JPS6313497Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an improvement of a current transformer for measuring high frequency and large current.

Conventionally, for example, in a power supply device for induction heating, etc., the current flowing through the device is measured and the power supply is controlled thereby. A feed-through current transformer is usually used for this type of current measurement, but high-frequency, large-current power supplies such as the above-mentioned induction heating power supplies range from several KHz to several tens of KHz, and from several Kw to several tens of KHz.
Generates several thousand Kw of power, and its output current is
In the 1000Kw class, the current reaches between several thousand A and nearly 10,000 A, so the iron core of the current transformer overheats and accelerates the deterioration of the insulation, resulting in damage in a relatively short period of time.

The present invention has been made in order to eliminate the above-mentioned drawbacks of conventional current transformers for measuring high frequency and large currents.

In solving the above drawbacks, the inventor of the present invention
First, we started by analyzing the overheating mechanism of current transformers. This will be explained with reference to FIGS. 1a to 1c.

A conventional through-type current transformer CT' is formed by winding a secondary coil 2 around an annular core 1 made of a laminated silicon steel plate, etc., and a conductor R through which a primary current _I1 flows through an annular hole in the annular core 1. The winding of the secondary coil 2 is attached to the power supply device so as to pass through the conductor R, and receives magnetic lines of force generated by the induced current induced in the iron core ₁ by the primary current I 1 flowing through the conductor R. The measuring device 3 measures the secondary current I ₂ according to the CT ratio determined by the number of times. In this case, the current transformer
To reduce circuit inductance, the CT' is generally installed in parallel conductors as shown in Figure 1b.
A U-shaped circuit is formed in one of R ₁ and R ₂ , for example, a part of the conductor R ₁ , and the conductor R ₁ is passed through the ring hole of the iron core 1. The inventor is a current transformer to the device
In the installed state of CT', the magnetic field line φ 1 from the conductor R ₁ a shown in Fig. 1c is shown in the direction of the arrow in the iron core 1 through which one side R _{1 a} of the U-shaped circuit of the conductor R ₁ is penetrated. It flows along the plate direction of the laminated silicon steel plate, and also tries to pass through the magnetic field line φ ₂ from the other side R ₁ b of the adjacent U-shaped circuit, but _the iron core 1 Since they are not concentric, the magnetic field line φ ₂
tries to penetrate from the direction perpendicular to the plate surface of the laminated silicon steel plate that forms the iron core 1, so an eddy current is generated in the part of the iron core 1 facing the adjacent conductor _R1b , causing a local induction heating phenomenon. I determined that it was causing overheating.

Based on the above judgment, the present inventor designed a current transformer CT for high frequency, large current measurement as shown in FIG. 2. A shield ring made of a good electrical conductor is attached to the outer periphery of a through-type current transformer in which a secondary wire ring 2 is wound around an annular core ₁ and a conductor R through which a primary current I1 flows is passed through an annular hole through an insulating material 3. It is formed by winding 4.

The shield ring 4 in the above configuration prevents the line of magnetic force φ ₂ generated by the adjacent conductor R _{1 b} shown in FIG. Even the eddy current generated in the ring 4 itself does not generate heat because the material is a good electrical conductor.

In the above embodiment, _the conductor R _{1 a} of the current measuring section passes through the current transformer CT on one side formed in a U-shape.
The conductor R ₁ b on the other side is the adjacent conductor, and the conductor R ₁ b
Although the present invention has been explained by citing the magnetic field line _{φ 2} generated by
It goes without saying that the shield ring 4 effectively acts on all lines of magnetic force generated from a conductor through which a large current flows near the CT and that attempts to penetrate the iron core 1 from the circumferential direction.

The current transformer for high-frequency, large-current measurement according to the present invention has no risk of overheating, so it does not accelerate deterioration of the insulator and has remarkable durability compared to conventional products.

[Brief explanation of the drawing]

Figures 1a and 1b are both perspective views showing a conventional high frequency, large current measuring current transformer and its installation state in a high frequency, large current power supply device, and Figure 1c is a drawback of the conventional high frequency, large current measuring current transformer. The first step to explain
FIG. 2 is a front view of the current transformer for measuring high frequency and high power according to the present invention. 1... Annular iron core, 2... Secondary wire ring, 3... Insulating material, 4... Shield ring, R・R ₁・R ₁ a・
R ₁ b・R ₂ ... Conductor, CT ... Current transformer for measuring high frequency large current, I ₁ ... Primary current.

Claims (1)

[Scope of utility model registration request] A through-type current transformer in which a secondary wire ring is wound around a ring-shaped core, and one side of a U-shaped bent part formed at a predetermined position on one side of a parallel conductor through which a high-frequency large current flows passes through the ring hole. A transformer for measuring high-frequency large currents, characterized in that a shield ring made of a good electrical conductor is wound around the outer circumference of the current transformer with an insulating material interposed therebetween to block magnetic flux generated from the other side of the bending part. Flushware.