JPS59113713A - Circuit breaker - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an improvement in a circuit breaker equipped with a static overcurrent trip device.

[Technical background of the invention and its problems]

As a circuit breaker equipped with a static overcurrent trip device,
Conventionally, there is a device configured as shown in FIG. In FIG. 1, reference numeral 1 denotes a power source, and a load 3 is connected to the power source 1 via main circuit contacts 2 to form a main circuit 4. As shown in FIG. 5 is a current transformer that detects the current flowing through the main circuit 40;
On the secondary side, a nonlinear surge absorbing element 6 and an input terminal of a rectifier circuit 7 such as a diode are connected in parallel.

In addition, a voltage conversion resistor 8 is connected in parallel to the output end of the rectifier circuit 7, and a non-linear surge absorbing element 10 is connected in parallel to one side via a resistor 9 to perform static overcurrent tripping. It is connected to the input end of the device 11.

This static overcurrent tripping device 1 operates when a voltage signal of a predetermined magnitude is input to its input terminal, and outputs a tripping command for opening the main circuit contact 2.

Next, the operation of the circuit breaker configured as described above will be described. That is, the current flowing through the main circuit 40 is detected by the current transformer 5, the detected current flowing to the secondary side is converted into a DC current by the rectifier circuit 7, and further converted into DC current by the voltage conversion resistor 8. It is converted into a corresponding voltage signal and input to the static overcurrent tripping device 11.

As shown in FIG.
) has a 3-yuan interest release characteristic. 3
As shown in Figure 2, the main and interest release characteristics are the long time series release characteristic LT, the short time side release characteristic ST, and the instantaneous tripping characteristic 1N5T. The overcurrent trip device 11 operates, outputs a trip command, and opens the main circuit contact 2.

In the above case, the number of turns on the primary and secondary sides of the current transformer 5 is N1.
, N2, IOl is the exciting current, and 11 is the current transformer 50.
The primary current, that is, the current flowing through the main circuit 40, I2 is transferred to the current transformer 5.
If the detection current on the secondary side is llN1=Lo1N1+I
A 2N2 relationship is established. In this case, I 2N2 is sufficiently large compared to I 01N1, so 11N1 = ■2N2
It can be expressed as Therefore, the current flowing through the main circuit 40, that is, the current transformer 5
The primary current 11 is a sine wave as shown in Figure 3 (,), and the detected current I2 on the secondary side of the current transformer 50 is as shown in Figure 3 (b).
As shown in the figure, the primary current IIK of the main circuit 40 is a sine wave proportional to the primary current IIK.

In order to make the currents on the primary and secondary sides of the current transformer 50 proportional as described above, conventionally, the cross-sectional area of the iron core of the current transformer 5 is increased, and the secondary winding is A thick one was used to prevent the impedance value from becoming too large even if the number of windings on the secondary side was several thousand to several hundred. For this reason, the current transformer 5 requires a large iron core and a winding wire with a large wire diameter, and as a result, the circuit breaker including the current transformer 5 has become large and expensive.

In addition, in the above three-dimensional interest release characteristic, the long time series release characteristic L
When T and the short-time side disconnection characteristic ST are combined, the current flowing in the primary side of the current transformer 50, that is, the main circuit 4, is 10
~100kA may flow for as long as 0.05-0.6 seconds. In this case, the cross-sectional area of the iron core of the current transformer 5 is large, the wire diameter of the secondary winding is large, and the impedance value of the secondary side is small, so the current transformer 5 is difficult to saturate. Therefore, there is a drawback that a large overvoltage occurs on the secondary side of the current transformer 5.

Therefore, in addition to the non-linear surge absorbing element 6, a resistor 9 and a non-linear surge absorbing element 10 are provided as means for absorbing the overvoltage. In this case, non-linear surge absorbing elements 6 and 10 having a large withstand capacity are separately provided to protect the static overcurrent tripping device 1 from overvoltage. However, as mentioned above, the nonlinear surge absorption element 6°10
Requires a large capacity, large size and high price.
Circuit breakers have also become larger and more expensive.

[Purpose of the invention]

The present invention has been made based on the above circumstances, and its purpose is to provide a circuit breaker that can reduce the size and cost while reliably suppressing the overvoltage generated from a current transformer. It is about providing the equipment.

[Summary of the invention]

The circuit breaker according to the present invention transforms a parallel circuit consisting of a resistor and a nonlinear resistance element having positive nonlinear characteristics that exhibits a low resistance value at room temperature and a high resistance value when heat is generated due to current flow. The above object is achieved by connecting the secondary side of the current flow device in series with the static overcurrent tripping device.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. Fourth
The figure is a circuit diagram showing an embodiment of the circuit breaker according to the present invention, and the same parts as in FIG.

That is, in this embodiment, the resistor 9 and the nonlinear surge absorbing element 10 in FIG. 1 are removed, and a current transformer 502 is used instead.
A non-linear resistance element 12 is placed between one side of the next side and one of the input ends of the rectifier circuit 70, and a resistor whose resistance value is much larger than that of the resistor 8 and has a resistance value of several hundred (Ω). This is a parallel circuit consisting of 13 connected in series.

In the above, the non-linear resistance element 12 has a positive non-linear characteristic that shows a low resistance value at room temperature and shows a high resistance value when heated by a current. Using lySwl tch Next, the operation of this embodiment configured as described above will be described.

First, a case where the current flowing through the main circuit 4 is a normal value will be described. That is, the current flowing through the main circuit 40 is detected by the current transformer 5, and the detected current on the secondary side is input to the rectifier circuit 7 through the non-linear resistance element 12 which exhibits a low resistance value at room temperature. After being rectified here, the static overcurrent trip device 1
1 is input.

On the other hand, when a large current such as a short-circuit current flows in the main circuit 4, a large fault detection current proportional to this large current flows to the secondary side of the current transformer 5.

When this fault detection current flows through the non-linear resistance element 12, the non-linear resistance element 12 generates heat and rapidly attains a high resistance value due to its positive non-linear characteristics.

Therefore, at this time, the fault detection current is input to the rectifier circuit 7 through the resistor 13, which has a low resistance value as well as the non-linear resistance element 12, and is rectified there. It is input to device 1.

In the above, until the detected current of the current transformer 5 is 10 times the rated value, a current conducting path is formed through the non-linear resistance element 12 in the characteristic region of several Ω at around 20° C. in FIG. Similarly, up to 20 times the rating is the number 100 in Figure 5.
An energizing path is formed through the non-linear resistance element 12 in the characteristic region. Similarly, at 20 times the rated value or more, the nonlinear resistance element 12 generates heat and exhibits a high resistance value as shown in FIG. 5, so that at this time a current conducting path is formed through the resistor 13 having a low resistance value.

As mentioned above, the current detected by the current transformer 5 uses either the nonlinear resistance element 12 or the resistor 13 as the current path depending on its magnitude, so the output load of the current transformer 5 is small. Therefore, since the output voltage of the current transformer 5 is also relatively small, a small iron core of the current transformer 5 is sufficient.

In addition, if the fault detection current flows to the secondary side of the current transformer 5,
The secondary voltage is mostly applied to the resistor 13 because the resistance value of the resistor 13 is much larger than the resistance value of the voltage conversion resistor 8.

Furthermore, the upper limit of the secondary side voltage of the current transformer 50 is determined by the nonlinear resistance element 1.
It depends on the suppression voltage of 2.

Therefore, the secondary voltage of the current transformer 5 is suppressed, and the rectifier circuit 7
A voltage signal having an appropriate voltage level is input to the static overcurrent tripping device 11. As explained in FIG. 1, the static overcurrent tripping device 11 to which this voltage signal is input, when the voltage signal satisfying the tripping characteristics continues for a predetermined time,
Outputs a trip command and opens main circuit contact 2.

In the above, as shown in Figure 6(a) ICys5,
The current flowing through the main circuit 4, that is, the primary current 11 of the current transformer 5 has a sine wave waveform, but the detected current 2 is the 6th
As shown in Figure (b) K, only the peak value is proportional to the above sine wave, but the rear part of the waveform is missing and distorted because the iron core of the current transformer 5 is saturated. Become. current transformer 5
Similarly to the current waveform, only the peak value of the voltage waveform on the secondary side is proportional, and the rear part of the waveform is missing, resulting in a distorted waveform. Also, if the diameter of the winding on the secondary side of the current transformer 5 is made thinner and the resistance value of the winding is increased, the impedance on the secondary side of the current transformer 5 will increase, and the secondary side voltage will be reduced by non-linear surge absorption. The voltage of the element 6 is largely shared by the secondary side of the current transformer 50. Therefore, as the non-linear surge absorbing element 6, one with a small capacity can be used.

As described above, in this embodiment, the non-linear resistance element 12
Alternatively, the resistor 13 forms a conduction path, and the overvoltage on the secondary side of the current transformer 50 is absorbed by the non-linear resistance element 12, so the non-linear surge absorption element 6 is It becomes possible to use a device with low withstand voltage and low capacity. Furthermore, since high voltage is not input to the static overcurrent tripping device 11, it is possible to use a device with low withstand voltage and low power consumption.

Next, another embodiment of the present invention will be described with reference to FIG. In FIG. 7, directly on the secondary side of the current transformer 5,
A rectifier circuit 7 is connected, a non-linear surge absorption element 6 is connected in parallel to the output terminal of the rectifier circuit 2, and a non-linear resistance element 1 is connected in parallel to the output terminal of the rectifier circuit 2.
2 and a resistor 13 are connected in series, and a voltage conversion resistor 8 is connected in parallel and connected to the input end of a static overcurrent tripping device 11.

Even with a circuit breaker having such a configuration, the operation and effect are similar to those of the circuit breaker shown in FIG. 6.

The present invention is not limited to the above embodiments, and can be implemented with various modifications without departing from the gist of the present invention.

〔Effect of the invention〕

As described above, according to the present invention, a parallel circuit consisting of a resistor and a nonlinear resistance element having positive nonlinear characteristics that exhibits a low resistance value at room temperature and a high resistance value when heat is generated due to current flow is provided. Since the configuration is connected in series between the secondary side of the current transformer for detecting the main circuit current and the static overcurrent trip device, the overvoltage generated from the current transformer can be reliably suppressed while still being compact. It is possible to provide a circuit interrupter that can be made more compact and inexpensive.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing a conventional circuit interrupter, Figure 2 is a diagram showing the trip characteristics of a static overcurrent trip device, and Figure 3 (
,)(b) is a waveform diagram for explaining the operation of the circuit breaker in FIG. 1, FIG. 4 is a waveform diagram for explaining the operation of an embodiment of the circuit breaker according to the present invention, and FIG. The figure is a circuit diagram showing another embodiment of the present invention. 1...Power supply, 2...Main circuit contact, 3...Load, 4
... Main circuit, 5... Current transformer, 6, 10... Non-linear surge absorption element, 7... Rectifier circuit, 8... Resistor,
9... Voltage conversion resistor, 11... Static overcurrent trip device, 12... Non-linear resistance element, 13... Resistor. Applicant's Representative Patent Attorney Takehiko Suzue Figure 1 Figure 2-1 (A') Figure 3 (a) (b) Figure 4 Figure 5 Figure 6 (a) (b) 17

Claims (1)

[Claims] A current transformer detects the main circuit current of the main circuit that supplies power to the load through the main circuit contacts of the power supply, and the current detected by the current transformer is large enough to be equivalent to an overcurrent fault. In this case, the circuit breaker that operates the static overcurrent trip device to open the main circuit contact has a positive nonlinearity that exhibits a low resistance value at room temperature and a high resistance value when heat is generated due to current flow. A circuit breaker 0 characterized in that a parallel circuit consisting of a non-linear resistance element having a characteristic and a resistor is connected in series between the secondary side of the current transformer and the static overcurrent tripping device.