JP2004187374A - Single phase three wire type voltage regulator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small and low-cost single phase three wire type voltage regulator in which a transformer of the single phase three wire type voltage regulator of an indirect switching system comprises a single shunting transformer 1 and a single serial transformer 2. <P>SOLUTION: The single phase three wire type voltage regulator comprises the shunting transformer 1 provided with a voltage regulating tap 5, the serial transformer 2 provided with a serial coil (+) 3a, a serial coil (-) 3b, and an exciting coil 4 of an identical induced voltage, a tap switch 6 and a controller 10. The serial coil (+) 3a is inserted in each phase so that the induced voltage from the exciting coil 4 becomes positive (or negative), while the serial coil (-) 3b is inserted in each phase so that the induced voltage becomes negative (or positive). The exciting coil 4 is connected to the shunting transformer 1 through a tap switch 6 so that the serial coil (+) 3a and the serial coil (-) 3b generate induced voltages at the same time. Therefore, the single serial transformer 2 can regulate voltages of + phase and - phase, and an indirect switching method requires less tap current for smaller/low-cost tap switch 6, resulting in a small size and a low price as the entire voltage regulator. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a single-phase three-wire voltage regulator that performs voltage adjustment in a single-phase three-wire low-voltage distribution line.
[0002]
[Prior art]
Conventionally, a voltage regulator for a single-phase three-wire low-voltage distribution line is composed of a two-turn or single-turn transformer in which the primary side and the secondary side are separately wound, as shown in FIG. A voltage adjustment tap is provided on the wire with a symmetrical winding ratio for the + phase and the-phase with respect to the N phase.
When the voltage is adjusted, the positive and negative phase taps are simultaneously switched by an appropriate tap switch.
[0003]
[Problems to be solved by the invention]
The conventional single-phase three-wire voltage regulator employs a direct switching method in which a rated current according to a transformer capacity flows through a tap. For this reason, a device having a relatively small capacity of about 5 to 10 kVA, which requires a relatively small tap current and a small switching current of the tap changer, is realized.
However, when the capacity is larger than this, the switching current of the tap switch becomes large, and it is difficult to realize the tap switching in terms of size, cost, and current switching performance. For example, if the rated voltage is 210 V and the rated capacity is 30 kVA, the tap current is about 150 A, and a tap switch that frequently opens and closes a tap current of this magnitude is large and expensive.
In such a case, as a means for reducing the tap current, an indirect switching method is known which comprises a shunt transformer and a series transformer as shown in FIG. 4 and can reduce the tap current to the amount required for voltage adjustment. . In this case, for example, if the voltage adjustment width is 10% of the rated voltage at a rated voltage of 210 V and a rated capacity of 30 kVA, the tap current can be reduced to about 15 A, and a relatively inexpensive electromagnetic contactor or the like is used as the tap changer. It can be adopted.
However, in a low-voltage single-phase three-wire system, it is necessary to adjust the voltage of the positive and negative phases evenly with respect to the N phase, so two series transformers are required, and the size and cost of the transformer section are reduced. It was difficult to realize.
SUMMARY OF THE INVENTION It is an object of the present invention to provide a single-phase three-wire voltage regulator having a larger capacity than conventional ones in a compact and inexpensive manner.
[0004]
[Means for Solving the Problems]
In order to solve these problems, the present invention comprises one shunt transformer and one series transformer, and this series transformer has two positive and negative pole series windings and one excitation winding. It is characterized by having.
By doing so, it is possible to reduce the number of series transformers required from two in the conventional single-phase three-wire system to one.
[0005]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to FIG.
The shunt transformer 1 is inserted between the + phase lead 7 and the − phase lead 8 in parallel. The shunt transformer 1 includes voltage adjusting taps 5a, 5b, and 5c drawn from an arbitrary portion of the winding. From the center of the winding of the shunt transformer 1, an N-phase lead 9, which is a neutral wire, is drawn out. In this embodiment, an autotransformer is used as the shunt transformer 1.
A tap changer 6 is connected to the voltage adjusting taps 5a, 5b, 5c. The tap changer 6 is configured to be able to select one of the arbitrary voltage adjusting taps 5a, 5b, 5c according to a command from the control device 10.
The series transformer 2 is configured by winding two series windings and one excitation winding 4 around the same iron core.
The series winding (+) 3 a is connected in the middle of the + phase lead 7 so that the induced voltage from the exciting winding 4 becomes positive. Similarly, the series winding (−) 3 b is connected in the middle of the − phase lead 8 so that the induced voltage from the exciting winding 4 becomes negative. Here, the series winding (+) 3a and the series winding (-) 3b have the same number of turns so that the magnitude of the induced voltage from the exciting winding 4 becomes equal. The winding ratio of the exciting winding 4 to the series winding (+) 3a and the series winding (-) 3b is an arbitrary ratio determined by a voltage width to be adjusted.
The exciting winding 4 has one end connected to the output from the tap changer 6 and the other end connected to the negative phase lead 8.
[0006]
The voltage adjustment operation of the above configuration will be described below.
When a voltage is applied to the input side, a voltage equal to the input voltage is applied to both ends of the shunt transformer 1. When the voltage adjustment tap 5a is selected here, a voltage equal to the input voltage is applied to the exciting winding 4. Since an induced voltage having a positive polarity is generated in the series winding (+) 3a, the output side of the + phase lead 7 has a positive polarity obtained by adding the input voltage and the voltage induced in the series winding (+) 3a. Is output. On the other hand, since an induced voltage having a negative polarity is generated in the series winding (−) 3 b, the input voltage and the voltage induced in the series winding (−) 3 b are added to the output side of the − phase lead 8. A voltage having a negative polarity is output.
As described above, a voltage can be applied to the output sides of the + phase lead 7 and the − phase lead 8 evenly, that is, without causing unbalance, to the N phase lead 9.
Further, by selecting an arbitrary voltage adjustment tap 5, the output voltage can be adjusted by changing the voltage applied to the excitation winding 4 from 0 to a voltage equal to the input voltage.
Further, if the polarity of the voltage applied to the excitation winding 4 is switched by an appropriate method, it is possible to switch between step-up and step-down, and to expand the range of voltage adjustment.
【The invention's effect】
As described above, according to the present invention, the transformer section of the single-phase three-wire voltage regulator of the indirect switching system can be constituted by one shunt transformer 1 and one series transformer 2. A large-capacity voltage adjusting transformer can be made smaller and less expensive than in the past. Furthermore, since the tap current is an indirect switching method with a small tap current, a small and inexpensive tap changer can be used. In the state where the voltage adjustment transformer and the tap changer are combined, a smaller and cheaper voltage than the conventional type can be used. A regulator can be provided.
[Brief description of the drawings]
FIG. 1 is a circuit diagram of a single-phase three-wire voltage regulator showing an embodiment of the present invention.
FIG. 2 is a circuit diagram of a voltage regulator based on a direct switching system showing a conventional embodiment.
FIG. 3 is a circuit diagram of a voltage regulator by a direct switching system showing a conventional embodiment.
FIG. 4 is a circuit diagram of a voltage regulator based on an indirect switching method showing a conventional embodiment.
[Explanation of symbols]
1 Shunt transformer 2 Series transformer 3a Series winding (+)
3b Series winding (-)
4 Excitation Windings 5, 5a, 5b, 5c Voltage Adjustment Tap 6 Tap Switch 7 + Phase Lead 8 -Phase Lead 9 N-Phase Lead 10 Controller 11 2-Wound Transformer 12 Auto-Transformer

Claims (1)

In the single-phase three-wire voltage regulator used for low-voltage regulation by switching the transformer tap,
The voltage regulator is
A shunt transformer having both terminals connected to the + and-phases and having an arbitrary number of taps on its winding;
A series transformer having two series windings having the same induced voltage and one excitation winding,
One of the series windings is inserted in series between the primary side and the secondary side of the + phase so that the induced voltage is positive (or negative), and the other one of the series windings is ,-Phase is inserted in series between the primary side and the secondary side so that the induced voltage is negative (or positive),
A single-phase three-wire voltage regulator, wherein a voltage is adjusted by connecting the tap to the excitation winding and switching the tap connected to the excitation winding.

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