JPH07282831A - Short circuit protecting device for fuel cell - Google Patents

Abstract

PURPOSE:To shorten restoration time when insulation drop occurs by separately monitoring an insulation drop of each insulation part with a resistor or fuse, and opening or closing a circuit with a switch for the resistor. CONSTITUTION:A gas manifold 2 and a water manifold 4 are electrically connected to a lower fastening plate 3 separately through each resistor 10 and switch 11, and a tie rod 5 is electrically connected to the plate 3 through a fuse 7. Both ends of the resistor 10 and the fuse 7 are monitored by a voltmeter, and a system is programed so as to immediately stop power generation when the fuse is blow out by dielectric breakdown of an insulation part in the tie rod 5. When insulation drop occurs, by turning off the switch 11, leak current is estimated, and based on the current value, power generation is stopped when the insulation drop is continued for a specified time or longer. When insulation is restored by its own ability, power generation stop becomes unnecessary, and even when restoration is necessary, since insulation drop part can be identified, restoration time is shortened.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a short circuit protection device for protecting a short circuit due to insulation deterioration of an insulator in a fuel cell.

[0002]

2. Description of the Related Art A conventional insulation structure for a fuel cell and a short-circuit protection device will be described with reference to FIG. In FIG. 7, the laminated body 1
Between the gas manifold 2, the water manifold 4, the water manifold 4, and the tie rod 5, there are insulators 14 made of resin or ceramic, respectively.
Electrically isolated by. The gas manifold 2, the water manifold 4, and the tie rods 5 are electrically connected to each other, and further electrically connected to the lower tightening plate 3 via a fuse. Therefore, the gas manifold 2, the water manifold 4, and the tie rods 5 are at the same potential as the lower tightening plate 3.
Further, the drain 6 is located above the insulator 14 and is located above the gas manifold 2.
And the lower part is connected to the gas pipe 9 of earth potential.

Since the stack 1 has a high potential, the vessel 8
And are insulated by a support insulator 12. With such a structure, when the insulation at a portion of the insulator 14 between the laminated body 1, the gas manifold 2, the water manifold 4, and the tie rod 5 is lowered, the fuse 7 is blown. As the cause of the insulation deterioration, deterioration of the insulator 14, contamination of cooling water, liquid junction due to phosphoric acid, and the like are considered.

Of these, deterioration of the insulator 14 requires repair and the battery must be stopped, but in the case of a liquid junction due to phosphoric acid between the laminated body 1, the gas manifold 2 and the drain 6, the insulation is made after a while. It may recover. If the cooling water is contaminated, it can be repaired simply by replacing the cooling water, which must be distinguished from the breakdown of the insulator.

[0005]

As described above, there are various cases where the insulation deterioration of the fuel cell may occur, and it may not always be necessary to stop the power generation. However, in the current method, the insulation deterioration may occur. First, the power must be stopped by blowing the fuse. In addition, since all insulators are protected by a single fuse, it is not possible to identify the location where insulation is degraded. It takes time and recovery takes time.

An object of the present invention is to estimate the damage at a location where insulation is degraded by identifying the location when insulation degradation occurs and further quantifying the leakage current. This is to determine the urgency of the response and continue power generation if there is a slight insulation deterioration that allows self-recovery, and if there is a need for repair, make a planned stop to shorten the recovery time. .

[0007]

SUMMARY OF THE INVENTION A short circuit protection device for a fuel cell according to the present invention comprises a switch and a resistance outside the cell body between the fuel cell stack and the gas manifold, and between the stack and the water manifold, respectively. It is electrically connected through the body, and when insulation deterioration occurs, the switch is turned off to estimate the leakage current, and based on this current value, power is generated when insulation insulation continues for a certain time or longer. It is characterized by stopping.

[0008]

In the present invention, the insulation lowering state of each insulation portion is independently monitored by the resistor or the fuse, and the resistor can be turned on and off by the switch. By independently monitoring the leakage current for each insulation site, the location where insulation is degraded can be specified, and by turning on / off the resistor, the resistance and current value at the time of insulation degradation can be obtained.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG.
Since the same parts as those of the prior art are designated by the same reference numerals, the description thereof will be omitted. In FIG. 1, the gas manifold 2 and the water manifold 4 are electrically connected to the lower tightening plate 3 via separate resistors 10 and switches 11, respectively. Further, the tie rod 5 is electrically connected to the lower tightening plate 3 via the fuse 7.

Both ends of the resistor 10 and the fuse 7 are monitored by a voltmeter. Since the insulating portion used for the tie rod 5 has almost no possibility of recovering after dielectric breakdown, it is programmed to immediately stop power generation when the fuse is blown.

Contamination of cooling water and the like in the water manifold 4 also causes deterioration of insulation. It is empirically known that the gas manifold 2 and the drain 6 are also caused by a liquid junction due to phosphoric acid to cause insulation deterioration, and when both are small, the insulation is restored by itself while continuing power generation. Therefore, when insulation deterioration occurs, it is necessary to determine whether or not power generation should be stopped.

Stopping the power generation is to suppress damage due to insulation deterioration within an allowable range, and it is necessary to obtain the leakage current value in order to estimate the degree of damage. Water manifold 4
Normally has sufficient insulation resistance if the cooling water is not contaminated, and the possibility of dielectric breakdown is small. On the other hand, the gas manifold 2 is the most severe part in terms of insulation because the insulating coating is apt to be violated by phosphoric acid having a strong corrosive property. Therefore, the insulation deterioration of the gas manifold 2 is actually the most important monitoring target.

The following method is used to estimate the leakage current values of the laminated body 1 and the gas manifold 2. FIG. 2 shows an equivalent circuit diagram when the insulation of the gas manifold 2 is lowered. In the figure, Ru is the upper part of the battery and the gas manifold 2.
, Rd represents the resistance between the lower part of the battery and the gas manifold 2.

When insulation degradation occurs, a voltage is generated in the resistor 10. However, turning on and off the switch 11 causes a difference in voltage, and Rd can be calculated from this difference. R in FIG.
The difference in voltage when the switch 11 is opened and closed when d = Ru is shown. As in the case of FIG. 3, the voltage difference due to switching on / off of the switch 11 can be calculated for any ratio of Rd and Ru.
Since Rd can be obtained from the voltage value when the switch 11 is off, Ru and Rd can be uniquely obtained by this method. If the resistance value is known, the leakage current value can also be calculated.

In the program, the voltage of the resistor 10 is read when the insulation is lowered to calculate Ru / Rd, and then the switch 11 is turned off to read the voltage, and Rd, Ru and the leakage current are calculated from the voltage difference. If the leakage current x duration exceeds a certain value, power generation is stopped. The same applies to the case of the water manifold 4.

An example in which a Wheatstone bridge circuit is introduced between the manifold and the upper part of the battery is shown in FIG. 4, and its equivalent circuit diagram is shown in FIG. Gas pipes and drain pipes are connected to the manifold, and these pipes are connected to a ground potential pipe through an insulator. The resistance of the insulator is Rx.

When Rx changes due to deterioration of the insulator, the voltage across the monitor resistor R5 changes. FIG. 6 shows the relationship between Rx and V when R1 to R5 are 5 kΩ.
Rx can be found by measuring V from FIG.
Program to stop operation when is below a certain value.

[0018]

As described above, according to the present invention, it is not necessary to stop the power generation when the insulation is restored by itself while continuing the power generation even if the insulation deterioration occurs, and the insulation is used even when the repair is necessary. Since it is possible to identify the location of deterioration, it is possible to shorten the time required for restoration.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is an equivalent circuit diagram of the laminated body and the gas manifold.

FIG. 3 is a characteristic diagram showing changes in voltage when the switch according to the present invention is turned on and off.

FIG. 4 is a configuration diagram showing another embodiment of the present invention.

FIG. 5 is an equivalent circuit diagram in another embodiment.

FIG. 6 is a characteristic diagram showing the relationship between the resistance of an insulator and the voltage.

FIG. 7 is a block diagram of a conventional example

[Explanation of symbols]

1 ... Laminated body, 2 ... Gas manifold, 3 ... Tightening plate, 4 ...
Water manifold, 5 ... Tie rod, 6 ... Drain, 7 ... Fuse, 8 ... Vessel, 9 ... Gas piping, 10 ... Resistor, 11
… Switch, 12… Supporting insulator, 13… Wheatstone bridge,
14 ... Insulator, Ru ... Upper resistance, Rd ... Lower resistance, Rm ...
Monitor resistance, E ... Battery electromotive force, V ... Voltmeter, R1-R
5 ... Wheatstone bridge resistance.

Claims (5)

[Claims] 1. A decrease in insulation occurs due to electrical connection between a stack of a fuel cell body and a gas manifold, and between the stack and a water manifold outside a cell body via a switch and a resistor. In this case, a leakage current is estimated by turning off the switch, and based on this current value, power generation is stopped when insulation degradation continues for a certain time or longer. 2. The short-circuit protection device for a fuel cell according to claim 1, wherein the leakage current is estimated and the power generation is stopped automatically. 3. The short-circuit protection device for a fuel cell according to claim 1, wherein a fuse is introduced between the stack and the tie rod, and when the fuse is blown, power generation is stopped. 4. The short-circuit protection device for a fuel cell according to claim 3, wherein the blowout of the fuse is detected and the power generation is automatically stopped. 5. A short circuit protection for a fuel cell according to claim 1, wherein a Wheatstone bridge circuit is introduced between the manifold and the upper portion of the cell to monitor the insulation resistance of the gas pipe and the drain pipe. apparatus.