JP2635344B2 - Power cable selection method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention calculates a required current flowing through a power cable under a certain load condition, selects a required cable, and calculates a conductor temperature when the cable is used. The present invention relates to a method for selecting a power cable for interactively interacting with a computer and automatically tabulating and outputting calculation results.

[Conventional technology]

Conventionally, when selecting the power cable size, the cable allowable current table given by the cable manufacturer (outside air temperature 40
° C), and based on the permissible current table of this cable, the current flowing at the working voltage capacity of the load is calculated, and the cable is obtained from the calculated current. Then, calculate the voltage drop based on the determined cable length (generally, the cable manufacturer only gives a conductor resistance of 90 ° C). If the voltage drop does not fall within the allowable value of the load, Up the size of the cable
It was necessary to repeat the cable selection procedure of selecting a thick cable and calculating again by obtaining it. For example, in a thermal power plant, about 200 to 300 motors are used, and each has a different capacity and cable length, so it was necessary to calculate each of them.

Moreover, as described above, the permissible current table of the cable is only for those of domestic manufacturers with an outside air temperature of 40 ° C, and when used in a place with an outside air temperature other than that, cables of domestic manufacturers as well as cables of foreign manufacturers are used. However, it was necessary to ask all cable manufacturers about the allowable current with respect to the outside air temperature at the place where they were used.

In calculating the short-circuit current capacity when the power supply is short-circuited,
Ignoring the actual conductor temperature of the power cable, the difference from the continuous allowable (rated) temperature to the short-time allowable temperature was adopted as a calculation parameter.

[Problems to be solved by the invention]

Since the conventional power cable selection method is implemented as described above, the permissible current table is for the limited cable temperature (for example, low temperature: 0 ° C, normal temperature: 25 ° C, high temperature: 50 ° C, etc.)
It is difficult to find the best cable. In addition, calculation of the allowable voltage drop of all loads, calculation of the short-circuit capacity of all circuits, and the like require many specialists and a lot of time.

The present invention has been made in order to solve the above-mentioned problems, and specializes in inputting various conditions indispensable for cable selection as a program condition and a parameter from an input device, calculating by a CPU, and outputting to an output device. It is an object of the present invention to obtain a power cable selection method that can obtain a cable specification in a short time without bothering a house.

[Means for solving the problem]

The method for selecting a power cable according to the present invention is as follows. A subroutine for calculating the current, preparing a cable selection table, and calculating the conductor temperature previously stored in a floppy disk and an OS are stored in the floppy disk and input from an input device. Enter program conditions and parameters interactively
The calculation is performed by the CPU, and the calculation result based on the common constant is automatically output via the output device.

[Action]

Basics required for selecting a power cable in the present invention
The operating system and the subroutines of the calculation formula are stored on the floppy disk, so the operator only needs to enter program conditions and parameters interactively from the input device, and calculate the current of the cable, create the cable selection table, and calculate the conductor temperature. The calculation result is automatically output from the output device.

(Example of the invention)

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of hardware in a general computer system. In FIG.
It comprises a storage device 3 and a computing device 4. 5
Is an input device such as a keyboard or a floppy disk, which is connected to a CRT, a printer, or the like, and outputs an arithmetic processing result calculated by the CPU 1.

Next, the operation will be described. First, FIG. 2A shows a main flow chart of a power cable selection program. For example, a basic OS (operating system) is input to an input device 5 composed of a computer system such as a personal computer.
System) and a floppy disk (hereinafter abbreviated as FDD) containing all the processing programs are started. Inquiry as to whether to calculate the current first as the execution order is made from CPU1 to CRT of output device 6.
(Step GF1). Therefore, when "Y" is input, a subroutine program for current calculation is invoked from the FDD of the input device 5 to execute current calculation. At this time, the operator must determine the program conditions required for current calculation, such as conductor temperature SA (° C.), ambient temperature SI (° C.), voltage E (V), power supply voltage drop DE (MAX, V), group factor GF, and load. The power factor PF is interactively input prior to the calculation (shown in FIG. 2 (B)). With this operation, the CPU 1 automatically executes the current calculation, summarizes the calculation result in a predetermined table format, and displays the result on the CRT. Print out as necessary (Step GF2). FIG. 3 is an example of creation of a cable allowable current calculation result calculated by a computer. When the current calculation is completed, the process proceeds to a calculation process for preparing a cable selection table (step GF3). The calculation of the cable selection is continuously executed in the form of receiving the program conditions input when the current of the cable is calculated. FIG. 4 shows an example of preparing a cable selection table based on the calculation results. When the operation in step GF3 is completed, some program conditions are replaced with other conditions (step GF3).
4) Execute the cable selection table creation calculation again (step GF5). Steps and G
After selecting "N" with F1 and inputting "Y" with step GF6, the next condition is set and the operation is started (step GF7). Then, FIG. 4 is output in succession to FIG. Calculate the cable size from the rated current of the motor determined by ISO, calculate the cable length from the allowable voltage drop,
Calculate all other necessary items for cable selection. In the next step, the number of the cable to be obtained by indicating the actual load current is selected from the cable displayed on the CRT, and the ambient temperature is input. Then, a Reducing Factor (reduction rate) GC is input, and then a current I is input. With these operations, the conductor temperature is calculated and the constant K1 for calculating the short-circuit capacity is calculated.
Is calculated. The calculation formula used at this time is, for example, the second
As shown in the figure. FIG. 5 shows a calculation example of the conductor temperature. The current calculation, cable selection table creation, and conductor temperature calculation are all subroutines, and the setting of program conditions and the use of common constant terms in the calculation formulas require parts of the constants related to each other. The calculation is performed by freely extracting only the values. Then, the operator only needs to input necessary items interactively in response to the inquiry items on the CRT.

This program was developed for personal computers and is not limited to a specific personal computer model. JIS (JCS), IEC, ANC
It can be applied to calculation of all cables such as I, BS, etc.

Instead of using the automatic start-up method, the same effects as in the embodiment can be obtained even if the same software is loaded and calculated after the computer is started by the OS.

〔The invention's effect〕

As described above, according to the present invention, an OS and a calculation program for selecting a cable are prepared so as to be compatible with all personal computers, and are stored in a floppy disk so that they can be applied. No equipment needed,
Further, even if there is no knowledge of the cable and the computer, there is an effect that the cable selection according to the load can be obtained with high accuracy and automatically in a short time.

[Brief description of the drawings]

FIG. 1 is a block diagram of the personal computer hardware to which the present invention is applied, FIG. 2A is a general flowchart of a power cable selection main program according to an embodiment of the present invention, and FIG. FIG. 3 is an explanatory diagram showing a calculation result of an allowable current of a cable according to an embodiment of the present invention, and FIG. 4 is a calculation result of an allowable current and a voltage drop according to an embodiment of the present invention. FIG. 5 shows a conductor temperature according to an embodiment of the present invention.
It is explanatory drawing which shows a conductor resistance and a short circuit coefficient calculation result. In the figure, 1 is a CPU, 5 is an input device, and 6 is an output device.

Claims (2)

(57) [Claims] An input device inputs a subroutine necessary for calculating a current of a power cable stored in a memory in advance to a CPU from an input device, and an operator inputs program conditions necessary for current calculation to the CPU from the input device. Performing a calculation, after the current calculation is completed, performing a calculation process of preparing a cable selection table of the current calculation result, and using the cable selection table based on a voltage drop that occurs when a rated current of a load flows. A first selection step of selecting a possible cable; and a second selection step of selecting a usable cable from the cable selection table by comparing the rated current with the allowable current of the cable. Power cable selection method. 2. A method for selecting a power cable according to claim 1, wherein a constant for calculating a conductor temperature and a short-circuit capacity at the time of a short-circuit accident is calculated by inputting an ambient temperature, a reduction rate, and a current.