CN2817016Y - Soft-excitation transformer without excitation flow and without switch-on over-voltage - Google Patents

Abstract

The utility model provides a soft excitation transformer without excitation flow and without switch-on over-voltage. A primary side of the transformer is provided with main power supply windings and a group of windings used for the soft excitation of a transformer iron core; the windings are controlled by a low-voltage transfer switch and controlled silicon so as to realize the soft excitation on the occasion of switching on and external output voltage of 380V on the occasion of running. The transformer eliminates that excitation flow and excess voltage damage devices on the occasion of switching on, and simultaneously, the utility model reduces the manufacturing cost of the transformer. The technique is applied to a phase-shifting transformer and makes up for the insufficiency of foreign correlation technique.

Description

The soft excitation transformer of no magnetizing inrush current, no closing overvoltage

Technical field

The utility model relates to the transformer that can eliminate combined floodgate magnetizing inrush current and closing overvoltage technology.Design a kind of soft excitation transformer that does not have magnetizing inrush current, no closing overvoltage specifically.

Background technology

After winding of transformer inserted electrical network, the magnetic flux in the electric current in the winding, voltage and the iron core all will experience the change procedure of from a kind of stable state (null value) to another kind of stable state (for example rated value), and this change procedure is called transient process.In transient process, exciting current and closing overvoltage all can reach maximum.Calculate and test shows: magnetizing inrush current can reach several times to tens times of rated current, closing overvoltage also can reach several times to tens times or higher of rated voltage, excessive magnetizing inrush current can cause switch trip, may be misinterpreted as transformer like this is out of order, magnetizing inrush current also may cause very big voltage drop in electric power system, near the electricity consumption department making is affected.

Common power consumption equipment all is to link to each other with Circuit Fault on Secondary Transformer by switch, and secondary winding and power consumption equipment disconnect during Transformer Close, even transformer has very high closing overvoltage can not have influence on electronic devices and components.But in some low-pressure high-power rectifying installation, and in unit cascade type multi-level high-voltage big-power transducer, rectifier diode must directly link to each other with transformer, and at this moment, too high closing overvoltage can puncture the electronic devices and components such as diode in the transformer secondary loop.

Studies show that: the magnetizing inrush current and the closing overvoltage of transformer have substantial connection, and the Transformer Close overvoltage that normally magnetizing inrush current is big is also high.

Therefore, in above-mentioned these power consumption equipments, be necessary to reduce transformer excitation flow and reduce closing overvoltage.

According to theory analysis: the maximum magnetizing inrush current during the three-phase transformer idle-loaded switching-on calculates as follows:

$\mathrm{Io}\max =\frac{2H{S}_t}{3W{S}_x{\mathrm{\μ}}_O}(2B_m+B_r-2.2)$ Peace

In the formula: H---closing coil height rice

S _t---area of core section rice ²

W---the closing coil number of turn

S _x---press the area of a circle rice that the closing coil average diameter is calculated ²

μ ₀---space permeability μ ₀=4 π * 10 ^-7Henry/rice

B _m---maximum magnetic induction Te Lasi in the iron core

B _r---remanence strength Te Lasi in the iron core

Reduce magnetizing inrush current and can take following measure:

1. reduce the closing coil height H

2. increase the coil width of cloth to size, promptly increase area coil S _xThe inrush phenomenon of interior loop big than exterior loop clearly.

3. reduce core area S _t

4. increase coil turn W

5. reduce magnetic induction density B unshakable in one's determination _m

But adopt above measure all can make transformer overall dimension become short and stout, it is big that impedance becomes, and copper loss increases, and the coil heat radiation is unfavorable.The transformer cost also can increase a lot.

The cut-off overvoltage that the overvoltage that produces during Transformer Close produces in the time of can be with its idle power-off carries out the branch folding:

The cut-off overvoltage U that produces when after deliberation, no-load transformer cuts off the power supply _CmWith rated voltage U _oRatio K v be that the overvoltage multiple is determined by following formula:

$K_V=\frac{U_{\mathrm{cm}}}{U_0}\&ap;\frac{I_0{Z}_0}{2\mathrm{\&pi;f}{L}_m{I}_0}=\frac{\sqrt{L_m/\mathrm{<figure-callout\; id="2"\; label="C"\; filenames="Y20042010569800071.png"\; state="\{\{state\}\}">C</figure-callout>}}}{2\mathrm{\&pi;f}{L}_m}=\frac{\frac{1}{2\mathrm{\&pi;}\sqrt{L_{m}C}}}{f}=\frac{f_0}{f}---1$

Wherein:

$U_{\mathrm{cm}}=\sqrt{{\left(I_{\mathrm{ch}}{Z}_0\right)}^2+U_0^2}\&ap;I_{\mathrm{ch}}{Z}_0=I_0{Z}_0=I_0\sqrt{\frac{L_m}{C}}---2$

I _Ch---the switch shut off value

I ₀---the no-load transformer electric current

Z ₀---the transformer characteristic impedance $Z_0=\sqrt{\frac{L_m}{C}}---3$

L _m---the static exciter inductance L _m≈ Z _m/ ω ... ..4

Z _m---the static exciter impedance

C---transformer interior loop (elementary) direct-to-ground capacitance

Fo---the frequency of oscillation after damming $\mathrm{fo}=\frac{1}{2\mathrm{\&pi;}\sqrt{L_{m}C}}---5$

F---electrical network power frequency

Clearly to reduce overvoltage.Can strengthen magnetizing inductance or coil inlet electric capacity.But this can make the transformer device structure complexity, and cost increases.

Summary of the invention

The purpose of this utility model is magnetizing inrush current and the closing overvoltage for thorough eliminating transformer, the ad hoc soft excitation transformer of having counted no magnetizing inrush current, no closing overvoltage.

Magnetizing inrush current when eliminating transformer closes a floodgate must directly link to each other with the secondary side of transformer with the load of this class transformer of the technology of closing overvoltage, as the phase shifting transformer in the high-voltage high-power frequency transformator, power rectifier transformer, furnace transformer etc.

The magnetizing inrush current of present technique eliminating transformer and the principle of closing overvoltage are:

In Side of transformer the precharge excitation winding is set, the supply power voltage of this winding is the three-phase 380V from same power supply.Before the high pressure winding of transformer closes a floodgate, close the precharge excitation winding earlier, transformer core is carried out soft excitation.Have by the method for excitation winding: 1) with controllable silicon or other electronic component pressure regulation soft excitation unshakable in one's determination; 2) use the voltage regulator pressure regulation; 3) use the series reactor pressure regulation; 4) other current limiting pressure-limiting methods.Detect the primary cut-out that closes immediately when meeting the breaker closing condition when excitation winding reaches rated value, high pressure sensor phase sequence to iron core excitation, this moment, the excitation of transformer was carried out simultaneously by excitation winding and high pressure winding.

Major technique content of the present utility model;

Magnetizing inrush current during a kind of can eliminating transformer combined floodgate the and the transformer of closing overvoltage, it is characterized in that: the primary side of transformer has one group of winding 2 that transformer core is carried out soft excitation in addition except that high voltage supply winding 1, this winding and low tension switch 4, be connected to after reverse-blocking tetrode thyristor 5 series connection and lead on the low-tension supply of power supply winding with phase sequence, low pressure change over switch 4 has two gears, a gear is connected 380V input voltage and reverse-blocking tetrode thyristor, another gear is connected the winding 2 and the 380V output of excitation, externally exports 380V voltage when soft excitation startup when being used to realize closing a floodgate and operation.

Phase shifting transformer with frequency converter is the principle that example specifies present technique below.(frequency converter and phase shifting transformer principle are seen Fig. 4 and Fig. 1)

A. set up one group of 380V precharge excitation winding 2 (double as 380V fan power, capacity are primary side high pressure winding 1%～2%) (see figure 1) at the primary side of phase shifting transformer.This excitation winding is by low pressure change over switch 4 (see figure 2) of connecting with controllable silicon 5 current-limiting resistances 7.Before the high pressure winding 1 of transformer inserts, the precharge excitation winding 2 of closing 380V earlier, this winding carries out soft excitation (the silicon controlled angle of flow from little change greatly up to complete conducting) through 5 pairs of transformer cores of controllable silicon.Thereby inrush phenomenon and closing overvoltage are all very low, simultaneously the electric capacity in the secondary side power cell are slowly charged, and charging current is very little.

B. when to the electric capacity precharge in the secondary side power cell when enough, high pressure sensor 11 detects the combined floodgate condition that meets, high-voltage switch gear 9 immediately closes, the main flux that this moment, high pressure winding 1 was responded in iron core is in full accord on phase place and size with the main flux of precharge excitation winding 2 generations, so can not produce magnetizing inrush current and closing overvoltage.

The utility model good effect: eliminated owing to shove and the infringement of switching overvoltage, also greatly reduced the manufacturing cost of transformer simultaneously to equipment.Present technique is applied in phase shifting transformer, and has remedied the deficiency of external correlation technique.

Description of drawings

Fig. 1 transformer principle figure

Fig. 2 electrical schematic diagram

Fig. 3 sequential chart

6 grades of 6KV transformer circuits of Fig. 4 schematic diagram

Fig. 5 transformer efficiency unit figure

Sequence number explanation among the figure:

1, high voltage supply winding, 2, excitation winding, 3, the 380V input, 4, the low pressure change over switch,

5, controllable silicon, 6, electric capacity, 7, ductility limit resistance, 8, the high pressure input,

9, high pressure isolation switch, 10, primary cut-out, 11, transducer, 12, transformer,

13, low pressure output winding, 14, asynchronous motor, 15, power cell, 16, interface,

17,380V output, 18, microprocessor.

A. low pressure change over switch is 1 among Fig. 3.

B. controllable silicon conducting.

C. the high pressure isolation switch closes.

D. the transducer phase sequence detects.

E. primary cut-out closes.

F. the low pressure change over switch is 2.

Embodiment

Embodiment 1:

Fig. 1 is the example of the phase shifting transformer of band excitation winding, and Fig. 2 is an electrical schematic diagram, and Fig. 3 is a sequential chart.Transformer input process is as follows:

1) earlier low pressure change over switch 4 is turned to a position---the 380V input.

2) controllable silicon is open-minded, from zero to full conducting to the transformer soft excitation, make the magnetic flux in the iron core reach rated value (full conducting in 3～10s), main flux reaches rated value in the transformer core, electric capacity has been full of electricity (about 120s), (seeing Fig. 3 A, B) in each power cell at this moment.

3) the high pressure isolation switch 9 that closes.(seeing Fig. 3 C).

4) detect the L of three-phase high-voltage transducer 11 ₁, L ₂Terminal voltage is zero, when promptly meeting the combined floodgate condition of primary cut-out, and the primary cut-out 10 that closes, (seeing Fig. 3 D, E).

5) low tension switch switches to the b position---380V output, (seeing Fig. 3 F).

Claims (1)

1. soft excitation transformer that does not have magnetizing inrush current, no closing overvoltage, it is characterized in that: the primary side of transformer has high voltage supply winding (1), excitation winding (2), low pressure change over switch (4), reverse-blocking tetrode thyristor (5), electric capacity (6), ductility limit resistance (7), high pressure isolation switch (9), primary cut-out (10); In the high voltage supply winding, be in series with high pressure isolation switch (9) and primary cut-out (10); In excitation winding (2), be in series with pair of contact, reverse-blocking tetrode thyristor (5) and the ductility limit resistance (7) of low pressure change over switch (4); Controllable silicon is parallel with electric capacity (6); Excitation winding have in addition that a branch road is in series with low pressure change over switch (4) another to the contact.

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