JPS6139512A - Feedback type current transformer - Google Patents

Abstract

PURPOSE:To obtain the feedback type current transformer of excellent error characteristics, small sized, light weight and high efficiency by a method wherein the core of a main current transformer and the core of an auxiliary current transformer are constituted by the cores having different magnetic characteristics. CONSTITUTION:The core 6 of a main current transformer and the core 7 of an auxiliary current transformer are constituted by the magnetic materials having different magnetic characteristics. For example, a magnetic material having excellent low magnetic flux density is used for the main current transformer core 6, and a magnetic material having high saturated magnetic flux density is used for the auxiliary current transformer 2. Consequently, as burden characteristics of the absolute value of error can be freely adjusted, a feedback type current transformer of excellent current characteristics can be obtained. Moreover, the number of turns can be reduced easily, this reduction in number of turns results in decrease of heating power when an excessive current is applied, and excessive current intensity can be increased, thereby enabling to obtain a feedback type current transformer of small size, light weight and high efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a current transformer, and particularly to a feedback type transformer i1#E that has excellent current characteristics, is small, lightweight, and has high PL performance.

In the conventional feedback type current transformer, as shown in Fig. 1, the voltage drop across the feedback impedance 3 connected to the secondary winding 2 of the auxiliary current transformer l is reduced to the terminal voltage of n:j Cf + old)4. Error compensation is performed by superimposing them so that the phases are opposite to each other so that the operating magnetic flux density of the iron core 6 of the main current transformer 5 becomes 0 and the excitation current becomes 0. Feedback type current transformation using this method In the transformer, the iron core 6 of the main current transformer 55 and the iron core 7 of the auxiliary current transformer l are made of one type of magnetic material with a single magnetic property, and silicon steel plates are usually used. Then, when the load on the current transformer changes, the terminal voltage of the load 4 changes, so the balance with the terminal voltage of the feedback impedance 3 is lost, the operating magnetic flux density of the iron core 6 of the main current transformer 5 increases, and the excitation current increases. There were drawbacks such as the error characteristics changing due to the increase and falling outside the error range specified by the standard.In addition, in Figure 1,
8 is a main current transformer secondary winding, 9 is a current transformer-secondary winding, Za is a compensation feedback impedance, and zb is a burden impedance.

The present invention solves these drawbacks! The purpose of the present invention is to provide a compact, lightweight, and microbiologically efficient (iXtX transformer) with good error characteristics.The present invention will be described in detail below with reference to FIG.

In the present invention, the auxiliary current transformer l is connected to 1. It is the same as the conventional one to reduce the magnetic flux density of the iron core 6 of the main current transformer 5 by multiplying the voltage of the feedback impedance 3 + + i so that the phase is opposite to the terminal voltage of the load 4. However, if the main current transformer core 6 and the auxiliary current transformer core 7 are made of magnetic materials with different magnetic properties, for example, a magnetic material with good characteristics in a low magnetic flux density region is used as the main current transformer core 6. However, a magnetic material with high saturation magnetic flux density is used for the auxiliary current transformer core 2.

A specific example of the former magnetic material is permalloy (Ni78
．． 5%, Fe 21.5%), and a specific example of the latter is silicon steel plate.

Since the load 4 of the current transformer is used at an arbitrary load between the rated load and 25% of the rated load, the operating magnetic flux density of the main current transformer 5 changes as the load 4 changes, and the excitation current changes. Although changes in error occur due to increases and decreases, since the main current transformer iron core 6 uses an iron core with good characteristics in a low density region, changes in excitation current are small and error characteristics are improved. Furthermore, since the auxiliary current transformer Zl 1 only feeds back the terminal voltage of the impedance 3 that returns to the main current transformer 5, even if the error is quite large, there is no problem and the core cross-sectional area and number of secondary turns are designed to be small.

In addition, from the above, the auxiliary current transformer 1 has a secondary load, that is, 4n, which is between the rated capacity 1u and about 25% of the rated load.
ii wine pedance 3 is connected.

Figure 2 is a graph showing the relationship between ratio error, load, and primary current.
It can be seen that in any case, the error (ratio error) in the example of the present invention (solid line) is smaller than that in the conventional example (dotted line). In addition, as shown in Fig. 3, not only can the phase angle and current characteristics be improved negatively, but also the load carrying capacity and the absolute value of the error can be freely adjusted to 1, providing a feedback type current transformer with excellent current characteristics. Not only is it possible to reduce the number of windings, but this reduction in the number of windings reduces the amount of heat generated when overcurrent is applied and increases the strength of overcurrent. High performance llnln transformer q.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the structure of a current transformer, and FIGS. 2 and 3 are graphs explaining the present invention in detail, respectively. 1 - J + li auxiliary current transformer 2 - - Auxiliary current transformer secondary winding 3 - - Feedback impedance 4 - - m - / fLlu 5 - Main current transformer 6 Main current transformer iron core 7 - - Auxiliary current transformer Current transformer core 8 Main current transformer secondary winding 9 ---- Current transformer - secondary winding Figure 1

Claims (1)

[Scope of Claims] An iron core is divided into a main current transformer iron core and an auxiliary current transformer iron core, and a secondary winding with a different number of turns is wound around each iron core,
In a feedback type current transformer in which a common primary winding is wound and a feedback impedance equivalent to the secondary load is connected to the auxiliary current transformer, the main current transformer iron core and the auxiliary current transformer iron core are made of iron cores with different magnetic characteristics. A feedback type current transformer characterized by the following configuration.