KR102349997B1 - Control method of switchboard with built-in image harmonic filter - Google Patents

Abstract

A control method of a switchboard with a built-in image harmonic filter comprises the steps of: turning on the switching unit to input a zigzag wiring transformer; calculating an image on the N-phase busbar; comparing the image segment and a reference value; when the zero fraction is smaller than the reference value, controlling the switching unit off, applying the maximum applied current to the Peltier module, and applying the maximum voltage to the cooling fan; measuring temperature and noise if the image is not smaller than the reference value; comparing the measured temperature signal and a critical temperature range; when the measured temperature signal is greater than or equal to the critical temperature range, controlling the switching unit off, applying a maximum applied current to the Peltier module, and applying a maximum voltage to the cooling fan; if the measured temperature signal is less than the threshold temperature range, controlling the switching unit on, not applying a current to the Peltier module, and controlling the cooling fan off; if the measured temperature signal is within the threshold temperature range, comparing the measured noise signal with the critical noise range; when checked as a high noise environment, controlling the switching unit off, applying a maximum applied current to the Peltier device, and applying a maximum voltage to the cooling fan; when the low-noise environment is checked, the switching unit maintains ON-controlled, applying a minimum current to the Peltier module, and applying a differential voltage to the cooling fan; and if it exists within the critical noise range, PWM control the switching unit, applying a differential current to the Peltier module, and applying a differential voltage to the cooling fan. Cooling operation can be efficiently controlled.

Description

Control method of switchboard with built-in image harmonic filter {CONTROL METHOD OF SWITCHBOARD WITH BUILT-IN IMAGE HARMONIC FILTER}

The present invention relates to a control method of a switchboard with a built-in image harmonic filter, and more particularly, to a control method for a switchboard with a built-in image harmonic filter, which can efficiently control a cooling operation by adding a Peltier module to minimize noise generation .

In general, an image harmonic filter for removing image harmonics is mounted on a switchboard. Harmonics refer to frequencies corresponding to integer multiples, such as 2, 3, or 4 times the fundamental frequency, and are also called distortion waves or distortion waves. In particular, high-frequency components whose high-frequency order is a multiple of 3, such as 3, 6, 9, etc. among high-frequency frequencies of various orders, are called image harmonics.

Due to the characteristics of the Korean distribution system that adopts the three-phase, four-wire system, single-phase and three-phase loads are mixed and an unbalanced current flows through the neutral wire. Due to the increase of non-linear loads such as (UPS), more image harmonics flow in the neutral wire. As for the image harmonics, since the phases of each of the three phases have the same value, they overlap the neutral wire as if three single-phase power sources are connected in parallel, so that up to three times the image harmonics flow. When excessive image harmonics flow through the neutral wire in this way, overheating of the neutral wire conductor, deterioration of distribution transformer performance, voltage distortion, communication line noise, malfunctions of electrical and electronic equipment, etc. occur.

Therefore, various methods have been proposed to attenuate such excessive image harmonics. Among them, by using a ZigZag-connected transformer connected to three phase lines and a neutral line, the zero-phase impedance is reduced to prevent the zero-phase harmonics from flowing from the neutral to the load system side. A typical example is a device that cancels the image harmonics by preventing them from being blocked and absorbing them to the zigzag connection transformer side. It is known that the image harmonic filter using such a zigzag connection transformer can effectively attenuate the third harmonic, which is the lowest order, that generates the most.

Such an image harmonic filter can block the image harmonics from flowing into the power supply side by removing the image component from the load side, but may cause problems such as an increase in electricity bills due to the image harmonics. Specifically, the zigzag in the image harmonics A connected transformer can act as a load and increase your electricity bill.

In order to solve the problem of increasing electricity bills, the driving speed of the cooling fan is differentially controlled while the switching unit that controls the input and trip of the zero harmonic filter, that is, the zigzag-connected transformer, is controlled on, PWM, and off according to the temperature and noise. A technology that minimizes the increase in electricity rates by driving it has been proposed.

However, when the cooling fan is driven at the maximum speed, there is a problem in that noise generation is very high.

Korean Patent Registration No. 10-1482191 (Jan. 07, 2015) (Switchboard and distribution board with integrated SPD and power-saving image harmonic filter) Korean Patent No. 10-1241859 (2013. 03. 05.) (Distribution panel with active image harmonic filter) Korean Patent Registration No. 10-1383263 (April 2014. 02.) (Distribution panel with built-in image harmonic filter of power saving type) Korean Patent Registration No. 10-2069615 (2020.01.17.) (switchboard with built-in image harmonic filter)

Accordingly, the technical problem of the present invention is based on this point, and an object of the present invention is to efficiently control the cooling operation by adding a Peltier module to minimize noise generated when the image harmonic filter is driven and the cooling fan is driven. An object of the present invention is to provide a control method for a switchboard with a built-in image harmonic filter.

In order to realize the object of the present invention, the control method of a switchboard with a built-in video harmonic filter according to an embodiment includes: (i) input of the zigzag wire transformer in the video harmonic filter built in the switchboard and input of the zigzag wire transformer; turning on a switching unit that controls the trip; (ii) calculating an image on the N-phase busbar; (iii) comparing the calculated image segment with a reference value; (iv) when it is checked that the image fraction calculated in step (iii) is smaller than the reference value, the switching unit is turned off, the maximum applied current is applied to the Peltier module, and the maximum voltage is applied to the cooling fan to drive the cooling fan at the maximum speed applying the ; (v) when it is checked that the image fraction calculated in step (iii) is not smaller than the reference value, measuring temperature and noise; (vi) comparing the measured temperature signal measured in step (v) with a critical temperature range; (vii) when the measured temperature signal is checked above the threshold temperature range in step (vi), controlling the switching unit off, applying a maximum applied current to the Peltier module, and applying a maximum voltage to the cooling fan; (viii) when the measured temperature signal is checked below the threshold temperature range in step (vi), controlling the switching unit on, not applying a current to the Peltier module, and controlling the cooling fan to be off; (ix) if it is checked that the measured temperature signal exists within the critical temperature range in step (vi), comparing the measured noise signal with the critical noise range; (x) When the noise signal measured in step (ix) is checked as a high-noise environment above the threshold noise range, the switching unit is turned off, the maximum applied current is applied to the Peltier element, and the maximum voltage is applied to the cooling fan step; (xi) When the noise signal measured in step (ix) is checked as a low-noise environment that is less than the threshold noise range, the switching unit maintains the ON control, applies a minimum current to the Peltier module, and applies a differential voltage to the cooling fan to do; and (xii) when it is checked that the measured noise signal is within the threshold noise range in step (ix), PWM control the switching unit, apply a differential current to the Peltier module, and apply a differential voltage to the cooling fan include

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According to this type of switchgear with a built-in zero harmonic filter, the switching unit that is installed on each of the R, S, and T phase branch lines to control the input and trip of the zero harmonic filter, that is, a zigzag-connected transformer, is turned on according to temperature as well as noise, PWM control, or By differentially driving the cooling fan's driving speed while controlling the off and applying a differential current to the Peltier module, while maintaining the function of filtering the zero harmonics, efficient cooling to reduce the noise and electricity bill increase caused by the operation of the zero harmonic filter action can be performed.

1 is a configuration diagram for explaining a switchboard with a built-in image harmonic filter according to an embodiment of the present invention.
FIG. 2 is a block diagram schematically illustrating the image harmonic filter shown in FIG. 1 .
3 is a flowchart for explaining a method of controlling a switchboard with a built-in image harmonic filter according to an embodiment of the present invention.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings. Since the present invention can have various changes and can have various forms, specific embodiments are illustrated in the drawings and described in detail in the text. However, this is not intended to limit the present invention to the specific disclosed form, it should be understood to include all modifications, equivalents and substitutes included in the spirit and scope of the present invention.

In describing each figure, like reference numerals have been used for like elements. In the accompanying drawings, the dimensions of the structures are enlarged than the actual size for clarity of the present invention.

Terms such as first, second, etc. may be used to describe various elements, but the elements should not be limited by the terms. The above terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, a first component may be referred to as a second component, and similarly, a second component may also be referred to as a first component. The singular expression includes the plural expression unless the context clearly dictates otherwise.

In the present application, terms such as "comprise" or "have" are intended to designate that a feature, number, step, operation, component, part, or a combination thereof described in the specification exists, but one or more other features It is to be understood that it does not preclude the possibility of the presence or addition of numbers, steps, operations, components, parts, or combinations thereof.

In addition, unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the related art, and should not be interpreted in an ideal or excessively formal meaning unless explicitly defined in the present application. does not

1 is a block diagram illustrating a switchgear with a built-in image harmonic filter according to an embodiment of the present invention. FIG. 2 is a block diagram schematically illustrating the image harmonic filter shown in FIG. 1 .

1 and 2, the switchboard with a built-in image harmonic filter according to an embodiment of the present invention includes an R-phase busbar (reference numeral not assigned), an S-phase busbar (reference numeral not assigned), and a T-phase busbar ( Reference numeral not assigned), N-phase bus bar (reference code not assigned), cooling fan 110, fan driving unit 120, temperature sensor 130, noise sensor 140, Peltier module 150, module It includes a driving unit 160 , an image harmonic filter 170 , and a switching unit 180 . Hereinafter, a switchboard having a built-in image harmonic filter 170 will be described, but those skilled in the art may similarly apply to a distribution board having a built-in image harmonic filter 170 .

Each of the R-phase busbar, S-phase busbar, T-phase busbar and N-phase busbar is connected to an output terminal of a main circuit breaker (MCCB) (not shown).

The cooling fan 110 is disposed in the switchboard close to the image harmonic filter 170 and is operated under the control of the fan driver 120 .

The fan driving unit 120 controls the driving of the cooling fan 110 in the switchboard.

The temperature sensor 130 is disposed in the switchboard close to the image harmonic filter 170 to measure the temperature and provide a measured temperature signal to the image harmonic filter 170 .

The noise sensor 140 is disposed in the switchboard close to the image harmonic filter 170 to measure the noise and provide a measured noise signal to the image harmonic filter 170 . The above noise is generated by the magnetization of the iron core by the harmonic current. That is, harmonics and noise may have a proportional relationship with each other.

The Peltier module 150 is attached to the image harmonic filter 170 to prevent the image harmonic filter 170 from being changed to a high temperature. As is well known, the Peltier module 150 connects two types of metal ends and sends a current to the duy device, one terminal absorbs heat according to the current direction, and the other terminal causes heat rejected. It is a device that uses the In Peltier effect. The Peltier module 150 is provided with a cooling chip, and one side of the cooling chip becomes a cooling surface that absorbs heat from the surroundings by the direction of a direct current supplied to the cooling chip, and the other side serves as a heat dissipation surface that radiates heat. . Here, since the heat dissipation surface of the cooling chip is determined by the current direction, the cooling chip is positioned inside the zero-phase harmonic filter 170 , and the heat-dissipating surface of the cooling chip to be radiated is exposed to the outside of the zero-phase harmonic filter 170 . It is preferable to do

The module driving unit 160 applies a current for driving the Peltier module 150 . The cooling efficiency by the Peltier module 150 is proportional to the magnitude of the applied current.

The image harmonic filter 170 is connected to each of the R-phase busbar, S-phase busbar, T-phase busbar, and N-phase busbar.

The switching unit 180 includes a first switch 182 , a second switch 184 , and a third switch 186 , and is installed on each of the R, S, and T-phase branch lines to input the image harmonic filter 170 . and trip control. Specifically, the first switch 182 is connected to the R-phase branch line to intercept the connection line between the R-phase branch line and the image harmonic filter 170 in response to the control of the image harmonic filter 170 to control the image harmonic filter 170 . It controls closing and tripping. The second switch 184 is connected to the S-phase branch line and intercepts the connection line between the S-phase branch line and the video harmonic filter 170 in response to the control of the video harmonic filter 170 to intercept and trip the video harmonic filter 170 . to control The third switch 186 is connected to the T-phase branch line and intercepts the connection line between the T-phase branch line and the video harmonic filter 170 in response to the control of the video harmonic filter 170 to intercept and trip the video harmonic filter 170 . to control

In this embodiment, the image harmonic filter 170 includes a zigzag connection transformer 172 and a filter control unit 174, an R-phase branch line branched from the R-phase bus bar, an S-phase branch line branched from the S-phase bus bar, It is connected to each of the T-phase branch line branched from the T-phase busbar and the N-phase branch line branched from the N-phase busbar.

Specifically, the zigzag connection transformer 172 is, as is well known, an R-phase branch line branched from an R-phase bus bar, an S-phase branch line branched from an S-phase bus bar, a T-phase branch line branched from a T-phase bus bar, and N It is connected to each of the N-phase branch lines branched from the phase busbar, and the image harmonics introduced into the N-phase busbars are circulated in the zigzag connection transformer 172 to remove the image harmonics. Since the zigzag-connected transformer 172 has a resistance component, heat may be generated in the process of removing the image harmonics. If the heat is excessive, there is a risk of performance degradation due to deterioration of the zigzag wiring transformer 172 and a fire in the distribution panel.

Therefore, it is necessary to prevent overheating or overload in the zigzag wiring transformer 172 . To this end, in the present embodiment, the temperature sensor 130, the noise sensor 140 and the Peltier module 150 are installed adjacent to the zigzag wiring transformer 172. The temperature sensor 130 may sense the temperature of the zigzag-connected transformer 172 , and transmit the sensed temperature value to the filter control unit 174 . The noise sensor 140 may sense the noise of the zigzag-connected transformer 172 , and transmit the sensed noise value to the filter control unit 174 . The Peltier module 150 performs a cooling operation in proportion to the current provided from the module driving unit 160 under the control of the filter control unit 174 .

At this time, the filter control unit 174 separates and controls the zig-zag-connected transformer 172 from each of the R-phase busbar, S-phase busbar, and T-phase busbar based on the temperature and noise of the zigzag-connected transformer 172, or a cooling fan ( The driving speed of 110) and the degree of cooling by the Peltier module 150 can be controlled.

Thereby, overload of the zigzag wiring transformer 172 can be prevented. Of course, when the temperature of the zig-zag-connected transformer 172 is lower than the preset upper limit value in the state in which the zig-zag-connected transformer 172 is separated, the zig-zag connected transformer 172 is connected to the R-phase busbar, S-phase busbar, and T It can be reconnected to each of the phase busbars.

The filter control unit 174 controls the operation of the cooling fan 110 , the Peltier module 150 , and the switching unit 180 based on the image on the N-phase bus bar, the measured temperature signal, and the measured noise signal. . In particular, when the measured noise signal is high, the filter control unit 174 flows the maximum applied current to the Peltier module 150 to lower the noise, and when the measured noise signal is low, the maximum applied current flows to the cooling fan 110 to improve cooling efficiency. elevate

Specifically, the filter control unit 174 controls the switching unit 180 to be off, and controls the maximum applied current to be applied to the Peltier module 150, when the zero phase on the N-phase bus bar is less than or equal to a preset zero threshold value, In order to drive the cooling fan 110 at the maximum speed, it is controlled so that the maximum voltage is applied to the cooling fan 110 . That is, the filter control unit 174 turns off the switching unit 180 to trip the zigzag-connected transformer 172, and applies the maximum to the module driving unit 160 in order to maximize the degree of cooling by the Peltier module 150. The output of the current is requested and the output of the maximum voltage is requested from the fan driving unit 120 to control the cooling fan 110 to be driven at the maximum speed.

On the other hand, the filter control unit 174 controls the switching unit 180 off to turn off the zigzag wire transformer 172 when the measured temperature signal is greater than or equal to the threshold temperature range while the image fraction on the N-phase bus bar exceeds the preset image fraction reference value. trips, and controls so that the maximum applied current is applied to the Peltier module 150, and controls so that the maximum voltage is applied to the cooling fan 110 for driving the cooling fan 110 at the maximum speed. That is, the filter control unit 174 turns off the switching unit 180 to trip the zigzag-connected transformer 172, and applies the maximum to the module driving unit 160 in order to maximize the degree of cooling by the Peltier module 150. The output of the current is requested and the output of the maximum voltage is requested from the fan driving unit 120 to control the cooling fan 110 to be driven at the maximum speed.

On the other hand, the filter control unit 174, when the measured temperature signal is less than the threshold temperature range, maintains the ON control of the switching unit 180, and controls so that the current is not applied to the Peltier module 150, the cooling fan 110 control so that no voltage is applied to the

On the other hand, when the measured temperature signal is within the critical temperature range, the filter control unit 174 checks whether the measured noise signal is greater than the critical noise range, and the cooling fan according to the result of the high noise environment, low noise environment, and medium noise environment. Controls the operation of the 110 , the Peltier module 150 and the switching unit 180 .

Specifically, the filter control unit 174 intermittently trips the zigzag-connected transformer 172 by PWM control of the switching unit 180 when the measured noise signal is above the threshold noise range, that is, in a high-noise environment, and the Peltier module ( 150) is controlled so that the maximum applied current is applied, and a differential voltage is controlled to be applied to the cooling fan 110 . The driving speed of the cooling fan 110 is differentially varied by the above-described differential voltage. The driving speed Vdn of the cooling fan 110 is calculated based on the measured noise signal, and the driving of the cooling fan 110 is controlled using the calculated driving speed Vdn.

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Meanwhile, the filter control unit 174 may calculate the duty ratio of the switching unit 180 based on the measured temperature signal, and calculate the driving speed of the cooling fan 110 based on the duty ratio of the switching unit 180 . have. The filter control unit 174 controls the switching unit 180 using the calculated duty ratio, and controls the driving of the cooling fan 110 using the calculated driving speed.

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On the other hand, the filter control unit 174, when the measured noise signal is less than the threshold noise range, that is, in a low noise environment, the switching unit 180 maintains the ON control, and applies a minimum current to the Peltier module 150, cooling The fan 110 is controlled to be off.

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On the other hand, the filter control unit 174, when the measured noise signal is within the threshold noise range, that is, in a medium noise environment, PWM control the switching unit 180, differentially apply a current to the Peltier module 150, and cooling The driving speed of the fan 110 is differentially controlled.

As described above, according to the present invention, the switching unit 180 installed in each of the R, S, and T-phase branch lines to control the input and trip of the image harmonic filter 170 is turned on according to the noise as well as the temperature. By differentially driving the operation of the Peltier module 150 and the driving speed of the cooling fan 110 while controlling /off control or PWM, while maintaining the function of filtering image harmonics, the image harmonic filter, especially overheating in the zigzag transformer can be reduced using a Peltier module and a cooling fan.

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In addition, in order to reduce the overheating described above, even if the cooling fan is not driven at the maximum speed, the cooling efficiency can be increased by using the Peltier module.

3 is a flowchart illustrating a control method of a switchboard having a built-in image harmonic filter 170 according to an embodiment of the present invention.

1 to 3 , the filter control unit 174 turns on the switching unit 180 to input the zigzag connection transformer 172 (step S100).

Next, the filter control unit 174 calculates an image on the N-phase busbar (step S110).

The filter control unit 174 checks whether the image segment calculated in step S110 is greater than a reference value (step S120).

If it is checked that the zero value calculated in step S120 is smaller than the reference value, the filter control unit 174 turns off the switching unit 180 to trip the zigzag connection transformer 172, and the maximum applied current is applied to the Peltier module 150 and control so that the maximum voltage is applied to the cooling fan 110 to drive the cooling fan 110 at the maximum speed (step S122).

If it is checked that the image fraction calculated in step S120 is not smaller than the reference value, the filter control unit 174 measures the temperature through the temperature sensor 130 and measures the noise through the noise sensor 140 (step S130).

The filter control unit 174 checks whether the measured temperature signal measured in step S130 is greater than a threshold temperature range (step S140).

When the measured temperature signal is checked above the threshold temperature range in step S140, the filter control unit 174 turns off the switching unit 180 by feeding back to step S122 to trip the zigzag wiring transformer 172, and the Peltier module 150 The maximum applied current is controlled to be applied to the , and the maximum voltage is applied to the cooling fan 110 to drive the cooling fan 110 at the maximum speed.

When the measured temperature signal is checked below the threshold temperature range in step S140, the filter control unit 174 maintains the ON control of the switching unit 180, controls the current not to be applied to the Peltier module 150, and the cooling fan ( 110), after controlling so that the voltage is not applied (step S142), it is fed back to step S110 to calculate the image component on the N-phase busbar.

If it is checked that the measured temperature signal exists within the threshold temperature range in step S140, the filter control unit 174 checks whether the measured noise signal is greater than the threshold noise range (step S150).

In step S150, when the measured noise signal is over the threshold noise range, that is, in a high-noise environment, the filter control unit 174 PWM controls the switching unit 180, and controls the maximum applied current to be applied to the Peltier module 150, , control so that a differential voltage is applied to the cooling fan 110 (step S152).

In step S150, when the measured noise signal is less than the threshold noise range, that is, when it is checked as a low-noise environment, the filter control unit 174 maintains that the switching unit 180 is on-controlled, and controls the minimum current to be applied to the Peltier module 150 After controlling so that no voltage is applied to the cooling fan 110 (step S154), it is fed back to step S110 to calculate the image on the N-phase bus bar.

In step S150, when the measured noise signal is within the critical noise range, that is, it is checked as a medium noise environment, the filter control unit 174 PWM controls the switching unit 180, and controls the differential current to be applied to the Peltier module 150, and , after controlling so that the minimum voltage is applied to the cooling fan 110 (step S156), it is fed back to step S110 to calculate the image on the N-phase bus bar.

As described above, the cooling process can be differentially performed according to the internal temperature of the switchboard with a built-in image harmonic filter. That is, the cooling treatment is primarily performed through the Peltier module, and the cooling treatment is performed through the cooling fan secondarily. In addition, it is possible to differentially perform cooling processing according to the noise environment of the switchboard with built-in image harmonic filter. That is, in a low-noise environment, cooling is mainly performed through a cooling fan, in a low-power driven Peltier module and a low-speed driven cooling fan in a low-noise environment, cooling is performed through a high-power driven Peltier module and a differential driven cooling fan in a high-noise environment. Cooling process through

As described above, according to the present invention, the switching unit 180 installed in each of the R, S, and T-phase branch lines to control the input and trip of the image harmonic filter 170 is turned on according to the noise as well as the temperature. While /off control or PWM control, the operation of the Peltier module 150 and the driving speed of the cooling fan 110 are differentially driven. Accordingly, it is possible to reduce overheating in the image harmonic filter, particularly the zigzag transformer, using the Peltier module and the cooling fan while maintaining the function of filtering the image harmonics.

In addition, in order to reduce the overheating described above, even if the cooling fan is not driven at the maximum speed, the cooling efficiency can be increased by using the Peltier module.

Although the above has been described with reference to the embodiments, those skilled in the art can variously modify and change the present invention within the scope without departing from the spirit and scope of the present invention described in the claims below you will understand

110: cooling fan 120: fan driving part
130: temperature sensor 140: noise sensor
150: peltier module 160: module driving unit
170: image harmonic filter 172: zigzag wiring transformer
174: filter control unit 180: switching unit
182: first switch 184: second switch
186: third switch

Claims (2)

(i) turning on a switching unit that controls the closing and tripping of the zigzag connection transformer in order to input the zigzag connection transformer in the image harmonic filter built into the switchboard;
(ii) calculating an image on the N-phase busbar;
(iii) comparing the calculated image segment with a reference value;
(iv) When the zero phase is checked to be less than the reference value in step (iii), the switching unit is turned off, and the maximum applied current is applied to the Peltier module attached to the zero phase harmonic filter adjacent to the zigzag connection transformer, and the switchboard applying a maximum voltage to the cooling fan to drive the cooling fan disposed therein at maximum speed;
(v) obtaining a measured temperature signal and a measured noise signal by measuring temperature and noise, respectively, when the image fraction calculated in step (iii) is checked to be greater than or equal to the reference value;
(vi) comparing the measured temperature signal measured in step (v) with a critical temperature range;
(vii) when the measured temperature signal is checked above the threshold temperature range in step (vi), the switching unit is turned off, the maximum applied current is applied to the Peltier module, and the maximum voltage is applied to the cooling fan. feeding back to step (ii);
(viii) when the measured temperature signal is checked to be less than the threshold temperature range in step (vi), the switching unit is turned on, no current is applied to the Peltier module, and the cooling fan is turned off, then step (ii) feedback to;
(ix) if it is checked that the measured temperature signal exists within the critical temperature range in step (vi), comparing the measured noise signal with a critical noise range;
(x) If the measured noise signal in step (ix) is checked as a high-noise environment above the threshold noise range, PWM control the switching unit, apply the maximum applied current to the Peltier module, and apply a differential voltage to the cooling fan feedback to step (ii) after application;
(xi) When the measured noise signal is checked as a low-noise environment that is less than the critical noise range in step (ix), the switching unit maintains the ON control, applies a minimum current to the Peltier module, and a differential voltage to the cooling fan After applying the feedback to step (ii); and
(xii) When the measured noise signal is checked as a medium noise environment within the threshold noise range in step (ix), PWM control the switching unit, apply a differential current to the Peltier module, and apply a minimum voltage to the cooling fan After performing cooling treatment through the Peltier module, including the step of feeding back to step (ii), and secondarily cooling treatment through the cooling fan,
(a) cooling processing through only the cooling fan in a low noise environment, (b) driving the Peltier module with low power and driving the cooling fan at a low speed in a low noise environment, and (c) the Peltier module in a high noise environment In order to reduce overheating by driving high power and differentially driving the cooling fan, cooling efficiency can be increased by using the Peltier module even if the cooling fan is not driven at the maximum speed to reduce overheating, so the noise caused by the driving of the cooling fan A control method of a switchboard with a built-in image harmonic filter, characterized in that it achieves low noise of the switchboard by reducing the occurrence of occurrence.

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