CN216162631U - Application circuit of equivalent 48-pulse rectifier transformer of direct-current arc furnace and submerged arc furnace - Google Patents

Abstract

The utility model relates to an application circuit of equivalent 48-pulse rectifier transformers of a direct-current electric arc furnace and a submerged arc furnace, which comprises 8 rectifier transformers, 8 groups of rectifier bridges, 8 direct-current reactors and 2 electrodes; the rectifier transformers are B1, B2, B3, B4, B5, B6, B7 and B8 rectifier transformers respectively; the 8 groups of rectifier bridges are A1, A2, A3, A4, A5, A6, A7 and A8 groups of rectifier bridges respectively, each group of rectifier bridges comprises six rectifier elements, and an independent 6-pulse rectifier circuit is formed; the rectifier bridges are respectively connected with the secondary outputs of the rectifier transformers, the primary windings of the rectifier transformers are wound in a regular triangle connection mode, the secondary windings of the B1, B3, B5 and B7 rectifier transformers are wound in an angle connection mode, and the secondary windings of the B2, B4, B6 and B8 rectifier transformers are wound in a star connection mode; the utility model has balanced and consistent rectified output voltage and current, can ensure that the equipment can stably work for a long time, and has extremely low failure rate.

Description

Application circuit of equivalent 48-pulse rectifier transformer of direct-current arc furnace and submerged arc furnace

Technical Field

The utility model relates to the field of alternating current-direct current conversion equipment, in particular to an application circuit of a direct current arc furnace and submerged arc furnace equivalent 48-pulse rectifier transformer.

Background

In the field of metal and non-metal and ferroalloy smelting, electric arc furnaces are commonly used as smelting equipment. Compared with a three-phase alternating current electric arc furnace, the direct current electric arc furnace has many advantages, but how to solve the problem of uneven current distribution among parallel rectifier elements generated by using the rectifier elements in parallel in a high-capacity rectifier power supply by using direct current is firstly considered, and how to effectively inhibit harmonic waves generated by rectifier devices and reduce the total harmonic wave distortion rate of a system is secondly considered, and a multi-pulse rectification technology is usually adopted.

For a conventional dc power supply, 6-pulse rectification is generally used. Although the 6-pulse rectifier circuit has the advantage of simple structure, the output direct-current voltage has a relatively large ripple coefficient, the ripple coefficient is 0.057, and 3, 5 and 7-order harmonics inevitably exist. Due to the limitation of the single capacity of the rectifying components, if a high-power direct-current power supply is used, a plurality of rectifying components are required to be connected in parallel for operation, however, the phenomenon that the current flowing through the rectifying components is uneven is more serious as the number of the rectifying components connected in parallel is more.

The Chinese patent application: a36-pulse rectifier (patent application number: CN201810410354.1) adopting a direct-current side double-passive harmonic suppression method and Chinese invention patents: 48-pulse transformer rectifiers (patent application number: CN201910409441.X) of the direct-current side passive harmonic suppression technology are developed to a certain extent for the multi-pulse rectification technology.

The applicant has also studied an equivalent 12-pulse rectifier transformer, and the scheme thereof is as in the chinese utility model patent: an improved DC arc furnace equivalent 12-pulse rectifier transformer application circuit (No. CN210745030U) can meet the application requirements of certain occasions, but the voltage ripple coefficient is still high, and the current fluctuation can still cause adverse effect on the use of a DC arc furnace and a submerged arc furnace.

For this reason, the applicant developed an equivalent 48-pulse rectifier transformer, and found in experiments that the voltage waveform of an equivalent 48-pulse direct-current power supply is smoother than that of 24 pulses.

When a high-power rectifying power supply is manufactured, because a single rectifying element in China cannot have too large capacity, the rectifying elements need to be connected in parallel for use, and because the parameters of each rectifying element are not completely the same and the crimping strength of each parallel element is not completely the same, the current distribution among the parallel elements is not uniform, the more the parallel elements are, the more the phenomenon of nonuniform current is caused, and the more the elements which are connected in parallel are burnt out, under the condition that the nonuniform degree exceeds 30%, the elements which have larger current and pass through the parallel elements are often burnt out.

Aiming at the current sharing problem, if the 48-pulse rectification is adopted, the rectifying elements are not connected in parallel, but are divided into 8 independent rectifying bridges, so that the phenomenon of uneven current distribution among the parallel rectifying elements can be effectively solved.

The conventional rectifier transformer for the 48-pulse furnace is only provided with 2 groups of primary side high-voltage windings, the secondary side voltage is very low, the number of turns of the secondary side winding is very small, the voltage born by each turn of the secondary side winding is few volts, more than ten volts, in the actual winding process, the winding of half turns for enabling the secondary voltages of 8 groups of low-voltage windings to be equal can not be realized, the number of turns can only be wound into an integer, the secondary output voltage of the 8 groups of low-voltage windings is different by a few volts or even ten volts, the output direct-current voltage of the 8 groups of rectifier bridges is different by a few volts or even ten volts, and the situation that the output sizes of the windings are different is generated. And because every 4 groups of low-voltage windings share one iron core, mutual interference on a magnetic circuit finally causes the phenomenon that the individual windings hardly output power, so that the rectifier elements connected with the windings with large output power are always burnt out ingeniously, and the transformer is hot.

In a conventional 48-pulse rectifier transformer, a thyristor is used as a rectifier element, and a general method is to increase a phase shift angle of a group of rectifier bridges with high input voltage to artificially suppress higher dc output voltage of the group of rectifier bridges so as to obtain that the dc output voltages of 8 groups of rectifier bridges are equal in magnitude, so that it is unknown that the method directly causes the power factor of the suppressed group of rectifier bridges to be seriously reduced, and thus the power factor of the whole dc output is dragged down, and the advantage of high natural power factor of a dc circuit cannot be seen.

Aiming at the phenomenon, an equivalent 48-pulse rectifier transformer applied to a direct-current arc furnace and a direct-current submerged arc furnace is designed, the defects of the phenomenon are fundamentally solved, the problem that rectifier elements are frequently burnt due to uneven current distribution is solved, natural power factors can reach 0.99, the voltage waveform of an equivalent 48-pulse direct-current power supply is found to be more stable than 24 pulses in an experiment, the voltage pulsation coefficient reaches 0.00087, the content of higher harmonics of 3 times, 5 times, 7 times, 9 times, 11 times and the like in the voltage waveform is observed to be extremely low by using an oscilloscope, the higher harmonics can hardly be seen, and a good scheme is found for producing the high-power rectifier power supply.

SUMMERY OF THE UTILITY MODEL

The utility model aims to provide an application circuit of a 48-pulse equivalent rectifier transformer of a direct-current electric arc furnace and a submerged arc furnace, which can realize the production of a high-power rectifier power supply.

In order to achieve the purpose of the utility model, the utility model provides an equivalent 48-pulse rectifier transformer application circuit of a direct current electric arc furnace and a submerged arc furnace, which comprises 8 rectifier transformers, 8 groups of rectifier bridges, 8 direct current reactors and 2 electrodes; 8 rectifier transformers are B1, B2, B3, B4, B5, B6, B7 and B8 rectifier transformers respectively; the 8 groups of rectifier bridges are A1, A2, A3, A4, A5, A6, A7 and A8 groups of rectifier bridges respectively, each group of rectifier bridges comprises six rectifier elements, and each group of rectifier bridges form an independent 6-pulse rectifier circuit; the 8 direct-current reactors are respectively a 1# direct-current reactor, a 2# direct-current reactor, a 3# direct-current reactor, a 4# direct-current reactor, a 5# direct-current reactor, a 6# direct-current reactor, a 7# direct-current reactor and an 8# direct-current reactor; the 2 electrodes are respectively a 1# electrode and a 2# electrode and are positioned in the furnace body; the A1, A2, A3, A4, A5, A5, A6, A7 and A8 groups of rectifier bridges are respectively connected with the secondary outputs of B1, B2, B3, B4, B5, B6, B7 and B8 rectifier transformers, the primary windings of the B1, B2, B3, B4, B5, B6, B7 and B8 rectifier transformers are wound in a regular triangle connection mode, the secondary windings of the B1, B3, B5 and B7 rectifier transformers are wound in an angle connection mode, and the secondary windings of the B2, B4, B6 and B8 rectifier transformers are wound in a star connection mode.

Further, the B1, B2, B3, B4, B5, B6, B7 and B8 rectifier transformers are respectively provided with independent iron cores.

Further, the B1 rectifier transformer is in a delta/delta-6 connection group, and the B2 rectifier transformer is in a delta/Y-5 connection group.

Furthermore, the B3 rectifier transformer is in a delta/delta-6 connection group, a phase shift coil L1 is additionally arranged on a primary winding, and the phase of the output voltage is shifted by 15 degrees after being compared with the phase of the output voltage of the B1 rectifier transformer; the B4 rectifier transformer is in a delta/Y-5 connection group, and a phase shift coil L2 is additionally arranged on a primary winding, so that the phase of the output voltage of the B4 rectifier transformer is shifted by 15 degrees after compared with the phase of the output voltage of the B2 rectifier transformer.

Furthermore, the B5 rectifier transformer is in a delta/delta-6 connection group, a phase shift coil L3 is additionally arranged on a primary winding, and the phase of the output voltage is shifted by 7.5 degrees after being compared with the phase of the output voltage of the B1 rectifier transformer; the B6 rectifier transformer is in a delta/Y-5 connection group, and a phase shift coil L4 is additionally arranged on a primary winding, so that the phase of the output voltage of the B6 rectifier transformer is shifted by 7.5 degrees after the phase of the output voltage of the B2 rectifier transformer.

Furthermore, the B7 rectifier transformer is in a delta/delta-6 connection group, a phase shift coil L5 is additionally arranged on a primary winding, and the phase of the output voltage is shifted by 22.5 degrees after being compared with the phase of the output voltage of the B1 rectifier transformer; the B8 rectifier transformer is in a delta/Y-5 connection group, and a phase shift coil L6 is additionally arranged on a primary winding, so that the phase of the output voltage of the B8 rectifier transformer is shifted by 22.5 degrees after the phase of the output voltage of the B2 rectifier transformer.

Furthermore, the positive output ends of the a1 rectifier bridges are connected to the 1# electrode through the 1# dc reactor, the positive output ends of the a2 rectifier bridges are connected to the 1# electrode through the 2# dc reactor, the positive output ends of the A3 rectifier bridges are connected to the 1# electrode through the 3# dc reactor, the positive output ends of the a4 rectifier bridges are connected to the 1# electrode through the 4# dc reactor, the positive output ends of the a5 rectifier bridges are connected to the 1# electrode through the 5# dc reactor, the positive output ends of the A6 rectifier bridges are connected to the 1# electrode through the 6# dc reactor, the positive output ends of the a7 rectifier bridges are connected to the 1# electrode through the 7# dc reactor, the positive output ends of the A8 rectifier bridges are connected to the 1# electrode through the 8# dc reactor, and the negative output ends of the a1, a2, A3, a4, a5, a5, A6, a7, and A8 rectifier bridges are respectively connected to the 2# electrode.

Further, the primary incoming line voltage of the rectifier transformer is 10KV, and the secondary voltage has eight levels of 70V, 80V, 90V, 100V, 110V, 120V, 130V and 140V.

Furthermore, the rectifier element adopts ZP type high-power rectifier diode or KP type silicon controlled rectifier.

Compared with the prior art, the application circuit of the equivalent 48-pulse rectifier transformer of the direct current electric arc furnace and the submerged arc furnace has the following advantages:

the 8 groups of rectified output voltage waveforms are balanced and consistent, the 8 groups of rectified output currents are balanced and consistent in magnitude, the direct current arc furnace and the direct current submerged arc furnace can stably work for a long time of 24 hours, the fault rate is extremely low, and good methods and ideas are found for manufacturing ultra-large-capacity rectified power supplies in the future.

Drawings

FIG. 1 is an equivalent 48-pulse rectification schematic diagram of a DC arc furnace.

Fig. 2 is a wiring diagram of a delta/delta-6 transformer.

Fig. 3 is a diagram of the connection group of the delta/delta-6 transformer.

Fig. 4 is a wiring diagram of the delta/Y-5 transformer.

Fig. 5 is a connection group diagram of the delta/Y-5 transformer.

FIG. 6 is a graph of the phase relationship between the output voltages of the B1 rectifier transformer and the B2 rectifier transformer.

FIG. 7 is a graph of the phase relationship of the output voltages of the B3 rectifier transformer, the B4 rectifier transformer, the B1 rectifier transformer and the B2 rectifier transformer.

FIG. 8 is a graph of the phase relationship of the output voltages of the B5 rectifier transformer, the B6 rectifier transformer, the B1 rectifier transformer and the B2 rectifier transformer.

FIG. 9 is a graph of the phase relationship of the output voltages of the B7 rectifier transformer, the B8 rectifier transformer, the B1 rectifier transformer and the B2 rectifier transformer.

FIG. 10 is a phase diagram of the rectified output DC voltage of a superimposed equivalent 48-pulse transformer.

Fig. 11 is a comparison graph of the rectified output dc voltage waveforms of the 6-pulse, 12-pulse, 24-pulse, and 48-pulse rectifier transformers.

Detailed Description

The utility model is further described below with reference to the following figures and specific examples.

As shown in fig. 1-11, the equivalent 48-pulse rectifier transformer application circuit of the dc arc furnace and the submerged arc furnace of the present invention is mainly applied to the dc arc furnace, the submerged arc furnace, etc., and comprises 8 rectifier transformers, 8 sets of rectifier bridges, 8 dc reactors, and 2 electrodes; the 8 rectifier transformers are B1, B2, B3, B4, B5, B6, B7 and B8 rectifier transformers respectively; the 8 groups of rectifier bridges are A1, A2, A3, A4, A5, A6, A7 and A8 groups of rectifier bridges respectively; the 8 direct current reactors are respectively a 1# direct current reactor, a 2# direct current reactor, a 3# direct current reactor, a 4# direct current reactor, a 5# direct current reactor, a 6# direct current reactor, a 7# direct current reactor and an 8# direct current reactor; the 2 electrodes are respectively a 1# electrode and a 2# electrode; each group of rectifier bridges comprises six ZP type high-power rectifier diodes (or KP type silicon controlled rectifiers), the anode output ends of 8 groups of rectifier bridges are connected to a # 1 electrode through respective direct current reactors, the cathode output ends of 8 groups of rectifier bridges are commonly connected to a # 2 electrode, namely the anode output ends of A1 groups of rectifier bridges are connected with the # 1 electrode through the # 1 direct current reactor, the anode output ends of A2 groups of rectifier bridges are connected with the # 1 electrode through the # 2 direct current reactor, the anode output ends of A3 groups of rectifier bridges are connected with the # 1 electrode through the # 3 direct current reactor, the anode output ends of A4 groups of rectifier bridges are connected with the # 1 electrode through the # 4 direct current reactor, the anode output ends of A5 groups of rectifier bridges are connected with the # 1 electrode through the # 5 direct current reactor, the anode output ends of A6 groups of rectifier bridges are connected with the # 1 electrode through the # 6 direct current reactor, the anode output ends of A7 groups of rectifier bridges are connected with the # 1 electrode through the # 7 direct current reactor, the positive output ends of A8 groups of rectifier bridges are connected with a 1# electrode through an 8# direct current reactor, the negative output ends of A1, A2, A3, A4, A5, A5, A6, A7 and A8 groups of rectifier bridges are respectively connected with a 2# electrode, the electrodes are positioned in a furnace body, each group of rectifier bridges form an independent 6-pulse rectifier circuit, the secondary outputs of A1, A2 and A2 groups of rectifier bridges are respectively connected with B2, B2 groups of rectifier bridges are respectively provided with independent iron cores, the primary windings of B2 and B2 are connected with a positive triangle, the primary windings of B2, the B2, B2 and B2 are wound on a primary winding of a rectifier transformer, the primary winding of the B2, B2 and B2 is arranged on a primary winding of the rectifier transformer, 2, a primary winding of the B2, a primary winding of which is arranged on a2, a primary winding of a2, a primary winding of a2, a primary winding of a2, A6-pulse rectifier bridge, a primary winding of a rectifier bridge, a primary winding of a rectifier bridge, a primary winding of a primary, The output voltage of B2 is phase-shifted by 15 °; the primary windings of B5 and B6 rectifier transformers are based on the winding method of the primary windings of B1 and B2 rectifier transformers, phase shift coils L3 and L4 are additionally arranged on the primary windings, and the phase of output voltages of B5 and B6 is shifted by 7.5 degrees backwards compared with the phase of output voltages of B1 and B2; the primary windings of B7 and B8 rectifier transformers are based on the winding method of the primary windings of B1 and B2 rectifier transformers, phase shift coils L5 and L6 are additionally arranged on the primary windings, the phases of output voltages of B7 and B8 are shifted by 22.5 degrees after compared with the phases of output voltages of B1 and B2, and therefore under the condition that the same power supply is connected to the primary windings of 8 transformers, the voltages generated on the secondary windings are the same in magnitude and 7.5 degrees in phase difference, and equivalent 48 pulse waves are formed.

The method comprises the following specific steps: firstly, 8 rectifier transformers are respectively provided with independent iron cores, the 8 rectifier transformers are separated from a magnetic circuit, and 8 groups of low-voltage windings do not interfere with each other when working; secondly, because the number of turns of the secondary side winding is small, the voltage born by each turn of the secondary side winding is high, and the balance of the output voltage cannot be adjusted by adjusting the number of turns of the secondary side winding, but 8 groups of high-voltage windings are manufactured, because the number of turns of the high-voltage winding is large, the voltage born by each turn is low, and if the difference is one turn on the high-voltage winding, the difference of the output voltage on the low-voltage winding is not more than 1 volt, so that the number of turns of the secondary side winding of 2 reference transformers can be made into an integer number of turns capable of outputting the same voltage value, the number of turns of the 8 groups of high-voltage windings is slightly different, and almost identical secondary voltages are obtained on the secondary side windings of 8 transformers.

Principle: the winding turns of the transformer coil can only be an integer and cannot be a fraction.

Assuming that a set of equivalent 12-pulse transformers with input voltage of 10KV and output voltage of 50V is manufactured, the design steps are as follows:

firstly, drawing a wiring schematic diagram of a transformer;

secondly, assuming that the structure of the B1 rectifier transformer is a delta/delta-6 connection group, wherein the primary winding of the B1 rectifier transformer is 1 ten thousand turns, and the secondary winding of the B1 rectifier transformer is 50 turns; the structure of the B2 rectifier transformer is a delta/Y-5 connection group, the primary winding of the B2 rectifier transformer is 1 ten thousand turns, and then the theoretical value of the secondary winding of the B2 rectifier transformer is 50/1.732/28.868 turns;

thirdly, adjusting design parameters: since the transformation ratio of the B1 rectifier transformer is 10000 ÷ 50 ÷ 200, and the secondary winding of the B2 rectifier transformer is set to 29 turns by rounding, the number of turns of the primary winding of the B2 rectifier transformer is 29 × 1.732 × 200 ═ 10045.6 turns, and the number of turns of the primary winding of the B2 rectifier transformer is 10046 turns;

fourthly, verifying the result: when 10KV is applied to the primary winding of the B2 rectifier transformer, the voltage output by the secondary winding of the B2 rectifier transformer is 49.998V, the voltage difference with the 50V voltage output by the secondary winding of the B1 rectifier transformer is 50V-49.998V-0.002V, and the proportional relationship between the difference and the 50V reference value is 0.002V/50V-0.004%, which is almost negligible;

fifthly, the phases of the B3 and B4 rectifier transformers are shifted backwards by 15 degrees through parameter adjustment of the coils L1 and L2.

Sixthly, the phases of the B5 and B6 rectifier transformers are shifted backwards by 7.5 degrees through parameter adjustment of the coils L3 and L4.

And seventhly, the phases of the B7 and B8 rectifier transformers are shifted backwards by 22.5 degrees through parameter adjustment of the coils L5 and L6.

And (4) conclusion: it is feasible to make 8 independent iron core rectifier transformers into equivalent 48 pulse rectifier transformers, and the error of 8 groups of secondary output voltages can be controlled to 0.004%.

When the circuit is used, 8 rectifier transformers can adopt 750KVA capacity, the primary incoming line voltage of the rectifier transformers is 10KV, and the secondary voltage of the rectifier transformers has eight grades of 70V, 80V, 90V, 100V, 110V, 120V, 130V and 140V.

In the description of the present specification, it is to be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicate orientations or positional relationships based on those shown in the drawings, and are used merely for convenience of describing the technical solutions of the present patent and for simplification of the description, but do not indicate or imply that the referred devices or elements must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be interpreted as limiting the present patent application.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of this patent application, "plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.

In this specification, unless expressly stated or limited otherwise, the terms "mounted," "connected," and "fixed" are to be construed broadly and may, for example, be fixedly connected, detachably connected, or integral to one another; can be mechanically or electrically connected; they may be directly connected or indirectly connected through intervening media, or they may be connected internally or in any other suitable relationship, unless expressly stated otherwise. The specific meanings of the above terms in the present specification can be understood by those of ordinary skill in the art as appropriate.

In this specification, unless explicitly stated or limited otherwise, a first feature may be "on" or "under" a second feature such that the first and second features are in direct contact, or the first and second features are in indirect contact via an intermediate. Also, a first feature "on," "over," and "above" a second feature may be directly or diagonally above the second feature, or may simply indicate that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature may be directly under or obliquely under the first feature, or may simply mean that the first feature is at a lesser elevation than the second feature.

In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the utility model. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.

Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.

Claims (9)

1. An application circuit of equivalent 48-pulse rectifier transformers of a direct-current electric arc furnace and a submerged arc furnace is characterized by comprising 8 rectifier transformers, 8 groups of rectifier bridges, 8 direct-current reactors and 2 electrodes; 8 rectifier transformers are B1, B2, B3, B4, B5, B6, B7 and B8 rectifier transformers respectively; the 8 groups of rectifier bridges are A1, A2, A3, A4, A5, A6, A7 and A8 groups of rectifier bridges respectively, each group of rectifier bridges comprises six rectifier elements, and each group of rectifier bridges form an independent 6-pulse rectifier circuit; the 8 direct-current reactors are respectively a 1# direct-current reactor, a 2# direct-current reactor, a 3# direct-current reactor, a 4# direct-current reactor, a 5# direct-current reactor, a 6# direct-current reactor, a 7# direct-current reactor and an 8# direct-current reactor; the 2 electrodes are respectively a 1# electrode and a 2# electrode and are positioned in the furnace body; the A1, A2, A3, A4, A5, A5, A6, A7 and A8 groups of rectifier bridges are respectively connected with the secondary outputs of B1, B2, B3, B4, B5, B6, B7 and B8 rectifier transformers, the primary windings of the B1, B2, B3, B4, B5, B6, B7 and B8 rectifier transformers are wound in a regular triangle connection mode, the secondary windings of the B1, B3, B5 and B7 rectifier transformers are wound in an angle connection mode, and the secondary windings of the B2, B4, B6 and B8 rectifier transformers are wound in a star connection mode.

2. The DC arc furnace, submerged arc furnace and equivalent 48-pulse rectifier transformer application circuit of claim 1, wherein the B1, B2, B3, B4, B5, B6, B7 and B8 rectifier transformers are respectively provided with independent iron cores.

3. The DC arc furnace, submerged arc furnace and equivalent 48-pulse rectifier transformer application circuit of claim 1, wherein said B1 rectifier transformers are in the delta/delta-6 connection group, and said B2 rectifier transformers are in the delta/Y-5 connection group.

4. The circuit of claim 1, wherein the B3 rectifier transformer is a delta/delta-6 connection group, and a phase shifting coil L1 is added to the primary winding to shift the phase of the output voltage by 15 ° backward compared with the phase of the output voltage of the B1 rectifier transformer; the B4 rectifier transformer is a delta/Y-5 connection group, and a phase shift coil L2 is additionally arranged on a primary winding, so that the phase of the output voltage of the B4 rectifier transformer is shifted 15 degrees later than that of the output voltage of the B2 rectifier transformer.

5. The circuit of claim 1, wherein the B5 rectifier transformer is a delta/delta-6 connection group, and a phase shifting coil L3 is added to the primary winding to shift the phase of the output voltage by 7.5 ° later than the phase of the output voltage of the B1 rectifier transformer; the B6 rectifier transformer is a delta/Y-5 connection group, and a phase shift coil L4 is additionally arranged on a primary winding, so that the phase of the output voltage of the B6 rectifier transformer is shifted by 7.5 degrees after the phase of the output voltage of the B2 rectifier transformer.

6. The circuit of claim 1, wherein the B7 rectifier transformer is a delta/delta-6 connection group, and a phase shifting coil L5 is added to the primary winding to shift the phase of the output voltage by 22.5 ° later than the phase of the output voltage of the B1 rectifier transformer; the B8 rectifier transformer is a delta/Y-5 connection group, and a phase shift coil L6 is additionally arranged on a primary winding, so that the phase of the output voltage of the B8 rectifier transformer is shifted by 22.5 degrees after the phase of the output voltage of the B2 rectifier transformer.

7. The circuit of claim 1, wherein the positive output terminal of the rectifier bridge of group A1 is connected to the electrode 1# via the DC reactor 1# and the positive output terminal of the rectifier bridge of group A2 is connected to the electrode 1# via the DC reactor 2# and the positive output terminal of the rectifier bridge of group A3 is connected to the electrode 1# via the DC reactor 3# and the positive output terminal of the rectifier bridge of group A4 is connected to the electrode 1# via the DC reactor 4# and the positive output terminal of the rectifier bridge of group A5 is connected to the electrode 1# via the DC reactor 5# and the positive output terminal of the rectifier bridge of group A6 is connected to the electrode 1# via the DC reactor 6# and the positive output terminal of the rectifier bridge of group A7 is connected to the electrode 1# via the DC reactor 7# and the positive output terminal of the rectifier bridge of group A8 is connected to the electrode 1# via the DC reactor 8# and the DC reactors A1, A2, A3, A1, A2, A3 and A3, The negative electrode output ends of the rectifier bridges of the A4, A5, A5, A6, A7 and A8 groups are respectively connected with the 2# electrode.

8. The dc arc furnace, submerged arc furnace and equivalent 48-pulse rectifier transformer application circuit as claimed in claim 1, wherein said rectifier transformer has a primary incoming line voltage of 10KV, and a secondary incoming line voltage having eight levels of 70V, 80V, 90V, 100V, 110V, 120V, 130V, and 140V.

9. The application circuit of the 48-pulse rectifier transformer for DC arc furnace, submerged arc furnace, etc. as claimed in claim 1, wherein said rectifier element is ZP type high power rectifier diode or KP type thyristor.

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