JPH06225479A - Ac switch change-over method of uninterruptible power supply apparatus and hybrid ac switch - Google Patents

Abstract

PURPOSE:To prevent the output of an external direct power supply and the output of an uninterruptible power supply apparatus from overlapping each other by a method wherein the possibility of the breakdown of a semiconductor switch caused by an overcurrent is detected. CONSTITUTION:The peak value of an overcurrent applied to an AC switch 20 composed of a semiconductor switch 21 and a mechanical switch 22 which are connected in parallel with each other is compared with the peak value of the overload strength value of the semiconductor switch 21. Or, the time variation of the overcurrent applied to the AC switch 20 is compared with the overload strength value of the semiconductor switch 21. With the comparison results, the breakdown or the possibility if the breakdown of the semiconductor switch 21 can be judged. Even if the overcurrent ceases, in accordance with the judgement, change-over of the power supply to a load 6 from an external direct power supply 1 to an uninterruptible power supply(UPS) 3 is not performed. With this constitution, even if the AC switch 20 has some abnormality, overlap of the output of the external direct power supply 1 and the output of the uninterrupted power supply(UPS) 3 can be avoided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an AC switch switching method used for switching between a direct power supply and a UPS output when an uninterruptible power supply (hereinafter referred to as UPS) detects overcurrent, and switching of AC power. , Or a hybrid AC switch used for shutting off.

[0002]

2. Description of the Related Art A conventional method of switching between a direct power supply and a UPS output will be described. FIG. 3 is a diagram showing a conventional example of a circuit for switching between a direct power supply and a UPS output, 1 is a direct power supply, 3 is a UPS, 4 is an inverter, 5 is a current transformer,
6 is a load, 7 is a current detector, 8 is a comparator, 9 is a setting device, 19 is a switching control device, 30 is an AC switch,
Reference numeral 31 is a semiconductor switch, and 32 is a fast-acting fuse.

The direct power supply 1 is connected to the U via an AC switch 30.
Connected to the output side of PS3, the output of UPS3 is the current transformer 5
The output of the UPS 3 is normally supplied to the load 6. When an overcurrent starts to flow to the load 6 on the load side due to a short circuit accident or the like, this overcurrent is detected by the current transformer 5 and the current detector 7. The value detected by the current detector 7 is the comparator 8
Is compared with the switching level preset in the setter 9. The result of the comparison in the comparator 8,
When the detected value exceeds the set value, the switching control device 18
Then, the AC switch 30 is turned on to start the power supply from the direct power supply 1 to the load 6. Inverter 4 at the same time
Is turned off, the output of UPS3 is turned off, and UPS3 is protected from excessive current.

If the overcurrent subsides and the value detected by the current detector 7 falls below the switching level set in the setting device 9, the switching control device 19 turns off the AC switch 30 to directly feed power to the load 6. Switch from power supply 1 to UPS 3. Further, the AC switch 30 for switching between the output of the UPS 3 and the direct power supply 1 is composed of a semiconductor switch 31 and a series circuit of a fast-acting fuse 32 in cooperation with the semiconductor switch. As described above, when the current detector 7 detects the overcurrent, the power supply to the load 6 is increased.
The output of S3 is switched to the direct power supply 1. Since the power from the direct power supply 1 is supplied to the load 6 via the AC switch 30, when the overcurrent further increases and the overcurrent approaches the overload withstanding capacity of the semiconductor switch 31 in the AC switch 30, The semiconductor switch 31 is protected by cutting the fast-acting fuse 32.

[0005]

However, since the safe passing current region of the fast-acting fuse, which is perfectly coordinated with the overload withstanding capability of the semiconductor switch, is considerably low, the overload withstanding capability of the direct feed side is set to this fast-breaking fuse. However, there is a problem in that the overload withstanding capacity on the direct delivery side is set lower than the capability of the semiconductor switch.

[0006] Here, if the fast-acting fuse is removed, the overload withstanding capacity of the direct feed side can be set to a value commensurate with the ability of the semiconductor switch, but when the semiconductor switch is destroyed by the increased overcurrent, most of them are in the conductive state. Therefore, it is difficult to detect the abnormality of the semiconductor switch. Furthermore, if the power is continuously supplied from the direct feed side and the overcurrent is subsided and then it is attempted to switch to the power feed from the UPS, the semiconductor switch cannot be turned off. There was a problem that it would be damaged.

Further, when the semiconductor constituting the AC switch is damaged due to the overcurrent, in order to replace the AC switch, the power supply to the load had to be temporarily stopped. The present invention has been made in view of the above-mentioned problems of the prior art, and does not use a fast-acting fuse for protection of an AC switch, and also rapidly detects the possibility of semiconductor switch destruction due to overcurrent, thereby directly transmitting power. And U
UPS AC switch switching method that does not overlap with PS output, and hybrid capable of replacing a semiconductor switch damaged or possibly damaged by an overcurrent without interrupting power supply from a direct power supply It is intended to provide an AC switch.

[0008]

In order to achieve the above object, in the present invention, a power supply source for a load is UP without using a fast-acting fuse for protecting a semiconductor switch.
After switching from S to the direct power supply, an overcurrent flowing through the AC switch is detected. The peak value of the overcurrent is obtained from the detected value of the overcurrent, and is compared with the peak value of the overload withstanding capacity of the semiconductor forming the AC switch. Alternatively, a temporal change of the overcurrent is obtained from the overcurrent detection value and compared with the overload withstand capacity of the semiconductor forming the AC switch.

As a result of this comparison, when the detected value exceeds the overload withstanding capacity of the semiconductor, it is judged that the semiconductor is "damaged" or "possibly damaged", and even if the overcurrent subsides thereafter, Do not switch the source of power to the load from direct power to UPS output. Further, the AC switch has a configuration in which a semiconductor switch and a mechanical switch that form the AC switch are connected in parallel, and this parallel connection is inserted into both ends of the semiconductor switch with plugs.
Sockets are provided at both ends of the mechanical switch, and the insertion plug is inserted into the sockets.

[0010]

[Function] The peak value of the overcurrent flowing through the AC switch and the AC
By comparing with the peak value of the overload withstanding capability of the semiconductor forming the switch, or by comparing the temporal change of the overcurrent flowing in the AC switch with the overload withstanding capability of the semiconductor forming the AC switch, “Damaged” or “possible damage” is determined.

Even if the overcurrent subsides, the source of the power to the load is not switched from the direct power source to the UPS output based on the above determination, so that the direct power source and the UPS output are prevented even if the AC switch is abnormal. Does not wrap. Further, the AC switch has a configuration in which a semiconductor switch and a mechanical switch that form the AC switch are connected in parallel, and a plug and a socket are used for this parallel connection, so that the semiconductor switch can be attached to and detached from the mechanical switch. .

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. Figure 1
FIG. 3 is a diagram showing a first embodiment according to the present invention. In FIG. 1, 10 is a comparator, 11 is a setting device, 12 is a memory, 18 is a switching control device, and 20 is a hybrid AC.
A switch, 21 is a semiconductor switch, 22 is a mechanical switch, 23 is an insertion plug provided at both ends of the semiconductor switch 21, and 24 is a socket provided at both ends of the mechanical switch 22. Besides, those having the same functions as those of the conventional example shown in FIG.

The hybrid AC switch 20 has a structure in which the semiconductor switch 21 and the mechanical switch 22 are connected in parallel by inserting the insertion plug 23 into the socket 24. Normally, a switching command from the switching control device 18 is issued. Thus, the semiconductor switch 21 is turned on / off to function as an AC switch. The direct power supply is connected to the output side of the UPS 3 via the hybrid AC switch 20, and the output of the UPS 3 is connected to the load 6 via the current transformer 5.
The output of the UPS 3 normally supplies electric power to the load 6.

When a short circuit accident occurs on the load side and an overcurrent begins to flow, the current is changed to a current transformer 5 and a current detector 7.
Detect by. The value detected by the current detector 7 is compared with the switching level set by the setter 9 in the comparator 8. When the detected value exceeds the set value as a result of the comparison, the switching control device 18 ignites the AC switch 2 and the power supply from the direct power supply 1 is started.
At the same time, the inverter 4 is turned off and protected from excessive current.

Immediately thereafter, if the overcurrent subsides and the value detected by the current detector 7 falls below the switching level set by the setter 9, the switching controller 18 extinguishes the AC switch 2 and the load 6 is supplied. Direct power supply 1
To the inverter 4. The overcurrent detection value input to the comparator 10 is compared with the peak value of the overload withstand amount of the semiconductor that constitutes the AC switch set in the setter 11. When the overcurrent continues to flow and further increases and the overcurrent detection value exceeds the overload withstanding peak value, the abnormal signal “there is a possibility of damage to the AC switch” is written in the memory 12. The abnormal signal is input to the switching control device 18, the overcurrent subsides, and even if the detection value of the current detector 7 falls below the switching level set by the setter 9, the power supply from the direct power supply 1 is continued, The inverter 4 is controlled so as not to be turned on, and at the same time, the abnormality occurrence is displayed outside.

FIG. 2 is a diagram showing a second embodiment according to the present invention. In the configuration shown in FIG. 2, in order to more accurately determine the abnormality of the AC switch, instead of the comparator 10 and the setter 11 in FIG. 1, a memory 13 that stores the output of the current detector 7 as instantaneous current data, A memory 14 for storing a short-time overload tolerance curve of a semiconductor constituting an AC switch as tolerance data and a digital comparator 15 are provided.

The memory 13 stores a trend of the instantaneous current at the time of overcurrent as digital data, and the digital comparator 15 compares the digital data with the overload withstand data of the AC switch stored in the memory 14. As a result of the comparison by the digital comparator 15, if even one of the instantaneous current data exceeds the predetermined overload withstand data of the AC switch, it is determined that the AC switch is abnormal, and the first embodiment is executed. Similarly to the above, an abnormal signal that "the AC switch may be damaged" is written in the memory 12. The abnormal signal is input to the switching control device 18, the overcurrent subsides, and even if the detection value of the current detector 7 falls below the switching level set by the setter 9, the power supply from the direct power supply 1 is continued, The inverter 4 is controlled so as not to be turned on, and at the same time, the abnormality occurrence is displayed outside.

Next, the hybrid AC switch will be described. As described above, the hybrid AC switch is such that the semiconductor switch 21 and the mechanical switch 22 are connected in parallel by using the insertion plug 23 and the socket 24 like the hybrid AC switch 20 of FIG. Normally (when power is being supplied from the UPS 3), both the semiconductor switch 21 and the mechanical switch 22 are off. When an overcurrent occurs due to some factor such as a load side short circuit and the inverter 4 must be turned off, a switching command from the switching control device 18 causes
The semiconductor switch 21 is instantly turned on, and at the same time, the inverter 4 is turned off.

As the overcurrent further increases, the semiconductor switch 2
When the overload withstanding capacity of 1 is exceeded, that is, when it is determined that "the AC switch may be damaged" in the first and second embodiments, even if the overcurrent has subsided, the As described above, the power supply to the UPS 3 is not switched and the power supply to the load 6 is continued from the direct power supply. Further, the semiconductor switch 21 that is damaged or may be damaged must be replaced with a normal one.

Therefore, the procedure for replacing the semiconductor switch 21, which may be damaged, with a normal one will be described below. First, the mechanical switch 22 is turned on, and then the semiconductor switch 21 which may be damaged is pulled out from the sockets 24 provided at both ends of the mechanical switch 22. Next, after the normal semiconductor switch 21 is inserted into the socket 24, the semiconductor switch 21 is turned on and the mechanical switch 22 is turned off, so that the semiconductor switch 21 can be replaced while the power supply to the load is continued. Ends.

If the overcurrent has subsided at this point, the power supply from the UPS 3 can be resumed by turning off the semiconductor switch 21 and starting the operation of the inverter 4 at the same time.

[0022]

As described above, in the first and second embodiments, it is determined that the AC switch is abnormal,
When the abnormal signal "the AC switch may be damaged" is written in the memory 12, the abnormal occurrence is displayed to the outside, and at the same time, the abnormal signal is input to the switching control device 18. When an abnormal signal is input to the switching control device 18, after the overcurrent is subsided, the control for returning from the direct feed to the inverter feed is stopped, so that the AC switch does not turn off and the direct feed and the UPS output overlap. Can be avoided.

Further, by providing a current detector to monitor the load current, the quick-acting fuse for protecting the semiconductor switch can be omitted, the cost can be reduced, and the AC switch may be damaged due to overcurrent. Can be done easily and accurately. Further, by connecting the semiconductor switch and the mechanical switch to the AC switch detachably in parallel using the plug and the socket, the AC switch can be exchanged while the power supply to the load is continued.

[Brief description of drawings]

FIG. 1 is a diagram showing a first embodiment according to the present invention.

FIG. 2 is a diagram showing a second embodiment according to the present invention.

FIG. 3 is a diagram showing a conventional example of a switching circuit.

[Explanation of symbols]

 1 Direct Power Supply 2 AC Switch 3 UPS 4 Inverter 5 Current Transformer 6 Load 7 Current Detector 8, 10 Comparator 9, 11 Setter 12 Memory 13 Instantaneous Current Data Memory 14 AC Switch Withstanding Data Memory 15 Digital Comparator 18, 19 Switching Control device 20 Hybrid AC switch 21, 31 Semiconductor switch 22 Mechanical switch 23 Plug plug 24 Socket 30 AC switch 32 Fast-acting fuse

Claims (4)

[Claims] 1. A method of switching an AC switch for switching between a direct power supply and an output of an uninterruptible power supply when a short-circuit accident occurs in a load to which the uninterruptible power supply supplies electric power. Provided with a current detector that detects the load current, a short-circuit accident occurred in the load to which the uninterruptible power supply is supplying power, and when an overcurrent was detected by the current detector, it was provided on the direct power supply side. Ignite the AC switch, turn off the uninterruptible power supply, switch the power supply to the load from the uninterruptible power supply to the direct power supply, and set the load current supplied from the direct power supply through the AC switch in advance. If the set value is exceeded, A
Judging that the C switch may have been destroyed, the command to turn off the AC switch is not output, and power is supplied from the direct power supply to the load without restarting power supply by the uninterruptible power supply. A method for switching an AC switch of an uninterruptible power supply characterized by the following. 2. The AC switch switching method for an uninterruptible power supply according to claim 1, wherein the set value is the AC
A method for switching an AC switch of an uninterruptible power supply, wherein a peak value of a short-time overload withstanding capability of a semiconductor used for a switch is set. 3. The AC switch switching method for an uninterruptible power supply according to claim 1, further comprising a storage device for storing a short-time overload withstanding curve of a semiconductor used for the AC switch, A method for switching an AC switch of an uninterruptible power supply, characterized in that a short-time overload withstanding curve stored in the storage device is used. 4. Inserting plugs at both ends of a semiconductor switch composed of semiconductor switching elements and sockets at both ends of a mechanical switch, respectively, and inserting plugs provided at both ends of the semiconductor switch to both ends of the mechanical switch. A hybrid AC switch characterized in that the semiconductor switch and the mechanical switch are connected in parallel by being inserted into a provided socket.