JPH0564459A - Overcurrent controller for inverter section in ups - Google Patents

Abstract

PURPOSE:To realize stabilized power supply to a load by constituting an overcurrent controller of a CT provided in the input circuit for an inverter, a current detector, and an overcurrent control circuit. CONSTITUTION:Upon detection of an overcurrent through a CT, an inverter is stopped and a switch 2 is switched to ON instruction (direct power supply) S8. When the inverter section is started again upon elapse of a set time of a timer 3 while sustaining direct power supply S8, a decision can be made whether the cause of overcurrent exists on the inverter side or on the load side. Overcurrent is produced due to overload on the load side if the inverter section starts smoothly whereas the overcurrent is produced due to inner failure at the inverter section if an overcurrent is detected again to stop the inverter. Consequently, power can be fed stably to a load without repeating inverter power supply S7 and direct power supply S8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an overcurrent control device for an inverter section in a UPS having a bypass circuit.

[0002]

2. Description of the Related Art FIG. 5 shows a UPS (Uninterruptible PowerS).
FIG. 2 is a block circuit diagram showing a schematic configuration of the ystem), in which the DC-converted power in the rectifier circuit 101 or the DC power supplied from the storage battery 102 is the inverter unit 10.
3 is converted into alternating current, and stable alternating current power is supplied to the load through the changeover switch 106 including the filter 105 and the semiconductor switch. In addition, the bypass circuit 10
8 is provided and commercial AC power is directly supplied to the load via the changeover switch 107 formed of a semiconductor switch while the inverter unit 103 is stopped. Inverter unit 103
Is composed of a plurality of semiconductor switching elements 110, and an HCT 109 for detecting an input current of the inverter 103 is provided on the input side thereof. When an overcurrent is detected by the HCT 109, the detection signal outputs an overcurrent signal (one shot “H”) S ₁ from the overcurrent detector 104 to stop the inverter unit 103 and the changeover switch 106 and the changeover switch. By switching 107, the inverter power supply was switched to direct power supply to supply power to the load.

[0003]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
In the overcurrent detection by the inverter, the cause of the overcurrent is the inverter unit 1
It was not possible to distinguish whether it was due to a defect in the semiconductor switching element constituting 03, a malfunction of the control circuit, or an overcurrent on the load side. That is, if there is an internal failure in the inverter section, direct feed should not be switched to inverter feed, but if it is just overload on the load side, it should be switched to inverter feed immediately when the cause of the overload disappears. . If the inverter power supply is switched without knowing the cause of the overcurrent, the damage of the inverter may be expanded if the inverter has a cause of failure. According to the present invention, the UPS is provided with an overcurrent control circuit capable of identifying whether the cause of the overcurrent is on the inverter side or the load side and supplying stable power to the load.

[0004]

In order to solve the above-mentioned problems, an overcurrent control device for an inverter section in a UPS according to the present invention has a C provided in an input circuit of the inverter section.
T, UPS that performs overcurrent control by a current detector that operates according to the overcurrent detection value detected by this CT, and two changeover switches that switch between inverter power feeding and direct power feeding
In the overcurrent control device for the inverter section, the overcurrent control circuit is provided. This overcurrent control circuit controls the switching between direct power feeding and inverter power feeding and starts / stops the inverter unit.If there is no malfunction in the inverter unit, the inverter unit is soft-started and synchronized with the bypass circuit. Switch the direct feed to the inverter feed. Further, when there is a failure in the inverter section, the restarted inverter section is immediately stopped and direct power feeding is continued.

[0005]

When the overcurrent is detected by CT, the inverter stops and switches to direct power feeding. In the state where the direct power feeding is continued, it is possible to know whether the cause of the overcurrent is the inverter unit or the load side by restarting the inverter unit after the timer setting time. That is, when the inverter unit is started without any trouble, overcurrent is generated due to overload on the load side, and when the inverter is stopped again due to overcurrent detection, overcurrent is generated due to internal failure of the inverter unit. Therefore, stable power can be supplied to the load without repeating the inverter power supply and the direct power supply.

[0006]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a circuit configuration of an overcurrent control circuit according to the present invention. Overcurrent signal (1 shot “H”) S ₁ , inverter power supply command signal (1 shot “H”) S ₂ , failure reset signal (1 shot “L”) S ₃ , failure signal (“H”) S ₄ and Inverter start / stop command (“H” in inverter start command) S ₅
Is input, and an inverter operation command (“H”) S ₆ , a changeover switch 1 · ON command (inverter power supply) S ₇ and a changeover switch 2 · ON command (direct power supply) S ₈ are output. Flop 1 and flip flop 2, timer 3, AND gates 5, 7, 9, 10, O
It is composed of an R gate 4 and NOT gates 6, 8 and 11.

The input signals S ₁ , S ₂ , S ₃ , S ₄ , S
₅ is input to the overcurrent control circuit 27 according to the flowchart shown in FIG. 2 and outputs the control signals S ₆ , S ₇ , and S ₈ as shown in the time charts of FIGS. 3 and 4.

FIG. 3 is a time chart of the control signal when an overcurrent occurs when there is a cause of failure on the inverter side. The overcurrent signal S ₁ is input to the set input terminal of the flip-flop 2 in FIG. 1, and its output signal is a signal S ₈ for turning on the changeover switch 2 and NOT.
A signal S ₇ for turning off the changeover switch 1 is provided via the gate 11. Further, the timer 3 is started by the output signal of the flip-flop 2 and its output signal S
₉ becomes "L", and outputs the inverter stop signal S ₆ from the AND gate 10. As a result, the inverter is stopped and the power is directly fed from the bypass circuit. Furthermore, since the timer output S ₉ is inverted after the elapse of the set time of the timer 3 which has started by the output signal of the flip-flop 2, the output signal of the AND gate 10 which inputs this signal is also inverted and the inverter is restarted. However, the inverter is stopped because the overcurrent signal S ₁ is instantaneously output. In this case, since the signals S ₇ and S ₈ do not change, the direct power feeding is continued and the power supply to the load is not hindered.

FIG. 4 is a time chart of the control signal when an overcurrent is generated by the load side, showing an overcurrent signal S ₁ , an inverter stop signal S ₆ , a signal S ₈ for turning off the changeover switch 1 and a changeover switch 2. The signal S _{7 to} be turned on is the same as that in FIG. Since the timer output S ₉ is inverted after the lapse of the set time of the timer 3, the inverter operation command S ₆ is output from the AND gate 10 in FIG.
The inverter starts soft start. The inverter power supply command signal (one shot “H”) S ₂ is ANDed in FIG. 1 on condition that the cause of the overcurrent on the load side has disappeared and that the direct power of the bypass circuit and the inverter are synchronized. Input to the reset terminal of the flip-flop 2 via the gate 9
The output signal from S is the signal S that turns off the changeover switch 2.
₈ and the NOT gate 11 to change the selector switch 1 to O
The signal S ₇ is set to N, and the direct feed is switched to the inverter feed.

[0011]

As described above, the U according to the present invention is
An overcurrent control device for an inverter in a PS includes a CT provided in an input circuit of the inverter, a current detector that operates by inputting an overcurrent detection value detected by the CT, and an output signal of the current detector for the inverter. An overcurrent control circuit that outputs a signal for instructing operation or stop and outputs a command signal for performing direct power feeding and inverter power feeding by turning ON / OFF the changeover switches 1 and 2, and soft starting the inverter via a timer. Composed by Therefore, it can be clarified whether the cause of the overcurrent is on the inverter side or the load side, so that the failure on the inverter side can be detected promptly and the spread of damage due to restart can be prevented. Further, there is an advantage that stable power can be supplied to the load without repeating the inverter power supply and the direct power supply.

[Brief description of drawings]

FIG. 1 is a block circuit diagram showing a circuit configuration of an overcurrent control circuit according to an embodiment of the present invention.

FIG. 2 is a flowchart of input signals and output signals of an overcurrent control circuit.

FIG. 3 is a time chart of a control signal when an overcurrent occurs when the inverter has a cause of failure.

FIG. 4 is a time chart of a control signal when an overcurrent is generated on the load side.

FIG. 5 is a block circuit diagram showing a schematic configuration of UPS.

[Explanation of symbols]

 1, 2 Flip-flop 3 Timer 4 OR gate 5, 7, 9, 10 AND gate 6, 8, 11 NOT gate

Claims (1)

[Claims] 1. A CT provided in an input circuit of an inverter section
And a current detector that operates by inputting the overcurrent detection value detected by the CT, a changeover switch (1) provided in the output circuit of the inverter section, and a changeover switch (2) provided on the output side of the bypass circuit. In the overcurrent control device of the inverter unit in the UPS that performs overcurrent control by switching between inverter power feeding and direct power feeding by operating the two changeover switches, A stop signal is output and the changeover switch (1) is turned on.
FF, the change-over switch (2) is turned on to directly feed power by the bypass circuit, and further, the inverter unit is started after a set time of a timer that starts operation by the output signal of the current detector has elapsed, and the inverter unit is When the engine is started without any trouble, the switching switch (1) is turned on and the switching switch (2) is turned off to synchronize the bypass circuit with the bypass circuit to switch the direct power feeding to the inverter feeding. Therefore, when an overcurrent is detected again, an overcurrent control circuit for immediately stopping the inverter unit to continue direct power feeding is provided in the UPS overcurrent control device for the inverter unit.