JPS6320086B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to input multiplexed power supplies.

FIG. 1 shows a configuration diagram of a conventional dual-input power supply device that rectifies two AC inputs and combines the outputs to obtain a power supply voltage as a result. In the figure, 10,2
0 is an input terminal connected to an AC power source of a separate system, 30 and 31 are rectifier circuits that rectify the AC voltage obtained through the input terminals 10 and 20, and the outputs of these two rectifier circuits are combined. , the DC power supply voltage is taken out from the output terminal 40. The rectifier circuits 30, 30 include diodes 11, 12, 13, 14, 15, 16, 21, 2, respectively.
2, 23, 24, 25, and 26. Furthermore, in order to prevent the load from stopping due to insufficient input voltage or failure, as shown in Japanese Utility Model Application No. 53-161231, a DC control power source (AVR) is connected to each of two or more input sources. There is a protection device for multiple DC power supplies that attempts to multiplex the DC power supply by stabilizing it through a diode and then combining it through a diode. The disadvantage is that the stability of the output voltage cannot be measured. In order to eliminate the above drawbacks, it is necessary to multiplex the inputs before the AVR.

Input terminal 10 for the power supply device configured as above,
An example of an AC power supply connected to 20 is shown in FIG.
In this figure, AC power supplies 50 and 51 are star-connected power supplies with a central ground plane. AC power supply 5 having such a configuration
In the case of 0.51, it has been confirmed that a relatively stable DC output voltage can be obtained from the output terminal 40. Specifically, a peak voltage that is sufficiently practical is a rectified voltage that is √2 times the effective voltage E of the input voltage. However, depending on on-site mounting conditions, circuit conditions, etc., there are cases where a delta-connected AC power source is connected to the input terminals 10 and 20 as an AC power source. A conventional example using this delta-connected AC power source is shown in FIG. This figure shows a configuration in which delta-connected AC power supplies 60 and 61 are connected to input terminals 10 and 20. However, since the AC power supplies 60 and 61 are not grounded at the center, the ground impedance 80,
81, an abnormally high output voltage may be generated from the output terminal 40. In addition, 70 in the figure
is a dummy resistor, and when abnormal voltage occurs,
By causing the overcurrent associated with this abnormal voltage to flow through the resistor 70, the abnormal voltage is suppressed to some extent. However, even with the provision of the dummy resistor 70, it was essentially impossible to eliminate the abnormal voltage. The above abnormal voltage generation process will be described in detail below.

Grounding impedance 8 of AC power supplies 60 and 61
Let the values of 0.81 be Z〓 _c and Z〓 _c ′, and
Line voltage E〓 ca , E〓 _ab , E〓 bc of ca, _ab , _bc Then, _the line voltages _of c′a′, _a′b ′, _{b′c ′} at AC _power supply 61 are shall be.

For convenience of explanation, FIG. 4 shows an equivalent circuit for each phase of E〓 _ca and E〓 _c ′ _a ′.

Now, when V _Zc > E〓 _c ′ _a ′ When V _Zc <E〓 _c ′ _a ′, V _D =E〓 _ca ………(4). However, R〓 _L is the value of the dummy resistor 70.
The maximum value V _Dnax in equation (3) is when θ=π in equation (2), becomes. FIG. 5 is a graph showing the above equations (4) and (5). As is clear from this figure, when the impedance when the rectified output peak voltage V _Dnax is √2E is Z〓, the ground impedance is 8
The sum of 0,81 (Z〓 _c +Z〓 _c ′) is the above impedance Z
〓
Peak voltage depending on whether it is larger or smaller than
The size of V _DNAx changes greatly. That is, Z〓 _c +
When Z〓 _c ′<Z〓, it becomes larger than √2E, reaching 2√2E at the maximum, and an excessive output voltage is generated. The above relationship also applies to duplication or multiplexing. Incidentally, in a single system multiple DC power supply as shown in Japanese Utility Model Application Publication No. 53-161231, the above-mentioned problem of overvoltage due to ground abnormality does not occur.

SUMMARY OF THE INVENTION An object of the present invention is to provide an input multiplex power supply device that detects when an output overvoltage occurs and protects a device such as an AVR that is a load.

The gist of the present invention is to detect an output overvoltage and, based on the detection result, to shut off the corresponding input of multiplexed AC power supply inputs. Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 6 is a diagram showing an embodiment of the present invention. The feature of this embodiment is that circuit breakers 97 and 98 are installed on each input power supply side.
and an overvoltage detection circuit 90 that detects when the output voltage has become excessive.Furthermore, when the overvoltage detection circuit 90 detects an overvoltage, it issues a shutdown command to each circuit breaker 97, 98. The reason is that cut-off circuits 95 and 96 are provided to cut off the input of AC power.

When an overvoltage is detected by the overvoltage detector 90 in such a configuration, overvoltage detection signals 91 and 92 are generated, and the interrupting circuits 95 and 96 are activated to interrupt the corresponding circuit breakers 97 and 98. This made it possible to prevent overvoltage from being generated from the output, thereby preventing any adverse effects on the load on the output side. Note that it is not always necessary to lock both AC power supply inputs when overvoltage is detected. This is to prevent the power supply from being completely stopped, and also because the generation of abnormal voltage can be prevented by stopping only one power supply input.
The value of the dummy resistor 70 is the input AC voltage
If the specified grounding impedance of 200V and 2 inputs is set to the grounding current of 15mA according to Japan Electronics Industry Technical Standard ACZ002, that is, the grounding resistance is 13.4KΩ, overvoltage prevention, which is the original function of the dummy resistor, becomes possible when R _L >20KΩ.

In this embodiment, three-phase input has been described, but the present invention can be applied to any case where the number of phases is one or more. Further, although the description has been made regarding duplex input, the present invention can also be applied to triple or higher multiplexing.

According to the present invention, an input power source that is not grounded at the center point can be received and redundant input can be performed, and a lightweight and inexpensive redundant input power source that does not require an internal insulation transformer can be obtained.

[Brief explanation of the drawing]

Figure 1 is a configuration diagram of a redundant input power supply, Figures 2 and 3 are specific examples thereof, Figure 4 is an equivalent circuit diagram, and Figure 5 is a diagram of an equivalent circuit.
The figure is a relationship between ground impedance and rectified output peak voltage, and FIG. 6 is a diagram showing an embodiment of the present invention. 30, 31... Rectifier circuit, 90... Overvoltage detection circuit, 95, 96... Circuit breaker breaking circuit, 97, 9
8... Circuit breaker.

Claims (1)

[Claims] 1. means for individually rectifying two or more systems of alternating current input; means for combining the individually rectified rectified voltages to obtain a rectified output; and direct current control means for obtaining a stabilized direct current output using the rectified output as input; an overvoltage detector that detects overvoltage of the rectified output when one or more AC input wires of each of the above systems are grounded at the same time; An input multiplexing power supply device comprising an input cutoff means for cutting off at least one input from each system.