JPH08214537A - Dc short-circuit detector for inverter - Google Patents

Abstract

PURPOSE: To suppress the surge voltage at the time of cutting OFF a current by composing a DC short-circuit detecting current transformer of small size and low cost and reducing the wiring inductance of a DC side electrolytic capaci tor circuit in an inverter having a rectifier, an inverter for converting the DC power of the rectifier to AC power and the capacitor connected between positive and negative buses P and N to connect the rectifier to the inverter. CONSTITUTION: A short-circuit current detector in which a current transformer 10, a small-capacity capacitor 11 and a resistor 12 are connected in series is connected in parallel with an electrolytic capacitor 3 to detect the discharge current flowing in the route of A' and B' at the time of DC short-circuit. Since the capacitor 11 has a small capacity and the discharge current is limited by the resistor 12, the transformer 10 may have the small size and the low cost. Since the transformer is not connected in series with the capacitor 3, the wiring inductance of the capacitor circuit is reduced, thereby suppressing its surge voltage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an uninterruptible power supply (CV).
The present invention relates to a high-speed detection method when a DC short-circuit mode occurs in a forward conversion unit and an inverse conversion unit of an inverter used in a CF device) and the like, and to a DC short-circuit detection device for an inverter.

[0002]

2. Description of the Related Art Conventionally, a detection circuit when a DC short circuit occurs in an inverter has been constructed as shown in FIG. In FIG. 2, 1 is a forward converter for converting AC power into DC power, 2
Is an inverse converter that converts the DC power of the forward converter 1 into AC power. Positive and negative bus bar P connecting the forward conversion unit 1 and the inverse conversion unit 2
The electrolytic capacitor 3 is connected between -N. Reference numeral 4 is a current transformer that detects the discharge current of the electrolytic capacitor 3 when a DC short circuit occurs, 5 is an output transformer, and 6 is an output-side filter capacitor.

For example, when a semiconductor element forming the forward conversion section 1 is damaged, a short-circuit current flows in a path indicated by a broken line arrow A,
When the semiconductor element forming the inverse converter 2 is damaged, a short-circuit current flows in the path indicated by the broken arrow B. The short-circuit currents A and B are detected by the current transformer 4, and processing such as stopping the device is performed.

[0004]

The conventional current transformer 4 as shown in FIG. 2 needs a current transformer for a large current in order to detect the discharge current of the electrolytic capacitor 3 of the main circuit. However, there are problems such as large size and high price. In addition, since the large-sized detecting current transformer 4 is connected in series with the DC side electrolytic capacitor 3, the wiring inductance of the DC circuit becomes large, and the surge when the current is cut off by the semiconductor elements of the forward conversion unit 1 and the reverse conversion unit 2. There was a problem that the voltage increased.

The present invention has been made in view of the above points, and an object thereof is to make it possible to construct a current transformer for detecting a DC short circuit with a small size and a low cost, and to reduce the wiring inductance of a DC side electrolytic capacitor circuit. Another object of the present invention is to provide a DC short-circuit detection device for an inverter that can suppress surge voltage when the current is cut off.

[0006]

According to the present invention, there is provided a forward converter for converting AC power into DC power, an inverse converter for converting DC power of the forward converter into AC power, the forward converter and the inverse converter. In an inverter having an electrolytic capacitor connected between positive and negative bus lines connecting a conversion unit, a short-circuit current detection circuit formed by connecting a current transformer, a small-capacity capacitor and a resistor in series to the electrolytic capacitor is connected in parallel. However, the short-circuit current flowing through the forward conversion unit or the reverse conversion unit is detected.

[0007]

When a DC short circuit accident occurs in the forward conversion unit or the reverse conversion unit, a discharge current flows to the forward conversion unit or the reverse conversion unit through the capacitor and the resistor of the short circuit current detection circuit. This discharge current is detected by the current transformer, and processing such as device stop is performed. Since the capacitor of the short-circuit current detection circuit has a small capacity and the short-circuit current (discharge current) is limited by the resistance, the current transformer may be small and inexpensive. Since the current transformer is not connected in series to the electrolytic capacitor, the wiring inductance of the electrolytic capacitor circuit becomes small. Therefore, the surge voltage when the current is interrupted by the semiconductor element of the forward conversion section or the reverse conversion section is suppressed.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. 1, the same parts as those in FIG. 2 are indicated by the same reference numerals. 1 is different from FIG. 2 in that a large current transformer 4 is removed and a small current transformer 10, a small-capacity capacitor 11 and a resistor 12 are connected in series to an electrolytic capacitor 3 to detect a short-circuit current. Are connected in parallel.

In the device constructed as described above, when the semiconductor element forming the forward conversion unit 1 is damaged, a short-circuit current flows in the path indicated by the broken line arrow A ', forming the reverse conversion unit 2. When the semiconductor element is damaged, a short-circuit current flows through the path indicated by the broken line arrow B '. In this way, the current discharged through the resistor 12 and the capacitor 11 is detected by the current transformer 10 and processing such as stopping the device is performed.

Since the short-circuit current flowing through the paths A'and B'is limited to a certain current value or less by the resistor 12, the current detecting current transformer 10 can be made small and inexpensive. Further, since the current transformer is not connected in series to the electrolytic capacitor 3, the wiring inductance becomes small, and the surge voltage when the semiconductor element of the forward conversion unit 1 or the reverse conversion unit 2 cuts off the current is suppressed.

[0011]

As described above, according to the present invention, a short-circuit current detection circuit formed by connecting a current transformer, a small-capacity capacitor and a resistor in series is connected in parallel to a DC side electrolytic capacitor of an inverter, and Since it is configured to detect the short-circuit current flowing on the side of the forward conversion unit or the reverse conversion unit, the following excellent effects can be obtained.

(1) Since the capacitor of the short-circuit current detection circuit has a small capacity, and the short-circuit current is limited to a certain current value or less by the resistor, the current detecting current transformer is small and inexpensive. be able to.

(2) Since it is not necessary to connect a large current detecting current transformer in series with the DC side electrolytic capacitor, the wiring inductance of the DC side electrolytic capacitor circuit can be reduced, and the forward conversion unit and the reverse conversion unit can be used. It is possible to suppress the surge voltage when the current is interrupted by the semiconductor element of the part.

[Brief description of drawings]

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

FIG. 2 is a circuit diagram showing an example of a conventional inverter device.

[Explanation of symbols]

 1 ... Forward conversion part 2 ... Inverse conversion part 3 ... Electrolytic capacitor 4, 10 ... Current transformer 5 ... Output transformer 6 ... Filter capacitor 11 ... Capacitor 12 ... Resistor

Claims (1)

[Claims] 1. A forward conversion unit for converting AC power into DC power, an inverse conversion unit for converting DC power of the forward conversion unit into AC power, and a positive and negative busbar connecting the forward conversion unit and the inverse conversion unit. In an inverter having an electrolytic capacitor connected to, a short-circuit current detection circuit formed by serially connecting a current transformer, a small-capacity capacitor, and a resistor to the electrolytic capacitor is connected in parallel, and the forward conversion unit or the reverse converter is connected. A direct-current short-circuit detection device for an inverter, which detects a short-circuit current flowing to the converter side.