected to the vacuum circuit breaker of the on-load tap-changer through cables for outputting the voltage.

[0033] The upper part of the reactor winding is assembled with a pressing plate 5 and an insulating spacer 7, and the lower part is assembled with a supporting plate 9 and an insulating spacer 7. Insulating spacers are placed between the winding and the iron core and between adjacent windings; the winding is pre-pressed and vacuum-dried, and is sleeved on the core body without clearance; eight low-magnetic screws 4 are used to connect the upper and lower clamping parts to fix the iron core column and the yoke. The upper limb plate 8 presses the pressing plate and the upper insulating spacer 7, and the lower limb plate presses the supporting plate and the lower insulating spacer, so as to uniformly clamp the winding of the core body, making the winding and the iron core form a firm overall structure and reducing the noise during the operation of the reactor.

[0034] As Figure 1 In an embodiment of the reactor for an on-load tap-changer of the reactance type as shown, it includes an iron core 1, a winding 2a, a winding 2b, a winding 3a, a winding 3b, a low-magnetic screw 4, a pressing plate 5, an insulating paper tube 6, an insulating spacer 7, a clamping part limb plate 8, and a supporting plate 9. The inner coil and the iron core are tightened by spacers and paper tubes. An insulating paper tube 6 is placed between the upper-end coil 2a (2b) and the coil 3a (3b) to separate the oil gap, and spacers are placed between the upper and lower coils axially. Six limb plates are welded on each clamping part, and the limb plates press the coils through insulating spacers, supporting plates and pressing plates.

[0035] As Figure 2As shown in the figure, the iron core assembly consists of clamping parts, iron core columns, yokes, and low-magnetic screws, etc. The iron core columns are composed of juxtaposed iron core discs and axially staggered air gaps. Four low-magnetic screws are evenly arranged on both sides of the long axis of the iron core. Screw positioning devices are welded on the upper and lower clamping parts, and the screws firmly assemble the core columns and yokes into a whole through the clamping parts.

[0036] As Figure 3 shown in the figure, the iron core discs are juxtaposed by multiple groups of silicon steel sheets in a circumferentially uniform distribution, and their cross-sections are approximately circular. Each group of silicon steel sheets is stacked by silicon steel sheets with the same height and an arithmetic progression of lengths. The lamination thickness is calculated according to the central angle corresponding to each group of laminations. A Φ30 round hole is designed in the center of the iron core disc. A through screw passes through the hole center to firmly clamp each phase of the core column. The screw is fastened on the end faces of the upper and lower yokes to reduce the vibration of the iron core disc and lower the noise.

[0037] As Figure 4 shown in the figure, the tail end of coil 2a is connected in series with the head end of coil 2b, and the tail end of coil 3a is connected in series with the head end of coil 3b. The four windings are arranged in an "X" cross pattern. And four leads P1, P2, P3, and P4 are led out vertically. The coils are wound with the same winding direction and the same number of turns to ensure that P1 and P3 are the same-named terminals, so as to form two electrical branches with opposite polarities.

[0038] As shown in Figure 5, the reactor winding terminals P1 and P4 are connected to the tap selector of the on-load tap-changer through cables for selecting the voltage grade. The winding terminals P2 and P3 are connected to the vacuum circuit breaker of the on-load tap-changer through cables for outputting the voltage. When the on-load tap-changer operates in the non-bridging state (5A), the polarities of the two branch windings of the reactor are opposite, and the magnetic coupling coefficient between the two branches is approximately 1. When the load current flows through the two branches, the generated magnetic fluxes cancel each other out, without choking effect, minimizing the influence of leakage magnetic flux on the transformer windings and improving the voltage regulation accuracy. When the on-load tap-changer operates in the bridging state (5B), the reactor is used to limit the circulating current caused by the voltage between two grades.

Claims

1. A reactor for a reactive on-load tap-changer, comprising a three-column core and windings; the core is a three-phase three-column structure, and the core is composed of vertical core columns and horizontal upper and lower yokes; windings are sleeved on the core. It is characterized in that: The core columns are axially arranged and installed by a number of juxtaposed core discs, and there is an air gap between two adjacent core discs; the upper and lower yokes are independently stacked, and the cross-section is rectangular; a number of low-magnetic screws connect the upper and lower clamping pieces to connect the upper and lower yokes, firmly assembling the core columns and the yokes into a whole; the front and rear upper clamping pieces clamp the upper yoke and are firmly fixed by bolts, and the front and rear lower clamping pieces clamp the lower yoke and are firmly fixed by bolts. The core discs of the reactor are fixedly composed of a number of groups of silicon steel sheets arranged side by side in a circumferentially uniform manner, and its cross-section is approximately circular; each group of silicon steel sheets is fixedly composed of silicon steel sheets with the same height and arranged in an arithmetic progression in length. This structure can reduce the loss caused by the magnetic flux bypassing the air gap to the core. The lamination thickness is calculated according to the central angle corresponding to each group of laminations; since the magnetic flux direction in the core is the same as the rolling direction of the grain-oriented silicon steel sheet, the juxtaposed core discs greatly reduce the loss caused by the magnetic flux bypassing the air gap to the core; there is a round hole in the center of the core disc, and the core discs of each column are firmly clamped by passing a through-screw through the center of the round hole. The screw is fastened on the end faces of the upper and lower yokes to reduce the vibration of the core disc; the core discs of each column are cured by resin casting, and the air gap between the discs is composed of high-strength epoxy resin plates; the core structure composed of the juxtaposed core discs has high mechanical strength, low noise and small core loss. On each phase core column of the reactor, four windings are coaxially arranged, with two windings arranged both above and below; the two axially arranged windings are cross-connected in series to form two parallel branches with opposite polarities, that is, the upper inner winding and the lower outer winding are connected in series, and the upper outer winding and the lower inner winding are connected in series, and are arranged in an "X" shape on the outside of the core column, and the two branches of the reactor are formed in parallel as P1 - P2 and P3 - P4; the leading ends of the windings of the two branches are marked as P1 and P3, and are led out vertically upward from their respective windings; the trailing ends are marked as P2 and P4, and are led out vertically downward from their respective windings.

2. A reactor for a reactive on-load tap-changer according to claim 1, It is characterized in that: The windings of the reactor are wound on an insulating paper tube with self-adhesive transposed conductors in the same winding direction and the same number of turns, ensuring that the leading ends P1 and P3 of the two branch windings are the same-name ends; the load currents flowing through the two branches cancel each other out in the core, reducing the influence of leakage magnetic flux on the transformer windings.

3. A reactor for a reactive on-load tap-changer according to claim 1 or 2, It is characterized in that : The winding terminals P1 and P4 of the reactor are connected to the tap selector of the on-load tap-changer through cables for selecting the voltage grade; the winding terminals P2 and P3 are connected to the vacuum circuit breaker of the on-load tap-changer through cables for outputting voltage.

4. A reactor for a reactive on-load tap-changer according to claim 1 or 2, It is characterized in that: The upper part of the reactor winding is equipped with pressing plates and insulating pads, and the lower part is equipped with supporting plates and insulating pads. Insulating spacers are placed between the winding and the iron core and between adjacent windings. The winding is pre-pressed and dried in vacuum, and the body is assembled with the iron core without clearance. Eight low-magnetic screws are used to connect the upper and lower clamping parts to fix the core column and yoke. The upper limb plate presses the pressing plate and the upper insulating pad, and the lower limb plate presses the supporting plate and the lower insulating pad, so as to uniformly clamp the winding of the body, making the winding and the iron core form a firm overall structure and reducing the noise during the operation of the reactor.

Images