THREE-PHASE ELECTRICAL REACTOR WITH MAGNETIC BIASING

Abstract

 The invention is related to the electrical engineering field and may be used for controllable magnetizing reactors installed for example in the electrical network to compensate for reactive power, stabilize the voltage, parallel operation with capacitor banks, to increase the capacity, etc.
The electrical three-phase magnetizing reactor contains the magnetic system, which is assembled of restored electric steel sheets, magnet core with coaxially arranged three upper and three lower vertical rods. The rods mount two-section windings. The magnet core has the upper, lower and middle horizontal and two side vertical yokes, the horizontal yokes have two middle and two extreme sections, four magnetic shunts as rectangular frames with horizontal and vertical sections, the horizontal sections of shunts are arranged on the winding butt ends along the upper, middle and lower yokes. Their closing vertical sections are arranged along the side yokes. The reactor contains also controllable semiconductive converters made of diodes an resistors and the control system. The reactor windings are connected to the three-phase network and converters. The difference from known devices is in that the reactor contains the three-winding insulating transformers installed between converters and control system, and nonmagnetic gaps are made in the sections of the middle horizontal yoke of the magnet core. Each magnetic shunt has two additional vertical sections located between windings. The ratio of nonmagnetic gap values of the magnet core in extreme sections of middle yoke Δ_extreme and nonmagnetic gap values in middle sections of middle yoke Δ_middle makes up 1.5 < (Δ_middle/(Δ_extreme<3, the ratio between the steel cross section of middle sections of middle yokes S_middle yoke and rod cross section S is within: 0. < (S_{middle yoke}/S) < 1.3, the ratio between steel cross section of all other sections of yokes S_yoke and rod cross section S is within 0.7 < (S_yoke /S) <0.9, the ratio between the steel cross section of all parts of magnetic shunts S_shunt and rod cross section S is within 0.07 < (S_yoke /S) < 0.3. Due to introduction of new components, new couplings between elements to the design and electric circuitry, optimization of ratios of parameters, obtained are reduction of the steel consumption and losses, the reliability is increased, functional potentialities of the reactor - expansion of the power adjustment range is increased.

Description

[0001] The invention is related to the electrical engineering field and may be used for controllable magnetizing reactors installed for example in a power network to compensate for reactive power, stabilize the voltage, for parallel operation with capacitor banks, to increase the capacity, etc.

[0002] Known is an electrical three-phase magnetizing reactor [1], containing the laminated core with the upper, lower and two side yokes, coaxial upper and lower rods located on the rods of the upper and lower windings, as well as lead-ins, semi-conducting diodes and thyristors. The disadvantage of this analog device is increased consumption of the steel of the magnet core due to increased magnetic flow in it (from the stray magnetic field) in the reactor load modes, as well as due to non-optimal selection of the magnet core parameters.

[0003] This disadvantage is partially eliminated in [2]. The electrical three-phase magnetizing reactor contains the laminated core with three upper and three lower coaxial rods, with upper, lower, medium and two side yokes, the horizontal yokes have two medium and two extreme sections. Windings located on each rod consist of two parts. The reactor lead-ins are connected to winding parts and to converters with the control system. Installed in the reactor are four magnetic shunts as rectangular frames with horizontal and vertical parts, the horizontal parts of the shunts are located on the winding butt ends along the upper, medium and lower yokes, and their closing vertical parts are located along the side yokes. The disadvantage of this prototype device is also increased consumption of the magnet core steel due to increased magnetic flow in it (from the stray magnetic field) in the reactor load modes, as well as due to non-optimal design and the magnet core and shunt parameters. Besides the reactor power adjustment range is limited and the reliability is reduced due to danger of appearance of high voltage on the control system due to the galvanic coupling with the reactor windings. In emergency cases.

[0004] The purpose of the invention is the reduction in steel consumption and losses, increase of the reliability, increase of functional abilities of the reactor - expansion of power adjustment range due to introduction of new elements to the design and electric circuitry, new couplings between elements, ,optimization of ratios of parameters.

[0005] The purpose in view is achieved by the fact that the magnetic structure of the electrical three-phase reactor, which is made of restored electric steel sheets and contains the magnet core with coaxially arranged three upper and three lower vertical rods, which house two-sectional windings, upper, lower and middle horizontal and two side vertical yokes, the horizontal yokes have two middle and two extreme sections, four magnetic shunts as rectangular frames with horizontal and vertical sections, , the horizontal sections of the shunts are located on the winding butt ends along the upper, middle and lower yokes, and their closing vertical sections are located along the side yokes. The reactor contains also the controllable semi-conductive converters from diodes and resistors and the control system, the above-mentioned windings are connected to the three-phase network and with converters. Entered into the reactor are three-winding insulating transformers installed between converters and control system. The nonmagnetic gaps are made on sections of the middle horizontal yoke of the magnet core. Each magnetic shunt has two additional vertical sections located between the windings. The ratio of nonmagnetic gap values of the magnet core in the extreme sections of middle yoke Δ_extreme and nonmagnetic gap values in the middle sections of middle yoke Δ_middle (Δ_middle/Δ_extreme) is as follows


The ratio between the steel section of the middle sections of middles of middle yokes S_mid. _Yoke and rod cross section S is within


ratio between the steel cross section of all other sections of yokes S_yoke and rod cross section S is within


ratio between the steel cross section of all parts of magnetic shunts S _shunt and rod cross section S is within

[0006] The suggested magnetizing reactor is explained by figures. Fig. 1 presents the reactor removable part (magnetic structure with windings) - front view, Fig. 2 - the same, top view, Fig. 3 - the same, side view. Fig. 4 presents the main magnet core assembled of restored electric steel sheets, Fig. 5 presents one of four magnetic shunts assembled of restored electric steel sheets as a rectangular three-window frame. Fig. 6 presents the reactor electrical circuitry.

[0007] The reactor magnetic structure restored of electric steel sheets consists of the main magnet core and four magnetic shunts.

[0008] The reactor magnet core (Figs 1-4) contains six coaxial rods - three upper ones 1, 2,3 and three lower ones 4, 5, 6. Each rod houses the winding, consisting of two sections 7 and 8. There are two side vertical yokes 9 and 10, as well as three horizontal yokes - upper yoke 11, lower yoke 12 and middle yoke 13. The rod steel cross section - S, steel cross section of all yokes except middle yoke - S yoke, steel cross section of the middle yoke - S_mid yoke.

[0009] Each horizontal yoke 11, 12 and 13 has four sections: two extreme and two middle ones.

[0010] All sections of middle horizontal yoke 13 have nonmagnetic gaps 14 (gap value in middle sections ^Δmiddle) and 15 (gap value in extreme sections Δ_extreme.).

[0011] Each of four magnetic shunts 16 is made as a rectangular three-window frame (Fig. 5). The shunt horizontal parts are arranged on the winding butt ends (between winding butt ends 7 and 8 and pressing beam 17, Fig. 3). Shunts 16 have two middle vertical parts 18 located between the windings. All parts of magnetic shunts have steel cross section S _shunt.

[0012] The reactor circuitry (Fig. 6) contains three phase lead-ins A, B and C.

[0013] Two winding sections 7 and 8 on upper rod 1 of phase A taps A1-A2 and A3-A4, on lower coaxial rod 4 - taps A5-A6 and A7-A8. Two winding sections on upper rod 2 of phase B have taps B1-B2 and B3-B4, on lower coaxial rod 5 - B5-B6 and B7-B8. Two winding sections on upper rod 3 of phase C have taps C1-C2 and C3-C4, on lower coaxial rod 6 - C5-C6 and C7-C8.

[0014] The windings are joined as two triangles and are connected to three phase lead-ins A, B and C.

[0015] A converter, consisting of parallel-connected diode D and resistor R, is cut in between two winding sections of each rod: converter Π_1A is cut in between taps A2 and A3; converter Π_2A between taps A6 and A7, converter Π_1B between taps B2 and B3, converter Π_2B between taps B6 and B7, converter Π_1C between taps C2 and C3, converter Π_2C - between taps C6 and C7. The converter terminals are designated in same way as the taps of the winding parts, to which they are connected. In all 6 converters diodes D and resistors R are the same.

[0016] Installed between the control system (CS) and converters are insulating three-winding transformers T_A, T_B and T_C. Each primary tapped transformer winding is connected with its lead-ins (Y_1A-Y_2A, Y_1B-Y_2B

Y_1C-Y_2C) to the CS. Each of two secondary windings is connected to the control winding section taps and to the converter terminals. One secondary winding of transformer T_A is connected to taps A2 and A6 and simultaneously to terminals of converters A2 and A6; the other one - taps A3 and A7 and simultaneously to terminals of converters A3 and A7. One secondary winding of transformer T_B is connected to taps B2 and B6 and to terminals B2 and B6, the other one to taps B3 and B7 and terminals B3 and B7. One secondary winding of transformer T_C is connected to taps C2 and C6 and to terminals C2 and C6, the other one to taps C3 and C7 and terminals C3 and C7.

[0017] Converters and insulating transformers are located on assembly panel 19 secured on the removable part (Fig. 2). The removable part is the reactor magnetic structure (magnet core and shunts) with windings and structural components of the press fitting - located in the oil tank.

[0018] Let us discuss the operation of the reactor.

[0019] The reactor is connected to the three-phase network by its lead-ins A, B and C, the network voltage is supplied to the reactor windings.

[0020] To switch over the reactor to the minimum power mode - idle mode the control system CS provides for minimum resistance at outputs Y_1A-Y_2A, Y_1B-Y_2B

Y_1C-Y_2C. As insulating transformers T_A, T_B and T_C are in this case in the short circuit mode and their dissipation resistance is low, the taps of winding sections A2 and A3, A6 and A7, B2 and B3 , B6 and B7, C2 and C3, C6 and C7 are practically short-circuited in pairs. In this case each converter Π_1A and Π_2A , Π_1B and Π_2B, Π_1C and Π_2C is practically short-circuited and there is no rod magnetizing of the magnet core.

[0021] When control system CS connects the maximum resistance to taps Y_1A-Y_2A, Y_1B-Y_2B and Y_1C-Y_2C, the reactor is transferred to the maximum power mode - rod full period saturation mode. It happens due to the fact that diodes D of converters Π_1A , Π_2A, Π_1B, Π_2B , Π_1C and Π_2C are connected to the taps of winding sections A2 and A3, A6 and A7, B2 and B3 , B6 and B7, C2 and C3, C6 and C7.

[0022] The intermediate modes from the idle mode to the maximum power mode are provided by control system CS according to the preset program, for example, for network voltage stabilization, or during the manual adjustment. In this case the nominal power mode is preset as a rule for one intermediate modes - half-period saturation reactor mode. In this mode the steel of each reactor rod is in the saturated state for half period.. Typical for such mode are not only minimum (theoretically zero) reactor distortion currents with high harmonics, but also optimum expenditure of active materials and optimum losses in the windings.

[0023] Insulating transformers, providing for absence of galvanic coupling and increased safety of the personal and low-voltage equipment against possible appearance of the high voltage of the network (for example in emergency situations), are installed between the CS (it is located on the control console in a room) and converters. Converters together with the insulating transformers are located on panel 19 in the reactor tank located on the open site of the substation.

[0024] Nonmagnetic gaps !4 and 15 are made on the sections of the middle horizontal yoke 13 of the magnet core. These gaps are required to extend the reactor power adjustment ranges. Nonmagnetic gap value should be minimum, which is selected during designing from the technological potentialities of the production and usually makes up fractions or units of mm.

[0025] In the magnet core the nonmagnetic gap value in extreme sections of middle yoke Δ_extreme should be less than the nonmagnetic gap value in middle sections of this yoke Δ_middle in (1.5-3) times, it means:

[0026] The upper boundary should not exceed , otherwise the magnetic dispersion flow in extreme vertical parts of the shunt will be reduced and in the middle ones will be increased. The lower boundary should be also observed, otherwise the magnetic dispersion flow will be increased in extreme parts of the shunt, in the middle vertical parts of the shunt will be reduced. Making the optimum ratio of the gap dimensions makes it possible to obtain favorable distribution of magnetic inductions along the rods, as well as minimum consumption of the steel during maximum efficiency of shunts from the point of view of unloading of the main magnet core of the reactor and reduction of additional losses in structural components and in the tank wall.

[0027] The selection of the steel cross section of all sections of the magnet core is important.

[0028] The ratio between the steel cross section of middle yoke S_{middle yoke} and cross section of rods S should be selected within:

[0029] The ratio between the steel cross section of all sections of yokes S_yoke and rod cross section S should be selected within:

[0030] If the yoke cross section exceeds the maximum boundary , the reactor will be with increased steel consumption in yokes. If the steel cross section of the yoke is less than the minimum value, the steel saturation appears in the reactor yokes in its definite operating modes. It results in unfavorable phenomena - increase of additional losses for eddy currents in structural components, increase in non-linear distortions in the reactor current.

[0031] Magnetic shunts 16 effectively channels the magnetic dispersion flow, which appears when the current flows in windings, i.e. during all modes when rods are magnetized. The magnetic dispersion flow circulates in the axial direction inside the windings and is closed in magnetic system yokes and along the magnetic shunts. If magnetic shunts 16 are absent, the magnetic flow gets closed on the structural components and in the tank wall, causing the eddy currents, additional losses and impermissible heating in them. For effective closing of the magnetic flow provision is made in shunts for middle longitudinal vertical sections 18 located between the windings. These two additional (as compared with the prototype) vertical sections are required for optimum distribution of the magnetic dispersion flows and reduction of the total steel consumption in shunts and the magnet core.

[0032] The steel cross section of magnetic shunts shall be the higher the radial size of the windings is higher, as during the reactor load the increased magnetic dispersion flow appears (as compared to the magnetic flow in rods and yokes of the magnet core in the idle mode).

[0033] The ratio between the steel cross section of all parts of each magnetic shunt S_shunt and rod cross section S should be selected within:

[0034] If the steel cross section of magnetic shunts is selected higher than the maximum value of the preset ratio, there is steel overconsumption. If the steel cross section of shunts is less than the minimum value, the shunts become of low efficiency and do not screen the dispersion flow of the windings. It results in unfavorable phenomena - increase of magnetic induction in the magnet core, main losses in the steel and additional losses in structural components.

[0035] The suggested three-window design of shunts improved as compared to the prototype provides for the optimum distribution of the magnetic flows of the reactor and thus optimum steel consumption in the magnetic system.

[0036] All discussed limits of the optimum ratio of sizes were determined as a result of the analysis of multiple calculations on the mathematical models of controllable magnetizing reactors within the wide range of variation of parameters. In case of necessity the results of these calculations may be presented to the examination.

[0037] The high-voltage reactor is usually made with oil cooling. The removable part is the magnetic system of the reactor (magnet core and shunts) with windings and structural components of the press fitting is located in the tank with oil, while the reactor lead-ins - on the tank cover. Converters and insulating transformers are located in the same tank on the assembly panel secured on the removable part.

[0038] The operating capacity of the suggested reactor and its high technical and economical indicators are approved by calculations, physical modeling, test results of prototypes of similar designs. In the suggested reactor as compared to the analogs and prototype the steel consumption is reduced, losses are reduced, reliability and labor costs are increased, overall dimensions and mass are reduced. It is scheduled for the nearest time to manufacture the developmental prototypes for serial production.

LITERATURE

[0039] 

1. Bryantsev A. M. "Electrical magnetizing reactor. PF patent." No. RU 2324251, application: 2006146290/09, 26.12.2006 . Published: 10.05.2008.

2. Bryantsev A. M. "Electric magnetizing reactor.". RF patent No. RU 2324250, application: 2006145299/09, 20.12.2006 .Published: 10.05.2008.

Claims

1. The electrical three-phase magnetizing reactor, the magnetic system o which is assembled of restored electric steel sheets and which contains the magnet core with coaxial-1y arranged three upper and three lower vertical rods, which house the two-section windings, upper, lower and middle and two side vertical yokes, the horizontal yokes have two middle and two extreme sections, four magnetic shunts as rectangular frames with horizontal and vertical sections, the horizontal sections of the shunts are located on the winding butt ends along the upper, middle and lower yokes, and their closing vertical sections are located along the side yokes, as well as the reactor contains controllable semiconductive converters from diodes and resistors and the control system, the above mentioned windings are connected to the three-phase network and to the converters, differing by that the reactor contains three-winding insulating transformers installed between converters and control system, nonmagnetic gaps are made in the sections of the middle horizontal yoke of the magnet core, each magnetic shunt has two additional vertical sections located between windings, the ratio of the nonmagnetic gap values of the magnet core in extreme sections of middle yoke Δ_extreme and nonmagnetic gap values in middle sections of middle yoke Δ_middle makes up as follows:


Ratio between the steel cross section of middle sections of middle yokes S_{middle yoke} and rod cross section is within:


The ratio between steel cross section of all other sections of yokes S_yoke and rod cross sections is within:


The ratio between the steel cross section of all parts of magnetic shunts S_shunt and rod cross section S is within:

Drawing