CN216793465U - Device for reducing excitation surge current of transformer - Google Patents

Abstract

The application relates to a device for reducing magnetizing inrush current of a transformer. The device includes: a main circuit and a control circuit; the main circuit comprises: the device comprises an alternating current contactor, a reactor, a transformer and a first breaker; the alternating current contactor is connected in series with the reactor and then connected between a power grid and a transformer; the first circuit breaker is connected between a power grid and a transformer; a first relay first contact is arranged in a closing branch of the first circuit breaker; an alternating current contactor contact is arranged in the alternating current contactor; the control circuit is connected with the power grid and comprises: a first relay coil and an ac contactor coil; the control circuit can control the alternating current contactor coil and the first relay coil to be electrified, so that the contact of the alternating current contactor is closed and the first contact of the first relay is closed through first time. The scheme provided by the application can reduce the magnetizing inrush current of the transformer, so that the electrical equipment of the line can stably operate.

Description

Device for reducing excitation surge current of transformer

Technical Field

The application relates to the technical field of transformers, in particular to a device for reducing magnetizing inrush current of a transformer.

Background

When the transformer is switched on in an idle state, a primary winding of the transformer may generate excitation inrush current with a very high amplitude, and the maximum peak value of the excitation inrush current can reach 6-8 times of the rated current of the transformer, so that electrical equipment of a line is greatly influenced, and even a relay protection device malfunctions.

Therefore, the device for reducing the magnetizing inrush current of the transformer aims at designing the device for reducing the magnetizing inrush current of the transformer, and the magnetizing inrush current of the transformer can be reduced, so that the electrical equipment of a line can stably run.

SUMMERY OF THE UTILITY MODEL

In order to overcome the problems in the related art, the application provides a device for reducing the magnetizing inrush current of a transformer, which can reduce the magnetizing inrush current of the transformer and enable electrical equipment of a line to operate stably.

The application provides a reduce device of transformer excitation inrush current includes: a main circuit and a control circuit;

the main circuit comprises: the system comprises an alternating current contactor KM, a reactor L, a transformer T and a first breaker QF 1;

the alternating current contactor KM is connected with the reactor L in series and then is connected between a power grid and the transformer T;

the first breaker QF1 is connected between the grid and the transformer T;

a first relay first contact KT11 is arranged in a closing branch of the first circuit breaker QF 1;

an alternating current contactor contact is arranged in the alternating current contactor KM;

the control circuit is connected with the power grid, and the control circuit includes: a first relay coil KT1 and an ac contactor coil KM;

the control circuit can control the ac contactor coil KM and the first relay coil KT1 to be energized so that the ac contactor contacts are closed and the first relay first contact KT11 is closed over a first time.

In one embodiment, the control circuit includes a first loop and a second loop;

the first circuit includes: a starting switch SB1, a second relay first contact KA11, a third relay contact KT2, a second relay coil KA1 and the first relay coil KT 1; the starting switch SB1 is connected with the first relay contact KA11 in parallel to form a first sub-loop of the first loop; the third relay contact KT2 is connected in series with the second relay coil KA1 and then connected in parallel with the first relay coil KT1 to form a second sub-loop of the first loop; the first sub-loop and the second sub-loop are connected in series and then connected between the phase line A of the power grid and the neutral line N of the power grid;

the second circuit includes: a second relay second contact KA12 and the ac contactor coil KM; the second relay second contact KA12 is connected in series with the ac contactor coil KM and then connected between the phase line a of the power grid and the neutral line N of the power grid.

In one embodiment, the control circuit further comprises: a third circuit;

the third circuit includes: a first relay second contact KT12 and a third relay coil KT 2; the first relay second contact KT12 with the third relay coil KT2 is connected in series after connecting between the A phase line of electric wire netting and the neutral conductor N of electric wire netting.

In one embodiment, the first relay and the third relay are energized time delay relays, and the second relay is an intermediate relay.

In one embodiment, the first relay first contact KT11 and the first relay second contact KT12 are time-delay closed normally open contacts;

the second relay first contact KA11 and the second relay second contact KA12 are instant normally open contacts;

the third relay contact KT2 is a normally closed contact for delaying disconnection;

and the contact of the alternating current contactor is an instantaneous normally open contact.

In one embodiment, the control circuit further includes an emergency stop button SB2 and a stop button SB 3;

the emergency stop button SB2 and the stop button SB3 are connected in series and then connected between the phase line A of the power grid and the first loop or the second loop or the third loop.

In one embodiment, the control circuit further comprises a second circuit breaker QF2, the second circuit breaker QF2 being connected between the a-phase line of the grid and the first or second or third circuit.

In one embodiment, the first time is a delay time of the first relay, and the delay time is 2 seconds to 4 seconds.

In one embodiment, the delay time of the third relay is 2 to 4 seconds.

In one embodiment, the primary circuit further comprises: a power indicator light;

the power indicator light is connected between the power grid and the first circuit breaker QF 1.

The technical scheme provided by the application can comprise the following beneficial effects:

the device comprises a main circuit and a control circuit, wherein an alternating current contactor KM and a reactor L of the main circuit are connected in series and then connected between a power grid and a transformer T, a first breaker QF1 is also connected between the power grid and the transformer T, an alternating current contactor coil KM for controlling the alternating current contactor KM to open and close and a first relay coil KT1 for controlling the first breaker QF1 to close are arranged in the control circuit, when the device starts to work, the control circuit controls the alternating current contactor coil KM and the first relay coil KT1 to be electrified, so that the contact of the alternating current contactor is closed and the first relay first contact KT11 is closed for the first time, as the contact of the alternating current contactor is arranged in the alternating current contactor KM, the first relay first contact KT11 is arranged in a closing shunt of the first breaker QF1, the alternating current contactor KM can be conducted on the main circuit for the first time in advance of the first breaker QF1, at the moment, the series circuit of the transformer T and the reactor L is conducted, the reactor L can perform a voltage division effect on the voltage of the power grid, the voltage of the two ends of the transformer T is reduced, the magnetizing inrush current passing through the transformer T is reduced, and the phenomenon that the first circuit breaker QF1 generates overlarge magnetizing inrush current after a main circuit is conducted is avoided, so that adverse effects on line equipment are caused.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the application.

Drawings

The foregoing and other objects, features and advantages of the application will be apparent from the following more particular descriptions of exemplary embodiments of the application, as illustrated in the accompanying drawings wherein like reference numbers generally represent like parts throughout the exemplary embodiments of the application.

FIG. 1 is a circuit diagram of an apparatus for reducing transformer inrush current according to an embodiment of the present application;

fig. 2 is a schematic diagram of a first circuit breaker in an apparatus for reducing transformer magnetizing inrush current according to an embodiment of the present application.

Detailed Description

Preferred embodiments of the present application will be described in more detail below with reference to the accompanying drawings. While the preferred embodiments of the present application have been illustrated in the accompanying drawings, it should be understood that the present application may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used in this application and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It should also be understood that the term "and/or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items.

It should be understood that although the terms "first," "second," "third," etc. may be used herein to describe various information, these information should not be limited to these terms. These terms are only used to distinguish one type of information from another. For example, first information may also be referred to as second information, and similarly, second information may also be referred to as first information, without departing from the scope of the present application. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present application, "a plurality" means two or more unless specifically limited otherwise.

When the transformer is switched on in an idle state, a primary winding of the transformer may generate excitation inrush current with a very high amplitude, and the maximum peak value of the excitation inrush current can reach 6-8 times of the rated current of the transformer, so that electrical equipment of a line is greatly influenced, and even a relay protection device malfunctions.

In view of the above problems, embodiments of the present application provide a device for reducing transformer inrush current, which can reduce transformer inrush current and enable electrical equipment of a line to operate stably.

The technical solutions of the embodiments of the present application are described in detail below with reference to the accompanying drawings.

Example one

FIG. 1 is a circuit diagram of an apparatus for reducing transformer inrush current according to an embodiment of the present application;

fig. 2 is a schematic diagram of a first circuit breaker in an apparatus for reducing transformer magnetizing inrush current according to an embodiment of the present application.

Referring to fig. 1-2, the device for reducing the magnetizing inrush current of the transformer comprises a main circuit 1 and a control circuit 2, wherein the main circuit 1 comprises an alternating current contactor KM, a reactor L, a transformer T and a first breaker QF1, the alternating current contactor KM is connected with the reactor L in series and then connected between a power grid and the transformer T, and the first breaker QF1 is connected between the power grid and the transformer T.

Be provided with first relay first contact KT11 in first circuit breaker QF 1's the combined floodgate branch road, be provided with the ac contactor contact in the ac contactor KM, control circuit 2 links to each other with the electric wire netting, and control circuit 2 includes first relay coil KT1 and ac contactor coil KM, and control circuit 2 can control ac contactor coil KM and first relay coil and get electric KT1 for ac contactor contact closure and first relay first contact KT11 is closed through the very first time.

In this embodiment, the first relay first contact KT11 is a time-delay closed normally open contact, and the ac contactor contact is an instantaneous normally open contact.

It should be noted that the first circuit breaker QF1 can be a universal frame circuit breaker, or other types of circuit breakers, and is not limited herein, and in this embodiment, the first circuit breaker QF1 is a universal frame circuit breaker.

The universal frame circuit breaker is a mechanical switch electric appliance which can be connected, bear and break current under normal circuit conditions, and can also be connected, bear and break current for a certain time under specified abnormal circuit conditions, and is used for distributing electric energy and protecting overload, undervoltage, short circuit and the like of circuits and power supply equipment; such circuit breakers typically have a steel frame with all the components mounted within the frame; the high-capacity high-voltage switch has large capacity, can be provided with a release with multiple functions and a plurality of auxiliary contacts, has high sectioning capability and thermal stability, and is commonly used in places requiring high breaking capability and selective protection.

The first time is a delay time of the first relay, and in this embodiment, the delay time is 2 seconds to 4 seconds, and may be 3 seconds.

The main circuit 1 comprises two branches, the first branch being from the grid to a first breaker QF1 and then to a transformer T, the second branch being from the grid to an ac contactor KM, then to a reactor L, and finally to the transformer T, when the device starts to work, the control circuit 2 controls the alternating current contactor coil KM and the first relay coil KT1 to be electrified, the alternating current contactor coil KM drives the contact of the alternating current contactor KM to be closed, after the first time, the first relay coil KT1 drives the first relay first contact KT11 in the closing branch of the first breaker QF1 to close, so that the first breaker QF1 is closed, the second shunt circuit is conducted in advance of the first shunt circuit for the first time, and the second shunt circuit is connected with the reactor T in series, so that the voltage of the transformer T can be divided before the first shunt circuit, the magnetizing inrush current is reduced, and the serious influence of the overlarge magnetizing inrush current on line equipment when the first shunt circuit is conducted is avoided.

The following advantageous effects can be obtained from the first embodiment:

the embodiment comprises a main circuit and a control circuit, wherein an alternating current contactor KM and a reactor L of the main circuit are connected in series and then connected between a power grid and a transformer T, a first breaker QF1 is also connected between the power grid and the transformer T, an alternating current contactor coil KM for controlling the alternating current contactor KM to open and close and a first relay coil KT1 for controlling the first breaker QF1 to close are arranged in the control circuit, when the embodiment device starts to work, the control circuit controls the alternating current contactor coil KM and the first relay coil KT1 to be electrified, so that the contact of the alternating current contactor is closed and the first relay first contact KT11 is closed through the first time, as the contact of the alternating current contactor is arranged in the alternating current contactor KM, the first relay first contact KT11 is arranged in a closing shunt of the first breaker QF1, the alternating current contactor KM can be conducted with the main circuit first time earlier than the first breaker QF1, at the moment, the series circuit of the transformer T and the reactor L is conducted, the reactor L can perform a voltage division effect on the voltage of the power grid, the voltage of the two ends of the transformer T is reduced, the magnetizing inrush current passing through the transformer T is reduced, and the phenomenon that the first circuit breaker QF1 generates overlarge magnetizing inrush current after a main circuit is conducted is avoided, so that adverse effects on line equipment are caused.

Example two

In practical applications, on the basis of the first embodiment, the control circuit includes two loops for controlling the ac contactor coil and the first relay coil to be energized, so that the ac contactor contacts are closed and the first relay first contact is closed over a first time.

Referring to fig. 1-2, the two circuits are a first circuit and a second circuit;

the first loop comprises a starting switch SB1, a first second relay contact KA11, a third relay contact KT2, a second relay coil KA1 and a first relay coil KT1, the starting switch SB1 is connected with the first second relay contact KA11 in parallel to form a first sub-loop of the first loop, the sub-loop is a self-locking loop of the first second relay contact KA11, and the first sub-loop can be kept to be conducted by self-locking of the first second relay contact KA11 after the starting switch is disconnected; the third relay contact KT2 is connected in series with the second relay coil KA1 and then connected in parallel with the first relay coil KT1 to form a second sub-loop of the first loop, and the first sub-loop and the second sub-loop are connected in series and then connected between the phase line A of the power grid and the neutral line of the power grid;

in this embodiment, this second relay first contact KA11 is instantaneous normally open contact, and third relay contact KT2 is time delay disconnection normally closed contact, and the second relay is auxiliary relay, then second relay coil KA1 is the auxiliary relay coil, and first relay is circular telegram time delay relay, then first relay coil KT1 is circular telegram time delay coil.

The power-on delay relay is a relay which drives a corresponding contact to act after a specific time after a power-on delay coil of the power-on delay relay is electrified.

The second loop comprises a second relay second contact KA12 and an alternating current contactor coil KM, and the second relay second contact KA12 is connected between the phase line A of the power grid and the neutral line of the power grid after being connected with the alternating current contactor coil KM in series;

in this embodiment, the second relay second contact KA12 is an instantaneous normally open contact, and the ac contactor coil KM can drive the ac contactor contact to instantaneously act.

The device reduces the magnetizing inrush current of the transformer in the following mode:

when a starting switch SB1 is pressed, a first loop of a control circuit 2 is conducted, a second relay coil KA1 and a first relay coil KT1 are electrified, a first contact KA11 of a second relay is closed to form self-locking, a second contact KA12 of the second relay is closed, a second loop is conducted, an AC contactor coil KM is electrified, a contact of an AC contactor in a main circuit 1 is closed, at the moment, a series circuit of a transformer T and a reactor L is conducted, the reactor L divides the voltage of a power grid, and the excitation surge current of the transformer T is reduced; first relay coil KT1 gets the back of electricity, through the very first time (can be 3 seconds) after drive first relay first contact KT11 is closed, first circuit breaker QF1 closes a floodgate, alternating current contactor KM switches on main circuit 1 than first circuit breaker QF1 very first time (can be 3 seconds) in advance, utilize reactor L to reduce transformer T's excitation inrush current earlier, avoid first circuit breaker QF1 to switch on and produce too big excitation inrush current behind main circuit 1, cause adverse effect to line equipment.

It should be noted that, after the first contact of the second relay is closed KA11 to form self-locking, the start switch SB1 can be released, and the first loop is still in a conducting state due to the self-locking of the first contact KA11 of the second relay.

The following advantageous effects can be obtained from the second embodiment:

this embodiment is through setting up two return circuits in control circuit, after pressing starting switch SB1, coil and contact in these two return circuits are mutually supported for ac contactor KM switches on the main circuit than first circuit breaker QF1 very first time (can be for 3 seconds) in advance, utilizes reactor L to reduce transformer T's excitation inrush current earlier, avoids first circuit breaker QF1 to switch on the main circuit after produce too big excitation inrush current, causes adverse effect to line equipment.

EXAMPLE III

In practical applications, on the basis of the above embodiments, the control circuit further includes a third circuit for opening the ac contactor to return the main circuit to the no-load operation state.

Referring to fig. 1-2, the third circuit includes a first relay second contact KT12 and a third relay coil KT2, and the first relay second contact KT12 and the third relay coil KT2 are connected in series and then connected between a phase line a of the power grid and a neutral line of the power grid;

in this embodiment, the first relay second contact KT12 is a time-delay closed normally-open contact, the third relay is an energization time-delay relay, the time delay is 2 seconds to 4 seconds, and may be 3 seconds, and then the third relay coil KT2 is an energization time-delay coil.

When first relay coil KT1 gets the electricity after, first relay second contact KT12 is closed after the very first time (can be 3 seconds), the third return circuit switches on, third relay coil KT2 gets the electricity, again through the time delay (can be 3 seconds) after, third relay contact KT2 disconnection, second relay coil KA1 loses the electricity, then second relay second contact KA12 disconnection, the disconnection of second return circuit, ac contactor coil KM loses the electricity, the ac contactor contact disconnection, ac contactor KM disconnection, because the closed back of first relay first contact KT11 is locked, first circuit breaker QF1 can keep the combined floodgate state, main circuit 1 gets back to the no-load running state this moment.

In addition, the second relay coil KA1 loses power to enable the second relay first contact KA11 to be opened, at the moment, the starting switch SB1 is also in an open state, namely, the first loop is opened, the first relay coil KT1 loses power, the first relay second contact KT12 is opened, the third loop is opened, the third relay coil KT2 loses power, the third relay contact KT2 is closed, and at the moment, all loops in the control circuit 2 return to an initial state.

The following beneficial effects can be obtained from the third embodiment:

in the embodiment, the third loop is arranged in the control circuit, and the third loop is matched with the first loop and the second loop, so that the alternating current contactor KM is turned off after the first breaker QF1 is switched on in a delayed manner (which may be 3 seconds), the main circuit is returned to the no-load running state, and each loop in the control circuit is returned to the initial state.

Example four

In practical application, on the basis of the above embodiment, the control circuit is further provided with an emergency stop button and a stop button, so that the control circuit can be conveniently subjected to emergency stop and normal stop operations.

Referring to fig. 1-2, the emergency stop button SB2 and the stop button SB3 are connected in series between the a-phase line of the power grid and the first or second or third circuit.

The emergency stop button SB2 and the stop button SB3 are connected in series and then connected between the phase A line of the power grid and the parallel circuit of the three circuits.

When the circuit is in fault and needs emergency stop, the emergency stop button SB2 is pressed, the undervoltage trip coil of the first breaker QF1 is electrified, so that the first relay first contact KT11 is disconnected, the main circuit 1 is disconnected, in addition, the power supply of the control circuit 2 is cut off, and the control circuit 2 stops working;

when the circuit needs to be normally stopped, the stop button SB3 is pressed, the shunt tripping coil of the first breaker QF1 is energized, the first relay first contact KT11 is opened, the main circuit 1 is opened, the power supply of the control circuit 2 is cut off, and the control circuit 2 stops operating.

Because the contact that carries out the circuit breaker operation of opening through undervoltage trip coil is normally closed, and the contact that carries out the circuit breaker operation of opening through shunt release coil is normally open, and the time that normally closed contact is by closed to the disconnection time will be shorter than the normally open contact by the time of disconnection to closed, consequently, after pressing scram button SB2, the disconnection of undervoltage trip coil control first relay first contact KT11 through first circuit breaker QF1 is more fast than the disconnection of shunt release coil control first relay first contact KT11 through first circuit breaker QF1, reaches the effect of scram.

The following advantageous effects can be obtained from the fourth embodiment:

the embodiment can quickly disconnect the main circuit and the control circuit by pressing the emergency stop button SB2 when the circuit is broken and normally disconnect the main circuit and the control circuit by pressing the stop button SB3 when the circuit needs to be normally stopped by providing the emergency stop button SB2 and the stop button SB3 in the control circuit.

EXAMPLE five

In practical applications, on the basis of the above embodiments, the control circuit is further provided with a second breaker to further protect the control circuit.

Referring to fig. 1-2, the second circuit breaker QF2 is connected between the phase a line of the grid and the first or second or third circuit, i.e. in series with the emergency stop button SB2 and the stop button SB 3.

When the control circuit 2 has serious faults of overload, short circuit, undervoltage and the like, the circuit can be automatically cut off.

The following beneficial effects can be obtained from the fifth embodiment:

this embodiment is through setting up second circuit breaker QF2 at control circuit, can guarantee circuit safety at the automatic circuit breaker when control circuit breaks down.

Example six

In practical application, on the basis of the above embodiment, the main circuit is further provided with a power indicator lamp.

Referring to fig. 1, the power indicator light is connected between the power grid and the first circuit breaker QF 1.

The number, display color and arrangement order of the power indicator lamps are not limited herein, and in the present embodiment, three power indicator lamps are provided, and the display colors thereof are yellow, green and red, respectively.

When the power grid supplies power normally, the power indicator lamp emits light normally and displays colors, and when the power grid supplies power abnormally, the power indicator lamp emits light abnormally or displays colors abnormally.

The following beneficial effects can be obtained from the sixth embodiment:

according to the embodiment, the power indicator lamp is arranged on the main circuit, whether power supply of a power grid power supply is normal or not can be identified through display of the power indicator lamp, and reference is provided for normal work of the circuit.

Having described embodiments of the present application, the foregoing description is intended to be exemplary, not exhaustive, and not limited to the disclosed embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen in order to best explain the principles of the embodiments, the practical application, or improvements made to the technology in the marketplace, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein.

Claims (10)

1. An apparatus for reducing transformer magnetizing inrush current, comprising: a main circuit (1) and a control circuit (2);

the main circuit (1) comprises: the system comprises an alternating current contactor KM, a reactor L, a transformer T and a first breaker QF 1;

the alternating current contactor KM is connected with the reactor L in series and then is connected between a power grid and the transformer T;

the first breaker QF1 is connected between the grid and the transformer T;

a first relay first contact KT11 is arranged in a closing branch of the first circuit breaker QF 1;

an alternating current contactor contact is arranged in the alternating current contactor KM;

the control circuit (2) is connected to the power grid, and the control circuit (2) comprises: a first relay coil KT1 and an ac contactor coil KM;

the control circuit (2) is capable of controlling the ac contactor coil KM and the first relay coil KT1 to be energized such that the ac contactor contact is closed and the first relay first contact KT11 is closed over a first time.

2. The apparatus for reducing transformer inrush current of claim 1, wherein:

the control circuit (2) comprises a first loop and a second loop;

the first circuit includes: a starting switch SB1, a second relay first contact KA11, a third relay contact KT2, a second relay coil KA1 and the first relay coil KT 1; the starting switch SB1 is connected with the first relay contact KA11 in parallel to form a first sub-loop of the first loop; the third relay contact KT2 is connected in series with the second relay coil KA1 and then connected in parallel with the first relay coil KT1 to form a second sub-loop of the first loop; the first sub-loop and the second sub-loop are connected in series and then connected between the phase line A of the power grid and the neutral line N of the power grid;

the second circuit includes: a second relay second contact KA12 and the ac contactor coil KM; the second relay second contact KA12 is connected between the phase line A of the power grid and the neutral line N of the power grid after being connected with the alternating current contactor coil KM in series.

3. The apparatus for reducing transformer inrush current of claim 2, wherein:

the control circuit (2) further comprises: a third circuit;

the third circuit includes: a first relay second contact KT12 and a third relay coil KT 2; the first relay second contact KT12 with the third relay coil KT2 is connected in series after connecting between the A phase line of electric wire netting and the neutral conductor N of electric wire netting.

4. The apparatus for reducing transformer inrush current of claim 2, wherein:

the first relay and the third relay are electrified delay relays, and the second relay is an intermediate relay.

5. The apparatus for reducing transformer magnetizing inrush current of claim 3, wherein:

the first relay first contact KT11 and the first relay second contact KT12 are time-delay closed normally open contacts;

the second relay first contact KA11 and the second relay second contact KA12 are instant normally open contacts;

the third relay contact KT2 is a normally closed contact for delaying disconnection;

and the contact of the alternating current contactor is an instantaneous normally open contact.

6. The apparatus for reducing transformer inrush current of claim 3, wherein:

the control circuit (2) further comprises an emergency stop button SB2 and a stop button SB 3;

the emergency stop button SB2 and the stop button SB3 are connected in series and then connected between the phase line A of the power grid and the first loop or the second loop or the third loop.

7. The apparatus for reducing transformer inrush current of claim 3, wherein:

the control circuit (2) further comprises a second circuit breaker QF2, the second circuit breaker QF2 being connected between the a-phase line of the grid and the first or second or third circuit.

8. The apparatus for reducing transformer inrush current of claim 1, wherein:

the first time is the delay time of the first relay, and the delay time is 2 seconds to 4 seconds.

9. The apparatus for reducing transformer inrush current of claim 4, wherein:

and the delay time of the third relay is 2-4 seconds.

10. The apparatus for reducing transformer inrush current of claim 1, wherein:

the main circuit (1) further comprises: a power indicator light;

the power indicator light is connected between the power grid and the first circuit breaker QF 1.

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