JPH04275038A - Power supply changeover method - Google Patents

Abstract

PURPOSE:To supply power from a bypass power source only to loads, which has become overload, and continue the power supply from USP to other loads. CONSTITUTION:The currents flowing to each load 16a, 16b,... are detected with a.c. machines 31a, 31b,..., and then these currents are given to an overcurrent detector 32. The detector 32 judges whether the input current is above the set value or more. The results of judgment are given from the detector 32 to the off command transmitter 33 and a gage signal generator 34. Hereby, power is supplied to the load 16a by turning off the second switch 17a and turning on a semiconductor switch 19a.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of switching power supply from an uninterruptible power supply (hereinafter referred to as UPS) and a bypass power supply.

0002

2. Description of the Related Art FIG. 3 is a schematic diagram showing a power supply switching method for supplying power to a load using a UPS and a bypass power supply device. In FIG. 3, 11a, 11b... are CVC
The outputs of the UPSs 11a, 11b... are connected to the common bus 1 via the first switches 12a, 12b...
3. 14a, 14b are each UPS 11a, 1
A current transformer that detects the current output from 1b..., and when an overcurrent is detected by the current transformers 14a, 14b..., the UPS 11
a, 11b... are stopped.

16a, 16b... are loads, and normally these loads 16a, 16b are connected from the common bus 13 to the second switch 17.
Power is supplied via a, 17b, . Furthermore, it is also possible to supply power from the bypass power supply device 18 by switching to the switches 20a, 20b, . . . as a backup circuit. The semiconductor switches 19a, 19b... are normally in an off state, and when the current transformers 14a, 14b... detect an overcurrent and the UPS 11a, 11b... stops,
The second switches 17a, 17b... are all turned off and simultaneously turned on. Note that the semiconductor switches 19a, 19b...
Switches 20a and 20b are connected in parallel to the semiconductor switch 19, and when the switches 20a and 20b are turned on, the semiconductor switch 19
a, 19b... are turned off.

FIG. 4 shows the second switch 17a shown in FIG.
17b... is a block diagram explaining the principle of on/off control of semiconductor switches 19a, 19b... and switches 20a, 20b..., and 21 indicates whether the current detected by each current transformer 14a, 14b... exceeds the set value. This is the judgment part that determines whether or not it is. The output determined by this determining unit 21 is output from an off command sending unit 22 which sends out a command to turn off the second switches 17a, 17b, and the semiconductor switches 19a, 19.
b... is supplied to an on-command sending unit 23 that gives an on-command to the on-commands. The on-command sending unit 23 also gives an on-command to the switches 20a, 20b, . . . after a certain period of time after sending the on-command.

[0005]

[Problem to be Solved by the Invention] In the power supply switching method using the UPS bypass power supply device shown in FIG. . Then, each current transformer 14a
, 14b... detects an overcurrent, and the determination unit 21 of FIG.
is input. When the determining unit 21 determines that the input current is equal to or higher than the set value, it stops the UPSs 11a, 11b, etc., and also outputs the off command sending unit 22 and the on command sending unit 23.
gives the output. In addition, from both the sending sections 22 and 23, off commands are given to the second switches 17a, 17b, . . . and on commands are given to the semiconductor switches 19a, 19b, . Therefore, power is supplied to the loads 16a, 16b, . . . from the bypass power supply device 18.

As described above, in the conventional power supply switching method, even if one load becomes overloaded, power is supplied to all loads from the bypass power supply, which reduces the reliability of power supply by the UPS. At the same time, the frequency of switching to power supply from the bypass power supply device may also increase.

[0007] This invention was made in view of the above circumstances, and even if one load becomes overloaded, power is supplied only to that load from the bypass power supply device, so that the UPS is not used to supply power to other loads. It is an object of the present invention to provide a power supply switching method using a UPS and a bypass power supply, which can continue a stable power supply from the beginning and greatly reduce the frequency of power supply switching.

[0008]

[Means and operations for solving the problems] In order to achieve the above object, the output ends of a plurality of uninterruptible power supply devices are connected to a common bus, and power is supplied from the common bus to a plurality of loads. At the same time, in the power supply switching method in which power is switched and supplied from the bypass power supply to the load when the power supply from the uninterruptible power supply is cut off, the current flowing to each load is detected respectively, and the detected current is set to the set value. When this happens, the power supply for the load exceeding the set value is switched from the uninterruptible power supply to the bypass power supply. Further, the present invention is characterized in that when the entire UPS becomes overloaded, after switching all the load power supply to the bypass power supply device, the power supply is switched one feeder at a time with a time delay.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings, in which the same parts as in FIG. 3 are denoted by the same reference numerals. In FIG. 1, current flowing through each load 16a, 16b, . . . is detected by current transformers 31a, 31b, . These current transformers 31a
, 31b is detected by the overcurrent detection section 3 shown in FIG.
2a, 32b... Overcurrent detection section 32a, 3
2b... individually determines whether the input current is equal to or higher than the set value, and sends the determination result to the off command sending units 33a, 3.
3b... and the gate signal generators 34a, 34b.... For example, when the overcurrent detection section 32a determines that there is an overcurrent, the cutoff command sending section 33a issues an off command to the second switch 1.
Give to 7a. On the other hand, the gate signal generator 34a provides an on-gate signal to the semiconductor switch 19a. As a result, the switch 17a is turned off, the semiconductor switch 19a is turned on, the bypass power supply 18 is connected to the load 16a, and power is supplied to the load 16a. Thereafter, when the switch 20a is turned on, the semiconductor switch 17a is turned off.

As described above, the current flowing through each load is detected and only the overloaded one is sent to the UPS 11a, 11b.
Since the power supply from ... is cut off, the loads that are not overloaded can continue to be supplied with power from the UPSs 11a, 11b, ....

[0011] Note that when the entire UPS 11a, 11b... is overloaded, it switches to the bypass side, but at this time,
UPS11a, 1 sequentially with a time lag
1b... to the bypass power supply 18, the transient voltage change at the time of switching can be kept small.

0012

[Effects of the Invention] As described above, according to the present invention,
By cutting off power supply from the UPS to loads that are overloaded, etc., and supplying power from the bypass power supply, it is reliable because the UPS continues to supply power to loads that are not overloaded. A system with high performance can be obtained.

[Brief explanation of the drawing]

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

FIG. 2 is a block diagram showing main parts of the embodiment.

FIG. 3 is a schematic configuration diagram showing a conventional example.

FIG. 4 is a block diagram showing main parts of a conventional example.

[Explanation of symbols]

11a, 11b...UPS, 13...Common bus, 16a, 1
6b...Load, 17a, 17b...Second switch, 18...Bypass power supply, 19a, 19b...Semiconductor switch, 20a
, 20b...Switch, 31a, 31b...Current transformer, 32...
Overcurrent detection section, 33... Off command sending section, 34... Gate signal generation section.

Claims (2)

[Claims] Claim 1: The output ends of a plurality of uninterruptible power supplies are connected to a common bus, and power is supplied from the common bus to a plurality of loads, and when power supply from the uninterruptible power supply is cut off, a bypass In a power supply switching method that switches and supplies power from a power supply to a load, the current flowing through each load is detected, and when the detected current exceeds a set value, the power supply to that load is switched to the uninterruptible power supply. A power supply switching method characterized in that the power supply is switched from the bypass power supply device to the bypass power supply device without momentary interruption. [Claim 2] According to claim 1, when the entire uninterruptible power supply is overloaded, after switching all load power supply to the bypass power supply, the power supply is switched to each feeder with a time delay. The power supply switching method described.