REACTOR HAVING A PLURALITY OF COAXIALLY DISPOSED WINDINGS

Abstract: Disclosed is reactor having a plurality of windings (1, 2, 11) disposed coaxially and connected to form a series circuit and a supporting member for supporting the plurality of wind­ ings, there are provided two terminals (3, 4) respectively con­ nected to the opposite ends of a specific one (1) of the plurality of windings and a further terminal (5, 10) connected to one end of each winding other than the specified winding, the terminals being capable of being selectively connected to an external power source. The winding arrangement enables to provide various kinds of terminal combinations to be connected to the external power source so that a plurality of inductance values can be selectively obtained by selecting the terminal combina­ tions.

Description: REACTOR HAVING A PLURALITY OF COAXIALLY DISPOSED WINDINGS The present invention relates to reactors of the air-core type and the iron-core type for use in electric installations, such as substations, power stations, and more particularly to the arrangement of windings in such reactors. Generally, in a reactor, such as an air-core reactor, an iron-core reactor having a gap called gapped core type reactor, one winding is provided for each phase as shown in Figs. 3 and 7 of Japanese Patent Application Laid-open No. 43820/80 and in Figs. 3 and 4 of Japanese Patent Application Laid-open No. 22837/80. Further, a multi-layer winding arrangement is known which is constituted by inner and outer windings 1 and 2 of substantially cylindrical form coaxially disposed and connected in series to each other, as shown in Fig. 1 of the present application. In Fig. 1, the reference numeral 6 designates a magnetic shielding constituted, generally, by a silicon steel plate, and the inner and outer windings 1 and 2 are supported by a supporting member, such as a winding insulator tube, (not shown). In reactor having such a winding arrangement as described above, the inductance value of the reactor is determined as a necessity if a necessary capacity (voltage x current) with respect to a predetermined circuit voltage is determined, and a reactor having such an inductance value is produced and disposed in an substation or in a power station. Accordingly, if the necessary capacity of the reactor is required to be increased, a further reactor is newly produced and disposed side by side with the previously disposed reactor, and the two reactors are connected in series or in parallel with each other. In the case where the necessary capacity of the reactor is to be decreased, on the other hand, another reactor has to be produced so that the existing reactor is replaced by the newly produced reactor. Considering the recent shortage of land required for a substation and a power station and the possible alteration of the necessary reactor capacity in the future, there is a problem that the required land has to be secured in advance in anticipation of additional provision of a further reactor or a further reactor has to be produced and disposed side by side, resulting in increase in charge of the original investment. Further, it is very uneconomical to produce and dispose a new reactor agreeable to a new requirement of the necessary reactor capacity every time the necessary reactor capacity be altered. An object of the present invention is to eliminate the defects in the prior art as described above and to provide a reactor which can cope with the alteration of required capacity, which requires a narrow area for the installation thereof, and which can be manufactured economically. According to the present invention, in the reactor having a plurality of windings disposed coaxially and connected to form a series circuit and a supporting member for supporting the plurality of windings, there are provided two terminals respectively connected to the opposite ends of a specific one of the plurality of windings and a further terminal connected to one end of each winding other than the specified winding, the terminals being capable of being selectively connected to an external power source. The winding arrangement enables to provide various kinds of terminal combinations to be connected to the external power source so that a plurality of inductance values can be selectively obtained by selecting the terminal combinations. The above and other objects, features and advantages of the present invention will be apparent from the following detailed description of preferred embodiments thereof taken in conjunction with the accompanying drawings, in which: Fig. 1 is a schematic sectional view of a prior art reactor having two windings arranged coaxially; Fig. 2 is a plan view of the winding for single phase of an air-core type reactor provided with a magnetic shielding according to a first embodiment of the present invention; Fig. 3 is a cross-section along the III-III line of the first embodiment shown in Fig. 2; Fig. 4 is a plan view of the winding for single phase of a gapped core type reactor according to a second embodiment of the present invention; Fig, 5 is a cross-section along the V-V line of the second embodiment shown in Fig. 4; and Figs. 6 and 7 show modifications of the embodiment of Fig. 3. Referring to the drawings,the present invention will be described in detail hereunder. Referring to Figs. 2 and 3, an inner winding 1 of cylindrical form and an outer winding 2 of cylindrical form are coaxially disposed and connected in series with each other through a connecting wire C. The windings 1 and 2 are wound in the same direction. Terminals 3 and 4 to be connected to an external power source are connected to one and the other end or the upper and lower end of the winding 1, in the drawing, respectively, and a terminal 5 to be connected to the external power source is connected to the lower end of the winding 2, in the drawing, that is to one end of the winding 2 which is in opposition to the other end CP of the same winding 2 to which the other or lower and of the winding 1 is connected. A magnetic shielding 6 is provided to substantially surround the inner and outer windings 1 and 2. The inductance L of the reactor is expressed by the following equation: S L X N2 x l ............ (1) where N represents the number of turns of a winding, S represents the effective area of magnetic flux, and Q represents the length of the gap. In order to obtain various values of inductance, accordingly, it will do to make the winding arragnement to provide various combinations of N, S and g in the equation (1). That is, in the reactor arranged as shown in Fig. 3, a first inductance value L1, which is the inductance of the winding 1 and which is expressed by the following equation (2), can be obtained by selectively using the terminals 3 and 4: L1 N1 x t (2) where N1 represents the number of turns of the winding 1, S1 represents the sectional area with respect to the average diameter D1 of the winding 1. Alternatively, a second inductance value L2, which is larger than the inductance value L1, that is the combined inductance value of the windings 1 and 2, can be obtained as shown in the following equation (3) by selectively using the terminals 3 and 5: L2 &alpha; (N1 +N2) x 1 (3) where N2 represents the number of turns of the winding 2 and S12 represents the sectional area with respect to the mean diameter D12 of the resultant winding of the combined windings 1 and 2. Alternatively, a third inductance value L3 different from each of the above-mentioned inductance values L1 and L2, that is the inductance value of the winding 2, can be obtained by selectively using the terminals 4 and 5, as expressed in the following equation (4): S2 L3 N x l ............... (4) where S2 represents the sectional area with respect to the mean diameter D2 of the winding 2. By suitably selecting any two of the three terminals 3, 4 and 5 in the manner as described above, three kinds of inductance values L1, L2 and L3 which are different from one another can be obtained in one reactor. Thus, the area of installation of reactor can be reduced in a substation or in a power station, resulting in reduction in cost of the substation or the power station. Although the description has been made in the embodiment with respect to the arrangement for single phase of a reactor, the same effect can be obtained by arranging the winding for each of phases in the case where the reactor is of the polyphase type. Referring to Figs. 4 and 5 showing a second embodiment of the present invention, an inner winding 1 and an outer winding 2 are coaxially disposed and connected in series through a connecting wire C, similarly to the winding arrangement shown in Fig. 3. The windings 1 and 2 are wound in the same direction. Terminals 3 and 4 to be connected to an external power source are connected to one and the other end or the upper and lower end of the winding 1, in the drawing, respectively, and a terminal 5 to be connected to the external power source is connected to the lower end of the winding 2, in the drawing, that is one end of the winding 2 which is in opposition to the other end CP of the same winding 2 to which the other or lower end of the winding 1 is connected. A yoke 7 is provided substantially to surround the windings 1 and 2, and a block core 8, which is constituted by a plurality of blocks, is provided coaxially with the windings 1 and 2. Reference numeral 9 designates a minute gap between adjacent blocks. In such a reactor of the iron-core type provided with a gap, the effective sectional area S in the equation (1) is determined to a fixed value substantially depending on the sectional area of the block core 8 in the direction perpendicularly crossing the axial direction of the windings, and, therefore, several kinds of inductance values can be obtained only by changing the number of turns N of each winding. This applies to the case where a reactor is provided with three or more windings provided coaxially with each other. The gap length Q can be obtained by multiplying the length EQ1 of each of the minute gaps 9 by the number n of the gaps 9. That is, assuming that the effective sectional area of magnetic flux is represented by Sconst' the number of turns of the winding 1 is represented by N1' and the number of turns of the winding 2 is represented by N2', in the embodiment of Fig. 5, a first inductance value of the reactance when the terminals 3 and 4 are selected can be expressed by the following equation (5): L1' &alpha; N1'2 x Sconst .............. (5) #l1 x n Alternatively, a second inductance value L2 of the reactance expressed by the following equation (6) can be obtained by selectively us nag the terminals 3 and 5: S Sconst ...... (6) L2' &alpha; (N1' + N2')ê x #l1 x n Alternatively, further, a third inductance value L3 of the reactance, when the terminals 4 and 5 are selected, can be expressed as the equation (7) as follows: L3' &alpha; N2'2 x Sconst ......... (7) #l1 x n Thus, three kinds of inductance values L1, L2 and L3 can be obtained in a single reactor, in the same manner as the first embodiment. Referring to Fig. 6, the windings 1 and 2 are wound in the opposite direction to each other differing from the first and second embodiments, while the windings 1 and 2 are disposed coaxially. In this arrangement, the series connection between the windings 1 and 2 may be performed by connecting the respective lower ends of the windings 1 and 2,- in the drawing, by a connecting lead C so that the length of the connecting lead C can be reduced in comparison with the first and second embodiments. In this embodiment, the terminal 5 is provided at the upper end of the winding 2 as seen in the drawing. Although Fig. 6 shows an embodiment in which the present invention is applied to a reactor of the air-core type, it is a matter of course that the present invention can be applied to a reactor of the iron-core type in the same manner as the embodiment of Fig. 6. Fig. 7 shows an embodiment in which three windings, 1, 2 and 11 are concentrically disposed. The effect similar to the previous embodiments can be obtained in this embodiment. That is, six kinds of inductance values can be obtained by selecting any two of four terminals 3, 4, 5 and 10. It is a matter of course that the number of the coaxially disposed windings is not limited to two or three but can be selected to four or more. In each of the embodiments described above, the current flowing in the respective winding varies depending on the selection of terminal when the applied voltage is constant. That is, for example in the first embodiment, assume that the inductance value is selected merely between L1 and L2, and that a current I1 flows only in the winding 1 when the inductance value L1 while current I2 flows in the windings 1 and 2 when the inductance value L2 is selected. The current I2 is smaller than the current I1. Accordingly, it is not necessary to set the sectional area Sb of the winding 2 to a value corresponding to the current that is to a value as large as the sectional area 5a of the winding 1. The sectional area Sb may be set to a value not smaller than that obtained by the following equation (8): I2 (8) b a a x the sectional area of the conductor of the winding 2 is reduced to the value obtained in the equation (8), the more the conductor material can be reduced. Although the advantage in reduction of conductor material has been described above in connection with the first embodiment, the similar advantage in reduction of conductor material can be obtained in other embodiments. Furthermore, although the windings of cylindrical form are applied to the embodiments shown in Figs. 2 to 7, square pillar windings can be applied to the present invention.

Claims: CLAIMS 1. A reactor having a plurality of windings (1, 2, 11) disposed coaxially and connected in series with each other and a supporting member for supporting said plurality of windings, characterized in that two terminals (3, 4) respectively connected to the opposite ends of a specific one (1) of said plurality of windings; a further terminal (5, 10) connected to one end of each winding other than said specified winding; and said two terminals and said further terminal being capable of being selectively connected to an external power source. 2. A reactor according to claim 1, characterized in that said reactor is of the air-core type and provided with a magnetic shielding (6) fixedly disposed substantially to surround the axially opposite surfaces of said plurality of windings and the radialy opposite sides of said plurality of windings. 3. A reactor according to claim 1, characterized in that said reactor is of the iron-core type and provided with a substantially cylindrical iron-core (8) disposed fixedly and coaxially with said plurality of windings, and a yoke (7) fixedly disposed substantially to surround the axially opposite surfaces of said plurality of windings and the radially opposite sides of said plurality of windings. 4. A reactor according to claim 1, characterized in that the respective numbers (N1, N2) of turns of said plurality of windings are different from each other. 5. A reactor according to claim 1, characterized in that said plurality of windings are wound in the same direction with each other, and in which said plurality of windings are connected in a manner so that one end of one of any adjacent windings disposed at one of the axially opposite surfaces of said adjacent windings is connected to one end of the other one of said adjacent windings disposed at the other one of said axially opposite surfaces of said adjacent windings to constitute a series circuit of said plurality of windings. 6. A reactor according to claim 1, characterized in that adjacent ones of said plurality of windings are wound in the opposite direction to each other, and in which said plurality of windings are connected in a manner so that one end of one of any adjacent windings disposed at one of the axially opposite surfaces of said adjacent windings is connected to one end of the other one of said adjacent windings disposed at said one of said axially opposite surfaces of said adjacent windings to constitute a series circuit of said plurality of windings. 7. A reactor according to claim 1, characterized in that the sectional area of a conductor constituting each of said plurality of windings is proportional to a maximum current flowing in said conductor so that the respective current densities of the conductors of said plurality windings are substantially equal to each other with respect to the maximum currents flowing in said conductors.

Inventors: OBATA, TOSHIMITSU
Applicants: HITACHI, LTD.
Application year: 1984
Main classification: H01F37
IPC codes: H01F27, H01F37, H01F30