JPS6237402Y2 - - Google Patents

Description

[Detailed description of the invention] This invention is a power supply circuit for a load that has a regular power source and a backup power source. Determines whether the power can be turned on or not.
The present invention relates to a power supply switching device that performs switching operations safely and reliably.

Conventional power supply switching devices of this type include those shown in FIGS. 1 and 2. In the figure, A is a regular power source, B is a backup power source, L is a load circuit, 1 and 10 are circuit breakers with tripping coils to protect circuits from short circuits and overloads, and 2 and 20 are respectively 3 is an undervoltage relay for detecting undervoltage in the regular power supply circuit; 2a and 20a are operating coils for opening and closing the switching switches 2 and 20, respectively; , 2b and 20b are auxiliary contacts of the switching switches 2 and 20, respectively, 3a and 3b are auxiliary contacts that open and close according to the operation of the undervoltage relay 3, 3a is closed only when the circuit voltage is above a predetermined value, and 3b The circuit is closed only when the circuit voltage is below a predetermined value. P and N indicate arbitrary control power supply buses.

In the circuit shown in FIG.
Turn on the circuit and disconnector 10 with the tripping coil of the power supply system. When the circuit breaker 1 is turned on, the undervoltage relay 3 receives a voltage higher than a predetermined value and is excited, and its contacts 3a are closed and contacts 3b are opened. At this time, make sure that the switching switch 20 of the B power supply system is not turned on, that is, the auxiliary contact 20b of this switch
On the condition that A is closed, the operation coil 2a of this switch is excited and the switch 2 is closed, and A
Power is supplied to the load L from the power supply system. here,
If a power loss accident occurs in the A power system,
The undervoltage relay 3 is activated, opening its contacts 3a and closing its contacts 3b. Then, when the switching switch operating coil 2a becomes de-energized, this switch 2 is opened and its auxiliary contact 2b is closed, causing switching. The switching operation coil 20a is excited and the switching switch 2
0 is closed, and the circuit from the B power supply system to the load L is closed.

Since the conventional power supply switching device is configured as described above, when power is being supplied to the load L from the power supply system A, which is a regular power supply, an accident such as a short circuit occurs from the switching switch 2 to the load side. Even if
The load L was switched to the B power system, which was a backup power source, and the B power system had the drawback that the same accident situation as the A power system was spread.

This idea was made to eliminate the shortcomings of the conventional power supply switching device as mentioned above. It is an object of the present invention to provide a power supply switching device that detects the power supply and, as a result, determines whether switching to a backup power supply is possible or not.

FIG. 3 is a block diagram of a power supply circuit according to an embodiment of this invention, and FIG. 4 shows its control circuit. In the figure, A, B, L, 1, 10, 2, 20, 3, etc. indicate exactly the same devices and equipment as shown in FIG. 3 and 4 are undervoltage relays for detecting undervoltage in the circuit; 2a and 20a are operating coils for opening and closing the switching switches 2 and 20, respectively;
b, 2c and 20b, 20c are auxiliary contacts that open and close in accordance with the opening and closing operations of the switching switches 2 and 20, respectively; 3a, 3b, and 4a are operating contacts of the undervoltage relays 3 and 4, respectively; and 5 is a contact. Auxiliary relays for amplification, 5a, 5b, 5
Reference numerals c and 5d designate contacts of an auxiliary relay 5, 6 a time-limited relay of instantaneous return type, 6a and 6b operating contacts thereof, and 7 a resistor for preventing a short circuit in the power supply C circuit.

Next, the operation of the power switching device of the present invention will be explained. As described in the explanation of the operation of the conventional technology, two power supply systems, the A power supply system and the B power supply system, are provided,
In a circuit where one power supply system A is used as a regular power supply and the power supply system B is used as a backup power supply, the trip coils and disconnectors 1 and 10 of the A power supply system and the B power supply system are turned on. At the same time as the circuit breaker 1 is turned on, the undervoltage relay 3 is energized, its contact 3a is closed, and the auxiliary relay contact 5a is inoperative and B
On the condition that the auxiliary contact 20b of the switching switch of the power supply system is closed, the operating coil 2 of this switch
a is excited. When this switch 2 is closed, the first switch supplies power from the A power supply system to the load.
Close the circuit.

In this way, if a power loss accident occurs due to a short circuit or the like during load operation, the accident will be handled by the undervoltage relay 3.
By detecting this and opening the contact 3a, the excitation circuit of the operation coil 2a of the switching switch is opened, and this switch 2 is opened. At this time, the auxiliary contact 2c is closed, and the open-side auxiliary contact 20c of the switching switch 20 of the B power supply system is closed, and due to the operation of the undervoltage relay 3, the contact 3b is closed.
is closed, and the auxiliary relay 5 is excited on the condition that the time-limited operation instantaneous return contact 6b of the time-limited relay 6 is also closed, and its contacts 5c and 5d are closed. When the contacts 5c and 5d are closed, the switching switches 2 and 20
A C power supply is connected to the area from to the load. Further, at the time when the contact 3b of the undervoltage relay 3 is closed, another undervoltage relay 4 connected to the C power source is already energized, and its contact 4a is closed, so the time limit relay 6 is energized. has been done.
If a short circuit occurs in the area from the switching switches 2 and 20 to the load before the time-limiting contacts 6a and 6b operate, the undervoltage relay 4 will operate and the contact 4a will open. Then, the time-limited relay 6 is de-energized and its contacts 6a and 6b are prevented from operating. The 6a contact is closed, and the 6b contact is opened, and the auxiliary relay 5 is de-energized and its contact 5
If B is not closed, the operating coil 20a of the switching switch 20 will not be excited, and therefore the B power supply system will not be switched. In addition, if the power loss accident due to a short circuit occurs on the power supply side from the switching switch 2, the fault will be removed when the C power supply is connected, so the fault caused by the undervoltage relay 4 will not be detected, and the time-limited relay contact will not be detected. 6a and 6b are operated, the operating coil 20a of the switching switch 20 is energized, the switch 20 is turned on, and the second circuit from the B power supply system to the load is closed. Furthermore, the resistor 7 provided in the C power circuit is provided to prevent the C power circuit from shorting when a short circuit occurs in the area from the switching switches 2 and 20 to the load. It is something. In the above embodiment, the case where the C power supply for accident detection is a different power supply from the A and B power supply systems has been explained, but the C power supply for accident detection may be the first or second circuit from the A or B power supply system to the load. may be a separate branch power source, and the same effect as in the above embodiment can be achieved.

In this way, according to this invention, in the event of a loss of power due to an accident in the regular power supply circuit, it is possible to first detect in which area the power loss accident occurred and determine whether it is possible to switch to a backup power source. This has the effect of safely and reliably switching the power supply.

[Brief explanation of the drawing]

Figure 1 is a circuit configuration diagram showing an example of a conventional power supply switching device, Figure 2 is its control circuit diagram, Figure 3 is a circuit diagram of a power supply switching unit according to an embodiment of this invention, and Figure 4 is its control circuit diagram. It is a control circuit diagram. In the diagram, A is a regular power supply, B is a backup power supply, and C
1 is a failure detection power source, L is a load, 1 and 10 are circuit breakers, 2 and 20 are switching switches, and 3 and 4 are low voltage relays.

Claims (1)

[Scope of utility model registration request] A first circuit that supplies power to the load from the regular power source via a switching switch; a second circuit that supplies power to the load from a backup power source via another switching switch in the event of an accident in the first circuit; An undervoltage relay that operates in response to a low voltage accident in one circuit, and in response to the operation of the undervoltage relay, the switching switch of the first circuit is opened, and the switch is connected to the load from the failure detection power source via the auxiliary relay. If the first circuit is opened due to the operation of the undervoltage relay, the fault detection circuit confirms that there is no accident in the load circuit, and then the switching switch of the second circuit is closed. and connects the backup power source to a load.