JP2562481Y2 - Uninterruptible power system - Google Patents

Description

[Detailed description of the invention]

[0001]

This invention is used, for example, as a power source for an electronic computer, and always supplies commercial AC power to a load. When a power failure is detected, the power of a built-in storage battery is converted to alternating power by an inverter and supplied to the load. And a standby type uninterruptible power supply.

[0002]

2. Description of the Related Art FIG. 2 shows a conventional uninterruptible power supply. One end of the pair of electric wires 11 and 12 is connected to the commercial power source 13,
The other end of the electric wire 11 is connected to one fixed contact a of the changeover switch 14.
The movable contact of the changeover switch 14 and the other end of the electric wire 12 are connected to both ends of the load 15. Electric wires 11, 12
Is connected to a storage battery 17 through a charging circuit 16, an inverter 18 is connected to the storage battery 17, one of a pair of output terminals of the inverter 18 is connected to the other fixed contact b of the changeover switch 14, and the other is connected to the electric wire 12. You. A synchronous circuit 19 connected to the electric wires 11 and 12 is connected to the inverter 18. A power failure detection circuit 21 is connected to the electric wires 11 and 12.

When power is supplied from the commercial power supply 13, the changeover switch 14 is connected to the fixed contact a side, and commercial AC power is supplied to the load 15. When the commercial power supply 13 loses power, this is detected by a power failure detection circuit 21, the switch 14 is switched to the fixed contact b side by the detection output, and the inverter 18 is started, and the alternating power synchronized with the commercial AC power up to that time is activated. Then, the power of the storage battery 17 is converted and supplied to the load 15.

[0004]

Becomes the power failure at time t ₁ in a state where a commercial AC voltage 22 as shown in FIG. 3A - devised is to solve the above is supplied to the load 15, the power failure at time t ₂ after which, for example, about 2 ms detected by the detection circuit 21, switch 14 is controlled by the detection output, it is switched to the time t ₃ for example, after about 4 milliseconds to complete. At this time, in order to output the output 23 of the inverter 18 synchronized with the commercial AC up to that time to the load 15, it is necessary to start the inverter 18 as soon as the switching of the switch 14 is completed. By doing so, the period during which power supply to the load is cut off can be shortened.

As shown in FIG. 3A, if the commercial AC power is suddenly cut off, and in FIG. 3A, the commercial AC power is cut off instantaneously at time t ₁ , and if the commercial power is lost during the switching operation of the changeover switch 14, No problem. But gradually decreases commercial AC voltage is relatively as shown in FIG. 3B, around the lower the effective value for example 90V of the commercial AC voltage, is detected at time t ₂ and becomes the power failure by the power failure detection circuit 21, the time t ₂ switching control of the switch 14 is performed, at the time t ₄ when the movable contact begins to move, it may still commercial AC voltage is applied between the wire 11 and 12. When the effective value of the commercial AC voltage and detects a power failure becomes 90V, the peak value at that time is 126V, therefore the fixed contacts a, arc between b occurs at time t ₄ when the movable contact starts to move, In some cases, a short circuit may occur between them.

For this reason, when the inverter 18 is started almost simultaneously with the completion of the movement of the movable contact, the uninterrupted commercial AC power may flow through the inverter 18 as a short-circuit current. That is, as shown in FIG. 4, the inverter 18 includes switching transistors Q ₁ and Q ₂ connected in series and switching transistors Q ₃ and Q 2
₄ are connected in series. These series circuits are connected in parallel and connected to both ends of the storage battery. The connection point of the transistors Q ₁ and Q _{2 and} the connection point of the transistors Q ₃ and Q ₄ Connected to the fixed contact b, each transistor Q _{1 to} Q ₄ has a reverse polarity diode D ₁
To D ₄ are connected in parallel, and the transistors Q ₁ , Q ₄ and Q
_2, and Q ₃ is turned on alternately at the same time. Therefore, for example, if an arc 24 is generated between the contacts a and b while the transistors Q ₁ and Q ₄ are simultaneously turned on, the commercial power supply 13 is short-circuited through the arc 24, the transistor Q ₄ , and the diode D ₂ , and is connected to the transistor Q ₄ . short-circuit current 25 flows, there is a possibility that the transistor Q ₄ is destroyed.

[0007]

According to the present invention, it is determined whether or not the commercial AC voltage suddenly drops or gradually drops during a power failure. Delay means is provided for delaying the activation of the inverter as compared to when it is determined that the voltage has decreased.

[0008]

FIG. 1 shows an embodiment of the present invention, in which parts corresponding to those in FIG. 2 are denoted by the same reference numerals. In this embodiment, the changeover switch 14 is immediately controlled by the detection output of the power failure detection circuit 21 as in the prior art, but the power failure detection output is supplied to the determination means 32 and the delay circuit 33 for controlling the inverter 18. . The output of the delay circuit 33 is supplied to the inverter 18 via the OR circuit 34 as a start signal. The delay time of the delay circuit 33 is, for example, a half cycle of the commercial AC voltage (10 milliseconds at 50 Hz).

At the time of a power failure, the judging means 32 judges whether the commercial AC voltage suddenly drops or gradually drops.
If it is determined that the voltage has suddenly dropped, the inverter start signal is supplied to the inverter 18 through the delay circuit 35 and further through the OR circuit 34 as necessary, and the delay time of the delay circuit 35 is made smaller than the delay time of the delay circuit 33. You. As the determination means 32, for example, the absolute value of the instantaneous value of the commercial AC voltage is detected by the absolute value circuit 36, and the absolute value of the instantaneous value is compared with the reference voltage V _r (intermediate between the power failure detection voltage and 0 volt) and the comparator. The comparison is made at 37, and the comparison output is supplied to the data terminal D of the D-type flip-flop 38. The power failure detection circuit 2 is connected to the trigger terminal and the reset terminal of the D-type flip-flop 38.
One output is provided.

Accordingly, the effective value of the commercial AC voltage is, for example, 90
When the commercial AC voltage is instantaneously cut off at this time, a power failure detection output is generated about 2 milliseconds later when the power failure detection circuit 21 detects that a power failure has occurred below V. At this time, the instantaneous value of the commercial AC voltage is equal to or lower than the reference voltage _Vr , the output of the comparator 37 is at a high level, and this is taken into the flip-flop 38 at the rise of the power failure detection output, and the output of the flip-flop 38 rises. The signal is supplied as a start signal to the inverter 18 through the delay circuit 35, and the inverter 18 is started relatively quickly. This operation is the same as the conventional operation in FIG. 3A.

However, when the commercial AC voltage gradually decreases, when the power failure detection output is obtained, the instantaneous value of the commercial AC voltage becomes higher than the reference voltage _Vr, and the output of the comparator 37 becomes low. This low level is taken into the flip-flop 38 at the rise of the power failure detection output, and the output of the flip-flop 38 does not change. On the other hand, the power failure detection output is supplied to the inverter 18 via the delay circuit 33 as a start signal. At this time, since the delay is caused by the delay circuit 33, as shown in FIG. 3C, even if an arc is generated by the switching of the changeover switch 14, the commercial AC voltage always cuts the zero point from the start point of the transition from the contacts a to b. That is, after the arc is extinguished, the inverter 18 is activated, and there is no possibility that a short-circuit current flows. Even if an arc is generated, since all the switching transistors of the inverter 18 are off, there is no possibility that a short-circuit current flows. The delay amount of the delay circuit 33 may be practically about 5 milliseconds. When the power failure recovers, the output of the power failure detection circuit 21 goes low, and the D-type flip-flop 3
8 is reset.

As described above, according to the state of the output of the comparator 37 at the time of detecting the power failure, it is determined whether the power failure has caused a sharp voltage drop or a gradual voltage drop. When it is determined that the commercial AC voltage has gradually decreased, the inverter 18
If the start-up is delayed, there is a concern that the power outage time to the load becomes longer and a practical problem occurs. However, the power outage time at this time does not increase much compared to the case where it is determined that the commercial voltage has suddenly dropped, and is not a practical problem. This will be described with reference to FIG.

First, when the commercial AC voltage suddenly drops,
The power failure occurs between the time when the power failure occurs at time t ₁ in FIG. 3A and the time when the power failure is detected by the power failure detection circuit and the time before the changeover switch 14 completes the operation. t ₃ −time t ₁ . Next, when the commercial AC voltage gradually decreases, when a power failure is detected by the power failure detection circuit, the AC voltage is still output to the load at a low voltage. The switch operation time in FIG. 3A includes the time from when the drive signal for the switch 14 is input to when the contact starts operating. During this time, as shown in FIG.
Up to ₄ output of the AC voltage is continued to the load. Therefore, FIG.
At time t ₁ when the decreased suddenly commercial AC voltage of A, power failure, as compared with the case of power failure detected at time t _2, the period from time t ₁ in the case of FIG. 3C to time t _4, the load Power supply time is long. Therefore, even if a delay time is provided to delay the activation of the inverter 18, the increase in the power failure time to the load is small and there is no practical problem.

The switch 14 is not limited to the relay switch, and the switch can be surely extinguished also in the case of an electronic switch 14 constituted by a triac element or the like having no forced extinguishing circuit. Can be.

[0015]

As described above, according to the present invention, at the time of a power failure in which the commercial AC voltage is suddenly cut off, the inverter can be started earlier and the power failure time can be shortened as in the prior art. When the AC voltage gradually decreases, the activation of the inverter is delayed, so that there is no possibility of damaging the elements of the inverter.

[Brief description of the drawings]

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

FIG. 2 is a block diagram showing a conventional uninterruptible power supply.

FIG. 3 is a diagram showing a switching state between a commercial AC voltage and an inverter output.

FIG. 4 is a diagram showing a state in which a short-circuit current flows at the time of switching due to a power failure.

Claims (1)

(57) [Scope of request for utility model registration] When receiving commercial AC power, commercial AC power is supplied to a load, and when a power failure detection unit detects a power failure, the power of a built-in storage battery is converted into alternating power by an inverter and supplied to the load. In the blackout power supply,
At the time of a power outage, a determining means for determining whether the commercial AC voltage suddenly decreases or gradually decreases, and when the determining means determines that the commercial AC voltage gradually decreases, the inverter is slower than when it is determined that the commercial AC voltage suddenly decreases. An uninterruptible power supply, comprising: delay means for activating the power supply.