JPH061962B2 - Power supply switching control circuit - Google Patents

Description

TECHNICAL FIELD The present invention relates to a switching control circuit for switching power supply from a main power supply in which a plurality of power supplies are connected in parallel to power supply from a standby power supply.

[Conventional technology]

Figure 2 is from page 22 of the December 1984 issue of the magazine "OHM" 2
This is a conventional power supply switching control circuit of this type shown on page 4. The output sides of the constant voltage constant frequency power supplies 1, 2 and 3 are connected in parallel to form a main power supply, and power is supplied from this main power supply to a load (not shown) via the changeover switch 5. On the other hand, power is supplied to the load from the standby power source 4 via the changeover switch 6. Switching control circuit 7
In the OR gate 11 and the AND gate 31, the stop state signals STP1, STP2 and STP3, which are output when the constant voltage constant frequency power supplies 1, 2 and 3 stop the power supply, and the AND gate 21 outputs the constant voltage constant frequency Stop status signals STP1 and STP2 of the power supplies 1 and 2, and the stop status signal ST of the constant voltage constant frequency power supplies 2 and 3 to the AND gate 22.
Further, P2 and STP3 are applied to the AND gate 23, and stop state signals STP1 and STP3 of the constant voltage constant frequency power supplies 1 and 3 are applied thereto.

The output STP11 of the OR gate 11 is given to one input terminal of the AND gate 13, and the output OL11 of the comparator 12 is given to the other input terminal of the AND gate 13. The output OL12 of the AND gate 13 is given to the OR gate 40. AND gate 2
Each output of 1,22,23 is given to OR gate 24, and OR gate 2
The output STP21 of 4 is given to one input terminal of the AND gate 26. The output OL21 of the comparator 25 is applied to the other input terminal of the AND gate 26. The output OL22 of this AND gate 26
The output STP31 of the AND gate 31 is given to the OR gate 40. The output of the OR gate 40 is given to the changeover switches 5 and 6 as the changeover command signal TRF.

Current sensor 8 detects the current flowing through the load from the changeover switch 5 or 6, the voltage signal I _L corresponding to the change in the load is given to one input terminal of the comparator 12 and 25. A voltage signal corresponding to a signal obtained by the current sensor 8 when a load of 200 kVA is applied to the other input terminal of the comparator 12 is given as a reference load signal R _ef1 , and another input terminal of the comparator 25 is loaded with a load of 100 kVA, for example. Sometimes current sensor 8
The reference load signal R is the voltage signal corresponding to the signal obtained in
_It is given as _ef2 .

This power supply switching control circuit includes constant voltage constant frequency power supplies 1, 2,
Assuming that the rated capacity per unit of 3 is 100 kVA, the power that can be supplied from the main power source is 300 kVA if the number of constant voltage constant frequency power sources 1, 2 and 3 that are operating normally is 300 kVA, 2 If it is a unit, it will be 200 kVA, and if it is a unit, it will be 100 kVA. If the power consumption of the load is 300 kVA, if the load power is, for example, 300 kVA when one of the constant voltage constant frequency power supplies 1, 2 and 3 stops supplying power, the main power supply is overloaded. Becomes

Therefore, in order to prevent the power supply to the load from stopping, the number of operating constant voltage / constant frequency power supplies and the load power at that time are checked.
Switch control to and continue power supply.

That is, the constant voltage constant frequency power supplies 1, 2 and 3 respectively output the stop state signals STP1, STP2 and STP3 when the power supply is stopped. The output STP11 of the OR gate 11 and the load power are 200
Output OL1 of comparator 12 which detected that it is more than kVA
When both 1 and 1 exist, at least one of the three constant-voltage constant-frequency power sources 1, 2, and 3 stops power supply, and the load power is 200 kVA or more.
The gate 13 outputs the output OL12. Also the output of OR gate 24
At the time when both the STP21 and the output of the comparator 26 that detects that the load power is 100 kVA or more are present, at least two of the three constant voltage constant frequency power supplies 1, 2 and 3 stop supplying power, Moreover, the AND gate 26 outputs the output OL22 in the overload state in which the load power is 100 kVA or more. Further, the AND gate 31 includes three constant voltage constant frequency power sources 1, 2, 3
Outputs the output STP31 assuming that power supply has been stopped. When any one of the outputs OL12, OL22, STP31 described above is output, the changeover command signal TRF is changed over to the changeover switch 5,
6, the changeover switch 5 is closed and the changeover switch 6 is opened to switch the power supply from the main power source composed of the constant voltage / constant frequency power sources 1, 2 and 3 to the power supply from the standby power source 4.

[Problems to be solved by the invention]

In such a conventional power supply switching control circuit, it is necessary to detect the load power with a current sensor. Further, the number of parts is large and the switching control circuit is complicated. Further, when a constant voltage constant frequency power source is added, there is a problem that the switching control circuit for switching the power supply from the constant voltage constant frequency power source to the standby power source becomes extremely complicated and it takes time to deal with it. Furthermore, when the load sharing of the individual constant voltage constant frequency power supplies is unbalanced, there is a problem that the set value for detecting overload must be reduced from the theoretical value.

In view of the above-mentioned problems, the present invention does not need to detect load power with a current sensor, has a small number of circuit components, and has a simple circuit, and can easily cope with the addition of a constant voltage constant frequency power supply. Moreover, it is an object of the present invention to provide a power supply switching control circuit that can perform power feeding switching operation without changing the load detection setting value even when the load sharing of each constant voltage constant frequency power supply is unbalanced.

[Means for solving problems]

A power supply switching control circuit according to the present invention includes a first OR gate that gives an overload signal to each power supply of a main power supply, an AND gate that gives a stop state signal of each power supply of a main power supply, and a first OR gate.
And a second OR gate for providing both outputs of the gate and the AND gate.

[Action]

When each power supply of the main power supply becomes overloaded, the overload signal is sent to the first OR
Give to the gate. Each power supply of the main power supply gives a stop state signal to the AND gate when power supply is stopped. First OR gate and A
The output of the ND gate is given to the second OR gate. When the overload signal is output, a changeover command signal is output and the changeover switch is changed over to change the power supply from the main power supply to the power supply from the standby power supply. When all of the main power supplies stop supplying power and a stop state signal is output, a switching command signal is output and the changeover switch is switched to switch the power supply from the main power supply to the power supply from the standby power supply.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to the drawings showing its embodiments.
FIG. 1 is a circuit diagram of a power supply switching control device according to the present invention. The output sides of a plurality of constant-voltage constant-frequency power supplies 1, 2, 3 serving as main power supplies are connected in parallel, and are connected to a load 9 via a changeover switch 5 composed of, for example, a thyristor switch. Further, the output side of the standby power source 4 which is different from the main power source is connected to the load 9 via a changeover switch 6 which is a thyristor switch. And usually constant voltage constant frequency power supply 1,
Power is supplied from 2 and 3 to the load 9 via the changeover switch 5,
When the power supply by the constant voltage constant frequency power sources 1, 2, 3 is stopped or when the constant voltage constant frequency power sources 1, 2, 3 are overloaded, the changeover switch 5 is opened and the changeover switch from the standby power source 4 is switched. Power is supplied to the load 9 via 6.

The power supply switching control circuit 7 includes a first OR gate 51 and an AND gate 61.
And a second OR gate 71. The overload signals OL1, OL2, OL3 output when the constant voltage, constant frequency power supplies 1, 2, 3 are in an overload state are given to the OR gate 51. In addition, the stop state signal ST that is output when the power supply is stopped due to a failure of the constant voltage / constant frequency power supplies 1, 2, 3
P1, STP2, STP3 are given to the AND gate 61. OR gate 5
The output OL of 1 is given to the OR gate 71, and the AND gate 61
The output STP of is applied to the OR gate 71.

When the overload signal OL or the stop state signal STP is given, the changeover command signal TRF output from the OR gate 71 is given to the changeover switches 5 and 6. When the changeover command signal TRF is given, the changeover switches 5 and 6 perform a changeover operation in which the changeover switch 5 is opened and the changeover switch 6 is closed.

Next, the operation of this power supply switching control circuit will be described.

Now, when the constant voltage constant frequency power supplies 1, 2 and 3 are normally operating and supplying power, none of the overload signals OL1, OL2, OL3 and the stop state signals STP1, STP2, STP3 are output, The switching command signal TRF is not output. Therefore, the changeover switch 5 is closed and power is supplied to the load 9 from the main power source including the constant voltage constant frequency power sources 1, 2, and 3 via the changeover switch 5.

Then, for example, when the constant voltage constant frequency power supply 1 is overloaded, the overload signal OL1 is given to the OR gate 51. Therefore, the OR gate 51 gives its output OL to the OR gate 71 and
The gate 71 outputs the changeover command signal TRF, and the changeover switch 5,
Will be given to 6. As a result, the changeover switch 5 is opened, the changeover switch 6 is closed, and the power supply to the load 9 is switched from the main power supply to the standby power supply 4. Further, such a switching operation is similarly performed when the other constant voltage constant frequency power supplies 2 and 3 are overloaded or when a plurality of constant voltage constant frequency power supplies are simultaneously overloaded.

On the other hand, for example, when the constant voltage constant frequency power source 2 fails and power feeding is stopped, the remaining constant voltage constant frequency power sources 1 and 3 bear the power feeding amount of the constant voltage constant frequency power source 2 which has been feeding until then. Become. In this case, when there is no change in the load power and the constant voltage constant frequency power supplies 1 and 3 are overloaded, the switching operation as described above is performed. In addition, constant voltage constant frequency power supply 1,
When the power supply to all 2 and 3 is stopped, the stop state signals STP1, STP2 and STP3 are output from the respective constant voltage and constant frequency power supplies 1, 2 and 3.
Are both supplied to the AND gate 61, and the AND gate 61 supplies the output STP to the OR gate 71.

As a result, the OR gate 71 outputs the changeover command signal TRF to the changeover switches 5 and 6, and the changeover switches 5 and 6 perform a changeover operation to change over from the main power source to the auxiliary power source 4 and the auxiliary power source 4 to the load 9. Power is supplied.

In this embodiment, the number of constant voltage / constant frequency power supplies is three, but it goes without saying that the number is just an example. Further, although the case where the main power source is a constant voltage constant frequency power source has been described, it may be another power source such as a generator or a DC power source device.

〔The invention's effect〕

As described above in detail, in the power supply switching control circuit of the present invention, the control circuit for switching the power supply from the main power supply to the power supply from the standby power supply is extremely simplified. Further, in the case of expanding the power supply constituting the main power supply, it can be easily dealt with by replacing the first OR gate and the AND gate with those having the number of input terminals suitable for the number of expansions. In other words, the first OR gate and
If the number of input terminals of the AND gate has a margin, it will be possible to quickly respond to the expansion of the power supply. Further, even when the load distribution of each power source is unbalanced, it is not necessary to perform control such as reducing the load detection set value from the theoretical value. Furthermore, an excellent effect such as not requiring a current sensor for detecting load electric power is exerted.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a power supply switching control circuit according to the present invention, and FIG.
The figure is a circuit diagram of a conventional power supply switching control circuit. 1, 2, 3 ... Constant voltage / constant frequency power supply 4 ... Standby power supply 5, 6 ... Changeover switch 51 ... OR gate 61 ... AND gate 71 ... OR gate In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A power supply switching control circuit for switching power supply from a standby power supply when the main power supply is abnormally operated when power is supplied from a main power supply in which a plurality of power supplies are connected in parallel. A first OR gate for giving an overload signal to be output in response to an overload of each power source, an AND gate for giving a stop state signal to be output in response to a power supply stop of each of the plurality of power sources, A second OR gate to which the output of the OR gate and the output of the AND gate are given, and the power supply from the main power supply is switched to the power supply from the standby power supply based on the output of the second OR gate. Characteristic power supply switching control circuit.