JPS6352631A - Non-imterrupted source - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an overload protection circuit for an uninterruptible power supply.

[Conventional technology]

Figure 1 is an example of OHM December 1984 issue pp22-2.
4 is a configuration example of an overload protection circuit of the uninterruptible power supply shown in FIG. In the figure, (1) is an inverter, and an AC filter (
2) to supply AC power to the load (5). The output of the transformer (4) is averaged once through the current sensor (12).
! ) (13), and this output activates the overload protection circuit (
14).

Next, the operation will be explained.

In this configuration, the load current of the uninterruptible power supply is controlled by the average value circuit (13), which is composed of a current transformer (4), a current sensor (12), and a rectifier circuit. Converted to DC average value. If this DC average value exceeds the overload number of the uninterruptible power supply, for example 1259610 minutes, the overload protection circuit (14)
) to reduce the output voltage of the inverter (i!) by performing current limiting uJ operation or stopping the operation of the inverter (1). ! 1
Protect from loads.

[Problem that Departure J is trying to solve] In this way, in the secondary F device, overload protection of the inverter is performed using the average value of the load current, so the actual load including offshore linear loads such as rectifier circuits is As shown in Figure 2, the current waveform becomes a distorted waveform that includes harmonic current, and the effective value of the distorted waveform is generally larger than the average value, but the overload of the inverter is determined by the effective value. There were drawbacks such as insufficient protection against high-dose resistance.

The present invention has been made in order to eliminate the drawbacks of the conventional ones as described above, and an object of the present invention is to provide an uninterruptible power supply that can sufficiently protect an inverter from overload. purpose.

[Methods for solving problems]

The uninterruptible power supply according to the present invention operates an overload protection circuit using the effective value of the output alternating current of the inverter.

(Function) The overload protection circuit according to the present invention protects the device from overload by using the effective value detection circuit, since the overload capacity of the inverter is determined primarily by the effective value of the inverter output current.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings. In FIG. 3, (3) and (11) are a current transformer and current sensor that detect the inverter output current, and (4) and (12) are a current transformer and current sensor that detect the load current. (Di
) and (D2) Ii is an OR circuit for inputting the value of the thicker b of the inverter output current and load current to the effective value circuit composed of the integrating circuit (13), and the overload protection circuit (14). The inverter is operated with the larger effective value of the inverter output current and the load current to provide overload protection for the inverter.

Overload capacity of uninterruptible power supply (e.g. 125% for 10 minutes)
are the effective value of the inverter output current and the effective value of the load current e
Therefore, it is determined that when the alternating current waveform is a sine wave, the average value and the effective value will be the same value, but in the case of a distorted current waveform as shown in Figure 2, the effective value will be higher than the average value. growing.

In this configuration, the inverter voltage L and load current are connected to each current transformer (J) (4) and current sensor (11) (1
2), and if the effective value of the larger of the inverter output current and load current exceeds the overload tolerance of the uninterruptible power supply, for example 125% IO, the overload protection circuit (14) is activated. Current-limiting operation that reduces the output voltage of the inverter (1) or the inverter (1)
1) The operation is stopped to protect the inverter from overload.

In the above embodiment, a current transformer and a current sensor are used to detect the inverter output current or load current, but other detectors such as a resistor may be provided. Further, although two sets of detectors are shown, it is also possible to use a negative set of detectors.

[Effects of the Invention] As described above, according to the present invention, all overload protection circuits are operated based on the effective value of the inverter output current that determines the amount of overload on the inverter. Even if a distorted ff1c waveform flows through the device, the inverter can be sufficiently protected against overload.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of an embodiment of an uninterruptible power supply according to the present invention, FIG. 2 is a load waveform ratio, and FIG. 3 is a circuit diagram of a conventional uninterruptible power supply. In the figure, (1) is an inverter, (2) is an AC filter, (3) and (4) is a current transformer, (11) (12)
is a current sensor, and (13) and (14) are weekly current protection circuits. In addition, in the figures, the same reference numerals indicate the same or equivalent parts. Agent Masuo Oiwa Figure 1 Figure 2 Figure 3 Procedural amendment (voluntary) 2. Name of the invention Uninterruptible power supply device 3. Relationship to the case of the person making the amendment Patent applicant address Chiyoda-ku, Tokyo 2-2-3 Marunouchi Name (601) Mitsubishi Electric Corporation Representative Shiki
Moriya 4, agent address 2-2-3-5 Marunouchi, Chiyoda-ku, Tokyo
, Subject of amendment (1) Detailed description of the invention column of the specification, Drawing 6 of the specification, Contents of amendment (1) The specification is amended as follows. that's all

Claims (4)

[Claims] (1) In an uninterruptible power supply that supplies AC power from an inverter to a load through an AC filter, detects the AC output current of the inverter, and activates the overload protection circuit of the inverter, the effective An uninterruptible power supply device characterized in that the above-mentioned overload protection circuit is activated depending on the value. (2) Detection of the effective value of the output alternating current of the inverter is performed using a current detector and an alternating current effective value circuit that detect the inverter output current from an alternating current filter. Outage power supply. (3) The uninterruptible power supply according to claim 1, wherein the current detector is provided on either the input side or the output side of the AC filter. (4) Uninterruptible power supply according to claim 2, characterized in that the current detectors are provided on the input side and the output side of the AC filter, respectively, and output the larger value of both current detection values. power supply.