JPS62285638A - Inverter output switching circuit - Google Patents

Abstract

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

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention [Field of Industrial Application] This invention relates to an inverter output switching circuit for an uninterruptible power supply or the like that switches the output of an inverter to a preliminary power supply to supply power to a load. It is.

[Conventional technology]

Figure 3 is an example of "Industry and Electric Power J, September 1984 issue I.
"15-16 are conventional inverter output switching circuits shown in the figure, and in the figure, 1 is an inverter.

2 is a commercial power supply (hereinafter referred to as a bypass power supply) using a backup ', 3 is a load, 4 is a contactor, 5 is a thyristor switch as a semiconductor switch, 6 is an overcurrent detection circuit, and 7 is a switching control circuit. be.

FIG. 4 is a time chart showing the operation of the inverter output switching circuit shown in FIG.

Next, the operation will be explained. Since the inverter 1 generally has only a certain overcurrent withstand capacity, protective interlocking such as stopping the inverter is taken in response to an output overcurrent.

On the other hand, when an uninterruptible power supply is required to supply power uninterrupted even during the startup current or inrush of load equipment, the power supply is automatically switched to the bypass power supply side with a large overcurrent capacity only while the overcurrent continues. Switch.

When the current returns to within the specified value, the system automatically switches to the inverter side again to continue supplying the load. However, the thyristor switch 5, etc., which is a switch on the bypass power supply side, also has a certain overcurrent rating. If a current exceeding this is applied, a continuity failure mode will often occur. In such a case, the automatic switching to the inverter side will not operate normally.

Figure 4 shows the situation. From time L1 to t2, a detection signal ○C is generated due to overcurrent on the load side, indicating that the switch has been switched to the bypass power supply side. However, if the thyristor switch 5 has a conduction failure at that time, the signal is switched to the inverter side at time t2. After the automatic switching, the thyristor switch 5 does not turn OFF, so the inverter and bypass power supply are in a lap state and a cross current flows, which causes overcurrent to be detected again and switches to the bypass power supply. There is. onwards.

This operation will be repeated.

[Problem that the invention seeks to solve]

Conventional inverter output and switching circuits are configured as described above, so if the bypass side thyristor switch has a continuity failure during bypass switching due to overcurrent, the problem is that the switching operation from inverter to bypass to inverter is repeated. there were.

This invention was made in order to solve the above-mentioned problems, and an object thereof is to obtain an inverter output switching circuit that can detect repeated switching operations, stop the switching operations, and continue stable load power supply. do.

[Means for solving problems]

In the inverter output switching circuit according to the present invention, switching operations due to overcurrent detection are detected and stored for a certain period of time, and when the number of detections exceeds a certain number of times, it is regarded as a failure and a signal is sent to the switching control circuit. It is equipped with a failure detection circuit.

[Effect]

The failure detection circuit of the present invention detects a failure in the bypass side thyristor switch by repeatedly switching between the output path of the inverter and the output path of the bypass power supply, thereby stopping the switching operation and stably supplying power to the load. continue.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. 1, in which the same parts as in FIG. 3 are denoted by the same reference numerals.

In FIG. 1, 8 is a failure detection circuit.

Fig. 2 is a time chart showing the operation. In Fig. 2, OC is an overcurrent detection signal, IN is a closing signal for contactor 4, BP is a firing signal for thyristor switch 5, and signal A is a bypass switching due to overcurrent. C1 and C2 are pulse signals generated in the failure detection circuit 8 in response to the OC signal during the above-mentioned fixed time T, and F is a signal that is held for a certain period of time T, and F is a signal that is held for a certain period of time T, and F is a signal that is held for a certain period of time T, and F is a signal that is held for a certain period of time T. This shows a failure detection signal output from the failure detection circuit 8 when .

Next, the operation will be explained. The operation up to time t4 is the same as that of the conventional device shown in FIG. 3, and shows that the switching operation due to overcurrent has been repeated twice during the fixed time T. As described in the explanation of the operation of the conventional device, this indicates a conduction failure in the bypass side thyristor switch 5, and the failure detection circuit 8 detects the overcurrent detection signal OC of the overcurrent detection circuit 6.
When a predetermined number of pulse signals C1 and C2 are generated in memory for a predetermined period of time, a failure is determined and a failure detection signal F is output. Therefore, the switching control circuit 7 fixes the thyristor switch 5 to the bypass individual mode based on the failure detection signal F.

In addition, although the case where the inverter side switch is a contactor was shown in the said Example, other mechanical switches or a semiconductor switch may be sufficient. Moreover, although the case where the bypass side switch is a thyristor has been described, other semiconductor switches can also produce the same effects as in the above embodiment.

〔Effect of the invention〕

As described above, according to the present invention, a failure detection circuit is added to the inverter output switching circuit that switches the output of the inverter to the standby power source to supply power to the load, and the semiconductor switch provided in the output path of the standby power source detects a continuity failure. When this happens, the switching operation between the inverter output path and the standby power supply output path is stopped, and the backup power supply output path is fixed in a conductive state, so the effect is that load power supply can be continued safely. There is.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an inverter output switching circuit according to an embodiment of the present invention, FIG. 2 is a time chart showing its operation, FIG. 3 is a block diagram showing a conventional inverter output switching circuit, and FIG. 4 is a block diagram showing an inverter output switching circuit according to an embodiment of the present invention. It is a time chart showing the operation. 1 is an inverter, 2 is a backup power source (commercial power source). 3 is a load, 5 is a semiconductor switch (thyristor switch)
, 6 is an overcurrent detection circuit, and 7 is a switching control circuit. 8 is a failure detection circuit. In addition, in the figures, the same reference numerals indicate the same or corresponding parts. Figure 1 Figure 2

Claims (1)

[Claims] In an inverter output switching circuit that switches an output path of an inverter to an output path of a standby power source to supply power to a load, an overcurrent detection circuit detects an output overcurrent of the inverter, and an output signal of the overcurrent detection circuit detects an overcurrent of the inverter. a switching control circuit for switching and controlling a switch provided in the output path and a semiconductor switch provided in the output path of the backup power supply; and a switching control circuit that stores the output signal of the overcurrent detection circuit and that the output signal is generated a predetermined number of times within a certain period of time. 1. An inverter output switching circuit comprising: a failure detection circuit that determines that the semiconductor switch is in failure and fixes the switching control circuit to the conductive side of the semiconductor switch.