JPH05276690A - Uninterruptible power source with current limiting function - Google Patents

Abstract

PURPOSE:To limit an excess rush current by limiting input AC current and DC output current of a charger to predetermined values or less in an intermediate circuit for converting an AC to a DC to charge a battery and connected to a DC side of an inverter. CONSTITUTION:An AC power source 2 supplies an AC to a charger 4 through an AC current detector 11 to charge a battery 6. On the other hand, an uninterruptible power source circuit supplies a DC to an inverter 5, and converts it to VVVF to drive a load 7. The AC current detected by the detector 11 is compared with a set current of a current setter 12 by an AC overcurrent detector 13, and if it exceeds the set current, it limits the AC input current of the charger 4 through an input current limiter 14. Further, a DC current obtained by a DC current detector 3 is compared with the set current of the setter by a DC overcurrent detector, and if it exceeds the set current, it limits a DC output current through an output current limiter 24. Thus, inputting of the excess current is prevented, and damage of a circuit is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention prevents a power supply supplying power to an uninterruptible power supply from being adversely affected even when an excessive inrush current flows through a load connected to the uninterruptible power supply. The present invention relates to an uninterruptible power supply device with a current limiting function.

[0002]

2. Description of the Related Art FIG. 3 is a main circuit connection diagram showing a general configuration of an uninterruptible power supply. As shown in FIG. 3, the uninterruptible power supply 3 is composed of a charger 4, an inverter 5 and a battery 6. The AC power from the AC power supply 2 is converted into a DC of a desired voltage by the charger 4. Output to DC intermediate circuit. The inverter 5 converts the DC power from the DC intermediate circuit into AC power having a desired voltage and frequency and supplies the load 7 with power. A battery 6 is also connected to this DC intermediate circuit, and is floatingly charged by the DC power from the charger 4. By configuring the uninterruptible power supply 3 in this way, normally, the AC power from the AC power supply 2 is converted by the charger 4 and the inverter 5 and supplied to the load 7. However, the AC power supply 2 fails. In this case, since the electric power stored in the battery 6 is discharged and supplied to the load 7 via the inverter 5, it is well known that the load 7 can continue its operation without power failure.

[0003]

By the way, an electric motor used in equipment (for example, a semiconductor manufacturing factory, a paper manufacturing factory, a steel manufacturing factory, etc.) that requires continuous work as a load whose operation is desired to be prevented from being interrupted by a power failure. However, the electric motor generally has a large starting current several times larger than that in the normal operation when the electric motor starts. An electronic device typified by a computer is also a device that dislikes power failure, but since an electronic device generally has a rectifier on its input side and a large-capacity smoothing capacitor for smoothing this rectified output, When a voltage is applied to such an electronic device, a large inrush current flows at that moment.

Charger 4 constituting uninterruptible power supply 3
Usually, the capacity of the inverter 5 is determined in consideration of the large starting current and the inrush current, but the AC power supply 2 and the wiring connecting the AC power supply 2 and the uninterruptible power supply 3 are In many cases, the capacity is determined without considering such things. Therefore, when a large inrush current flows through the load 7 connected to the uninterruptible power supply 3, a corresponding large current also flows from the AC power supply 2 to the uninterruptible power supply 3,
A voltage drop occurs due to power source impedance and wiring impedance. As a result, the undervoltage relay operates to trip the power source, and even if the power source does not trip, this voltage drop adversely affects other loads connected to the AC power source 2.

Therefore, an object of the present invention is to prevent the uninterruptible power supply unit from being adversely affected even when a large inrush current flows through the load connected to the uninterruptible power supply unit.

[0006]

In order to achieve the above object, an uninterruptible power supply device with a current limiting function of the present invention includes a charger for converting alternating current to direct current and an inverter for converting direct current to alternating current. In an uninterruptible power supply composed of a battery connected to a DC intermediate circuit connecting the DC side of the charger and the DC side of the inverter, the AC current input to or output from the charger is a predetermined value. An overcurrent detection unit that detects the increase and a current limiting unit that limits the output current of the charger so as not to exceed a preset value when the overcurrent is detected.

[0007]

According to the present invention, when an excessive current flows through the load, a large current also flows through the charger which constitutes the uninterruptible power supply corresponding to the excessive current. Therefore, the input current (or output current) of this charger is ) Detects that the overcurrent exceeds a predetermined value, the charger output current is restricted so as not to exceed the set value. Since the load requires a current above this set value, the battery supplies the current shortage. Therefore, even if the capacity of the power supply that supplies power to the uninterruptible power supply is not large, it is possible to avoid occurrence of inconvenience such as voltage drop.

[0008]

FIG. 1 is a main circuit connection diagram showing a first embodiment of the present invention. The AC power supply 2 and the uninterruptible power supply 3 shown in the circuit of the first embodiment of FIG. 1 are configured. Name of charger 4, inverter 5, battery 6, and load 7
The applications and functions are the same as those in the case of the conventional circuit described above with reference to FIG.

In this first embodiment circuit, the charger 4
AC current detector 1 for detecting AC current input to
1, an electric current setting device 12, an alternating current overcurrent detection circuit 13 and an input current limiting circuit 14 for detecting that the detected alternating current value exceeds the value set by the electric current setting device 12,
If the AC overcurrent detection circuit 13 detects an overcurrent, the input current limiting circuit 14 sends a signal to the charger 4,
The alternating current to the current setting device 12 is limited to the value set by the current setting device 12 or less. As a result, the battery 6 supplies the shortage current to the load 7 via the inverter 5.

FIG. 2 is a main circuit connection diagram showing a second embodiment of the present invention. The AC power supply 2 and the uninterruptible power supply 3 shown in the circuit of the second embodiment of FIG. Since the names, applications, and functions of the charger 4, the inverter 5, the battery 6, and the load 7 that are used are the same as those in the conventional circuit described above with reference to FIG. 3, their description will be omitted. In the second embodiment circuit, the DC current detector 21 for detecting the DC current output from the charger 4, the current setting unit 22, and the DC current detection value exceeds the value set by the current setting unit 22. The output current limiting circuit 24 sends a signal to the charger 4 when the DC overcurrent detection circuit 23 detects an overcurrent. The DC current output from the charger 4 is limited to the value set by the current setting device 22 or less. As a result, the battery 6 supplies the shortage current to the load 7 via the inverter 5. If the output current of the charger 4 is limited, the input current to the charger 4 is correspondingly limited.

[0011]

According to the present invention, when the current supplied to the load connected to the uninterruptible power supply becomes excessive, the current flowing through the charger constituting the uninterruptible power supply responds to this. (AC input current or DC output current) also becomes excessive, but the current flowing through the charger is limited so that it does not exceed the appropriate value, so the excessive current value required by the load and this appropriate value The difference current (that is, the shortage current) is supplied by the battery that constitutes the uninterruptible power supply.
Therefore, the current supplied by the power source does not exceed an appropriate value, and therefore an effect of avoiding a situation in which an inconvenience such as a voltage drop occurs can be obtained.

[Brief description of drawings]

FIG. 1 is a main circuit connection diagram showing a first embodiment of the present invention.

FIG. 2 is a main circuit connection diagram showing a second embodiment of the present invention.

FIG. 3 is a main circuit connection diagram showing a general configuration of an uninterruptible power supply.

[Explanation of symbols]

 2 AC power supply 3 Uninterruptible power supply device 4 Charger 5 Inverter 6 Battery 7 Load 11 AC current detector 12 Current setting device 13 AC overcurrent detection circuit 14 Input current limiting circuit 21 DC current detector 22 Current setting device 23 DC overcurrent Detection circuit 24 Output current limit circuit

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H02M 7/48 M 9181-5H

Claims (2)

[Claims] 1. A charger for converting alternating current to direct current, an inverter for converting direct current to alternating current, and a battery connected to a direct current intermediate circuit connecting the direct current side of these chargers and the direct current side of the inverter. In the uninterruptible power supply configured, the AC overcurrent detection means for detecting that the AC current input to the charger has increased to a predetermined value or more, and the output current of the charger is detected in advance if the AC overcurrent is detected. An uninterruptible power supply unit with a current limiting function, which is provided with a current limiting unit that limits a value not to exceed a set value. 2. A charger for converting AC to DC, an inverter for converting DC to AC, and a battery connected to a DC intermediate circuit connecting the DC side of these chargers and the DC side of the inverter. In the uninterruptible power supply configured, the DC overcurrent detection means for detecting that the DC current output by the charger has increased to a predetermined value or more, and if the DC overcurrent is detected, the output current of the charger is previously determined. An uninterruptible power supply unit with a current limiting function, which is provided with a current limiting unit that limits a value not to exceed a set value.