JPH04105512A - Electronic switchgear - Google Patents

Abstract

PURPOSE:To limit a current due to a trouble of a circuit such as a short-circuit by opening first electronic switching means when the amplitude of a current signal is larger than a first predetermined value, and opening second electronic switching means when the amplitude of the signal is larger than a second predetermined value after the first means is opened. CONSTITUTION:A load current I flowing to a breaker is converted to a voltage signal by a current sensor 16, and input to a terminal M. The voltage is compared with a voltage of an IS value setter 22 by a comparator 21, and in the case of I>IS, the comparator 21 generates a signal to a discrimination circuit 67. The discrimination circuit 67 judges that a current flowing to the breaker is a rated current or more based on the signal, and outputs a transistor open signal to terminals N, S, T, U after T1 [s], T2 [s], T3 [s], T4 [s], respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electronic switching device for switching on and off an electric circuit.

[Conventional technology]

Figures 6 and 7 are, for example, "PESC75 RECORD J No. 151-160"
D. E. Baker (D, E.
, Baker), “Three Types of Solid State Remote Power Controllers (THREE TYPES OF 5OLID 5T)”
ATE REMOTE POWERC0NTR0L-L
This figure shows a semiconductor circuit breaker (hereinafter referred to as a circuit breaker), which is a conventional electronic switchgear in the ER3). Figure 6 is an overall circuit diagram, and Figure 7 is a block diagram of a trip control circuit. , (1) is a DC power supply, (2) is a load supplied with power from this DC power supply (1), and (3) is inserted between the positive terminal P of the DC power supply (1) and the terminal load P1 on the load (2) side. The first transistor (2) is an electronic switching means for switching the load current.
), the second transistor (51) is connected to the base B of this second transistor (a) and supplies its base current IB3, (51 is the third transistor connected to this second transistor (a) and supplied with its base current IBI, and (6) is this Third transistor (9
a first resistor connected to limit the base current IBI, (
7) is a second resistor connected to the third transistor (5) to limit its base current IB2; 8 is a normal control circuit and a trip control circuit (20) for controlling the base current IB2 of the third transistor (5); A base drive control circuit (9) is connected to this base drive control circuit (9), and the base drive control circuit (9) is connected to the base drive control circuit (9) to control the base drive when a circuit breaker opening/closing signal is supplied from the outside. a fourth transistor, (10) supplying a switching signal to the circuit diagram;
~(15) is the base current IB in the first transistor (3)
(10) is a transformer, (11) and (12) are the components for the base drive power supply for supplying the transformer (10). The transistor (13) is the transistor (11), (12)
) and the fourth transistor θ), the third resistors (14) and (15) are connected between the secondary side of the transformer (10) and the second
These are first and second diodes connected between the transistor (4). (16) is a current sensor connected between the DC power supply (1) and the first transistor (3), which detects the current flowing in the main circuit and outputs a voltage signal proportional to the current in parentheses.

Next, the operation of the circuit breakers shown in FIGS. 6 and 7 will be explained with reference to the trip curve shown in FIG.

In the conventional circuit breaker, it is assumed that the load (2) is the rated load. When a circuit breaker close signal is supplied from the outside to the base of the fourth transistor (9), the fourth transistor (9) becomes conductive and one end of the third resistor (13) reaches the potential of the N side of the DC power supply (1). On the other hand, the fifth and sixth transistors (11)
, (12) are input with switching signals alternately at a predetermined period from a signal source (not shown), and one end of the third resistor (13) becomes the N-side potential of the DC power supply (1). As a result, an alternating voltage is generated in the transformer (10). This AC voltage is applied to the first and second diodes (14) and (15).
The current is converted into a direct current by , and is supplied between the emitter of the second transistor 4 and the collector C of the first transistor G). Further, when the fourth transistor (9) becomes conductive, a circuit breaker closing signal is input to the terminal of the base drive control circuit 6, and a base current IB2 flows through the third transistor (5) by the base drive control circuit (to). This base current IB2 makes the third transistor (5) conductive, and the base current IBI flows through the second transistor (a). This base current IBI makes the second transistor (a) conductive, and the base current IB3 flows through the first transistor (a).
is conductive, and current flows from the DC power supply (1) to the load (2). That is, at this time, the circuit breaker is closed, and the base drive control circuit (5) supplies sufficient base current IB3 so that the first transistor (31) operates in the saturation region.

Also, when the circuit breaker open signal is supplied, the fourth transistor (
9) is opened, and by inputting this open signal to the terminal of the base drive control circuit (2), the base drive control circuit 6 makes the value of the base current IB2 of the third transistor (to) zero. As a result, the third transistor (b) becomes open, and subsequently the second and first transistors (a) and [3] also become open. At this time, the value of the current flowing through the circuit breaker becomes zero, and the circuit breaker is opened.

Next, the operation when the current (2) flowing through the load (2) exceeds the rated current Is (overcurrent) will be described.

The trip curve in Figure 8 shows the relationship between the current flowing through the circuit breaker and the trip time at that current.
The dotted line is the trip curve of the circuit breaker's required specifications, but in the actual machine, an approximate trip curve shown by the solid line is used for manufacturing reasons.For example, in the trip curve shown by the solid line, which is an approximate characteristic, Current I=16
At [A], the trip time T is 0.02 (s). The relationship between the trip time T and the current I is specified as the characteristic shown by the dotted line in the figure, that is, T = 5/(I2-
62), and in the actual machine, this is changed to the relational expression %) to have the characteristics shown by the solid line.

Here, approximate relational expression T=0.025 (25-I)/
(I-6) is realized by the trip control circuit (2o) of the base drive control circuit (to) shown in the block diagram of FIG. Details will be explained below with reference to the block diagram of FIG. 7 and the flowchart of FIG. 9. The difference between the load current obtained as the output voltage signal of the current sensor (16) and the rated current value (IS> set in advance as a voltage signal by the IS value setter (22)) is determined by the comparator (21) in a comparative step. 1), load current I is rated current value I
If S has not been exceeded, return to the original start; if it has exceeded S, start the timer (23) and measure the elapsed time t (step 2);
) by subtracting the current ■ from the set value B (constant) of the signal B-I.
is output to the amplifier (26), and the amplifier (26) multiplies the set value of the A value setter (27) by A (constant) to produce the signal A (B
-I) is output. Also, the adder (28) adds the current I
Subtract the set value C (constant) of the C value setter (29) from
A signal I-C is output to a divider (30).

The divider (30) calculates the trip time TS=A (B-I)/(I-C) based on the inputs A(B-I) and I-C from the amplifier (26) and adder (28). The 0 time comparator (31) calculates and outputs (step 3) the timer (2
The elapsed time t from 3) is compared with the trip time TS from the divider (30) (step 4), and if t>TS, a circuit breaker trip signal is output (step 5).

In case of overcurrent, the base drive control circuit (8) operates as described above and opens the first transistor (3).

If we compare the relational expression between the actual machine and the specifications, we can see that the actual machine does not include a multiplication (square) term in the denominator, so when this relational expression is realized in an electric circuit, the circuit can be simplified. It also has characteristics such as being less affected by temperature drift.

[Problem to be solved by the invention]

However, the conventional circuit breaker is configured as above,
When the current flowing through the load exceeds the rated current, the trip time TS = A (
The circuit for determining B-I)/(I-C) requires a divider (30) because it includes a dividing element, and the configuration of the trip control circuit (20) becomes complicated; Additionally, there were other problems such as difficulty in adjusting the trip curve.

Furthermore, when a large current flows due to, for example, a short circuit in a circuit, a current of 10 times or more of the rated value may flow until the circuit breaker enters the breaking operation, and then the circuit breaker performs the breaking operation. In this case, there is a problem in that when an instantaneous large current flows to a circuit breaker higher up than the current circuit breaker, the circuit breaker at the higher end reacts to the large current and performs an unnecessary breaking operation. For example, as shown in the main circuit configuration diagram in Figure 10, an excessive current flows due to a failure such as a load short circuit in the circuit of the lower-order circuit breaker (41).
) performs the interrupting operation at the same time, other circuit breakers (42), (
43) etc., there was a problem in that even normal circuits that were supplied with power were cut off.

This invention was made to solve the above-mentioned problems, and the control device has a simple configuration and is easy to adjust.
It is an object of the present invention to provide an electronic switching device that can prevent excessive current from flowing by performing current-limiting operation even in the event of a circuit failure such as a short circuit.

[Means to solve the problem]

The electronic switching device according to the present invention connects the first electronic switching means and the second electronic switching means in parallel via a resistor, obtains a current signal according to the load current by the current detection means,
Based on the difference between the current signal and a predetermined value, the control device opens the first electronic switching means when the magnitude of the current signal is larger than the first predetermined value, and after opening the first electronic switching means, the current The second electronic switching means is opened when the magnitude of the signal is larger than a second predetermined value.

[Effect]

In this invention, when the first electronic switching means is opened, the load current flows through the series circuit of the second electronic switching means and the resistor, and is limited by the resistor.

Therefore, it is possible to prevent excessive current from flowing.

By selecting the resistance value of the resistor, arbitrary current limiting characteristics can be obtained.

Note that when the load current is larger than the second predetermined value after the first electronic switching means is opened and the load current is limited, the electronic switching device is switched on by opening the second electronic switching means. to open.

In addition, the comparison of the load between the magnitude of the flow and the predetermined value is performed based on the difference between the two, rather than by division, and since no arithmetic means for division is required, the configuration of the control device is simple and adjustment is easy. .

〔Example〕

1 and 2 show an embodiment of the present invention. FIG. 1 is a circuit diagram showing the overall configuration, and FIG. 2 is a circuit diagram showing the main circuit switching section. 50) is the main circuit opening/closing part, and (51) to (53) are the first circuit switching parts in this embodiment.
Transistors (54) to (56) are electronic switching means added to transistor e), and transistors (51)
~ (53) is a resistor that limits the collector current, and the first
Transistor (51) on collector C of transistor B)
The collector C of ~(53) is connected, and the emitter E of the first transistor (31) is connected to the transistor (51)~(53).
The emitter E of is connected to each resistor (54) to (56) as shown in Figure 2.
) to form a main circuit switching section (50). In addition, S.

T and U are base terminals of each transistor (51) to (53).

(60) is a trip control circuit, which is configured as follows. 61) to (63) are current value setters,
Predetermined current values 114, 113°112 (I 14
>I 13 > I 12) (described later). (64) to (66) are comparators, which compare the voltage value corresponding to the current value detected by the current sensor (16) and the set value of each current value setter (61) to 63). A signal is generated when I exceeds the set values 114 to 112, respectively. (67) is a discrimination circuit, a comparator, (
Based on the signals of 21), (64) to (66) and the circuit breaker closing signal sent to the terminal by the fourth transistor (9), each transistor [31, (51) to (
53) is issued (details will be described later).

Since the other configurations are the same as those of the conventional example shown in FIG. 6, corresponding parts are given the same reference numerals and explanations will be omitted.

Next, the operation will be explained with reference to the trip curve shown in FIG. 3 and the waveform diagrams shown in FIGS. 4 and 5.

When the load (2) is in a normal state and the load current is less than the rated current IS, which is the first predetermined value, when a circuit breaker close signal is supplied from the outside to the base of the fourth transistor (9), the base A circuit breaker close signal is input to the terminal of the drive control circuit 8, and a transistor close signal is output to the terminals N, S, T, and U by the discrimination circuit (67). When a transistor close signal is output to the terminal N, the first transistor (31) becomes conductive as in the conventional example described above.Furthermore, when a transistor close signal is output to the terminals S, T, and U, the transistors (51) to
(53) becomes conductive. As a result, the circuit breaker is closed, and load current flows from the DC power supply (1) to the load (2). In this case most of the current flows through the first transistor B).

Further, when the circuit breaker open signal is supplied, the fourth transistor θ) is opened, and the circuit breaker open signal is input to the terminal of the base drive control circuit 6, and the determination circuit (67) determines the terminal N.
, S, T, and U are output with transistor open signals. When a transistor open signal is output to the terminal N, the first transistor (3) is opened as in the conventional example described above. Also, terminal S
, T, and U, transistors (51) to (53) are opened. As a result, the value of the current flowing through the circuit breaker becomes zero, and the circuit breaker is opened.

Next, an explanation will be given of the operation when the load current I flowing through the load (2) exceeds the rated current IS, for example, when the load is short-circuited.

In FIG. 3, the dotted line is the trip curve of the circuit breaker specifications, and the stepped solid line is the trip curve of this embodiment.

Here, the time domain after exceeding the rated current IS is defined as O~T.
lC5], Tl~T2[s], T2~T3[s], T3
It is divided into four parts: ~T4 [s].

The load current flowing through the circuit breaker is converted into a voltage signal by a current sensor (16) and input to terminal M. This voltage and the voltage of the IS value setter (22) are compared by the comparator (21), and when I>Is, the comparator (21) issues a signal to the discrimination circuit (67). , Based on this signal, it is determined that the current flowing through the circuit breaker is higher than the rated current, and Tl is applied to terminals N, S, T, and U, respectively.
After [s:], T2 [s], T3 [s], and T4 [S], a transistor open signal is output. The details of the operation at each time will be explained below with reference to the waveform diagrams of FIGS. 4 and 5.

(a) Discrimination circuit after T1 [S] after exceeding the rated current IS (
A transistor open signal is output from terminal N of (67).
(point a in FIG. 4(b)), the first transistor (3) becomes open. In this case, the current I4 flowing through the circuit breaker is the sum of the currents flowing through the transistors (51) to (53), and the resistance values of the resistors (54) to (56) are R1°R2,
If R3 and the power supply voltage are E, then l4-E (1/R
1+1/R2+1/R3) (point a in FIG. 4(a)).

(b) After T2 (s) after exceeding the rated current IS, a transistor open signal is output from the terminal S of the discrimination circuit (67) (point b in Fig. 4(c)), so the transistor (51
) becomes open. The current I3 flowing through the circuit breaker in this case is:
This is the sum of the currents flowing through the transistors (52) and (53), and the current is limited to a current 3 expressed by I3=E (1/R2+1/R3) (point b in FIG. 4(a)).

(c) After T3[:s] after exceeding the rated current IS, a transistor open signal is output from the terminal T of the discrimination circuit (67) (point c in Fig. 4(d)), so the transistor (52
) becomes open. In this case, the current flowing through the circuit breaker 2 is:
Only the current flows through the transistor (53), and l2=
The current is limited to the current wire 2 indicated by E/R3 (Fig. 4 (a)
) point c).

(d) After T4 (s) after exceeding the rated current IS, a transistor open signal is output from the terminal U of the discrimination circuit (67) (point d in Fig. 4 (e)), so the transistor (53)
As a result, the value of the current flowing through the circuit breaker becomes zero, and the circuit breaker becomes open (point d in FIG. 4(a)).

(e) If the load current returns to below the rated value on the way to T4 (s) The current sensor (16), current value setter (61) to (63) indicates that the load current I has returned to below the rated current IS. ), comparators (64) to (66), and discrimination circuit (67). For example, in FIG. 5, the current ■ flowing through the circuit breaker is limited to ■4 after Tl (s) (a) point a)
When the load (2) returns to the rated load after , T5(S) (T5>T2> (point e in Figure 5(a)), the current 114 flowing through the circuit breaker is as follows, assuming the rated load resistance value is RL. 114
≦E/ (RL+1/ (1/R1+1/R2+1/R
3)).

Therefore, the setting value of the current value setter (61) is set to 114, which is the value of the above formula.
Set to . The comparator (64) causes the current sensor (16
) is compared with the set voltage of the current value setter (61), and when I<I 14, a signal is input to the discrimination circuit (67).

Based on this signal, the determination circuit (67) determines that the load current I has returned to the rated current IS or less, and the terminals N, S, T,
Output the transistor close signal (continuous) to U (Fig. 5 (
b) Point e and FIGS. 5(C) to (d)).

The above explanation is for the case where the current flowing through the circuit breaker is limited to 114, but even when the current limit value is 13°112, the discrimination circuit (67) is ) to determine that the current is below the rated current, and connect terminals N, S, T, and U.
Outputs a transistor close signal (continuous) to

Here, the current value setters (62) and (63) are set to the following values 113 and 112, respectively.

I 13=E/ (RL+1/ (1/R2-+-1/
R3)) I 12=E/ (RL+R3) In addition, in the above embodiment, a case was described in which the time domain after exceeding the rated current IS was divided into four, but the trip curve of the actual machine is In order to get as close as possible to , the number of divisions may be further increased to increase the degree of approximation, or conversely, the number of divisions may be decreased to lower the degree of approximation for simplification.

Note that the first transistor (3) in the embodiment shown in FIG. 2 is an example of the first electronic opening/closing means of the present invention, and the transistor (53) is an example of the second electronic WIA closing/closing means. , the first predetermined value and the second predetermined value were selected as the same rated current value IS, but the main circuit switching section (50 ),
Configure the trip control circuit (60) (for example, comparator (21)
), a plurality of IS value setters (22) may be provided), and in the above embodiment, the electronic switching means is a transistor, but a thyristor, GTO or other electronic switching means may be used. However, the same effect can be achieved.

Further, the electronic switching device is not limited to a circuit breaker, but may be another switching device.

〔Effect of the invention〕

As described above, according to the present invention, the current detection means obtains a current signal according to the load current, and the control device determines the magnitude of the current signal based on the difference between the current signal and the first predetermined value. When the magnitude of the current signal is larger than a second predetermined value, the first electronic switching means is opened, and after opening the first electronic switching means, when the magnitude of the current signal is larger than a second predetermined value, the second electronic switching means is opened. Therefore, by selecting the resistance value of the resistor, arbitrary current limiting characteristics can be obtained, and excessive current can be prevented from flowing.

Furthermore, since the magnitude of the load current and the predetermined value are compared based on the difference between the two, rather than by division, the configuration of the control device is simple and adjustment is easy.

[Brief explanation of the drawing]

Figures 1 and 2 show an embodiment of the present invention. Figure 1 is a circuit diagram showing the overall configuration, Figure 2 is a circuit diagram showing the main circuit switching section, and Figure 3 is a circuit diagram showing the main circuit switching section. The trip curve of one embodiment, FIGS. 4 and 5 are waveform diagrams for explaining the operation of one embodiment of the present invention, and FIGS. 6 to 9 show a conventional circuit breaker. 6 is an overall circuit diagram, FIG. 7 is a block diagram of the trip control circuit, FIG. 8 is a trip curve, and FIG. 9 is a flowchart showing the operation of the trip control circuit.
FIG. 10 is a main circuit configuration diagram showing an example of circuit breaker connection. In the figure, (1) is the DC power supply, (2) is the load, and (3)
is the first transistor, (21), (64) to (66) are comparators, (22) is the IS value setter, (50) is the main circuit switching section, (51) to (53) are transistors, (54) )~
(56) is a resistor, (61) to (63) are current value setters,
(67) is a discrimination circuit. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims] A first electronic switching means inserted between a power supply and a load and through which a load current flows; a second electronic switching means connected in parallel to the first electronic switching means via a resistor; and the load current. current detection means for generating a current signal in response to the current signal; and based on the difference between the current signal and a first predetermined value, when the magnitude of the current signal is larger, the first electronic switching means is opened; An electronic switching device comprising: a control device that opens the second electronic switching means when the magnitude of the current signal is larger than a second predetermined value after opening the first electronic switching means.