JPS6349075Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a protection device for electric circuits, and in particular, to a device that protects an electric circuit whose load is a superconducting coil when an abnormality such as overvoltage or overcurrent occurs in the circuit. be.

FIG. 1 shows an example of the configuration of a conventional electric circuit protection device. In Figure 1, 1 is a power supply, 2 is a load,
3 is a shield and a disconnector, and 4 is a protective resistor.

When an abnormality occurs in the electrical circuit, the shield breaker 3 is disconnected to protect the circuit, but when the shield breaker 3 is disconnected, the current flowing through the load 2 becomes parallel to the load 2. The current is commutated to the connected resistor 4 and attenuated.

However, the current flowing from the power supply 1 during normal operation also flows through the resistor 4, and the energy consumption thereof becomes a loss during normal operation, so this must be kept as small as possible.

As an example, the load 2 is a superconducting coil, its inductance L is 1 Henry, the DC output voltage V of the power source 1 is 100 volts, and the resistance R of the line (including the breaker 3) connecting the power source 1 and the load 2. Assuming that R is 1 milliohm and the resistance Rr of the protective resistor 4 is infinite, the current I flowing through the load 2 is given by the following equation for time t seconds.

In other words, a large current of approximately 63 kiloamperes flows during a time period of ¹⁰³ seconds. As more time passes and a steady state is reached, the current becomes large, approximately 100 kiloamperes.

Therefore, when commutating the current to the shunt breaker 3 to the shunt resistor 4 in the event of an abnormality, the superconducting coil 2 serving as the load
There is a resistor with a current of approximately 100 kiloamps between the ends of the
A high voltage of the value multiplied by Rr (ohm) is generated.
Now, if the resistance Rr is 10 milliohms, the voltage Vl generated in the load coil will be 1 kilovolt.

On the other hand, under normal conditions when the shield breaker 3 is connected, the DC output voltage of the power supply 1 is applied to the resistor 4 if the resistance of the line is ignored. The maximum power consumed by is approximately 1
It becomes megawatt.

This power consumption decreases as the current flowing through the superconducting coil 2 increases over time, but it is extremely large at the beginning of time, which is a problem.

The first method to reduce this power consumption is
It is possible to increase the value of resistor Rr, but
Load terminal voltage generated when the shield breaker 3 is disconnected
Vl increases proportionally. For superconducting coils, etc., we want to set the withstand voltage of the coil as low as possible, so we do not want to make the resistance Rr too large.

In addition, as shown in FIG. 2, a unidirectional conductive semiconductor element 5 such as a diode is connected in series with the resistor 4, so that no current flows through the resistor 4 even when the DC output voltage of the power supply 1 is applied during normal operation. You can also prevent it from flowing.

However, semiconductor elements such as the above-mentioned diodes are generally limited in voltage and current ratings, and those with large capacities are expensive.

The present invention was devised in view of the problems of the prior art as described above, and provides an electrical circuit protection device that consumes little energy during normal operation, reliably protects the load during abnormality, and is highly economical. It is something.

FIG. 3 shows an embodiment of the present invention. In FIG. 3, 6 is a resistor, 7 is a closing device, and the other parts are the same as in FIG. 1. As shown in FIG. 3, resistor 6 is connected in series with resistor 4, and the series-connected resistors 4 and 6 are connected in parallel with load 2. Further, the input device 7 is connected in parallel with the resistor 6.

In the above configuration, during normal operation, the closing device 7 is in an open state, and the DC output voltage of the power source 1 is applied to both the load 2 and the series circuit of the resistors 4 and 6. If the resistance value of resistor 6 is made sufficiently large, the current flowing through the series circuit of resistors 4 and 6 can be made sufficiently small.

DC output voltage of power supply 1 shown in the example above
When the voltage is 100 volts and the resistance Rr of resistor 4 is 10 milliohms, for example, if the resistance value of resistor 6 is 1 ohm, the current flowing through the series circuit of resistors 4 and 6 is approximately
100A, which can be made sufficiently small.

On the other hand, if an abnormality occurs in the electric circuit, the breaker 3 is energized and the energizer 7 is turned on at the same time, the resistor 6 is short-circuited and the current flowing through the load 2 is commutated to the resistor 4. and consume energy to protect.
In this case, as mentioned above, the resistance Rr of the resistor 4 is
If the voltage is smaller than the allowable terminal voltage of the load, resistor 4
It can be set so that it does not occur between the terminals.

As the charger 7, if a mechanical charger operated by compressed air or a charger using a vacuum valve is used, an inexpensive and large-capacity charger can be realized.

The configuration shown in FIG. 3 shows one embodiment, and in general, the power source 1 may be either alternating current or direct current, and the input device 7 may include a semiconductor element.
Furthermore, the resistors 4 and 6 may be constructed of a plurality of resistors, and may be not only pure resistance but also impedance including inductance and capacitance depending on the application.

As explained above, according to the present invention, by appropriately selecting the value of the protective impedance, a protective device is constructed that reduces energy loss during normal operation and can limit the terminal voltage of the load to an appropriate value during abnormal conditions. Moreover, the use of a mechanical switch as a dosing device with the components of the protection device makes it possible to create a very economical protection device.

[Brief explanation of the drawing]

1 and 2 are circuit diagrams showing a conventional electric circuit protection device, and FIG. 3 is a circuit diagram showing an embodiment of the present invention. 1...Power supply, 2...Load, 3...Shiya disconnector,
4, 6...Resistor, 5...Diode, 7...Inserter.

Claims (1)

[Scope of utility model registration request] In an electric circuit protection device that protects an electric circuit with a breakout switch between the power source and the load by cutting off the breakout switch in the event of an abnormality, two or more sets of impedance elements are connected in series in parallel to the load. At least one set of energizers is provided to connect the circuit and short-circuit a part of the impedance elements of the series circuit, and when the breaker is interrupted, the energizer is energized and the impedance element is short-circuited. An electric circuit protection device characterized by short-circuiting a part of an element.