阅读说明：本技术 电梯漏电保护方法和装置 (Elevator leakage protection method and device ) 是由 姚金玲 谭伯军 赵正军 于 2021-07-20 设计创作，主要内容包括：本申请公开了电梯漏电保护方法和装置。其中方法包括：获取电梯的疑似漏电电流的谐波特征值；将谐波特征值与制动阈值进行比较；若谐波特征值小于制动阈值,则执行漏电保护,否则不执行漏电保护。该技术方案将通常意义上认为的漏电电流作为疑似漏电电流加以分析,利用疑似漏电电流的谐波特征,区分真正漏电的状况与电梯变频器、电缆及电机对地电容等干扰源引起的“假漏电”状况,在谐波特征值小于制动阈值的情况下才进行漏电保护,可有效防止误触发漏电保护动作,保证了电梯的正常运行使用,又大幅提高了电梯的使用安全性。(The application discloses an elevator leakage protection method and device. The method comprises the following steps: obtaining a harmonic characteristic value of suspected leakage current of the elevator; comparing the harmonic characteristic value with a braking threshold value; and if the harmonic characteristic value is smaller than the braking threshold value, performing leakage protection, otherwise, not performing leakage protection. According to the technical scheme, the leakage current considered in the general sense is used as the suspected leakage current to be analyzed, the harmonic characteristic of the suspected leakage current is utilized, the real leakage condition and the 'false leakage' condition caused by interference sources such as a frequency converter, a cable and a motor to the ground capacitance are distinguished, the leakage protection is carried out under the condition that the harmonic characteristic value is smaller than the braking threshold value, the leakage protection action can be effectively prevented from being triggered by mistake, the normal operation and use of the elevator are guaranteed, and the use safety of the elevator is greatly improved.)

1. An elevator leakage protection method is characterized by comprising the following steps:

obtaining a harmonic characteristic value of suspected leakage current of the elevator;

comparing the harmonic characteristic value with a braking threshold value;

and if the harmonic characteristic value is smaller than the braking threshold value, performing electric leakage protection, otherwise, not performing electric leakage protection.

2. The method of claim 1, wherein the obtaining harmonic characteristic values of suspected leakage current of the elevator comprises:

acquiring a fundamental component effective value and a harmonic component effective value of the suspected leakage current;

and determining the total harmonic distortion rate of the suspected leakage current according to the fundamental component effective value and the harmonic component effective value, and taking the total harmonic distortion rate as the harmonic characteristic value.

3. The method of claim 2, wherein the obtaining the effective values of the fundamental component and the harmonic component of the suspected leakage current comprises:

and determining the effective value of the fundamental component and the effective value of the harmonic component of the suspected leakage current by a Discrete Fourier Transform (DFT) method.

4. The method of claim 2, wherein determining the total harmonic distortion rate of the suspected leakage current based on the fundamental component effective value and the harmonic component effective value comprises:

and determining the total harmonic distortion rate of the suspected leakage current according to the effective value of the fundamental component and the effective values of the harmonic components of the 2 nd harmonic to the 128 th harmonic.

5. The method of claim 1, wherein the method further comprises:

acquiring a sampling value of residual current of a power supply line of an elevator;

determining the effective value of the residual current by a root mean square method according to the sampling value;

and if the effective value is larger than the leakage threshold value, taking the residual current as the suspected leakage current.

6. An elevator earth leakage protection device, characterized in that the elevator earth leakage protection device comprises:

the acquisition module is used for acquiring a harmonic characteristic value of suspected leakage current of the elevator;

the comparison module is used for comparing the harmonic characteristic value with a braking threshold value;

and the control module is used for executing leakage protection if the harmonic characteristic value is smaller than the braking threshold value, otherwise, not executing leakage protection.

7. The apparatus of claim 6,

the obtaining module is configured to obtain a fundamental component effective value and a harmonic component effective value of the suspected leakage current, determine a total harmonic distortion rate of the suspected leakage current according to the fundamental component effective value and the harmonic component effective value, and use the total harmonic distortion rate as the harmonic characteristic value.

8. The apparatus of claim 7,

the obtaining module is configured to determine the effective value of the fundamental component and the effective value of the harmonic component of the suspected leakage current by a Discrete Fourier Transform (DFT) method.

9. The apparatus of claim 7,

the obtaining module is configured to determine a total harmonic distortion rate of the suspected leakage current according to the effective value of the fundamental component and the effective values of the harmonic components of the 2 nd-128 th harmonics.

10. The apparatus of claim 6, wherein the apparatus further comprises:

the sampling module is used for acquiring a sampling value of residual current of a power supply line of the elevator;

the suspected leakage current determining module is used for determining the effective value of the residual current by a root mean square method according to the sampling value; and if the effective value is larger than the leakage threshold value, taking the residual current as the suspected leakage current.

Technical Field

The application relates to the field of electric power safety, in particular to an elevator leakage protection method and device.

Background

The earth leakage protector is a common safety device for electric equipment, but is different in the field of elevators. The reason is that if the existing leakage protector is arranged in the elevator, the elevator has a certain amount of higher harmonics, so that misoperation can be frequently caused, and the normal use of the elevator is seriously influenced. Therefore, a leakage protection method that can be adapted to an elevator is required.

Disclosure of Invention

The embodiment of the application provides an elevator leakage protection method and device, so that misoperation is reduced and normal use of an elevator is guaranteed while leakage protection is provided for the elevator.

The embodiment of the application adopts the following technical scheme:

in a first aspect, an embodiment of the present application provides an elevator leakage protection method, including: obtaining a harmonic characteristic value of suspected leakage current of the elevator; comparing the harmonic characteristic value with a braking threshold value; and if the harmonic characteristic value is smaller than the braking threshold value, performing leakage protection, otherwise, not performing leakage protection.

In some embodiments, obtaining a harmonic characteristic value of suspected leakage current of the elevator comprises: acquiring a fundamental component effective value and a harmonic component effective value of the suspected leakage current; and determining the total harmonic distortion rate of the suspected leakage current according to the effective value of the fundamental component and the effective value of the harmonic component, and taking the total harmonic distortion rate as a harmonic characteristic value.

In some embodiments, obtaining the effective value of the fundamental component and the effective value of the harmonic component of the suspected leakage current comprises: and determining the effective value of the fundamental component and the effective value of the harmonic component of the suspected leakage current by a Discrete Fourier Transform (DFT) method.

In some embodiments, determining the total harmonic distortion rate of the suspected leakage current based on the fundamental component effective value and the harmonic component effective value comprises: and determining the total harmonic distortion rate of the suspected leakage current according to the effective value of the fundamental component and the effective values of the harmonic components of the 2 nd harmonic to the 128 th harmonic.

In some embodiments, the method further comprises: acquiring a sampling value of residual current of a power supply line of an elevator; determining the effective value of the residual current by a root mean square method according to the sampling value; and if the effective value is larger than the leakage threshold value, taking the residual current as the suspected leakage current.

In a second aspect, an embodiment of the present application provides an elevator leakage protection device, including: the acquisition module is used for acquiring a harmonic characteristic value of suspected leakage current of the elevator; the comparison module is used for comparing the harmonic characteristic value with a braking threshold value; and the control module is used for executing leakage protection if the harmonic characteristic value is smaller than the braking threshold value, or not executing leakage protection.

In some embodiments, the obtaining module is configured to obtain a fundamental component effective value and a harmonic component effective value of the suspected leakage current, determine a total harmonic distortion rate of the suspected leakage current according to the fundamental component effective value and the harmonic component effective value, and use the total harmonic distortion rate as the harmonic characteristic value.

In some embodiments, the obtaining module is configured to determine the effective value of the fundamental component and the effective value of the harmonic component of the suspected leakage current by a discrete fourier transform DFT method.

In some embodiments, the obtaining module is configured to determine the total harmonic distortion rate of the suspected leakage current according to the effective value of the fundamental component and the effective values of the harmonic components of the 2 nd harmonic to the 128 th harmonic.

In some embodiments, the apparatus further comprises: the sampling module is used for acquiring a sampling value of residual current of a power supply line of the elevator; the suspected leakage current determining module is used for determining the effective value of the residual current by a root mean square method according to the sampling value; and if the effective value is larger than the leakage threshold value, taking the residual current as the suspected leakage current.

The embodiment of the application adopts at least one technical scheme which can achieve the following beneficial effects: the leakage current considered in the general sense is used as the suspected leakage current to be analyzed, the harmonic characteristic of the suspected leakage current is utilized to distinguish the real leakage condition from the false leakage condition caused by interference sources such as a frequency converter, a cable and a ground capacitance of a motor, and the leakage protection is carried out under the condition that the harmonic characteristic value is smaller than a braking threshold value, so that the leakage protection action can be effectively prevented from being triggered by mistake, the normal operation and use of the elevator are ensured, and the use safety of the elevator is greatly improved.

Drawings

The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the application and together with the description serve to explain the application and not to limit the application. In the drawings:

fig. 1 shows a schematic flow diagram of an elevator leakage protection method according to an embodiment of the present application;

fig. 2 shows a schematic structural diagram of an elevator earth leakage protection device according to an embodiment of the present application;

fig. 3 presents a diagrammatic illustration of the structure of an elevator according to an embodiment of the application.

Detailed Description

In order to make the objects, technical solutions and advantages of the present application more apparent, the technical solutions of the present application will be described in detail and completely with reference to the following specific embodiments of the present application and the accompanying drawings. It should be apparent that the described embodiments are only some of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

Generally, in the principle of the earth leakage protector in the prior art, when an earth leakage event occurs, the balance of three-phase currents is damaged, residual currents appear, and if the residual currents are detected to be larger than a certain value (an earth leakage threshold value), the earth leakage can be considered to occur.

When the existing leakage protector is additionally arranged in the elevator, misoperation is easily caused when the elevator is started or stopped. The reason is that when the elevator operates in a steady state, the residual current is very small, but when the elevator starts or stops, the residual current is obviously increased, if the leakage protector is simply installed, because the starting current of the general leakage protector is only 20 mA-100 mA, the misoperation of the leakage protection is possibly caused when the elevator starts or stops, and the normal use of the elevator is influenced.

That is, it is difficult to realize leakage protection by simply setting a leakage threshold. The adoption "delay type" earth-leakage protector avoids the impulse current when the motor starts and stops to avoid taking place the malfunction, is a solution thinking, but needs to notice, and some elevators open and stop time is longer, "delay type" earth-leakage protector hardly satisfies earth-leakage protection's snap-action nature requirement.

The inventor finds that the large residual current generated when the elevator is started or stopped is caused by interference sources such as a frequency converter, the ground capacitance of a cable, a motor and the like in the power supply line of the elevator. The fundamental reason for the "leakage current" of the interference source is caused by higher harmonics, for example, the current output by the frequency converter is not a pure sine wave, which necessarily contains a certain amount of higher harmonics, and the 3 rd order harmonics are the same in phase and same in size, and the effect caused by such "zero sequence higher harmonics" is obviously the same as the residual current. In addition, the existence of the ground capacitance of the motor and the cable thereof provides a path for zero sequence higher harmonics. In a sense, the two factors of the zero sequence higher harmonic and the earth capacitance cause the frequency converter to generate leakage current.

Therefore, the inventor thinks that when the leakage current is detected, the harmonic characteristics of the leakage current are further analyzed, so that similar effects caused by interference sources can be eliminated, and misoperation of elevator protection can be avoided.

Based on the above thought, the embodiment of the application provides an elevator leakage protection method.

Fig. 1 shows a schematic flow chart of an elevator leakage protection method according to an embodiment of the present application. As shown in fig. 1, the method includes:

and step S110, obtaining a harmonic characteristic value of suspected leakage current of the elevator. For example, as described above, the harmonic characteristic value can be determined from the effect of the 3 rd order harmonic and the multiple harmonic of 3, which is the same as the residual current.

The embodiment of the present application may multiplex a part of the prior art, for example, the leakage protector in the prior art may detect the leakage current, and the embodiment of the present application may analyze the leakage current as the suspected leakage current. Specifically, in order to obtain the harmonic characteristic value through calculation, the fundamental component effective value and the harmonic component effective value of the suspected leakage current may be determined first.

It can be understood that, in order to enable the leakage protector implemented based on the elevator leakage protection method of the present application to have more functions, various parameters related to the suspected leakage current, such as harmonic voltage, etc., can be further acquired.

Step S120, comparing the harmonic characteristic value with a braking threshold value. Wherein, the braking threshold value can be set according to the preset elevator leakage test result.

In step S130, if the harmonic characteristic value is smaller than the braking threshold, the leakage protection is performed, otherwise, the leakage protection is not performed. The judgment mode of the numerical comparison is not complex, for example, the judgment mode can be realized through a comparison circuit, the consumption of resources is low, and meanwhile, the misjudgment rate is low. The present application can utilize existing earth leakage protection techniques to perform specific earth leakage protection actions.

It can be seen that, in the method shown in fig. 1, the leakage current considered in the general sense is analyzed as the suspected leakage current, the harmonic characteristic of the suspected leakage current is utilized to distinguish the real leakage condition from the false leakage condition caused by the interference sources such as the frequency converter of the elevator, the cable, the capacitance of the motor to the ground and the like, and the leakage protection is performed only when the harmonic characteristic value is smaller than the braking threshold value, so that the false triggering of the leakage protection action can be effectively prevented, the normal operation and use of the elevator are ensured, and the use safety of the elevator is greatly improved.

In some embodiments, obtaining a harmonic characteristic value of suspected leakage current of the elevator comprises: acquiring a fundamental component effective value and a harmonic component effective value of the suspected leakage current; and determining the total harmonic distortion rate of the suspected leakage current according to the effective value of the fundamental component and the effective value of the harmonic component, and taking the total harmonic distortion rate as a harmonic characteristic value.

When the elevator is started and stopped, the suspected leakage current is mainly caused by self harmonics of interference sources such as an elevator frequency converter, and the like, the suspected leakage current contains a small fundamental component, higher harmonics, particularly 3-order and 3-order multiple harmonic components, and the total harmonic distortion rate of the leakage current is large.

If the 3 rd harmonic and the effective value of the multiple harmonic of 3 are considered and matched with corresponding threshold values, the application range is narrow, for example, different zero sequence higher harmonics are generated by different types of equipment, and different threshold values need to be set. Therefore, the embodiment of the application provides a method for using the total harmonic distortion as the harmonic characteristic value, and not only considers the 3 rd harmonic and the multiple harmonic of 3, but also considers other subharmonics, so that the application scenarios are wider.

In some embodiments, obtaining the effective value of the fundamental component and the effective value of the harmonic component of the suspected leakage current comprises: and determining the effective value of the fundamental component and the effective value of the harmonic component of the suspected leakage current by a Discrete Fourier Transform (DFT) method.

The embodiment of the application can determine the effective value of the fundamental component and the effective value of the harmonic component of the suspected leakage current by using a Discrete Fourier Transform (DFT) method, and particularly can be implemented by using Fast Fourier Transform (FFT).

In some embodiments, determining the total harmonic distortion rate of the suspected leakage current based on the fundamental component effective value and the harmonic component effective value comprises: and determining the total harmonic distortion rate of the suspected leakage current according to the effective value of the fundamental component and the effective values of the harmonic components of the 2 nd harmonic to the 128 th harmonic.

Typically, only the 39 th harmonic is considered in calculating the total harmonic distortion rate, with higher harmonics being easily ignored due to their smaller absolute values. However, in the scenario of the application, as the leakage protection is more stable and safe, and more harmonics are selected for calculation, the misjudgment can be further reduced; also, as previously mentioned, the harmonics of multiples of 3 are still of reference in the higher harmonics. Through experiments, the total harmonic distortion rate of the suspected leakage current is calculated by selecting the effective values of the harmonic components of 2-128 harmonics, and the efficiency, the resource consumption and the accuracy can be considered at the same time.

In some embodiments, the method further comprises: acquiring a sampling value of residual current of a power supply line of an elevator; determining the effective value of the residual current by a root mean square method according to the sampling value; and if the effective value is larger than the leakage threshold value, taking the residual current as the suspected leakage current.

The effective value of the current obtained by calculation through the root mean square method is related to the energy in the area enclosed by the current waveform and is unrelated to the shape of the current waveform, and the effective value of the residual current containing fundamental wave components and harmonic wave components can be accurately calculated through the root mean square method. The subsequent step of determining whether the residual current is the suspected leakage current according to the leakage threshold may refer to a manner of determining whether the residual current is the leakage current by a leakage protector in the prior art, which is not described in detail herein.

When the harmonic characteristic value of the suspected leakage current of the elevator is obtained, the harmonic characteristic value can be calculated according to the sampling value of the residual current which is judged to be the suspected leakage current.

In some embodiments, by using the elevator leakage protection method of the present application, a good interaction with a power engineer may also be achieved, for example, a display interface is implemented, and parameters such as a waveform of a suspected leakage current are displayed; the realization operation desk receives the operation instruction and executes corresponding operation; and recording the occurred leakage event, elevator fault recording and the like.

The embodiment of the application also provides an elevator leakage protection device. Fig. 2 shows a schematic structural diagram of an elevator earth leakage protection device according to an embodiment of the present application. As shown in fig. 2, the elevator earth leakage protection device 200 includes:

the obtaining module 210 is configured to obtain a harmonic characteristic value of a suspected leakage current of the elevator. For example, as described above, the harmonic characteristic value can be determined from the effect of the 3 rd order harmonic and the multiple harmonic of 3, which is the same as the residual current.

The embodiment of the present application may multiplex a part of the prior art, for example, the leakage protector in the prior art may detect the leakage current, and the embodiment of the present application may analyze the leakage current as the suspected leakage current. Specifically, the elevator leakage protection device of the application can contain a residual current collection module for collecting residual current (as suspected leakage current) of an elevator power supply line, obtain a current sampling value, and an acquisition module acquires an effective value of the suspected leakage current of the elevator according to the current sampling value.

It can be understood that, in order to enable the leakage protector implemented based on the elevator leakage protection method of the present application to have more functions, various parameters related to the suspected leakage current, such as harmonic voltage, etc., can be further acquired.

A comparison module 220 for comparing the harmonic characteristic value with a braking threshold value. Wherein, the braking threshold value can be set according to the preset elevator leakage test result.

And the control module 230 is configured to perform leakage protection if the harmonic characteristic value is smaller than the braking threshold, and not perform leakage protection otherwise.

The judgment mode of the numerical comparison is not complex, for example, the judgment mode can be realized through a comparison circuit, the consumption of resources is low, and meanwhile, the misjudgment rate is low. The present application can utilize existing earth leakage protection techniques to perform specific earth leakage protection actions. Specifically, a switching value output module can be used for outputting corresponding switching values to control the switching of the electric brake of the power supply line.

It can be seen that the apparatus shown in fig. 2 analyzes the leakage current considered in the general sense as the suspected leakage current, and distinguishes the real leakage condition and the "false leakage" condition caused by the interference sources such as the frequency converter of the elevator, the cable and the motor to the ground capacitance by using the harmonic characteristic of the suspected leakage current, and performs leakage protection only when the harmonic characteristic value is smaller than the braking threshold value, so as to effectively prevent the false triggering of the leakage protection action, ensure the normal operation and use of the elevator, and greatly improve the use safety of the elevator.

In some embodiments, the obtaining module 210 is configured to obtain a fundamental component effective value and a harmonic component effective value of the suspected leakage current, determine a total harmonic distortion rate of the suspected leakage current according to the fundamental component effective value and the harmonic component effective value, and use the total harmonic distortion rate as the harmonic characteristic value.

If the 3 rd harmonic and the effective value of the multiple harmonic of 3 are considered and matched with corresponding threshold values, the application range is narrow, for example, different zero sequence higher harmonics are generated by different types of equipment, and different threshold values need to be set. Therefore, the embodiment of the application provides a method for using the total harmonic distortion as the harmonic characteristic value, and not only considers the 3 rd harmonic and the multiple harmonic of 3, but also considers other subharmonics, so that the application scenarios are wider.

In some embodiments, the obtaining module 210 is configured to determine the effective value of the fundamental component and the effective value of the harmonic component of the suspected leakage current by a discrete fourier transform DFT method.

The embodiment of the application can determine the effective value of the fundamental component and the effective value of the harmonic component of the suspected leakage current by using a Discrete Fourier Transform (DFT) method, and particularly can be implemented by using Fast Fourier Transform (FFT).

In some embodiments, the obtaining module 210 is configured to determine the total harmonic distortion rate of the suspected leakage current according to the effective value of the fundamental component and the effective values of the harmonic components of the 2 nd harmonic to the 128 th harmonic.

Typically, only the 39 th harmonic is considered in calculating the total harmonic distortion rate, with higher harmonics being easily ignored due to their smaller absolute values. However, in the scenario of the application, as the leakage protection is more stable and safe, and more harmonics are selected for calculation, the misjudgment can be further reduced; also, as previously mentioned, the harmonics of multiples of 3 are still of reference in the higher harmonics. Through experiments, the total harmonic distortion rate of the suspected leakage current is calculated by selecting the effective values of the harmonic components of 2-128 harmonics, and the efficiency, the resource consumption and the accuracy can be considered at the same time.

In some embodiments, the apparatus further comprises: the sampling module is used for acquiring a sampling value of residual current of a power supply line of the elevator; the suspected leakage current determining module is used for determining the effective value of the residual current by a root mean square method according to the sampling value; and if the effective value is larger than the leakage threshold value, taking the residual current as the suspected leakage current.

The effective value of the suspected leakage current calculated by the root mean square method is related to the energy in the area enclosed by the current waveform and is unrelated to the shape of the current waveform, and the effective value of the residual current containing fundamental wave components and harmonic wave components can be accurately calculated by the root mean square method. The subsequent step of determining whether the residual current is the suspected leakage current according to the leakage threshold may refer to a manner of determining whether the residual current is the leakage current by a leakage protector in the prior art, which is not described in detail herein.

When the harmonic characteristic value of the suspected leakage current of the elevator is obtained, the harmonic characteristic value can be calculated according to the sampling value of the residual current which is judged to be the suspected leakage current.

In some embodiments, the apparatus further includes an operation module, configured to receive an operation instruction, and perform a corresponding operation according to the operation instruction.

In some embodiments, the apparatus further includes a display module, configured to display parameters of the suspected leakage current, such as waveforms, and/or display states of other modules, and other information that needs to be displayed in various services.

In some embodiments, the elevator leakage protection device further includes a storage module implemented by a non-volatile memory, for example, to record an occurred leakage event, an elevator fault record, and the like, and may further store a fixed value parameter such as a braking threshold. The record of the leakage event may include the time at which the leakage occurred, parameters related to the leakage current, etc.

In some embodiments, the elevator leakage protection device further comprises a communication module, which may be used to communicate with an external device, such as to send a recorded leakage event, etc.

An embodiment of the present application further provides an elevator, and fig. 3 shows a schematic structural diagram of an elevator according to an embodiment of the present application, and as shown in fig. 3, an elevator 300 is provided with the elevator protection device 200 according to any of the above embodiments, and specifically, the elevator protection device can be disposed adjacent to a power supply line of the elevator 300, for example, a residual current sensor is used to collect a suspected leakage current of the elevator, and the residual current sensor can be sleeved on the power supply line.

In conclusion, the technical scheme of the application analyzes the leakage current considered in the general sense as the suspected leakage current, distinguishes the real leakage condition and the false leakage condition caused by interference sources such as an elevator frequency converter, a cable, a ground capacitance and the like by utilizing the harmonic characteristic of the elevator leakage current, and performs leakage protection under the condition that the harmonic characteristic value is smaller than the braking threshold value, so that the leakage protection action can be effectively prevented from being triggered by mistake, the normal operation and use of the elevator are ensured, and the use safety of the elevator is greatly improved. In addition, the method can acquire the residual current of the power supply line of the elevator, calculate the effective value of the residual current containing the fundamental wave component and the harmonic component by using a root mean square method based on the acquired sampling value, judge that the residual current is suspected leakage current if the residual current is greater than a preset leakage threshold value, and determine the harmonic characteristic value by using the sampling value, wherein the residual current can be realized by adding a small number of devices and/or adding processing logic in the existing leakage protector, the cost is low, and the effect is obvious.

It should also be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in the process, method, article, or apparatus that comprises the element.

The above are merely examples of the present application and are not intended to limit the present application. Various modifications and changes may occur to those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.