CN217428009U - Improved DC arc furnace equivalent 96 pulse wave rectifier transformer application circuit - Google Patents

Abstract

The utility model discloses an improved generation direct current electric arc furnace equivalence 96 pulse wave rectifier transformer application circuit, connect the 6 pulse wave rectifier circuits of same load, every including 16 parallelly connected together 6 pulse wave rectifier circuits, including an independent rectifier transformer, a set of rectifier bridge and a DC reactor, a rectifier transformer connects a set of rectifier bridge, and a DC reactor is connected to the anodal output of a set of rectifier bridge, and whole among 16 6 pulse wave rectifier circuitsThe current transformers are divided into two kinds, each has 8, one of them is directly connected with three-phase power source, the rest 7 are connected with three-phase shifter and then connected with three-phase power source, in the same 8 rectifier transformers, the output voltage phase is backward shifted compared with that of directly connected three-phase power source

n ∈ {1,2,3,4,5,6,7}, each value in the set can only be taken once. The utility model discloses DC power supply's voltage waveform is more steady.

Description

Improved DC arc furnace equivalent 96-pulse rectifier transformer application circuit

Technical Field

The utility model belongs to the technical field of the interchange, direct current conversion technique and specifically relates to an improved generation direct current electric arc furnace equivalence 96 pulse wave rectifier transformer application circuit is related to.

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 ripple coefficient of the output direct-current voltage is relatively large, 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.

Chinese patent document CN 201810410354.1: a 36-pulse rectifier adopting a dc-side dual passive harmonic suppression method, chinese patent document cn201910409441. x: 48-pulse transformer rectifiers of the direct-current side passive harmonic suppression technology are researched and developed to a certain extent for the multi-pulse rectification technology.

The inventor also has studied an equivalent 48-pulse rectifier transformer, and the results thereof are shown in chinese patent CN 202120351096.1: a DC arc furnace and a submerged arc furnace equivalent 48-pulse transformer application circuit, and an equivalent 48-pulse rectifier transformer can meet the application requirement of a certain occasion, but the voltage ripple coefficient is still higher.

SUMMERY OF THE UTILITY MODEL

The inventor develops an equivalent 48-pulse rectifier transformer, and finds that the voltage waveform of an equivalent 96-pulse direct-current power supply is more stable than 48 pulses in experiments, and meanwhile, when a high-power rectifier power supply is manufactured, according to the current practical situation, a single rectifier element in China cannot have too large capacity, so that the rectifier elements need to be connected in parallel for use; and because the parameters of each rectifying element are not identical and the crimping strength of each parallel element is not identical, the current distribution among the parallel elements is not uniform, the more the parallel elements are, the more the phenomenon of nonuniform current is serious, and the more the nonuniform degree exceeds 30%, the elements with larger current in the parallel elements are often burnt out firstly.

Aiming at the current sharing problem, if the 96-pulse rectification is adopted, the rectifying elements are not connected in parallel, but are divided into 16 independent rectifying bridges, so that the phenomenon of uneven current distribution among the parallel rectifying elements can be effectively solved.

The conventional 96-pulse furnace rectifier transformer 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 and more dozens of volts, in the actual winding process, the winding of half turns for enabling the secondary voltages of 16 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 voltages of the 16 groups of low-voltage windings are different by a few volts or even dozens of volts, the output direct-current voltages of the 16 groups of rectifier bridges are different by a few volts or even dozens of volts, and the situation that the output sizes of the windings are different appears. And because every 8 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 structure of a conventional 96-pulse rectifier transformer using a thyristor as a rectifier element, a general method is to artificially suppress a higher dc output voltage of a set of rectifier bridges with a higher input voltage by increasing a phase shift angle of the set of rectifier bridges with the higher input voltage, so as to obtain a dc output voltage of 16 sets of rectifier bridges with the same magnitude.

Aiming at the phenomenon, an equivalent 96-pulse wave rectifier transformer applied to a direct current electric arc furnace is designed, the defects of the phenomenon are fundamentally solved, the fault that rectifier elements are often burnt out due to uneven current distribution is solved, the natural power factor can reach 0.99, the voltage waveform of an equivalent 96-pulse wave direct current power supply is found to be more stable than 48 pulse waves in experiments, the voltage pulse coefficient of the direct current power supply reaches 0.00035, 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 by an oscilloscope and is almost not seen, and a good scheme is found for producing a high-power rectifier power supply.

In view of the above, the present invention provides an improved dc arc furnace equivalent 96-pulse rectifier transformer application circuit.

In order to achieve the above purpose, the utility model adopts the following technical scheme:

an improved DC arc furnace equivalent 96-pulse rectifier transformer application circuit comprises 16 6-pulse rectifier circuits connected in parallel with the same load, each 6-pulse rectifier circuit comprises an independent rectifier transformer, a group of rectifier bridges and a DC reactor, one rectifier transformer is connected with a group of rectifier bridges, the positive output end of one group of rectifier bridges is connected with one DC reactor, the rectifier transformers in the 16 6-pulse rectifier circuits are divided into two types, each type comprises 8 rectifier transformers, namely a primary side triangle winding method and a secondary side triangle winding method, a primary side triangle winding method and a secondary side star winding method, each type is directly connected with a three-phase power supply, the rest 7 rectifier transformers are connected with a three-phase shifter and then connected with a three-phase power supply, and in the same 8 rectifier transformers, the three-phase shifter is connected with a phase shifter compared with the three-phase power supply directly connected with the three-phase power supply, output voltage phase back shift

n ∈ {1,2,3,4,5,6,7}, each value in the set can only be taken once.

Further, the load is a positive electrode and a negative electrode of the direct current electric arc furnace, and the positive electrode and the negative electrode generate electric arcs after being electrified, so that the electric arc furnace is heated.

Further, the voltage of a primary side line of the rectifier transformer is 10 KV.

Furthermore, the secondary side of the rectifier transformer is provided with 50-240V, and 27-gear output is achieved.

Furthermore, the rectifying elements in the rectifier bridge are ZP type high-power rectifying diodes of the same type.

The utility model relates to an application circuit of an equivalent 96-pulse rectifier transformer of an improved DC electric arc furnace,

the utility model has the advantages that:

1. the utility model discloses an improved generation direct current electric arc furnace equivalence 96 pulse wave rectifier transformer application circuit adopts 16 same loads of 6 pulse wave rectifier circuit parallel connection, and the technical difficulty is low, and the natural power factor reaches 0.99, and its voltage pulsation coefficient reaches 0.00035, observes with oscilloscope, and 3 times in the voltage waveform, 5 times, 7 times, 9 times, 11 times etc. higher harmonic's content is extremely low, can't see hardly.

2. The utility model discloses an improved generation direct current electric arc furnace equivalence 96 pulse wave rectifier transformer application circuit, 16 rectifier bridge output voltage wave shape are balanced, unanimous, and 16 rectifier bridge output current size are balanced, unanimous, can make direct current electric arc furnace 24 hours long-term steady operation, and the fault rate is extremely low.

Drawings

Fig. 1 is a diagram of the equivalent 96-pulse rectification principle of a direct-current electric arc furnace.

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

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

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

Fig. 5 is a diagram of the connection group 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 diagram of the phase relationship of the rectified output dc voltage of the equivalent 96-pulse transformer formed after the superposition.

Fig. 11 is a graph comparing waveforms of rectified output dc voltages of 6-pulse, 12-pulse, 24-pulse, 48-pulse, and 96-pulse rectifier transformers.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative efforts belong to the protection scope of the present invention.

Example (b):

as shown in fig. 1-11, the present invention relates to an improved dc arc furnace equivalent 96-pulse rectifier transformer application circuit, wherein the load is the positive electrode and the negative electrode of a dc arc furnace, the circuit comprises 16 6-pulse rectifier circuits connected in parallel to the same load, each of the 6-pulse rectifier circuits comprises an independent rectifier transformer, a set of rectifier bridges and a dc reactor, one rectifier transformer is connected to one set of rectifier bridges, and the positive output terminal of one set of rectifier bridges is connected to one dc reactor, i.e. B1, B2, B3, B4, B5, B6, B7, B8, B9, B10, B11, B12, B13, B14, B15, B16, these 16 rectifier transformers are respectively connected to D1, D2, D3, D4, D72, D4, D72, D4, a group of these rectifier bridges, a rectifier transformers are connected to the rectifier bridge, The positive electrodes of 16 groups of rectifier bridges of D9, D10, D11, D12, D13, D14, D15 and D16 are respectively connected with 16 direct current reactors of L1, L2, L3, L4, L5, L6, L7, L8, L9, L10, L11, L12, L13, L14, L15 and L16 and then connected with the same positive electrode, the negative electrodes of 16 groups of rectifier bridges of D1, D2, D3, D4, D5, D6, D7, D8, D9, D10, D11, D12, D13, D14, D15 and D16 are connected with the same negative electrode, and the positive electrode and the negative electrode are two electrodes in the same direct current arc furnace.

The 16 groups of rectifier bridges, namely D1, D2, D3, D4, D5, D6, D7, D8, D9, D10, D11, D12, D13, D14, D15 and D16, are ZP type high-power rectifier diodes with the same model.

The 16 pulse wave rectifying circuits are divided into two rectifying transformers, each of which has 8 transformers, and respectively comprises B1, B1 and B1 which are wound by primary side triangles and secondary side triangles, B1 and B1 which are wound by the primary side triangles and the secondary side stars, each of which has one rectifying transformer directly connected with three-phase power, namely, the two rectifying transformers of the B1 wound by the primary side triangles and the secondary side triangles and the B1 wound by the primary side triangles and the secondary side stars are directly connected with three-phase power, the remaining three-phase power of the B1, P1 and P1 which are connected with three-phase power after the three-phase power is connected with the three-phase power, the other 7 rectifier transformers of the primary side triangle-connected winding and the secondary side star-connected winding, namely B4, B6, B8, B10, B12, B14 and B16, are respectively connected with three-phase shifters P2, P4, P6, P8, P10 and then connected with a three-phase power supply, among 8 rectifier transformers of the primary side triangle-connected winding and the secondary side triangle-connected winding, B10 and B10, the 7 rectifier transformers of the three-phase shifters P10, B10 and B10 are connected with the three-phase shifters P10, B10 and B10, B10 is connected with the output voltage of the B10 phase-shifted rectifier transformer which is connected with the B10, B10 output voltage of the B10-phase-shifted rectifier transformer, B-phase-3 output voltage-phase shifted-phase-shifted rectifier transformer, B-phase-shifted-phase-shifted rectifier transformer, B-phase-shifted-phase-, The phase of the output voltage of the rectifier transformer B is shifted backward by 3.75 degrees, and the phase of the output voltage of the rectifier transformer B is shifted backward by 3.75 degrees, The phase of the output voltage of rectifier transformer B8 is 3.75 ° later than that of rectifier transformer B6, the phase of rectifier transformer B10 is 3.75 ° later than that of rectifier transformer B8, the phase of the output voltage of rectifier transformer B12 is 3.75 ° later than that of rectifier transformer B10, the phase of rectifier transformer B14 is 3.75 ° later than that of rectifier transformer B12, and the phase of the output voltage of rectifier transformer B16 is 3.75 ° later than that of rectifier transformer B14.

Thus, under the condition that 16 transformers, namely B1, B2, B3, B4, B5, B6, B7, B8, B9, B10, B11, B12, B13, B14, B15 and B16, are connected to the same three-phase power supply directly or through a three-phase shifter, voltages generated on the secondary winding side are the same in magnitude and are different in phase by 3.75 degrees, and equivalent 96 pulses are formed.

The method comprises the following specific steps: firstly, letting 16 rectifier transformers B1, B2, B3, B4, B5, B6, B7, B8, B9, B10, B11, B12, B13, B14, B15 and B16 respectively have independent iron cores, namely, each rectifier transformer has an independent magnetic circuit, so that the low-voltage winding of each rectifier transformer is not interfered by other transformers; secondly, because the number of turns of the secondary side winding of each rectifier transformer 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, however, the high-voltage winding of each rectifier transformer has a large number of turns and a low voltage born by each turn, and if the high-voltage winding is different by one turn, the difference of the output voltage on the low-voltage winding is not more than 1V, so that the number of turns of the secondary side windings of the two rectifier transformers B1 and B2 can be made into an integer number of turns capable of outputting the same voltage value, the number of turns of the high-voltage windings of the 16 rectifier transformers is slightly different, and the secondary voltages which are almost completely equal are obtained on the secondary side windings of the 16 rectifier 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 with the primary side and the secondary side wound in a delta/delta-6 connection mode is a delta/delta-6 connection mode, 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 with the primary side delta connection winding and the secondary side star connection winding is a delta/Y-5 connection group, the primary winding of the B2 rectifier transformer has 1 ten thousand turns, and 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 wound by the primary side delta connection and the secondary side delta connection is 10000 ÷ 50 ═ 200, the secondary winding of the B2 rectifier transformer wound by the primary side delta connection and the secondary side star connection is set to 29 turns according to the principle of rounding off, then the number of turns of the primary winding of the B2 rectifier transformer wound by the primary side delta connection and the secondary side star connection is 29 × 1.732 × 200 ═ 10045.6 turns, and the number of turns of the primary winding of the B2 rectifier transformer wound by the primary side delta connection and the secondary side star connection is 10046 turns;

fourthly, verifying the result: when a voltage of 10KV is applied to the primary winding of the B2 rectifier transformer wound in the primary side delta connection and the secondary side star connection, the voltage output by the secondary winding of the B2 rectifier transformer wound in the primary side delta connection and the secondary side star connection is 49.998V, the voltage difference value of 50V output by the secondary winding of the B1 rectifier transformer wound in the primary side delta connection and the secondary side star connection is 50V-49.998V is 0.002V, and the proportional relationship between the voltage difference value and the 50V reference value is 0.002V/50V/0.004%, which can be almost ignored;

and (4) conclusion: it is feasible to make 16 independent iron core rectifier transformers into equivalent 96 pulse rectifier transformers, and the error of 16 groups of secondary output voltages can be controlled to 0.004%.

The utility model discloses a circuit when using, can adopt 750 KVA's capacity with 16 rectifier transformers, rectifier transformer is inlet wire voltage 10KV once, and secondary voltage has 27 shelves totally of 50V ~ 240V.

Finally, the above embodiments are only used for illustrating the technical solutions of the present invention and are not limited, and other modifications or equivalent replacements made by the technical solutions of the present invention by those of ordinary skill in the art should be covered within the scope of the claims of the present invention as long as they do not depart from the spirit and scope of the technical solutions of the present invention.

Claims (5)

1. Improved generation direct current electric arc furnace equivalence 96 pulse wave rectifier transformer application circuit, its characterized in that: the 6-pulse rectification circuit comprises 16 6 pulse rectification circuits which are connected in parallel and are connected with the same load, each 6-pulse rectification circuit comprises an independent rectifier transformer, a group of rectifier bridges and a direct current reactor, one rectifier transformer is connected with one group of rectifier bridges, the positive electrode output end of one group of rectifier bridges is connected with one direct current reactor, the 16 pulse rectification circuits are divided into two types, 8 types are respectively arranged in each 6 pulse rectification circuit, and the four types are respectively one of a primary side triangle winding method, a secondary side triangle winding method, a primary side triangle winding method and a secondary side triangle winding method, and one of the primary side triangle winding method and the secondary side triangle winding method and the other one of the secondary side triangle winding methodThe star connection winding is characterized in that one of the three-phase power supplies is directly connected with a three-phase power supply, the rest 7 of the three-phase power supplies are connected with a three-phase shifter and then connected with the three-phase power supply, and in the same 8 rectifier transformers, the output voltage phase of the three-phase shifter is shifted backwards compared with the output voltage phase of the three-phase power supplies directly connected with the three-phase power supplies

Each value in the set can only be taken once.

2. The improved DC arc furnace equivalent 96-pulse rectifier transformer application circuit as claimed in claim 1, wherein: the load is a positive electrode and a negative electrode of the direct current electric arc furnace.

3. The improved DC arc furnace equivalent 96-pulse rectifier transformer application circuit as claimed in claim 1, wherein: and the voltage of a primary side line of the rectifier transformer is 10 KV.

4. The improved DC arc furnace equivalent 96-pulse rectifier transformer application circuit as claimed in claim 3, wherein: the secondary side of the rectifier transformer is provided with 50-240V, and the total output is 27.

5. The improved DC arc furnace equivalent 96-pulse rectifier transformer application circuit as claimed in claim 1, wherein: and the rectifying elements in the rectifier bridge are ZP type high-power rectifying diodes of the same type.

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