JPH049011B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an overcurrent relay applied to a microcomputer that detects the current flowing through a load such as a motor and protects the load from burnout, and in particular, an overcurrent relay that detects the current flowing through a load such as a motor and protects the load from burnout. This invention relates to a configuration that can reduce capacity.

[Conventional technology]

This type of overcurrent relay is normally required to have inverse timing characteristics as shown in FIG. That is, the third
In the figure, the horizontal axis shows the load current I flowing through the load, and the vertical axis shows the load current I at time t that rises to I in a stepwise manner from a value below the minimum operating current I _b at which the relay can operate. In this case, it shows the elapsed time T from time t until the relay starts outputting an overcurrent signal. In Figure 3, Q, S ₁ ,
S ₂ , L ₁ , and L ₂ each show a different inverse time limit characteristic line, and as is clear from this figure, an overcurrent relay having such characteristics has a shorter operating time as the load current increases. T _q , T _S1 , T _S2 , W _L1 ,
T _L2 is the characteristic line Q corresponding to the load current I,
At points on S ₁ , S ₂ , L ₁ , L ₂ , in this case, for example (1)
It is set up so that there is an expression relationship. In other words, the relay operates gradually in the order of characteristic lines Q, S ₁ , S ₂ , L ₁ , and L ₂ for the same magnitude of load current.

T _S1 = 2・T _q , T _S2 = 4・T _q T _L1 = 8・T _q , T _L2 = 16・T _q ...(1) Figure 4 is the same as shown in Figure 3 using a microcomputer. This is a configuration diagram of a conventional overcurrent relay that operates with inverse time- _{limiting characteristics} . , L ₁ , and L ₂ , a large number of sets of data are stored. 2 is a setting circuit for selecting a characteristic line for selecting which characteristic line in FIG. 3 the microcomputer 1 should be operated according to. In the figure, a load current flowing through a motor, etc. is detected by a current detection circuit 3 such as a current transformer, and an analog signal _3a corresponding to the load current outputted from the current detection circuit 3 is converted into a digital signal by a signal conversion circuit 4. When the microcomputer 1 receives _the signal _4a , it operates according to the inverse time characteristic set in the setting circuit 2 and outputs the output signal _1a to the circuit 5. Output to. The output circuit 5 is, for example, a switch that performs an overcurrent protection operation on the load when the signal 1 _a is input.

[Problem to be solved by the invention]

The overcurrent relay shown in FIG. 4 operates as described above, and since the computer 1 stores inverse time characteristic data related to all the characteristic lines shown in FIG. By appropriately selecting the inverse time limit characteristic line, one relay can support overcurrent protection of many types of loads that require various time limit characteristics from short to long time limits. In such a relay, a large number of inverse time characteristic line data must be stored in the memory space of the microcomputer 1 for each characteristic line shown in Fig. It has the disadvantage that it requires storage space and cannot be easily handled by microcomputers with limited storage capacity.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to eliminate the drawbacks of the conventional overcurrent relay as described above, and to provide an overcurrent relay for use in a microcomputer that can perform many inverse time characteristic operations even with a small memory capacity. be.

[Means to solve the problem]

In order to achieve the above-mentioned object, the present invention includes a current detection circuit that detects the current flowing through a load, and a first digital signal that converts the output signal of the current detection circuit into a digital signal when a third signal or a preset signal is input.
a signal conversion circuit that converts the signal into a signal and outputs a second signal indicating completion of the signal conversion; a current/time conversion means that converts the first signal into a time data signal corresponding to the signal; A clock means that receives a data signal and starts a time counting operation upon input of the second signal and outputs a pulse-like time-up signal after a time corresponding to the time data signal has elapsed, and outputs a variable initial value signal. initial value generating means for outputting the preset signal by manual operation or by a fourth signal; and initial value setting means for outputting the preset signal by manual operation or by a fourth signal; The device includes a first counting section that counts the number of signals according to the input, and outputs the third signal every time the time-up signal is input when the count of the first counting section does not reach a predetermined value. death,
a first counting means for outputting a pulsed first count up signal to clear the counted content of the first counting unit when the counted content of the first counting unit reaches the predetermined value; The second counting section includes a second counting section for counting the number of pieces, and a set value storage means for storing a set value, and outputs the fourth signal every time the first count-up signal is input, and the second counting section a second counting means that outputs a second count-up signal when the counted content reaches the stored content of the set value storage means; and when the second count-up signal is input, an overcurrent protection operation is performed for the load. It is characterized by consisting of an output circuit.

[Effect]

In the overcurrent relay according to the present invention, by appropriately changing the initial value signal output from the initial value generating means, one type of inverse time characteristic line data stored in the storage means in the current/time converting means can be obtained. Even if the overcurrent relay corresponds to the characteristic line , it is possible to obtain an overcurrent relay that operates in the same manner as an overcurrent relay having a large number of inverse time limit characteristic lines.

〔Example〕

FIG. 1 is a block diagram showing an embodiment of the present invention. In the figure, when the third signal _9b or preset signal _11a is input, 6 converts the output signal _3a of the current detection circuit into a first signal _6a as a digital signal proportional to the load current and outputs it. A signal conversion circuit also outputs a second signal _6b indicating the end of signal conversion, and 7 is a current/time conversion means for converting the first signal _6a into a time data signal _7a corresponding to this signal. 7 is provided with a storage means _7b , and this storage means _7b stores, for example, combination data of time (T _q /N _n ) corresponding to the load current I according to the inverse time characteristic Q shown in FIG. When the signal 6 _a is input to the current/time converting means 7, the converting means 7 outputs the time (T _q /N _n ) corresponding to the load current I represented by the signal 6 _a . A time data signal _7a is output. Here, N _n is a positive integer representing a setting value set in the second counting means 12, which will be described later. N _n is a number set appropriately. 8
The second signal _6b and the time data signal _7a are inputted, and when the second signal _6b is inputted, the timekeeping operation is started, and after the elapse of time according to the time data signal _7a , a pulse-like signal is output. A clock means 10 outputs the time-up signal _8a to the first counting means 9, and 10 is an initial value generation means that outputs a 4-bit signal of hexadecimal E as an initial value signal _10a by means of a code switch, for example. is configured to be able to change the initial value signal _10a . Reference numeral 11 denotes an initial value setting means which is driven by manual operation or by inputting the fourth signal _12b and outputs the aforementioned preset signal _11a to the first counting means 9 and the signal conversion circuit 6. The first counting means 9 presets the initial value signal _10a by inputting the preset signal _11a , and adds the number of this signal to the preset value each time the time-up signal _8a is inputted. A first counting section 91 is provided, and the first counting means 9 includes a first counting section 91.
For example, when the addition content of 1 does not reach 0 from hexadecimal F, the third signal 9 _b is output every time the time-up signal 8 _a is input, and the first counting section 91
When the addition content reaches 0 from hexadecimal F, the pulse-like first count-up signal _9a is output to the second counting means 12, and at the same time, the addition content of the first counting section 91 is cleared. . The second counting means 12 receives the first count up signal 9 _a
a second counting section 121 which receives input signals and adds the number of the signals; and a set value storage means 122 in which the aforementioned set value N _n is stored by a setting mechanism 13 such as a switch. Every time the count up signal _9a is input, the fourth signal _12b is output to the initial value setting means 11, and the second counting section 12
When the addition content of 1 reaches the storage content of the set value storage means 122, the second count-up signal _12a is output to the output circuit 5. When the output circuit 5 receives the signal _12a , it performs an overcurrent protection operation for a load (not shown). 14 is a microcomputer in which each function of the above-mentioned current/time conversion means 7, time measurement means 8, first counting means 9 and second counting means 12 is provided in software;
are current detection circuit 3, output circuit 5, and signal conversion circuit 6
This is an overcurrent relay consisting of an initial value generating means 10, an initial value setting means 11, a setting mechanism 13, and a microcomputer 14.

Next, the operation of the overcurrent relay 15 will be explained with reference to the flowchart of FIG. 2. First, it is assumed that the first counting section 91 has a 4-bit configuration, and that N _n =256 is set in the set value storage means 122 after a power-on operation, which will be described later. SCT and ACT are symbols representing the first counting means 9 and the second counting means 12, respectively. In the relay 15, when the power is turned on, the addition contents of the second counting section 121 are automatically cleared in step 21, and then the hexadecimal number E set by the initial value generation means 10 is cleared in steps 22 and 23. The initial value signal _10a consisting of a bit signal is read by the preset signal _11a from the initial value setting means 11, and the hexadecimal number E is preset in the first counting section 91 in step 24. At the same time, in step 25, the signal conversion circuit 6 A/D conversion is performed in which signal 3 _a is converted to signal 6 _a ,
In step 26, the current/time converting means 7 outputs a time data signal _7a corresponding to the load current I, and in step 27, the time measuring means 8 starts a time measuring operation. When the timer 8 outputs the time-up signal _8a after the elapse of time (T _q /N _n ), the process proceeds to step 28.
At this point, 1 is added to the first counting means 9, and at this time, the content of the first counting section 91 becomes F in hexadecimal. Therefore, the process returns from step 29 to step 25, and the signal conversion circuit 6 again changes the third signal _9b to the first one. Since the signal is input from the counting means 9, an A/D conversion operation is performed, and after a further time (T _q /N _n ) has elapsed, a second time-up signal 8 _a is output from the clocking means 8 . in this case,
Since the value of the load current detected by the current detection circuit 3 prior to A/D conversion is not necessarily the same in the first case and the second case, the time in the first case is
T _q may be different from the time T _q in the later case,
This result does not necessarily match the time (T _q /N _n ) in the previous case. When the second time-up signal _8a is input to the first counting section 91, the content of the counting section 91 changes from hexadecimal number F to 0, so the first count-up signal _9a is output from the first counting means 9. At the same time, the contents of the first counting section 91 are cleared, and as a result, the contents of the second counting section 121 are increased by 1 in step 30, and the count value of the second counting means 12 has reached the set value in step 31. If it is determined that there is no preset signal, the process proceeds to step 24, where the fourth signal _12b is inputted from the initial value setting means 11, so that the preset signal _11a is output.
The initial value of the hexadecimal number E is preset in the first counting section 91 again. In step 31, the second counting means 12
When it is determined that the count value has reached the set value, the second count-up signal _12a is output. Since each part of the overcurrent relay 15 operates as described above, the content of the second counting part 121 increases by 1 every time two time-up signals _8a are output from the clocking means 8, and as a result, the content of the second counting part 121 increases by 1. The second count-up signal _12a outputted from the second count-up signal 12a is outputted in accordance with the inverse time limit characteristic _S1 shown in FIG.

In the above explanation, from the initial value generation means 10
The hexadecimal number E is output as the initial value, but if this initial value is changed appropriately, the second count-up signal _12a can be outputted according to any of the characteristics Q, S ₂ , L ₁ , and L ₂ shown in FIG. It is clear that it can be output. That is, in the overcurrent relay 15, the storage means 7 _b in the current/time conversion means 7
Even if the inverse time characteristic data stored in the memory corresponds to only one type of characteristic line _Q in FIG. It is possible to perform the same operation as an overcurrent relay having a time-limiting characteristic line, and as a result, even an overcurrent relay having many inverse time-limiting characteristics can be manufactured using a microcomputer with a small memory capacity. become.

In the above description, it is assumed that input pulses are added to both the first and second counting sections 91 and 121, but subtraction is performed each time a pulse is input to both or one of both counting sections. It is clear that these counting sections may be configured in any of the following ways. Also,
Second counting section 121 in second counting means 12
The set value storage means 122 may be replaced with a single counting means having the functions of both the counting section 121 and the storage means 122, which sequentially subtracts from the set value each time a pulse is input, for example. It's good.

[Effects of the Invention] As explained above, the present invention includes a current detection circuit that detects the current flowing through a load, and a circuit that converts the output signal of the current detection circuit as a digital signal when a third signal or a preset signal is input. The second signal is converted to the first signal and output, and the second signal indicates the end of the signal conversion.
a signal conversion circuit that also outputs a signal; a current/time conversion circuit that converts the first signal into a time data signal corresponding to the signal; a timekeeping means that starts a timekeeping operation and outputs a pulse-like time-up signal after a time elapsed according to the time data signal; an initial value generation means that outputs a variable initial value signal; initial value setting means that is driven by the preset signal and outputs the preset signal;
A first counting section is provided in which the initial value signal is preset by inputting the preset signal and the number of the signals is counted by inputting the time-up signal, and the count content of the first counting section is set to a predetermined value. When the time-up signal does not reach the predetermined value, the third signal is outputted each time the time-up signal is input, and when the count content of the first counting section reaches the predetermined value, a pulse-like first count-up signal is outputted. The first count-up signal includes a first counting means for clearing the count contents of the first count-up signal, a second counting section for counting the number of the first count-up signals, and a set value storage means for storing the set value. outputting the fourth signal each time a signal is input;
and a second counting means for outputting a second count-up signal when the count content of the second counting unit reaches the memory content of the set value storage means; By configuring an overcurrent relay with an output circuit that performs an overcurrent protection operation, the initial value signal output from the initial value generation means can be changed appropriately to be stored in the storage means of the current/time conversion means. Even if the inverse time characteristic data corresponds to one type of characteristic line, it is possible to obtain a relay that operates in the same way as an overcurrent relay that has multiple inverse time characteristic lines. Even if a computer is used, it is possible to obtain an overcurrent relay having a large number of inverse time-limiting characteristics.

[Brief explanation of drawings]

1 and 2 are a block diagram and a flowchart showing the operation of an embodiment of the present invention, FIG. 3 is a diagram explaining the inverse time characteristic of an overcurrent relay, and FIG. 4 is a block diagram of a conventional overcurrent relay. It is. 3... Current detection circuit, 5... Output circuit, 6...
Signal conversion circuit, _6a ...first signal, _6b ...second signal, 7...current/time conversion means, _7a ...time data signal, 8...timekeeping means, _8a ...time-up signal, 9...First counting means, _9a ...First count up signal, _9b ...Third signal, 10...Initial value generation means, _10a ...Initial value signal, 11...
Initial value setting means, _11a ...Preset signal, 1
2... Second counting means, 12 _a ... Second count up signal, 12 _b ... Fourth signal, 15... Overcurrent relay, 91... First counting section, 121... Second counting section, 122 ...Setting value storage means.

Claims (1)

[Claims] 1 A current detection circuit that detects the current flowing through the load, and when a third signal or preset signal is input, converts the output signal of the current detection circuit into a first signal as a digital signal and outputs it, and also terminates the signal conversion. a signal conversion circuit that also outputs a second signal representing the signal; a current/time conversion circuit that converts the first signal into a time data signal corresponding to the first signal; a timekeeping means that starts a timekeeping operation in response to an input and outputs a pulse-like time-up signal after a time period corresponding to the time data signal has elapsed; an initial value generation means that outputs a variable initial value signal; initial value setting means that is driven by a signal and outputs the preset signal; the initial value signal is preset by input of the preset signal, and the number of the signals is counted by input of the time-up signal; a first counting section; when the counting content of the first counting section does not reach a predetermined value, the third signal is output every time the time-up signal is input; a first counting means that outputs a pulse-like first count-up signal when a predetermined value is reached to clear the counting contents of the first counting section; and a second counting section that counts the number of the first count-up signals. a set value storage means that stores a set value, outputs the fourth signal every time the first count-up signal is input, and the count contents of the second counter are stored in the set value storage means. It is characterized by comprising a second counting means that outputs a second count-up signal when the content is reached, and an output circuit that performs an overcurrent protection operation for the load when the second count-up signal is input. Overcurrent relay.