JPH0556094B2 - - Google Patents

Description

[Detailed Description of the Invention] (a) Field of Application The present invention relates to circuit breakers and breakers, and in particular, detects current by using an air-core current transformer and an electronic circuit provided in the circuit breakers and performs delayed operation. The present invention relates to a tripping device for a circuit breaker, which performs the following operations and drives a trip coil for a tripping operation.

(b) Prior Art For example, the configuration shown in FIG. 5 is known as a circuit breaker. In FIG. 5, reference numeral 1 indicates the input terminal of the circuit breaker and 2 indicates the output terminal, respectively.
The input terminal 1 and the output terminal 2 are connected by an internal conductor 3 via a contact 4 of a switch. This contact point 4
is opened or closed by an opening/closing mechanism 5, and the opening/closing mechanism 5 is further operated by a trip coil 6.

The tripping device provided in the circuit and disconnector is configured as follows. That is, the inner conductor 3
The current flowing through the current is detected as a voltage proportional to the current by air-core current transformers (CT) 7, 8, 9 and a detection circuit 10, and is applied to a level discrimination circuit 11.
The level discrimination circuit 11 discriminates the level of the voltage value,
The signal is outputted to the time delay circuit 12 or the instantaneous operation circuit 13 depending on the discrimination level. The discrimination level of the level discrimination circuit 11 is freely set by the operating characteristic setting circuit 14. The time delay circuit 12 outputs a drive signal to the trip drive circuit 15 after a predetermined time delay depending on the input voltage. Furthermore, when the instantaneous operation circuit 13 receives an input signal, it instantaneously outputs a drive signal to the trip drive circuit 15. The trip drive circuit 15 excites the trip coil 6 when a drive input is applied thereto.
Further, the current flowing through the internal conductor 3 is applied to the power supply circuit 19 via cored current transformers (CTs) 16, 17, and 18. This power supply circuit 19 not only supplies power to the trip coil 6 but also supplies power to the electronic circuit section of the tripping device described above.

FIG. 6 shows the circuit configuration of the detection circuit 10,
It consists of a rectifier circuit 21 and a detection resistor 22 connected in parallel to the rectifier circuit 21. The rectifier circuit 21 includes four sets of diodes 23, two of which are connected in series.
and 24, 25 and 26, 27 and 28, and 29 and 30 are connected in parallel between the anodes and between the cathodes of each set. One end of each output from the air-core current transformers 7, 8, 9 is connected to diodes 23, 24, 25, 26, 27, respectively.
and 28, and the other end of each output is commonly connected to the intermediate connection point of diodes 29 and 30. Outputs from the air-core current transformers 7, 8, and 9 are rectified by a rectifier circuit 21, and a detection resistor 2
2, a detection voltage corresponding to the current flowing through the internal conductor 3 is obtained.

FIG. 7 shows a circuit configuration in the case where only a single pole, that is, a single phase conductor among the three-phase internal conductors 3 is energized, and this equivalent circuit is shown in FIG. 8th
In the figure, the air-core current transformer 7 has been rewritten as its internal resistance 32 and its electromotive force 31. Moreover, the air-core current transformers 8 and 9 are shown as internal resistances 33 and 34, respectively. Internal resistance of each air-core current transformer 32, 33,
34 resistance value is R _C , the resistance value of the detection resistor 22 is R _L ,
Assuming that the value of the electromotive force 31 is E and the voltage across the detection resistor 22 is V _RL , then V _RL ≈E/ _RC + R _L · R _L (1).

FIG. 9 shows a circuit configuration diagram in the case where only one phase, that is, two phase conductors of the three-phase internal conductors 3 are energized, and this equivalent circuit is shown in FIG. 10. In FIG. 10, the electromotive force 3 of the air core transformer 8
5 is further added to the circuit of FIG. In this case, the voltage V _RL across the detection resistor 22 is V _RL ≈E/R _C +R _L/2 ·R _L (2).

(c) Problem to be solved From equations (1) and (2), the internal resistance value of the air-core current transformer
If R _C is sufficiently larger than the detection resistance value R _L , the output voltage V _RL of the detection circuit 10 for the same current will be approximately equal during single-polar energization and during single-phase energization. However, since air-core current transformers are constructed by winding copper wire, the temperature coefficient of internal resistance R _C is 0.00393Ω/
℃, the voltage output of the detection circuit 10 changes depending on the ambient temperature, and as a result, the tripping characteristics of the circuit breakers and breakers fluctuate, creating an unfavorable problem in the use of the circuit breakers. In particular, there was a problem in that the circuit and disconnection characteristics differed due to the difference in detected voltage output when single-pole current was applied and when single-phase current was applied.

The purpose of this invention is to improve the variation in the tripping characteristics of circuit breakers and disconnectors due to ambient temperature, and to provide circuit breakers and disconnectors whose tripping characteristics do not change even when single-pole and single-phase current is applied. An object of the present invention is to provide a tripping device.

(d) Means for solving the problem This invention connects a current detection compensation resistor having a sufficiently large value with respect to the internal resistance of the air-core current transformer in series, and It is configured by giving the output of 2 to a detection circuit.

(E) Embodiment FIG. 1 shows an embodiment of the circuit breaker of the present invention, and the difference from the configuration shown in FIG. 5 is that one end of each output of the air-core current transformers 7, 8, and 9 is Resistor 4 for detecting and compensating for the current flowing in the circuit and disconnector correspondingly.
1, 42, and 43, each of the resistors 4
The other ends of 1, 42, and 43 are connected to the detection circuit 10. In FIG. 1, the other configurations are completely the same as those in FIG. 5, so the same parts are given the same reference numerals and the explanation will be omitted.

FIG. 2 shows the detection circuit 10 of FIG. 1 in detail, and its configuration is the same as that of FIG. 6. In FIG. 2, the resistors 41, 42, 4
The other ends of 3 are connected to diodes 23 and 24, 25 and 26, 27 which constitute the rectifier circuit 21, respectively.
and 28 intermediate connection points.

FIG. 3 shows an equivalent circuit when single-pole current is applied in FIG. 2. The difference between the equivalent circuit shown in FIG. 7 and the equivalent circuit shown in FIG. This is what is being done. The resistance values of resistors 41, 42, and 43 are
Assuming that R _b , the voltage V _RL across the detection resistor 22 becomes V _RL ≈E/R _C +R _b +R _L ·R _L (3).

FIG. 4 is an equivalent circuit diagram when single-phase current is applied in FIG. 2. FIG. 4 corresponds to the equivalent circuit shown in FIG. 10, and the difference from the circuit is that the detection compensation resistors 41, 42, 43 correspond to the circuits of the air-core current transformers 7, 8, and 9, respectively. They are connected in series. The voltage V _RL in this case is V _RL ≈E/R _C +R _b +R _L/2 ·R _L (4).

As is clear from equations (3) and (4), the sum (R _C +R _b ) of the internal resistance value R _C and the resistance value R _b of the air-core current transformers 7, 8, and 9 is detected as the resistance value R _L If it is made sufficiently larger than VRL, the output voltage V _RL of the detection circuit 10 for the same current flowing through the circuit or disconnector becomes approximately equal during single-pole current flow and during single-phase current flow. Furthermore, if the resistance value R _b for detection compensation is made sufficiently larger than the internal resistance value R _C , fluctuations in the output voltage V _RL due to changes in ambient temperature will not be a problem in practice. That is, the windings and wire diameters of the air-core current transformers 7, 8, 9, and the resistances 41, 42, 43.
If the combination of the resistance value R _b , the resistance value of the detection resistor 22, and R _L is appropriate, and for example, metal oxide film resistors are used for the resistors 41, 42, and 43, the temperature coefficient will be
The temperature coefficient is an order of magnitude better than the internal resistance of an air-core current transformer made of copper wire at 350 ppm/℃, so the resistances 41, 42, 43 and internal resistances 32, 33, 34
The overall temperature coefficient of each series-connected resistor is approximately equal to the temperature coefficient of the detection resistor 22, and as a result, the detection voltage V _RL in equations (3) and (4) is hardly influenced by the ambient temperature.

(f) Effects According to the present invention, the tripping characteristics of a circuit or disconnector can be performed without being affected by the ambient temperature, and the tripping accuracy can be improved. Furthermore, almost uniform tripping characteristics can be obtained without fluctuations in the tripping characteristics even when the internal conductor of the circuit or disconnector is energized by a single pole or a single phase.

[Brief explanation of the drawing]

FIG. 1 is a schematic circuit configuration diagram showing an embodiment of the circuit breaker of the present invention, FIG. 2 is a detailed circuit configuration diagram of the detection circuit section of FIG. 1, and FIG. Fig. 2 is an equivalent circuit diagram, Fig. 4 is an equivalent circuit diagram of Fig. 2 when single-phase current is applied, Fig. 5 is a schematic circuit diagram of a conventional circuit breaker, and Fig. 6 is a diagram of Fig. 1. A detailed circuit configuration diagram of the detection circuit section. Figure 7 is a circuit configuration diagram when only a single pole is energized in Figure 6. Figure 8 is an equivalent circuit diagram of Figure 7. Figure 9 is a diagram of the circuit diagram in Figure 6. Circuit configuration diagram when only single phase is energized, Part 1
FIG. 0 is an equivalent circuit diagram of FIG. 3... Internal conductor, 7, 8, 9... Air core current transformer,
10...detection circuit, 21...rectification circuit, 22...
Detection resistor, 23-30...Diode, 41,4
2, 43...Resistance for detection compensation.

Claims (1)

[Scope of Claims] 1. An air-core current transformer that detects three-phase current, a rectifier circuit that rectifies the output of the air-core current transformer, and a voltage that is connected in parallel to the rectifier circuit and is proportional to the current. and a detection circuit having a detection resistor for detecting current, and selectively detects single-phase, two-phase, or three-phase current. A resistance for current detection compensation is connected between the rectifier circuits and has a value sufficiently larger than the internal resistance of the air-core current transformer, and the temperature coefficient of resistance for current detection compensation is equal to that of the internal resistance of the air-core current transformer. The total resistance temperature coefficient of the resistor and the current detection compensation resistor is smaller than the resistance temperature coefficient of the internal resistance of the air-core current transformer so that the resistance temperature coefficient of the entire resistance temperature coefficient of the resistor and the current detection compensation resistor is approximately equal to the resistance temperature coefficient of the detection resistor. Features: A tripping device for circuits and disconnectors. 2. The circuit breaker tripping device according to claim 1, wherein the detection compensation resistor is an oxide film resistor.