JPH0534203Y2 - - Google Patents

Description

[Detailed Description of the Invention] A. Field of Industrial Application The present invention relates to a switching device for an uninterruptible power supply.

B. Summary of the invention This invention minimizes the parallel operation time of both power supplies when switching from the bypass power supply side to the constant frequency voltage regulator side of an uninterruptible power supply, and reduces the cross current flowing from the bypass power supply side to the constant frequency voltage regulator side. It is designed to reduce the current.

C. Prior Art FIG. 2 shows the configuration of a conventional switching circuit.

Now, when power is being supplied to the load 5 from the bypass power supply 2 for some reason, a case will be explained in which the power is switched to the constant frequency constant voltage device (hereinafter referred to as CVCF) 1 side.

In this case, at the same time as a switching command is given to the changeover switch 3, an output is generated to the gate control circuit 6 to turn on the AC switch 4 made of a semiconductor switching element or the like. When the movable contact piece of the changeover switch 3 switches from the A end to the B end,
The CVCF 1 and the bypass power supply 2 operate in parallel, and after confirming the parallel operation, the AC switch 4 is turned off by a command from the gate control circuit 6, and the switching is completed.

Next, the case of switching from CVCF1 to bypass power supply 2 will be explained.

After the CVCF1 is started, the AC switch 4 is turned on by a command from the gate control circuit 6 on the condition that it is synchronized with the bypass power supply 2, and the CVCF1
The bypass power supply 2 is operated in parallel, the changeover switch 3 is switched under the condition of the parallel operation, and the AC switch 4 is turned off under the condition that the changeover switch 3 has been switched, and the changeover is completed.

D. Problems that the invention aims to solve When switching between the CVCF and bypass power supplies, the condition is that the switching should be without momentary interruption, so both power supplies must be operated in parallel for a certain period of time, but when switching from the bypass power supply to the CVCF side. , due to the long parallel operation period, cross current flows from the bypass power supply to the CVCF side.
CVCF enters an overcurrent state. A cross-current control device is added to prevent this overcurrent, but this device has the problem of being complicated.

Therefore, an object of the present invention is to provide a non-instantaneous switching device that does not require cross-current control by simply adding a simple circuit.

E. Measures to solve the problem Connect a series circuit of a rectifier, reactor, and resistor in parallel with the load side end and CVCF side connection end of the changeover switch. A control power supply is connected to the AC input side of the rectifier, and a detector is provided in the series circuit to detect the series current flowing in the series circuit, and the output of this detector is sent to the gate control circuit via a comparator. The AC switch is configured to be controlled by the output signal of this gate control circuit.

F Function The AC switch is controlled via the gate control circuit depending on the presence or absence of DC current flowing in a closed loop consisting of a series circuit and the C and B ends of the changeover switch.

G. Embodiment An embodiment of the present invention will be described below in detail based on FIG. In FIG. 1, the same reference numerals as in FIG. 2 indicate the same parts, and the explanation thereof will be omitted.

8 is a rectifier, and this rectifier 8 is connected in a diode bridge, and a reactor L and a resistor R are connected in series on its DC output side. This series circuit is connected between terminals B and C of the changeover switch 3.

Further, a control power source 7 is connected to the AC input side of the rectifier 8.

10 is a detector that detects when a shunt resistor, Hall CT (current exchanger using a Hall element), etc. is used to form a closed loop consisting of the C and B terminals of the changeover switch and a series circuit. Detects direct current flowing through the current.

Therefore, when forming this closed loop, 7 is connected in advance so that a minute current using 7 as the power source flows through the closed loop.
The power supply voltage and impedance values of L and R are determined in advance. 9 is a comparator, 61 is a gate control circuit, and the output signal of this gate control circuit 61 controls the AC switch 4.

Next, its operation will be explained.

It is assumed that the CVCF 1 has failed or is under inspection, and the load 5 is being supplied with power from the bypass power supply 2, and from this state it is switched to the CVCF 1 side.

The CVCF 1 is started, and the control power supply 7 is turned on when it is synchronized with the bypass power supply 2. At this time, since the movable contact piece of the changeover switch 3 is in contact with the contact point A, a closed loop of the rectifiers 8, L, and R is not formed, so that no signal is detected by the detector 10. Knowing that there is no input from the comparator in the gate control circuit 61 even though the control power source 7 is turned on, it is determined that the movable contact piece of the changeover switch 3 is on the contact A side. Based on this determination, the gate control circuit 61 outputs an on command to the AC switch 4 to turn it on. Therefore, at this time, the changeover switch 3 and the AC switch 4 are connected in parallel to the load 5, and after the parallel connection is confirmed, the changeover switch 3
Switch the movable contact piece from the A end to the B end. During switching from A end to B end, load 5 is applied from AC switch 4.
Supplying power to is the same as before. At the moment when the movable contact piece of the changeover switch 3 touches the B end, the B end → rectifier 8 → L → R → C end → movable contact piece → B
Since a closed loop is formed at the end, a small amount of direct current flows from the rectifier 8. This minute direct current is detected by the detector 10 and output to the comparator 9. The comparator 9 outputs a detection signal to the gate control circuit 61 and
1 issues an off command to the AC switch 4 to turn it off. In other words, the movable contact piece is contact B.
CVCF1 and bypass power supply 2 are in contact with load 5
Since the AC switch 4 is turned off the moment the two power supplies are connected in parallel, the period of parallel connection of the two power supplies is shortened to about the operation delay time of the AC switch 4. The switching is completed when the AC switch 4 is turned off, the control power source 7 is turned off, and the CVCF 1 enters normal operation.

Next, when switching from the CVCF 1 to the bypass power supply 2, when a switching signal is output to the changeover switch 3 due to an accident signal or the like, the control power supply 7 is turned on. Since a closed loop has already been formed in the detection circuit when the control power source 7 is turned on, a small amount of direct current flows through this closed loop. Therefore, this minute direct current is detected by the detector 10 and sent to the gate control circuit 61 via the comparator 9.
Then, an on command is generated to turn on the AC switch 4. After the movable contact piece of the changeover switch 3 is connected to the A end, the AC switch 4 is turned off and the changeover is completed.

H. Effects of the invention According to the invention, when switching from the bypass power supply to the CVCF side where a cross current flows, the presence or absence of a minute DC current flowing in the closed loop is detected and the AC switch is controlled. Since the lap period between the two power supplies is about half a cycle of the delay in the operation of the thyristor switch, special cross-current control is not required, and the reliability of the device is increased and both devices are made smaller.

[Brief explanation of the drawing]

FIG. 1 is a circuit configuration diagram showing an embodiment of the present invention, and FIG. 2 is a configuration diagram of a conventional switching circuit. 1 is a CVCF, 2 is a bypass power supply, 3 is a changeover switch, 4 is an AC switch, 5 is a load 5, 6 and 61 are gate control circuits, 7 is a control power supply, 8 is a rectifier, 9 is a comparator, 10 is a detector, R is a resistor and L is a DC reactor.

Claims (1)

[Scope of utility model registration request] Switch the power supplied to the load between the bypass power supply and the constant frequency constant voltage device via a switch,
In an uninterruptible power supply that switches without momentary interruption while controlling an AC switch connected between a bypass power source and a load during this switching, a brittle connection is made in parallel with the load side end of the changeover switch and the connection end of the constant frequency voltage regulator. When a series circuit of a rectifier, a reactor, and a resistor is connected, and a control power source is connected to the AC input side of the rectifier, a detector that detects the presence or absence of DC power flowing through the series circuit and this detection 1. A switching device for an uninterruptible power supply, comprising: a gate control circuit for controlling the AC switch depending on the presence or absence of an output signal from the switch.