JPH10155239A - Power-factor improving method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the power factor of an electric circuit, to decrease the reactive power and the voltage drop and to reduce the loss, by providing a tap in an inserting transformer, and using a resistance-type or inductance-type switching unit in interlocking with a phase meter. SOLUTION: A tap 4 is provided in an insertion transformer 2. A resistance- type or inductance switching unit is used in interconnection with a phase meter. Furthermore, a tertiary winding is provided in power-supply transformer 1. A capacitor 3 can be connected to this winding. That is to say, the capacitor 3 is connected to a transmission circuit through the insertion transformer 2. Therefore, the connecting point becomes the intermediate point of a transmission transformer in balance in the case of a three-wire system. In the delta connection in a three-phase system, the connection is performed to the intermediate part of the transformer winding or to an external line. In the star connection, the connection is performed between the common connecting point, which is the grounding point, and the winding of the individual phase transformer. Thus, the high frequency can be controlled. Therefore, the power factor of the electric circuit can be improved, the reactive power is reduced, the voltage drop is also decreased and the loss can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention has more windings on the secondary side than on the primary side of the transformer,
Although the ratio is n, when a capacitor is connected to the secondary side, the voltage applied to the capacitor is n times that of the primary side, whereas the capacity of the capacitor viewed from the primary side is n times the capacity of the connected capacitor. This is to take advantage of the fact that the effect is improved even if the capacity of the condenser is small due to the square multiplication. The method of using the present invention is to improve the power factor associated with the use of equipment or the like, to reduce the voltage drop by canceling the inductance of the transmission circuit, or to form a low-frequency resonance circuit. The power factor is improved by installing a capacitor in the necessary place, but the power factor of large-capacity special equipment varies depending on the use condition, so it is quite difficult to change the connection of the capacitor following this, If a resistance type or inductance type switching device is used in conjunction with a phase meter by providing a tap, the operation can be effectively performed, the effect on the power supply side is reduced, and the voltage fluctuation is advantageously reduced. In this case, it is also possible to provide a tertiary winding in a power transformer without using an insertion transformer and connect a capacitor to the tertiary winding. In a power transmission circuit, the voltage drop due to inductance is large as the current value is large and the loss is large. Therefore, the inductance can be reduced by inserting a capacitor in series. That is, since the capacitor is connected to the transmission circuit through the insertion transformer, the problem is where to connect the capacitor. In the case of the three-wire system, it is considered that the capacitor is located at the middle point of the transmission transformer on balance. In a three-phase inner delta connection, there is no choice but to connect to the middle or outer line of the transformer winding. In the star connection, it is connected between the common connection point which is a ground point and the winding of each phase transformer. In any case, since a voltage close to the voltage generated in the inductance is generated, insulation and maintenance problems will occur, so care must be taken, and the generation of large current due to line grounding etc. must be considered. Determine the capacitor value. The apparent increase in the capacitance of the capacitor due to the combination of the transformer and the capacitor can be used for suppressing a high frequency or the like because a low-frequency resonance circuit can be easily configured in combination with a wire that does not use a magnetic material. As described above, the present invention has many advantages and can be used effectively.

[Brief description of the drawings]

Fig. 1 shows the most common power factor correction method, 1 is a power transformer, 2 is an insertion transformer, 3 is a capacitor, 4 is a tap,
5 is a load. FIG. 2 shows a power transformer in which a winding for connecting a capacitor is provided. FIG. 3 shows a power transmission circuit, and 6 is an inductance. 4 and 5 show a three-phase delta connection, and FIG. 6 shows a three-phase star connection. Reference numeral 7 denotes a secondary winding of the transformer and the primary winding is omitted. Seventh
The figure shows a series resonance circuit, and FIG. 8 shows a parallel resonance circuit, where 8 is the same as the insertion transformer and 9 is an inductance without a magnetic core.

Claims (5)

[Claims] 1. When connecting a capacitor in series or parallel to a circuit, when connecting through a transformer (hereinafter referred to as an insertion transformer), a tap is provided directly or on a secondary winding,
A method to improve power factor or circuit constant. 2. A method in which a capacitor is connected to an insertion transformer having a large number of secondary windings in a power supply circuit, or a connection is made after a tap is provided in the secondary winding. 3. A method in which a winding for connecting a capacitor is provided in a transmission transformer so that the number of windings is larger than the number of secondary windings, and a capacitor is connected directly to the winding or by providing a tap on the winding. 4. When a capacitor is connected to a circuit by an insertion transformer to reduce the inductance of the circuit, in the case of a two-wire system, the center of the winding of the transmission transformer is a three-phase system. Or in an external line, and in the case of a star connection, an insertion transformer is connected between the common connection point and the winding of each phase. 5. A method of forming a resonance circuit by connecting a transformer combined to increase the capacity of a capacitor in series or parallel with another inductance.