JPS6255285B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a resin molded transformer in which an iron core and a coil are integrally molded, and particularly to one in which the winding structure of a toroidal winding constituting a low voltage coil is improved.

Conventionally, some resin-molded transformers are constructed by toroidally winding a low-voltage coil around an iron core, combining it with a high-voltage coil, and molding the iron core and coil together. FIG. 1 shows this type of resin molded transformer, in which the outer periphery of an iron core 1 is covered with an insulating case 2, on which a low voltage coil 3 is toroidally wound. The toroidal winding of the low voltage coil 3 is generally arranged and wound evenly around the entire circumference of the iron core 1 with the inner circumference as a reference, as shown in FIG. Thereafter, it is combined with the high voltage coil 4 to form a transformer element, and this transformer element is molded with synthetic resin 5 or the like to obtain a resin molded transformer.

However, in such a resin molded transformer, when the number of turns of the low voltage coil 3 is small, the pitch P between the strands on the outer periphery of the iron core 1 is P ₁₁ = P ₁₂ > P ₁₃
This results in misalignment as shown in _FIG .

Also, if the number of turns of the low voltage coil 3 is small,
Due to the temperature rise during overcurrent strength, low voltage coil 3
The cross-sectional area of the wire becomes larger. To explain this with a cross section of the main part of the winding part of the low voltage coil 3 in Fig. 3, _the cross-sectional area S ₁ of the wire of the low voltage coil 3 is calculated as S _{1 =} /2) In ² , the gap between the wires
G ₁ becomes G ₁ = P ₁ − d ₁ .

However, in the resin molded transformer with the above configuration, the iron core 1 is wound with a silicon steel plate due to the effects of shrinkage stress etc. that occur when the molded synthetic resin 5 etc. hardens.
An air gap 6 is provided between the insulating case 2 and the iron core ₁ in order to prevent the magnetic properties of the coil from changing. Because the electric field is disturbed, partial discharge may occur in the air gap 6, and even lead to dielectric breakdown. Furthermore, since the cross-sectional area S ₁ , that is, the diameter d ₁ of the wire of the low-voltage coil 3 is large, when performing toroidal winding, excessive force may be applied to the insulating case 2 and damage the insulating case 2. During molding, the synthetic resin 5 penetrated through the damaged insulation case 2, deteriorating the core properties.
Furthermore, since the diameter _d1 of the wire of the low-voltage coil 3 is large, the workability of toroidal winding is poor, and the winding dimension of the wound coil becomes large.

An object of the present invention is to provide a resin-molded transformer that can prevent partial discharge between the core and the coil and improve winding workability in a configuration in which a low-voltage coil is toroidally wound around the entire circumference of the core. It's about getting.

The present invention will be described below based on an embodiment shown in the drawings. 4 and 5 are cross-sectional views showing the main parts and internal structure of the resin molded transformer according to the present invention. Apply the insulation case 2 to the outer periphery of the iron core 1,
A low voltage coil 13 is wound on it, and a high voltage coil 4 is wound thereon.
As in the conventional method, a transformer element is formed by combining the transformer element with a synthetic resin 5 as shown in FIG. The present invention is characterized in that the low voltage coil 13 is composed of parallel wires. That is, the wires of the low-voltage coil 13 are made thinner than conventional ones and wound in parallel. For example, the wire diameter d ₂ of the low voltage coil 13 is changed from the conventional wire diameter d ₁ .
1/2, and when the current density of the parallel strands of the low voltage coil 13 is the same as that of a conventional single strand, and the cross-sectional area of each parallel strand is S ₂ , S ₁ = 4S ₂
Therefore, it is sufficient to wind four wires of d ₂ in parallel. The pitch P ₂ between the wires of the low voltage coil 13 wound in this manner is approximately the pitch P ₁ between the wires of the conventional low voltage coil 3.
It becomes 1/4, and the gap G ₂ between the strands also becomes smaller. In this way, the low-voltage coil 13 forms a substantially uniform shielding surface, which reduces disturbances in the electric field and prevents partial discharge from occurring in the air gap 6 between the iron core 1 and the insulating case 2. become. In addition, the wire diameter of the low voltage coil 13
Since d ₂ is small, toroidal winding can be performed without damaging the insulating case 2, and the winding work is easier and workability is improved. Furthermore, the winding dimension of the low voltage coil 13 can be reduced It can be made small.

As described above, according to the present invention, it is possible to obtain a resin molded transformer that prevents the occurrence of partial discharge, improves electrical characteristics, and improves winding workability.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a resin molded transformer, Fig. 2 is a sectional view of the internal structure of a conventional resin molded transformer, and Fig. 3 is a sectional view of the main part of the coil winding part of a conventional resin molded transformer. FIG. 4 is a sectional view of a main part of a coil winding part of a resin molded transformer according to the present invention;
FIG. 5 is a sectional view of the internal structure of the resin molded transformer according to the present invention. 1...Iron core, 2...Insulation case, 3, 13...Low voltage coil, 4...High voltage coil, 5...Synthetic resin, 6...Air gap, _P1 , _P2 ...Pitch between strands, _G1 , _G2 ...Element wire Gap, d ₁ , d ₂ ...diameter of the strands.

Claims (1)

[Claims] 1 The outer periphery of the iron core is covered with an insulating case, a low voltage coil is toroidally wound around the outer periphery, and a transformer element combined with a high voltage coil is molded with resin, where the low voltage coil has a small diameter and consists of several pieces connected in parallel. A resin molded transformer characterized in that the wires are toroidally wound to reduce the pitch between the wires of the low voltage coil.