JPH01117650A - Current limiting circuit - Google Patents

Abstract

PURPOSE:To eliminate loss, by bringing a superconducting wire in a circuit bypassing a limiting resistor uner actually loaded state from normal conducting state to superconducting state upon finish of charging of a load side capacitor. CONSTITUTION:A power source circuit comprises a power source switch 1, a rectifying circuit 2, a capacitor 4 and the like and feeds power to a load 5. A circuit for limiting surge current upon throw-in of power source comprises a limiting resistor 3 and a delay circuit 6, and a superconducting wire 10 providing a current path under actually loaded state, a permanent magnet 11 for producing magnetic field for bringing the superconducting wire 10 into normal conducting state, an electromagnet 12 and a power source for its coil 13 are further provided. A superconducting wire 10 is employed in a circuit for bypassing the limiting resistor 3 under actually loaded state upon finish of charging of the load side capacitor 4, and the wire 10 is brought from normal conducting state to superconducting state. Consequently, loss in a current limiting circuit can be eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a current limiting circuit that limits the rush current of a power supply circuit when the power is turned on.

[Prior art] Fig. 4 shows, for example, Fmic Lambda Catalog 1987.
This is the current limiting circuit shown on page 23 of the current edition.

In Figure 4, (1) is a power switch, (2) is a rectifier circuit that converts AC input to DC, (3) is a limiting resistor that limits current, and (4) is a series load or smoothing circuit. A capacitor, (5) a load, (6) a delay circuit that delays a power ON signal, (7) a trigger circuit that generates a gate signal for a thyristor, and (8) a thyristor.

Next, the operation will be explained. The AC power input to the terminal (101) is turned on when the power is applied to one terminal (, 102).
Rectifier circuit via power switch (1) activated by the signal! The voltage becomes a DC voltage of 1. As shown in FIG. 5(C), the thyristor (8) connected to the output side of the rectifier circuit receives the gate input signal from the terminal (10) shown in FIG. 5(a).
Since the power ON signal applied to 2) is delayed by the time T by the delay circuit (6), it is in a cut-off state when the power is turned on.

Therefore, the DC output (1) of the rectifier circuit (2) traces the limiting resistor (3) connected in parallel with the thyristor (8) and charges the capacitor (4) on the load side. Since the charging current at this time is limited by the limiting resistor (3), the rush current when the power is turned on can be reduced. As shown in FIG. 5(b), after a time (T) when the charging of the capacitor is completed and its voltage becomes almost equal to the output voltage of the rectifier circuit (2), 1.
The circuit that generates the gate signal as shown in Figure 5 (C) (
7), and when applied to the gate of the thyristor (8), the thyristor (8) becomes conductive, and the rectifier circuit (3)
can be supplied to the load (5). However, even if the thyristor (8) becomes conductive, it is not completely conductive and a voltage drop of (■5) occurs - this voltage is about 0.5 to 0.7 V in the case of a general thyristor. , a loss is generated as shown by the product of the load current 10. Especially when the output voltage is low and the current IO is large,
The loss rate in this thyristor (8) increases.

[Problem that the invention seeks to solve]

Conventional current limiting circuits are configured as described above, so especially in the case of power supplies with low output voltage and large current,
There was a problem of large losses.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a current limiting circuit that can limit inrush current without loss.

[Means for solving problems]

The current limiting circuit according to the present invention includes a superconducting wire, a permanent magnet placed near the superconducting wire, an electromagnet that acts to cancel the magnetic force of the permanent magnet, and a resistor connected in parallel with the superconducting wire.

[Effect]

The current limiting circuit according to the present invention is configured to transition the super-heavy and S wires used in the circuit that bypasses the limiting resistor from the normal conducting state to the superconducting state in the actual load state after the charging of the load side capacitor is completed. Try to eliminate losses.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, (1) to (6) are the same as the conventional one.

αB is a superconducting wire that becomes a current path under actual load, αυ is a permanent magnet that generates a magnetic field that makes the superconducting wire a normal conductor, (1
2+ is an electromagnet that generates a magnetic force that cancels the magnetic force of the permanent magnet 1υ, and 11m is a coil power source that supplies current to the electromagnet.

Next, the operation will be explained.

The AC power input to the terminal (101) is connected to the terminal (102).
It is controlled by a relay that operates with a power ON signal input from the power source, and is converted into DC heavy pressure (vl) by a rectifier circuit.

On the other hand, the power ON signal input to the spreading circuit (6) is the second
As shown in figure (d), the coil power supply α is delayed by # interval T.
3 is applied. During the delay time T in the delay circuit αJ, there is no output from the coil A power supply 113+, and the eldest son (b) of the permanent magnet 0υ crosses the superconducting wire αα, and the magnetic field (b) at this time
is set to a value larger than the critical magnetic field (yO) of the superconducting wire, and the superconductor acts as a normal conductor.

The impedance (resistance value) is set to be large. If you select a delay time (T) that is larger than the time to charge the load-side capacitor (4) after turning on the power, the charging current of the capacitor (4) when the 1M power is turned on will be limited by the limiting resistor (3). The inrush current can be limited to

Also, after time (T) has elapsed, the power source uJ for the light coil of the capacitor (4) becomes active, and the electromagnet U receives a current (
The electromagnet d2 is set so that the magnetic field (ai) caused by the current has a direction and size that cancels out the magnetic force (b) of the permanent magnet.
The number of coil turns and current (I) are chosen to make the resultant magnetic field smaller than the critical magnetic field (da0) of the superconducting wire. As a result, the superconducting wire Q was in a high impedance state in a normal conducting state.
G becomes superconducting and its impedance (resistance value)
In this case, the resistance value, which is a characteristic of superconducting wires, becomes zero, and the loss due to the load current (10) also becomes zero.

In the above embodiment, 11 magnets @ that cancel the magnetic force of the permanent magnet uD were provided separately from the permanent magnet (Iυ), but as shown in FIG. The effect is the same even if you wind the coil 1 (14) and flow the current (■1) in the direction of canceling the magnetic field of the permanent magnet (I). Same as Figure 1.

In addition, in the above two embodiments, the effect was only to limit the rush current when one source is turned on, but as shown in FIG. In 2Q51, the load current (10) is applied in the direction of canceling the magnetic force created by the electromagnet, and when an excessive current such as a load short circuit flows, the magnetic force of the 'iii' magnet uz is struck ln, and the permanent magnet α
Due to the magnetic force of υ, the critical magnetic field (00) of the super 1M conducting wire aα is exceeded, and the superconducting wire OG becomes a normal conductor, producing the effect of preventing the continuous flow of short circuit current.

〔Effect of the invention〕

As described above, according to the present invention, the superconducting wire used in the circuit that bypasses the limiting resistor is made to transition from the normal conductive state to the superconducting state in the actual load state after the charging of the load side capacitor is completed. This has the effect of providing a current limiting circuit in which no loss occurs under actual load conditions.

[Brief explanation of the drawing]

119'l is a configuration diagram showing one embodiment of the present invention, and FIG.
Fig. 3 is a current limiting circuit diagram that limits the inrush current when the power is turned on according to the present invention, as well as excessive current caused by short circuits of one load, and Fig. 4 shows the conventional current limiting circuit. Limiting circuit diagrams - FIGS. 5(a), 5(b), 5(c), and 5(d) are explanatory diagrams for explaining the operation of a conventional current limiting circuit. (1) is the power switch, (2) is the rectifier circuit, (3) is the limiting resistor, and (4) is the capacitor representing the load side capacitance (
5) is the load, (6) is the delay circuit, (7) is the generation circuit, (8) is the thyristor, αG is the superconducting wire, ul) is the permanent magnet, u is the electromagnet, u3 is the source for the coil, (141
is coil-1-■ is coil-2゜

Claims (1)

[Claims] A current limiting circuit consisting of a superconducting wire, a permanent magnet placed near the superconducting wire, an electromagnet that works to overcome the magnetic force of the permanent magnet, and a resistor connected in parallel with the superconducting wire.