JPS6162317A - Method of protecting dc power source - 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 a method for protecting a DC power source used in a nuclear fusion power source or the like.

[Technical background of the invention and its problems] Research on nuclear fusion has become active in recent years. Nuclear fusion requires a load coil that can be multiplied by N and a large-capacity power supply. Due to the large amount of energy involved, sufficient consideration must be given to the protection of the load coil and power supply.

If the load coil were to be damaged, it would take much more time and cost to restore it than the power supply, so protection of the load coil is highly important. Further, it is difficult to increase the withstand capacity of the load coil because it requires a large amount of energy, and the load coil becomes very octagonal.

Hereinafter, a conventional protection method for a DC power supply will be explained using FIG. In FIG. 3, 24 is a load coil that generates a strong magnetic field. 21 is a diode rectifier that supplies DC power to the load coil 24; 22 is a diode rectifier 21;
This is a thyristor converter that is connected in series with the thyristor converter and also supplies DC power.

23 is a protective closing device for protecting the load coil 24;
Reference numeral 11 denotes a breaker that cuts off the AC power supplied to the diode rectifier 22. 31 is a thyristor converter 22
The phase control circuit 32 is an overcurrent detector that monitors the coil current and detects overcurrent.

In the circuit of FIG. 3, protection when an overcurrent occurs in the load coil 24 is performed as follows.

First, the thyristor converter 22 is gate-shifted and the circuit breaker 11 is cut off, thereby stopping the supply of DC power to the load coil 24. Thereafter, it is detected that the circuit breaker 11 is opened, and the protective closing device 23 is closed to attenuate the energy of the load coil 24. Normally, when the firing angle of the thyristor converter 22 is delayed to the maximum allowable value, the output voltage of the thyristor converter 22 becomes negative, cancels out the output voltage of the diode rectifier 21, and the voltage applied to the load coil 24 becomes zero. The increase in current can be suppressed. If the thyristor converter 22 fails to commutate during gate shift and does not operate normally and the voltage applied to the load coil 24 does not become zero, the current increases and an excessive current flows to the load coil 2.
It is possible that it will flow to 4. For this reason, load coil 2
The tolerance level of 4 must be made that high,
Since the energy of the load coil 24 is large, it is difficult to increase the resistance to m.

If the load coil 24 were to be damaged, due to its nature, a large amount of cost and time would be required for restoration, and the system would have to be stopped for a long period of time.

On the other hand, if the protective switch 23 is turned on at the same time as overcurrent detection, it will be safer to protect the load coil 24, but it will cause a DC short circuit to the diode rectifier 21 and the thyristor converter 22°, and the diode rectifier 21, This would add unnecessary stress to the thyristor converter 22.

As described above, the conventional DC power supply protection method has the problem that an excessive current is caused to flow through the load coil 24 in the event that the thyristor converter 22 is unable to perform its protective operation properly.

[Object of the Invention] The present invention eliminates the above-mentioned disadvantages and provides direct current 'I!' that can sufficiently protect the load coil. The purpose is to provide a protection method for 8m.

[Summary of the Invention] The present invention sets the overcurrent detection level of the load coil to two levels: a first level and a second level set higher than the first level, and at the first level, gate-shifts the si-risk converter and Open the breaker on the AC side of the diode rectifier, confirm that the breaker is open, and then turn on the protective switch.

The second level is characterized in that a protective closing device connected in parallel to the load coil is closed to protect the load coil.

[Embodiments of the invention] An embodiment of the present invention will be described below with reference to FIG.

Components in FIG. 1 that are the same as those in FIG. 3 are given the same reference numerals. The difference from FIG. 3 is that an overcurrent detector 33 is added. The detection level of this overcurrent detector 33 is set higher than the detection level of the overcurrent detector 32. Second
The figure is an explanatory diagram of FIG. 1, and shows the current waveform of the load coil 24 of the power supply system of FIG.

In the circuit shown in Fig. 1, when the current in the load coil 24 becomes an overcurrent and reaches the level shown in Fig. 2, the overcurrent detector 3
This is detected by 2. The output signal of the overcurrent detector 32 is given to the phase control circuit 31 of the thyristor converter 22 and the breaker 11, gate shifting is performed in the phase control circuit 31, the breaker 11 is opened, and after confirming the opening, the protective circuit is turned on. Insert the container 23. It is detected at the point tl in FIG. 2, and if the current decreases as indicated by the curve (a) due to the above-mentioned protective operation, then the protection operation is completed.

On the other hand, during the above-mentioned protective operation, if the thyristor converter 22 does not operate normally and the current does not decrease as shown in curve (b) but continues to increase, the overcurrent detector detects the level shown in Figure 2 L-2. Detected by 33. The output of this overcurrent detector 33 is given to the high-speed closing device 23 to close the protective closing device 23. This operation causes the current in the load coil 24 to decrease.

As described above, when an overcurrent occurs in the load coil 24, the load coil 24 is protected by gate shifting the thyristor converter 22 and opening the breaker 11 of the diode rectifier 21. If the current does not decrease and continues to increase, it is detected by the overcurrent detector 33, the protective energizer 23 is activated, and the current in the load coil 24 is decreased.

Therefore, even if the current increases due to the thyristor converter 22 not operating normally during the protective operation by the output of the overcurrent detector 32, the overcurrent withstand capacity of the load coil 24 will not be exceeded, and the load coil 24 can be prevented from being damaged.

[Effect of the Invention J] According to the present invention, when an overcurrent occurs in the load coil, a protective operation is first performed at the first detection level. During this protection operation,
Even if the current continues to increase due to malfunction of the thyristor converter, etc., the increase in current is detected at the second detection level before the overcurrent tolerance of the load coil is exceeded, and the thyristor converter is connected in parallel to the load coil. Insert the protective dosing device. This allows the current in the load coil to be reduced and damage to the load coil to be prevented.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a diagram for explaining the present invention in detail, and FIG. 3 is a block diagram of a conventional device. DESCRIPTION OF SYMBOLS 11... Breaker, 21... Diode rectifier, 22... Diode rectifier, 23... Protection # closing device, 24... Load coil, 31... Phase control circuit, 3
2... Overcurrent detector, 33... Overcurrent detector. Applicant's agent Patent attorney Takehiko Suzue Figure 1

Claims (1)

[Claims] A load coil that generates a magnetic field, a diode rectifier that supplies DC power to the load coil, a thyristor converter connected in series to the diode rectifier, a protective closing device connected in parallel to the load coil, and the diode rectifier. In a DC power supply having a circuit breaker connected to the AC side of the thyristor converter, the overcurrent detection of the load coil is divided into a first level and a second level, and when it is detected that the first level has been reached, the thyristor converter and detects that the current flowing through the coil continues to increase and reaches a second level set higher than the first level. A method for protecting a DC power supply, comprising turning on the protective turning device.