CN104566837A - Air conditioning unit loading control method and system - Google Patents

Abstract

The application discloses an air conditioning unit loading control method and system, when the air conditioning unit is in an operating state, when the current water inlet and outlet temperature of the air conditioning unit is detected not to reach the allowable range of the temperature set by a user, if the current increasing rate of the compressor is judged to be greater than the current changing rate of the preset compressor in a first preset time period, the compressor is forbidden to be loaded in a second preset time period. It can be seen that the invention adopts the method of monitoring the current increase rate of the compressor to realize the control of the loading of the compressor, thereby effectively reducing the unstable unit output or the protective shutdown condition caused by the over-fast loading of the compressor, ensuring the stable increase of the load of the air conditioning unit and leading the output of the air conditioning unit to be more stable.

Description

A kind of air-conditioner set loading control method and system

Technical field

The present invention relates to air-conditioner control system technical field, in particular, relate to a kind of air-conditioner set loading control method and system.

Background technology

General cooling water air conditioner unit, user has the target temperature of a setting, after the Inlet and outlet water temperature of air-conditioner set being detected, if the Inlet and outlet water temperature of air-conditioner set does not reach the target temperature of user's setting, then at set intervals, the output by strengthening compressor strengthens the output of air-conditioner set.

If interval time is long, then unit output can not reach the demand of user for a long time, if interval time is too short, then may causes and cause unit to export unstable or protection shutdown because loading too fast.

In summary, how to provide a kind of air-conditioner set loading control method and system to ensure that air-conditioner set load steadily increases, making air-conditioner set export more stable is those skilled in the art's technical problems urgently to be resolved hurrily.

Summary of the invention

In view of this, the invention provides a kind of air-conditioner set loading control method and system, steadily increase to realize air-conditioner set load, air-conditioner set is exported more stable.

A kind of air-conditioner set loading control method, comprising:

Receive current set model and user's design temperature of the air-conditioner set that display board sends;

Obtain the current Inlet and outlet water temperature of described air-conditioner set;

Judge whether described current Inlet and outlet water temperature reaches the allowed band of the described user's design temperature mated with described current set model;

If not, then the present current value of compressor is obtained;

Utilize described present current value and preset formula, calculate the current loads of described compressor;

The current value of the described compressor utilizing described present current value and obtained before the first preset time period, calculates compressor current Magnification, and described first preset time period is compressor current Magnification computing cycle;

Judge whether described compressor current Magnification is greater than preset compressor current changing rate;

If so, then forbid that described compressor loads in the second preset time period.

Preferably, described judge whether described current Inlet and outlet water temperature reaches the allowed band of the described user's design temperature mated with described current set model after, also comprise:

If so, then control described compressor and maintain current output.

Preferably, after judging whether described compressor current Magnification is greater than preset compressor current changing rate, also comprise:

If not, then control described compressor to continue to load output on described current loads.

Preferably, the allowed band of described user's design temperature that described and described current set model mates comprises:

When described current set model is refrigeration mode, the allowed band of the described user's design temperature mated with described refrigeration mode is for being no more than described user's design temperature;

When described current set model is heating mode, the allowed band of the described user's design temperature mated with described heating mode is for being not less than described user's design temperature.

Preferably, described preset formula is:

$Q1=(100\%-50\%)\×\left(\frac{K\×I-I_{50\%}}{I_{100\%}-I_{50\%}}\right)+50\%,$

In formula, Q1 is the current loads percentage of compressor, and I is the current flow of compressor, I _50%for nominal current value when compressor exports 50% load, I _100%for nominal current value when compressor exports 100% load, K is electric current correction value.

A kind of air-conditioner set Loading Control System, comprising:

Receiving element, for receiving current set model and user's design temperature of the air-conditioner set that display board sends;

First acquiring unit, for obtaining the current Inlet and outlet water temperature of described air-conditioner set;

First judging unit, for judging whether described current Inlet and outlet water temperature reaches the allowed band of the described user's design temperature mated with described current set model;

Second acquisition unit, for judging that at described first judging unit described current Inlet and outlet water temperature does not reach the allowed band of the described user's design temperature mated with described current set model, obtains the present current value of compressor;

First computing unit, for utilizing described present current value and preset formula, calculates the current loads of described compressor;

Second computing unit, for the current value of the described compressor that utilizes described present current value and obtained before the first preset time period, calculate compressor current Magnification, described first preset time period is compressor current Magnification computing cycle;

Second judging unit, for judging whether described compressor current Magnification is greater than preset compressor current changing rate;

Forbidding unit, for judging that described compressor current Magnification is greater than described preset compressor current changing rate at described second judging unit, forbidding that described compressor loads in the second preset time period.

Preferably, also comprise:

First control unit, for judging that at described first judging unit described current Inlet and outlet water temperature reaches the allowed band of the described user's design temperature mated with described current set model, controlling described compressor and maintaining current output.

Preferably, also comprise:

Second control unit, for judging that described compressor current Magnification is not more than described preset compressor current changing rate at described second judging unit, controlling described compressor and continuing to load output on described current loads.

Preferably, the allowed band of described user's design temperature that described and described current set model mates comprises:

When described current set model is refrigeration mode, the allowed band of the described user's design temperature mated with described refrigeration mode is for being no more than described user's design temperature;

When described current set model is heating mode, the allowed band of the described user's design temperature mated with described heating mode is for being not less than described user's design temperature.

Preferably, described preset formula is:

$Q1=(100\%-50\%)\×\left(\frac{K\×I-I_{50\%}}{I_{100\%}-I_{50\%}}\right)+50\%,$

In formula, Q1 is the current loads percentage of compressor, and I is the current flow of compressor, I _50%for nominal current value when compressor exports 50% load, I _100%for nominal current value when compressor exports 100% load, K is electric current correction value.

As can be seen from above-mentioned technical scheme, the invention provides a kind of air-conditioner set loading control method and system, when air-conditioner set is in running status, when detecting that the current Inlet and outlet water temperature of air-conditioner set does not reach the allowed band of user's design temperature, if judge in the first preset time period, compressor current Magnification is greater than preset compressor current changing rate, then in the second preset time period of setting, forbid compressor loads.Can find out; the present invention adopts the control of method realization to compressor loads of monitoring compressor current Magnification; thus effectively reduce the situation that the unit caused because compressor loads is too fast exports instability or protection shutdown; ensure the steady increase of air-conditioner set load, air-conditioner set has been exported more stable.

Accompanying drawing explanation

In order to be illustrated more clearly in the embodiment of the present invention or technical scheme of the prior art, be briefly described to the accompanying drawing used required in embodiment or description of the prior art below, apparently, accompanying drawing in the following describes is only embodiments of the invention, for those of ordinary skill in the art, under the prerequisite not paying creative work, other accompanying drawing can also be obtained according to the accompanying drawing provided.

Fig. 1 is a kind of air-conditioner set loading control method flow chart disclosed in the embodiment of the present invention;

Fig. 2 is another kind of air-conditioner set loading control method flow chart disclosed in the embodiment of the present invention;

The structural representation of Fig. 3 a kind of air-conditioner set Loading Control System disclosed in the embodiment of the present invention;

The structural representation of Fig. 4 another kind of air-conditioner set Loading Control System disclosed in the embodiment of the present invention.

Detailed description of the invention

Below in conjunction with the accompanying drawing in the embodiment of the present invention, be clearly and completely described the technical scheme in the embodiment of the present invention, obviously, described embodiment is only the present invention's part embodiment, instead of whole embodiments.Based on the embodiment in the present invention, those of ordinary skill in the art, not making the every other embodiment obtained under creative work prerequisite, belong to the scope of protection of the invention.

The embodiment of the invention discloses a kind of air-conditioner set loading control method and system, steadily increase to realize air-conditioner set load, air-conditioner set is exported more stable.

See Fig. 1, a kind of air-conditioner set loading control method flow chart disclosed in the embodiment of the present invention, comprises step:

Step S11, the current set model receiving the air-conditioner set that display board sends and user's design temperature;

Wherein, current set model comprises refrigeration mode and heating mode.

Step S12, obtain the current Inlet and outlet water temperature of described air-conditioner set;

Step S13, judge whether described current Inlet and outlet water temperature reaches the allowed band of the described user's design temperature mated with described current set model, if not, then perform step S14;

Concrete, when described current set model is refrigeration mode, the allowed band of the described user's design temperature mated with described refrigeration mode is for being no more than described user's design temperature, that is, if the current set model of air-conditioner set is refrigeration mode, then judge whether the current Inlet and outlet water temperature of air-conditioner set is no more than user's design temperature;

When described current set model is heating mode, the allowed band of the described user's design temperature mated with described heating mode is for being not less than described user's design temperature, that is, if the current set model of air-conditioner set is heating mode, then judge whether the current Inlet and outlet water temperature of air-conditioner set is not less than user's design temperature.

The present current value of step S14, acquisition compressor;

Step S15, utilize described present current value and preset formula, calculate the current loads of described compressor;

Wherein, preset formula is see formula (1):

$Q1=(100\%-50\%)\×\left(\frac{K\×I-I_{50\%}}{I_{100\%}-I_{50\%}}\right)+50\%---\left(1\right),$

In formula, Q1 is the current loads percentage of compressor;

I is the current flow of compressor;

I _50%for nominal current value when compressor exports 50% load, during different compressors, this value is generally different;

I _100%for nominal current value when compressor exports 100% load, during different compressors, this value is generally different;

K is electric current correction value, generally selects empirical value.

It should be noted that, the current loads of compressor adopts the current loads percentage of compressor to represent.

Step S16, the current value of described compressor utilizing described present current value and obtained before the first preset time period, calculate compressor current Magnification;

Wherein, described first preset time period is compressor current Magnification computing cycle.

Suppose, compressor current Magnification computing cycle is X second, and current time is t1, and the present current value of compressor is I _t1, then the computing formula of compressor current Magnification Δ I is see formula (2),

$\mathrm{\ΔI}=\frac{I_{t1}-I_{(t1-X)}}{I_{(t1-X)}}---\left(2\right),$

In formula, I _(t1-X)for the current value of compressor detected before t1 moment X second.

Step S17, judge whether described compressor current Magnification is greater than preset compressor current changing rate, if so, then perform step S18;

Wherein, the value of preset compressor current changing rate is concrete determines according to actual needs, and the present invention does not limit at this.

Step S18, forbid that described compressor loads in the second preset time period.

Second preset time period refers to forbids the compressor loads time, concrete numerical basis actual needs and determining.

It should be noted that, step S15 in the present embodiment and step S16 two calculation procedures are not limited to order disclosed in the present embodiment in practical implementation, also first can perform step S16, rear execution step S15, or two steps perform simultaneously, the present invention does not limit at this.

In summary it can be seen, a kind of air-conditioner set loading control method provided by the invention, when air-conditioner set is in running status, when detecting that the current Inlet and outlet water temperature of air-conditioner set does not reach the allowed band of user's design temperature, if judge in the first preset time period, compressor current Magnification is greater than preset compressor current changing rate, then in the second preset time period of setting, forbid compressor loads.Can find out; the present invention adopts the control of method realization to compressor loads of monitoring compressor current Magnification; thus effectively reduce the situation that the unit caused because compressor loads is too fast exports instability or protection shutdown; ensure the steady increase of air-conditioner set load, air-conditioner set has been exported more stable.

For optimizing above-described embodiment further, see Fig. 2, a kind of air-conditioner set loading control method flow chart disclosed in another embodiment of the present invention, on basis embodiment illustrated in fig. 1, after step s 13, also comprises:

Step S19, when described current Inlet and outlet water temperature reaches the allowed band of the described user's design temperature mated with described current set model, then control described compressor and maintain current output.

For optimizing above-described embodiment further, after step S17, also comprise:

Step S20, when described compressor current Magnification is not more than preset compressor current changing rate, then control described compressor continue on described current loads load export.

It should be noted that, in above-described embodiment, compressor current Magnification computing cycle, preset compressor current changing rate, forbid the compressor loads time, the nominal current value of compressor when exporting 100% load, compressor nominal current value when exporting 50% load, electric current correction value send by display board, adopts RS485 to communicate between display board with mainboard.

In summary it can be seen, a kind of air-conditioner set loading control method provided by the invention, when air-conditioner set is in running status, when detecting that the current Inlet and outlet water temperature of air-conditioner set does not reach the allowed band of user's design temperature, if judge in the first preset time period, compressor current Magnification is greater than preset compressor current changing rate, then in the second preset time period of setting, forbid compressor loads.Can find out; the present invention adopts the control of method realization to compressor loads of monitoring compressor current Magnification; thus effectively reduce the situation that the unit caused because compressor loads is too fast exports instability or protection shutdown; ensure the steady increase of air-conditioner set load, air-conditioner set has been exported more stable.

For convenience of the understanding to compressor fan-out capability, the application has done following elaboration to compressor:

(1) compressor export can regulate in 25% ~ 100% scope, when compressor just starts, output 25% ability of compressor, then rapid loading is to 50%, follow-up can electrodeless adjustment in 50% ~ 100% scope.

(2) compressor holds adjust magnetic valve to be connected with two, first holds tune magnetic valve exports 25% ability for controlling compressor, if second holds tune magnetic valve output fixed level, then controls compressor and exports 50% ability, if output pulse signal, then control compressor and unload.

(3), when compressor loads, the pulse signal exported by the loading magnetic valve be connected with compressor controls.

(4) compressor startup or close controlled by the start-stop control contactor be connected with compressor.

Corresponding with said method embodiment, present invention also offers a kind of air-conditioner set Loading Control System.

See Fig. 3, a kind of structural representation of air-conditioner set Loading Control System disclosed in the embodiment of the present invention, comprising:

Receiving element 31, for receiving current set model and user's design temperature of the air-conditioner set that display board sends;

Wherein, current set model comprises refrigeration mode and heating mode.

First acquiring unit 32, for obtaining the current Inlet and outlet water temperature of described air-conditioner set;

First judging unit 33, for judging whether described current Inlet and outlet water temperature reaches the allowed band of the described user's design temperature mated with described current set model, if not, then performs second acquisition unit 34;

Concrete, when described current set model is refrigeration mode, the allowed band of the described user's design temperature mated with described refrigeration mode is for being no more than described user's design temperature, that is, if the current set model of air-conditioner set is refrigeration mode, then judge whether the current Inlet and outlet water temperature of air-conditioner set is no more than user's design temperature;

When described current set model is heating mode, the allowed band of the described user's design temperature mated with described heating mode is for being not less than described user's design temperature, that is, if the current set model of air-conditioner set is heating mode, then judge whether the current Inlet and outlet water temperature of air-conditioner set is not less than user's design temperature.

Second acquisition unit 34, for judging that at the first judging unit 33 described current Inlet and outlet water temperature does not reach the allowed band of the described user's design temperature mated with described current set model, obtains the present current value of compressor;

First computing unit 35, for utilizing described present current value and preset formula, calculates the current loads of described compressor;

Wherein, preset formula is see formula (1):

$Q1=(100\%-50\%)\×\left(\frac{K\×I-I_{50\%}}{I_{100\%}-I_{50\%}}\right)+50\%---\left(1\right),$

In formula, Q1 is the current loads percentage of compressor;

I is the current flow of compressor;

I _50%for nominal current value when compressor exports 50% load, during different compressors, this value is generally different;

I _100%for nominal current value when compressor exports 100% load, during different compressors, this value is generally different;

K is electric current correction value, generally selects empirical value.

It should be noted that, the current loads of compressor adopts the current loads percentage of compressor to represent.

Second computing unit 36, for the current value of the described compressor that utilizes described present current value and obtained before the first preset time period, calculates compressor current Magnification;

Wherein, described first preset time period is compressor current Magnification computing cycle.

Suppose, compressor current Magnification computing cycle is X second, and current time is t1, and the present current value of compressor is I _t1, then the computing formula of compressor current Magnification Δ I is see formula (2),

$\mathrm{\ΔI}=\frac{I_{t1}-I_{(t1-X)}}{I_{(t1-X)}}---\left(2\right),$

In formula, I _(t1-X)for the current value of compressor detected before t1 moment X second.

Second judging unit 37, for judging whether described compressor current Magnification is greater than preset compressor current changing rate, if so, then performs and forbids unit 38;

Forbidding unit 38, for judging that described compressor current Magnification is greater than described preset compressor current changing rate at the second judging unit 37, forbidding that described compressor loads in the second preset time period.

It should be noted that, the first computing unit 35 in the present embodiment and the second computing unit 36 are not limited to order disclosed in the present embodiment in practical implementation, also the second computing unit 36 can first be performed, rear execution first computing unit 35, or two unit perform simultaneously, the present invention does not limit at this.

In summary it can be seen, a kind of air-conditioner set loading control method provided by the invention, when air-conditioner set is in running status, when detecting that the current Inlet and outlet water temperature of air-conditioner set does not reach the allowed band of user's design temperature, if judge in the first preset time period, compressor current Magnification is greater than preset compressor current changing rate, then in the second preset time period of setting, forbid compressor loads.Can find out; the present invention adopts the control of method realization to compressor loads of monitoring compressor current Magnification; thus effectively reduce the situation that the unit caused because compressor loads is too fast exports instability or protection shutdown; ensure the steady increase of air-conditioner set load, air-conditioner set has been exported more stable.

For optimizing above-described embodiment further, see Fig. 4, a kind of structural representation of air-conditioner set Loading Control System disclosed in another embodiment of the present invention, on basis embodiment illustrated in fig. 3, also comprises:

First control unit 39, for judging that at the first judging unit 33 described current Inlet and outlet water temperature reaches the allowed band of the described user's design temperature mated with described current set model, controlling described compressor and maintaining current output.

For optimizing above-described embodiment further, also comprise:

Second control unit 40, for judging that described compressor current Magnification is not more than described preset compressor current changing rate at the second judging unit 37, controlling described compressor and continuing to load output on described current loads.

It should be noted that, in above-described embodiment, compressor current Magnification computing cycle, preset compressor current changing rate, forbid the compressor loads time, the nominal current value of compressor when exporting 100% load, compressor nominal current value when exporting 50% load, electric current correction value send by display board, adopts RS485 to communicate between display board with mainboard.

In summary it can be seen, a kind of air-conditioner set loading control method provided by the invention, when air-conditioner set is in running status, when detecting that the current Inlet and outlet water temperature of air-conditioner set does not reach the allowed band of user's design temperature, if judge in the first preset time period, compressor current Magnification is greater than preset compressor current changing rate, then in the second preset time period of setting, forbid compressor loads.Can find out; the present invention adopts the control of method realization to compressor loads of monitoring compressor current Magnification; thus effectively reduce the situation that the unit caused because compressor loads is too fast exports instability or protection shutdown; ensure the steady increase of air-conditioner set load, air-conditioner set has been exported more stable.

For convenience of the understanding to compressor fan-out capability, the application has done following elaboration to compressor:

(1) compressor export can regulate in 25% ~ 100% scope, when compressor just starts, output 25% ability of compressor, then rapid loading is to 50%, follow-up can electrodeless adjustment in 50% ~ 100% scope.

(2) compressor holds adjust magnetic valve to be connected with two, first holds tune magnetic valve exports 25% ability for controlling compressor, if second holds tune magnetic valve output fixed level, then controls compressor and exports 50% ability, if output pulse signal, then control compressor and unload.

(3), when compressor loads, the pulse signal exported by the loading magnetic valve be connected with compressor controls.

(4) compressor startup or close controlled by the start-stop control contactor be connected with compressor.

Finally, also it should be noted that, in this article, the such as relational terms of first and second grades and so on is only used for an entity or operation to separate with another entity or operating space, and not necessarily requires or imply the relation that there is any this reality between these entities or operation or sequentially.And, term " comprises ", " comprising " or its any other variant are intended to contain comprising of nonexcludability, thus make to comprise the process of a series of key element, method, article or equipment and not only comprise those key elements, but also comprise other key elements clearly do not listed, or also comprise by the intrinsic key element of this process, method, article or equipment.When not more restrictions, the key element limited by statement " comprising ... ", and be not precluded within process, method, article or the equipment comprising described key element and also there is other identical element.

In this description, each embodiment adopts the mode of going forward one by one to describe, and what each embodiment stressed is the difference with other embodiments, between each embodiment identical similar portion mutually see.

To the above-mentioned explanation of the disclosed embodiments, professional and technical personnel in the field are realized or uses the application.To be apparent for those skilled in the art to the multiple amendment of these embodiments, General Principle as defined herein when not departing from the spirit or scope of the application, can realize in other embodiments.Therefore, the application can not be restricted to these embodiments shown in this article, but will meet the widest scope consistent with principle disclosed herein and features of novelty.

Claims (10)

1. an air-conditioner set loading control method, is characterized in that, comprising:

Receive current set model and user's design temperature of the air-conditioner set that display board sends;

Obtain the current Inlet and outlet water temperature of described air-conditioner set;

Judge whether described current Inlet and outlet water temperature reaches the allowed band of the described user's design temperature mated with described current set model;

If not, then the present current value of compressor is obtained;

Utilize described present current value and preset formula, calculate the current loads of described compressor;

The current value of the described compressor utilizing described present current value and obtained before the first preset time period, calculates compressor current Magnification, and described first preset time period is compressor current Magnification computing cycle;

Judge whether described compressor current Magnification is greater than preset compressor current changing rate;

If so, then forbid that described compressor loads in the second preset time period.

2. air-conditioner set loading control method according to claim 1, is characterized in that, described judge whether described current Inlet and outlet water temperature reaches the allowed band of the described user's design temperature mated with described current set model after, also comprise:

If so, then control described compressor and maintain current output.

3. air-conditioner set loading control method according to claim 1, is characterized in that, after judging whether described compressor current Magnification is greater than preset compressor current changing rate, also comprises:

If not, then control described compressor to continue to load output on described current loads.

4. air-conditioner set loading control method according to claim 1, is characterized in that, the allowed band of described user's design temperature that described and described current set model mates comprises:

When described current set model is refrigeration mode, the allowed band of the described user's design temperature mated with described refrigeration mode is for being no more than described user's design temperature;

When described current set model is heating mode, the allowed band of the described user's design temperature mated with described heating mode is for being not less than described user's design temperature.

5. air-conditioner set loading control method according to claim 1, is characterized in that, described preset formula is:

$Q1=(100\%-50\%)\×\left(\frac{K\×I-I_{50\%}}{I_{100\%}-I_{50\%}}\right)+50\%,$

In formula, Q1 is the current loads percentage of compressor, and I is the current flow of compressor, I _50%for nominal current value when compressor exports 50% load, I _100%for nominal current value when compressor exports 100% load, K is electric current correction value.

6. an air-conditioner set Loading Control System, is characterized in that, comprising:

Receiving element, for receiving current set model and user's design temperature of the air-conditioner set that display board sends;

First acquiring unit, for obtaining the current Inlet and outlet water temperature of described air-conditioner set;

First judging unit, for judging whether described current Inlet and outlet water temperature reaches the allowed band of the described user's design temperature mated with described current set model;

Second acquisition unit, for judging that at described first judging unit described current Inlet and outlet water temperature does not reach the allowed band of the described user's design temperature mated with described current set model, obtains the present current value of compressor;

First computing unit, for utilizing described present current value and preset formula, calculates the current loads of described compressor;

Second computing unit, for the current value of the described compressor that utilizes described present current value and obtained before the first preset time period, calculate compressor current Magnification, described first preset time period is compressor current Magnification computing cycle;

Second judging unit, for judging whether described compressor current Magnification is greater than preset compressor current changing rate;

Forbidding unit, for judging that described compressor current Magnification is greater than described preset compressor current changing rate at described second judging unit, forbidding that described compressor loads in the second preset time period.

7. air-conditioner set Loading Control System according to claim 6, is characterized in that, also comprise:

First control unit, for judging that at described first judging unit described current Inlet and outlet water temperature reaches the allowed band of the described user's design temperature mated with described current set model, controlling described compressor and maintaining current output.

8. air-conditioner set Loading Control System according to claim 6, is characterized in that, also comprise:

Second control unit, for judging that described compressor current Magnification is not more than described preset compressor current changing rate at described second judging unit, controlling described compressor and continuing to load output on described current loads.

9. air-conditioner set Loading Control System according to claim 6, is characterized in that, the allowed band of described user's design temperature that described and described current set model mates comprises:

When described current set model is refrigeration mode, the allowed band of the described user's design temperature mated with described refrigeration mode is for being no more than described user's design temperature;

When described current set model is heating mode, the allowed band of the described user's design temperature mated with described heating mode is for being not less than described user's design temperature.

10. air-conditioner set Loading Control System according to claim 6, is characterized in that, described preset formula is:

$Q1=(100\%-50\%)\×\left(\frac{K\×I-I_{50\%}}{I_{100\%}-I_{50\%}}\right)+50\%,$

In formula, Q1 is the current loads percentage of compressor, and I is the current flow of compressor, I _50%for nominal current value when compressor exports 50% load, I _100%for nominal current value when compressor exports 100% load, K is electric current correction value.