JP2010257657A - Molded-case circuit breaker for counting duration of excess current - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely protect a wiring path from heating, by keeping changes of a line current as a history in the duration of an excess current to early actuate a cutoff mechanism. <P>SOLUTION: In an electronic molded-case circuit breaker, a CPU determines the excess current based on the detected value of the line current, accumulates the duration of the excess current, and opens a main contact by actuating a trip coil when the accumulated value reaches an upper limit value. When the line current increases, the duration is accumulated by an addition coefficient, and when the line current decreases, the accumulated value during the increase is accumulated by two subtraction coefficients. In an initial section of the decrease, the first substraction coefficient having a large value is applied, and after that, the second substraction coefficient having a small value is used. The addition coefficient is set at a value smaller than the first substraction coefficient and larger than the second subtraction coefficient, and the accumulated value of the duration is made approximate to the temperature change in an electric wire. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an electronic circuit breaker that determines overcurrent by a CPU based on a detected value of line current and counts the duration of the overcurrent.

  2. Description of the Related Art Conventionally, a circuit breaker for wiring is known in which a CPU performs overcurrent determination, overcurrent continuation time counting, and interruption mechanism control. For example, the circuit breaker described in Patent Document 1 detects a line current with a current transformer, the CPU determines an overcurrent based on the output of the current transformer, counts the duration, and the count value is the upper limit. When reaching the value, a trip command is output to the interruption mechanism, and when the line current becomes lower than the lower limit value, the count value of the duration is reset to zero.

Japanese Patent Laid-Open No. 11-205999

  However, according to a conventional circuit breaker for wiring, when the line current becomes lower than the lower limit value, the overcurrent duration is reset to 0, so that the current change up to that time cannot be left as a history. For this reason, the energized state in which the line current repeats ascending, descending, ascending and so on cannot be regarded as abnormal, the timing for operating the shut-off mechanism is delayed, and the wires in the wiring path are sufficiently separated from heat generation. There was a problem that it could not be protected.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a circuit breaker capable of reliably protecting a wiring path from heat generation by leaving a change in line current as a history during the overcurrent duration, operating the breaking mechanism early. .

  In order to solve the above-mentioned problems, the present invention provides an interrupting mechanism for determining an overcurrent by a CPU based on a detected value of a line current, counting a duration of the overcurrent, and when the duration reaches an upper limit value. In the circuit breaker for wiring that operates, the following configuration is adopted.

(1) The CPU accumulates the duration of the overcurrent with a predetermined addition coefficient when the line current increases, and accumulates the accumulated value with the predetermined subtraction coefficient when the line current decreases. Wiring circuit breaker.

(2) The subtraction coefficient includes a first subtraction coefficient used at the beginning of the drop of the line current and a second subtraction coefficient used thereafter, and the first subtraction coefficient is set to a value larger than the second subtraction coefficient. A circuit breaker for wiring.

(3) The circuit breaker for wiring, wherein the addition coefficient is set to a value smaller than the first subtraction coefficient and larger than the second subtraction coefficient.

  According to the circuit breaker of (1) above, the CPU switches the addition coefficient and the subtraction coefficient alternately in accordance with the rise and fall of the line current, and continuously accumulates the overcurrent duration. The change of the line current is left as a history in the accumulated value of the above, and the interruption mechanism is operated at an early stage so that the wiring path can be reliably protected from heat generation.

  According to the circuit breaker of (2) above, the first subtraction coefficient having a large value is used at the beginning of the fall of the line current and the second subtraction coefficient having a small value is used thereafter. An approximate cumulative value is obtained, and the shut-off mechanism can be operated at an appropriate timing.

  According to the circuit breaker of (3) above, since the addition coefficient is set to a value that is smaller than the first subtraction coefficient and larger than the second subtraction coefficient, the total that approximates both the rise characteristic and the drop characteristic of the wire temperature. A value is obtained and the shut-off mechanism can be operated at a more appropriate timing.

It is a block diagram of the circuit breaker for wiring which shows one Embodiment of this invention. It is a flowchart which shows the total procedure and interruption | blocking method of overcurrent continuation time. It is a graph which shows the correlation of an energization state, the cumulative value of overcurrent continuation time, and electric wire temperature. It is a graph which shows the correlation of the energization state in which a line current changes repeatedly, and a cumulative value.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 1, in the circuit breaker 1 for wiring, the trip coil 2 and its drive circuit 3 constitute a breaking mechanism that opens the main contact 5 of the single-phase three-wire wiring path 4. The wiring path 4 is provided with a current sensor 6 that detects a line current flowing through the electric wires (X, Y, N), and a power supply circuit 8 that supplies an operating voltage to the CPU 7.

  The CPU 7 is provided with an A / D conversion unit 10, a control program 11, a data storage unit 12, and an arithmetic control unit 13. The A / D conversion unit 10 converts the analog signal input from the current sensor 6 into a digital signal and transmits the digital signal to the arithmetic control unit 13. The data storage unit 12 stores various parameters such as a rated current value for current determination, an addition coefficient and a subtraction coefficient for cumulative duration, and an upper limit value for setting a cutoff timing.

  Then, the arithmetic control unit 13 determines an overcurrent based on the detected value of the line current and the rated current value according to the control program 11, accumulates the duration of the overcurrent using the addition coefficient and the subtraction coefficient, and measures the time counter 14 When the cumulative value reaches the reference value, the trip coil 2 is operated via the drive circuit 3 and the interruption state of the wiring path 4 is displayed on the display unit 15.

  Next, a cumulative procedure of overcurrent duration and a method of interrupting the wiring path 4 will be described. As shown in FIG. 2, when the main contact 5 is closed by a manual operation handle (not shown), the CPU 7 starts the control program 11, and first initializes the value of the time counter 14 (S1). Next, the detected value of the line current is input from the current sensor 6, the detected value is compared with the rated current value, and the overcurrent of the wiring path 4 is determined (S2).

  Subsequently, the rise or fall of the line current is determined based on the output of the current sensor 6 (S3), and the continuation time of the overcurrent is accumulated with a predetermined addition coefficient at the time of rise (S4). When the cumulative value reaches a preset upper limit value (for example, 100 counts shown in FIG. 3) (S5), a trip command is output to the drive circuit 3, the trip coil 2 is operated, and the main contact 5 Is released (S6).

  On the other hand, when the line current is lowered, the cumulative value of the duration time obtained at the time of rise is accumulated with two subtraction coefficients. That is, in the initial fall period (see FIG. 3) immediately after the line current has changed from the rise to the fall (see FIG. 3), the duration obtained at the rise is accumulated by the first subtraction coefficient (S7 → S8), and the initial fall period is completed. Later, the duration is subsequently accumulated with the second subtraction coefficient (S7 → S9).

  When the accumulated value becomes 0, the accumulation of the duration time is finished (S10 → end), and when the accumulated value remains, the process returns to the overcurrent determination process (S10 → S2). Thereafter, the cumulative value obtained when the line current decreases is increased when the line current is increased, the cumulative value determined when the line current is increased is decreased when the line current is decreased, and a series of processes is repeated to continue monitoring the wiring path 4.

  Here, the cumulative value of the overcurrent duration is along a straight line L1 having a gradient corresponding to the addition coefficient in the period from the determination of the overcurrent to the opening of the main contact 5, as exemplified by one model in FIG. In the period from when the main contact point 5 is opened until the main contact point 5 becomes 0, it gradually increases along the straight line L2 corresponding to the first subtraction coefficient, and then reaches the straight line L3 corresponding to the second subtraction coefficient. Decrease along.

  The absolute values of the three coefficients are set such that the first subtraction coefficient> the addition coefficient> the second subtraction coefficient so that the change in the cumulative value approximates the temperature change of the electric wire. For example, an addition coefficient of 0.07 counts / second is applied when the line current rises, a first subtraction coefficient of 0.2 counts / second is applied to the initial fall of the line current, and then 0.006 counts / second. The second subtraction coefficient can be applied.

  Note that the initial fall period to which the first subtraction coefficient is applied can be set to, for example, about 0.1 hour (6 minutes) in accordance with the time when the wire temperature rapidly drops immediately after the main contact 5 is opened. The temperature change shown in FIG. 3 is a temperature change of the triplex-type vinyl insulated wire CVT 22 mm having an allowable temperature of 90 ° C.

  In the circuit breaker 1 of this embodiment, as shown in FIG. 4, the CPU 7 alternately switches the addition coefficient and the subtraction coefficient as the line current increases and decreases, and continuously accumulates the overcurrent duration. Calculate. For this reason, the change in the line current is left as a history in the cumulative value of the continuous time, and the cumulative value is quickly led to the upper limit value in an energized state where the rise and fall are repeated, and the trip coil 2 is operated early, and the overcurrent The amount of heat generated by the wire can be suppressed. In addition, since the values of the three coefficients are set so that the first subtraction coefficient> the addition coefficient> the second subtraction coefficient, the cumulative value of the duration time is approximated to the temperature change of the electric wire, and the trip coil 2 is operated at the optimum time. It can also be made.

  In addition, this invention is not limited to the said embodiment, For example, it applies to the circuit breaker of a single phase 2 wire type or a 3 phase 3 wire type, or the value of an addition coefficient and a subtraction coefficient is appropriate. It is also possible to change the configuration of each part without departing from the spirit of the invention, such as changing.

DESCRIPTION OF SYMBOLS 1 Circuit breaker 2 Trip coil 3 Drive circuit 4 Wiring path 5 Main contact 6 Current sensor 7 CPU

Claims (3)

On the basis of the detected value of the line current, the CPU determines the overcurrent, counts the duration of the overcurrent, and when the duration reaches the upper limit value,
The CPU accumulates the overcurrent duration with a predetermined addition coefficient when the line current increases, and accumulates the accumulated value at the time of increase with a predetermined subtraction coefficient when the line current decreases. Circuit breaker for wiring.   The subtraction coefficient includes a first subtraction coefficient used at the beginning of the fall of the line current and a second subtraction coefficient used thereafter, and the first subtraction coefficient is set to a value larger than the second subtraction coefficient. The circuit breaker for wiring according to 1.   The circuit breaker according to claim 2, wherein the addition coefficient is set to a value smaller than the first subtraction coefficient and larger than the second subtraction coefficient.

Images