JP2000224761A - Dc power supply system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent shunt current of another system from running through a chassis after a circuit breaker is tuned off if a short circuit occurs in a chassis, by making a Zener diode connection between the output return of a power supply system and the chassis. SOLUTION: The output return of a power supply system 1 is connected with a chassis by means of a Zener diode 8. If a short circuit occurs in a chassis, an internal breaker 4n in a switching device 2n on the upstream side of a failure position B detects overcurrent, so that it turns off automatically, and a part of current 1a to 1n-n of a normal system passes through the flywheel diode 5n in the failed system and returns to a point A via the Zener diode 8 from the chassis. As a result, the flywheel diode 5n is not actually turned on because a cathode potential exceeds an anode potential. It is thus possible to prevent current from running through the chassis after the breaker 4 is turned off even if a short circuit occurs in the chassis.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC power supply for a device used in an environment where a chassis (device structure) itself is charged, such as a space station. It is about connection.

[0002]

2. Description of the Related Art FIG. 4 shows a configuration of a conventional DC power supply device (hereinafter referred to as a DC power system). In the figure, 1 is a power supply device, 2a to 2n are switch devices, and 3a to 3n are system loads. 4a to 4n are switch devices 2a to
2n is a circuit breaker that can open and close according to system operation, and automatically shuts off when an overcurrent is detected (OF).
F) has the function of 5a to 5n are switch devices 2
a to 2n, and when the circuit breakers 4a to 4n are turned off, the system load 3
It functions as a path for the induced electromotive voltage generated by the inductance of a to 3n. Reference numeral 6 denotes a system hot side wire from the power supply device 1 to a branch point of the switch devices 2a to 2n. Similarly, reference numeral 7 denotes a system return side wire. In the conventional DC power system, at the output point A of the power supply device 1, the output return and the chassis are connected. This connection has the meaning of fixing the return potential of the DC power system for electrical design standards and safety in handling of devices connected to the system. In particular, when the chassis (equipment structure) itself is charged, as in a space station, it is important to eliminate the potential difference between the chassis and the power system to prevent discharge. However, this connection is usually made at only one location because the chassis itself is not used as a current path. Note that 1a to 1n are system loads 3a
3TN, and IRTN is a return current returning to the power supply 1 from a branch point of the switch devices 2a to 2n.

FIG. 5 shows a case where a chassis short-circuit fault occurs in a conventional DC power system (FIG. 4). Point B in FIG. 5 is a chassis short-circuit failure point. The fault current at this time flows from the point B into the chassis, flows through the chassis (chassis current IChassis), and returns to the power supply device 1 via the point A connected to the chassis.

When the above-mentioned chassis short-circuit fault occurs, B
In the switch device 2n upstream of the point, the internal circuit breaker 4n detects an overcurrent and turns off automatically. At this time, the switch devices 2a to 2n-1 continue to supply power to the normal system loads 3a to 3n-1.

[0005] The internal circuit breaker 4 is
FIG. 6 shows the state after n is turned off. In the figure,
The circuit breaker 4n of the fault occurrence system is in the OFF state. However, when the currents Ia to In-1 of the normal system return to the power supply device 1, they pass through (a) the route (IRTN) flowing through the system return side wire 7 and (b) the failed system flywheel diode 5n. In some cases, the flow may be branched from point B to a route (IChassis) returning to point A via the chassis. That is, the current IChassis may continue to flow through the point B (short-circuit point) and the chassis even though the circuit breaker 4n is turned off.

Here, the cause of the current flowing through the chassis along the route (b) after the interruption in the case of the chassis short circuit will be examined. First, the cathode potential of the flywheel diode 5n is almost equal to the potential of the point A because the cathode is short-circuited to the chassis at the point B and the impedance of the chassis is sufficiently small. Next, assuming that all the currents 1a to 1n-1 of the normal system flow as the current IRTN through the route (a), a voltage drop VRW due to the resistance of the wire and the current IRTN is applied to the system return side wire 7. appear. Therefore, the anode potential of the flywheel diode 5n becomes higher than the point A by the voltage drop VRW. Therefore, the potential difference between the anode and cathode of the flywheel diode 5n is
It becomes almost equal to the voltage drop VRW. At this time, the voltage drop VRW
Is greater than 0.6V, the flywheel diode 5
Since n is turned on, a part of the normal system currents Ia to In-1 is diverted, and the chassis current IChassis flows.

If the current IChassis continues to flow despite the circuit breaker 4n being turned off according to the above principle, the current value becomes larger than the maximum rated value of the flywheel diode 5n, and the flywheel diode 5n is damaged. is there. In addition, flywheel diode 5
There is also a safety issue in that current continues to flow through the chassis, even if n is not damaged. Further, the voltage drop VRW is reduced to 0.
When the current IChassis is set to 6 V or less to prevent the current IChassis from flowing, the system return side wire 7 needs to be thickened or a plurality of wires need to be arranged in parallel, thereby increasing the size and weight.

[0008]

Since the conventional DC power system is configured as described above, in the case of a chassis short circuit, a shunt current from another system continues to flow through the chassis even if the circuit breaker is turned off. There is a problem on safety and a problem that the current leads to damage of the flywheel diode. Further, when the resistance value of the wire is reduced in order to solve the above problem, there has been a problem that the size and weight increase due to the increase in the wire amount.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and is intended to prevent a shunt current from another system from continuing to flow through the chassis after the circuit breaker is turned off when the chassis is short-circuited. The purpose is to obtain strains.

[0010]

According to a first aspect of the present invention, there is provided a DC power system in which an output return of a power supply device is connected to a chassis by a zener diode.

In a DC power system according to a second aspect of the present invention, the zener voltage of the zener diode is set to be larger than a voltage drop generated in the output return wire.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 is a system diagram showing Embodiment 1 of the present invention.
2n are switch devices, and 3a to 3n are system loads. Reference numeral 8 denotes a zener diode connected between point A of the output return of the power supply device 1 and the chassis.

FIG. 2 shows a case where a chassis short-circuit fault occurs in the DC power system (FIG. 1) according to the present invention. Point B in FIG. 2 is a chassis short-circuit failure point. At this time, since the output voltage of the power supply device 1 is sufficiently higher than the zener voltage of the zener diode 8, the fault current flows from the point B into the chassis, and after flowing through the chassis (chassis current IChas
sis) and return to the power supply 1 from point A via the zener diode 8.

When the above-mentioned chassis short-circuit fault occurs, B
In the switch device 2n upstream of the point, the internal circuit breaker 4n detects an overcurrent and turns off automatically. At this time, the switching devices 2a to 2n-1 continue to supply power to the normal system loads 3a to 3n-1.

Internal circuit breaker 4 for chassis short circuit fault
FIG. 3 shows the state after n is turned off. In the figure,
The circuit breaker 4n of the fault occurrence system is in the OFF state. First, it is assumed that a part of the currents 1a to 1n-1 of the normal system is diverted to the route which returns from the chassis to the point A via the Zener diode 8 through the flywheel diode 5n of the faulty system. At this time, the cathode potential of the flywheel diode 5n is short-circuited to the chassis at the point B and the impedance of the chassis is sufficiently small, so that the cathode potential becomes higher than the point A by the zener voltage VZ of the zener diode 8. Similarly, the anode potential of the flywheel diode 5n is higher than the point A by the voltage drop VRW generated in the return wire 7 of the system. Here, the zener voltage VZ of the zener diode 8 is set to be higher than the voltage drop VRW generated in the return wire 7 of the system. Therefore, the flywheel diode 5n
Does not actually turn on because the cathode potential is higher than the anode potential. That is, when the chassis is short-circuited, no current flows through the chassis after the circuit breaker 4n is turned off.

[0016]

According to the first and second aspects of the present invention, the zener diode is connected between the output return of the power supply device and the chassis, so that when the chassis is short-circuited, the shunt current from another system is turned off after the circuit breaker is turned off. Will not flow.

[Brief description of the drawings]

FIG. 1 is a first embodiment of a DC power system according to the present invention;
FIG.

FIG. 2 is a first embodiment of a DC power system according to the present invention;
FIG. 3 is a system diagram showing a case where a chassis short circuit occurs in FIG.

FIG. 3 is a first embodiment of a DC power system according to the present invention;
FIG. 3 is a system diagram showing a situation after the circuit breaker is turned off when the chassis is short-circuited.

FIG. 4 is a system diagram showing a conventional DC power system.

FIG. 5 is a system diagram showing a case where a chassis short circuit occurs in a conventional DC power system.

FIG. 6 is a system diagram showing a situation after a breaker is turned off when a chassis is short-circuited in a conventional DC power system.

[Explanation of symbols]

1 power supply device, 2 switch device, 3 system load, 4
Circuit breaker, 5 flywheel diode, 6 system hot side wire, 7 system return side wire, 8 zener diode.

Claims (2)

[Claims] 1. A DC power supply device comprising a power supply device and a plurality of switch devices for distributing an output of the power supply device to a plurality of loads, wherein a Zener is provided between an output return of the power supply device and a chassis. A DC power supply device having a diode connected thereto. 2. A DC power supply device, wherein a zener voltage of the zener diode is set to be larger than a voltage drop generated in the output return side wire.