JPH0480908A - transformer - Google Patents

Abstract

PURPOSE:To reduce no-load loss, to miniaturize and reduce weight, to cut down the cost of manufacture, and to reduce the space of setting by a method wherein three positive group windings, three negative group windings and three power source windings are provided on each leg of a three-legged core. CONSTITUTION:The three-leg type core 21, which constitutes a transformer, is composed of three legs 22 to 24 and two iron-cut parts 25 with which the legs will be electromagnetically coupled to their upper and lower ends. First, three positive group windings Xpu, Ypu and Zpu are provided in axial direction on the innermost layer on the outer circumference of the leg 22, three power source windings Ua, Ub and Uc are arranged on the outer circumference of the above-mentioned positive group windings in the same manner as above, three negative group windings Xnu, Ynu and Znu are arranged on the outermost layer of the power source windings, and each of the three windings is concentrically arranged. The wiring arrangement same as above is provided on the other two legs 23 and 24. Xpv to Zpv and Xpw to Zpw are the positive group windings provided on the legs 23 and 24 respectively, Xny to Zny and Xnw to Znw are the negative group windings provided on the legs 23 and 24 respectively, and Va to Vc and Wa to Wc are the powder source windings provided on the legs 23 and 24 respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a transformer suitable for use as a power transformer for a cycloconverter.

(Prior Art) A circulating current type cycloconverter using this type of transformer is disclosed, for example, in Japanese Patent Application Laid-open No. 186563/1983. This will be explained with reference to FIG. 6. In this figure, 1 is Three-phase AC power supply, 2 is a three-phase transformer consisting of a power supply winding (minus winding), positive group winding 2 and negative group winding 3 (both secondary windings), 6 is a three-phase transformer that connects thyristor 7 8 is a negative group converter formed by connecting thyristors 9 in a three-phase bridge connection; 10 and 11 are circulating current limiters connected between the positive and negative DC output terminals of both converters 6 and 8; Akudor, 12 is both reactor 10
．． This is a load connected between 11 neutral points. In such a cycloconverter, when a gate signal of a predetermined pattern is applied to the gate of the thyristor 7.9 of each converter, a signal is generated between the output terminals of the positive group converter 6, between the output terminals of the negative group converter 8, and between the terminals of the load 12. , voltages e, 2, eo, and eo of waveforms shown by thick lines in FIG. 7 are obtained. Here, e, is the average value of e, and e,1. Note that the thin lines represent the output voltage waveform of the three-phase AC power supply 1, and the dotted lines represent the respective voltages e, , eo. and the fundamental wave component of eo. In this way, the cycloconverter is used as a frequency conversion circuit that directly converts the power supply frequency to any frequency within a lower range by controlling the gate signal applied to the gate of the thyristor.

In such a cycloconverter, the load current i as shown in FIG. Of which, the positive half-wave current i. , is supplied from the thyristor 7 of the positive group converter 6, and the negative half-wave current 10
ゎ is supplied from the thyristor 9 of the negative group converter 8. Taking lap as an example, for the converter 6, the current is also in the forward direction during the period when the thyristor 7 is forward biased as shown in the period t2-t3. It performs a forward conversion function, and also performs a reverse conversion function during a period in which the current continues to flow in the forward direction even after the thyristor 7 shifts to the reverse bias state, as shown in the period t3-t4. While one converter 6 is performing the forward conversion and inverse conversion functions in this manner, the other converter 8 is in a standby state that prevents the passage of current. However, although such a standby state is formed every half cycle, in reality, as shown in FIG. 7, the voltage contains harmonics, so both converters 6.
8, a circulating current flows through the reactor 10.11. Only half-wave current flows through the positive group winding 4 and negative group winding 5 of the transformer 2, whereas both positive and negative group windings 4 flow in the power supply winding 3.
, 5 so that the ampere turns are the same, so if the current capacity of the positive group or negative group winding is 1, the current capacity of the power supply winding 3 may be approximately (T).

(Problem to be Solved by the Invention) A conventional three-phase transformer used as a power transformer for such a cycloconverter has one positive group winding on the - leg for one phase of the three-phase winding. A configuration is adopted in which the wire, one negative group winding 5, and one power supply winding interposed between these two windings are provided in a concentric arrangement. Therefore, if the load is three-phase, the number of converters must be increased to six, and the number of three-phase transformers must be increased to three. Increasing the number of three-phase transformers to three increases manufacturing costs and installation space, and furthermore, since the core volume increases significantly, there is a problem that no-load loss, especially iron loss, increases. Such an increase in no-load loss goes against the purpose of adopting the cycloconverter, which is to reduce energy consumption by using a variable speed control method as the operation method of the induction motor.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to enable a power transformer connected to a cycloconverter to supply three-phase alternating current from the cycloconverter to a three-phase load with a single iron core, and as a result, reduce no-load loss. It is an object of the present invention to provide a transformer that can be reduced in size and weight, as well as manufacturing costs and installation space.

[Structure of the Invention] (Means for Solving the Problems) A transformer according to the present invention includes an iron core having a tripod, a positive group winding,
It consists of a negative group winding and a power supply winding, and is characterized in that each leg of the iron core is provided with three positive group windings, three negative group windings, and three power supply windings.

(Function) This transformer is used as a power transformer for a cycloconverter that supplies three-phase AC power to a three-phase load. Three positive group and negative group windings are assigned to each converter, and one power supply winding is assigned to each pair of positive and negative group windings to make the winding circuit impedance the same between the positive and negative groups. These windings are magnetically coupled to each other by a single tripod core and have the structure of a single transformer.

Although a transformer with this structure has the same function as three three-phase transformers, it only requires one iron core.
As a result, in the case of a tripod core, the core yoke portions are provided at two locations per tripod core, so a total of six locations would be required for three yokes, but in the present invention, only two locations are required, and the core volume is reduced accordingly.

(Example) Hereinafter, an example of the present invention will be described with reference to FIGS. 1 to 4. As shown in FIG. 4, a tripod-shaped iron core 21 constituting the transformer 20 in this embodiment magnetically couples three legs 22 to 24 and the legs 22 to 24 at their upper and lower ends. It consists of two yoke parts 25 for the purpose. The winding structure of the monopod 22 is shown in FIG. 2, and as shown in this figure, on the outer periphery of one leg 22, first, three positive group windings X pu, Y pu are arranged in the innermost layer. ,
Z pu are arranged in line in the axial direction, three power supply windings Ua, Ub, and Uc are similarly arranged on the outer periphery, and three negative group windings X nu, Y nu, and Z n are arranged on the outermost layer.
u so that each of the three windings is concentrically arranged.

The same winding arrangement is carried out for the other two legs 23,24. The relationship between each leg and the winding arranged therein in this case is shown in FIG. In this Figure 1, X pv
~Z pv, X pv -Z pv are each leg 23°2
Positive group winding provided at 4, X nv −Z nv,
nw to Znv are negative group windings provided on the legs 23.24, respectively, and V a to V c and W a -W c are power supply windings provided on the legs 23.24, respectively. FIG. 3 shows a three-phase cycloconverter using the transformer 20 as a power source. In FIG. 3, 26 is a three-phase induction motor consisting of stator windings 26X, 26Y, and 26Z corresponding to each of the three phases x, y, and z of a star-connected three-phase load. The stator windings are connected so that AC voltage is applied from each of three sets of cycloconverters 27X, 27Y, and 27Z, each set corresponding to one phase. Each set of cycloconverters has the same structure as the positive group cycloconverter 6 and the negative group cycloconverter 8 shown in FIG. That is, 6X, 6Y, and 6Z are the stator windings 26X corresponding to the Sanwa, ie, x, y, and z phases on the motor 26 side, respectively.
Positive group converter compatible with 26Y and 26Z, 8X
, 8Y, and 8Z are negative group converters corresponding to stator windings 26X, 26Y, and 26Z, respectively. The connection relationship between each of these converters and the windings of the transformer 20 is as follows. First, three power supply windings U provided on the same leg 22
a.

Ub and Uc are connected in parallel to form the three-phase U and V of the three-phase AC power supply 1.
, the three power supply windings Va, Vb, and Vc are connected in parallel to the V phase of the three-phase AC power supply 1, and the three power supply windings Va, Vb, and Vc provided on the leg 23 are connected to the U phase of the W phase and are provided on the leg 24. The three power supply windings Wa, Wb, and Wc are connected in parallel and the W of the three-phase AC power supply 1 is
At the same time, the three sets of parallel windings are connected as a whole in a three-phase connection, for example, a star connection. On the other hand, three legs 22~
Three positive group windings Xpu=Xpν and three negative group windings Xnu to X corresponding to U, V, and W phases distributed in 24
nw is a positive group converter 6X and a negative group converter 8X, each connected to a three-phase connection, for example, a star connection, and corresponding to the X phase, respectively.
The positive group windings Ypu-Ypν and the negative group windings Ynu-Ynv corresponding to the Y phase and which are similarly arranged in three legs 22 to 24 are star-connected to form a positive group corresponding to the Y phase. A positive group winding Zpu-Zpw and a negative group winding Znu- corresponding to the Z phase are connected to the converter 6Y and the negative group converter 8Y, and are also distributed over the three legs 22 to 24.
Znv are star-connected and connected to a positive group converter 6Z and a negative group converter 8Z corresponding to the Z phase.

As a result of this connection configuration, a three-phase AC voltage is applied from the cycloconverter to the stator windings 26X, 26Y, and 26Z of the induction motor 26, and the frequency of the three-phase AC voltage is applied to the stator windings 26X, 26Y, and 26Z of the induction motor 26. It is variable by controlling the gate signal to.

The transformer 20 of this embodiment used in a cycloconverter for applying a three-phase AC voltage to a three-phase load is conventionally constructed using three transformers, that is, three independent transformers, as shown in FIG. Three iron cores 28 are required, but only one iron core 21 is required. Therefore, using FIGS. 4 and 5, the conventional and this embodiment will be compared with respect to the volume of the iron core using the illustrated dimensions (in this case, the thickness of the iron core is assumed to be 1 for convenience).

The volume of the conventional iron core (volume of three units combined) is expressed by the following formula.

V ”= 3 (W (2A +h) −2W h1
■6W A + 3W h -6w h On the other hand, the volume V' of the iron core 21 in this embodiment is expressed by the following equation.

V - - W (2A + 3h) - 2wh = 2 W A + 3 W h -6w hAs is clear from the difference between this V and V'', it can be seen that the volume of the iron core 21 of this example is smaller by 4WA. That is, in the case of a tripod core, the iron core has two yoke parts, so for three yoke parts, a total of six yoke parts are required, but in the present invention, only two yoke parts are required, and the core volume is reduced accordingly. If the material and magnetic flux density of the iron core are the same, the no-load loss in the iron core is proportional to the volume of the iron core, so in this example, the no-load loss equivalent to 4WA is reduced compared to the conventional case. Since most load losses occur in the diagonally shaded areas of the yoke parts of the iron core, in this embodiment, where the number of yoke parts is reduced compared to the conventional one, the no-load loss is further reduced. With the decrease in , material costs can be reduced accordingly, and the number of man-hours for assembling the iron core is reduced to about 1/3, so manufacturing costs can be significantly reduced, and the installation space for the iron core is also reduced to about 1/3.

Although the winding arrangement in the above embodiment is a concentric arrangement in which the power supply winding is interposed between the positive group winding and the negative group winding in the radial direction of the leg, the present invention is not limited to this. A coaxial arrangement may be used in which the wire is interposed between the positive group winding and the negative group winding in the axial direction of the leg. Furthermore, in the above embodiment, the connection relationship between each winding and each converter is such that all the windings provided on the same leg correspond to only one of the three phases on the power supply side. Since the legs are magnetically coupled to each other, there is no need for such a connection.

[Effects of the Invention] As described above, the present invention is suitable for use as a power transformer connected to a cycloconverter in order to supply three-phase alternating current from the cycloconverter to a three-phase load, and This can be configured with a single core, and as a result, it is possible to provide a transformer that can reduce no-load loss, be smaller and lighter, and also reduce manufacturing costs and installation space.

[Brief explanation of the drawing]

Figures 1 to 4 relate to an embodiment of the present invention, in which Figure 1 shows the overall correspondence between the windings of a transformer, and Figure 2 shows the windings of one leg of the transformer. A schematic vertical cross-sectional view showing the arrangement of lines, Figure 3 is a wiring diagram of a cycloconverter,
Figure 4 is a front view of the iron core, Figure 5 is a front view of a conventional iron core,
FIG. 6 is a wiring diagram of the cycloconverter in the case of a single-phase load, FIG. 7 is a voltage waveform diagram of each part in FIG. 6, and FIG. 8 is a time chart shown together with voltage and current waveforms. In the figure, 21 is an iron core, 22 to 24 are legs, 26 is an induction motor, 6X to 6Z are positive group converters, 8X to 8Z are negative group converters, Xpυ to Zpv are positive group windings, and Xnu-Znν are negative group windings. The line U a - W c is the power winding. Agent Patent Attorney Noriyuki ChikaXnu-Znw: MtJ8m

Claims (1)

[Claims] 1. It consists of an iron core having a tripod, a positive group winding, a negative group winding, and a power supply winding, and each leg of the iron core has three of the positive group windings, three of the negative group windings, and three of the negative group windings. A transformer comprising the power supply winding.