RU17748U1 - TRANSFORMER - Google Patents

Description

Belozerov Vladimir Yakovlevich

Starodubtsev Yuri Nikolaevich

Zelenin Victor Alexandrovich

Atnagulov Marcel Nigamatovich

The utility model relates to the field of electrical engineering, in particular, to measuring current transformers that operate in circuits with a constant current component.

The measuring transformer must convert the signal to a value proportional to the primary signal. Deviation from this proportionality is due to the error of the measuring transformer. The measurement error is the smaller, the higher the magnetic permeability of the material of the magnetic circuit. Therefore, it is preferable to use magnetic material with high magnetic permeability in measuring transformers.

Known current transformer, consisting of a magnetic circuit (1) and several windings (3 and 4) inductively coupled to it (Fig. 1) 1. The measured current passes through the primary winding of the transformer (4). The converted current in the secondary winding (3) is proportional to the primary current, and its value is measured by standard devices. An amorphous cobalt-based alloy with a relative initial magnetic permeability of more than 100,000 is used as the material of the magnetic circuit (1). However, if there is a constant current component in the measured circuit, the magnetic circuit is magnetized to saturation. In the region of magnetic saturation, the magnetic permeability is low, as a result of which the measurement error sharply increases in this region.

001 V about 20

TRANSFORMER

H01F3 / 04, C22C19 / 07

current 2 with two windings inductively connected to the magnetic circuit, which has an air gap and which is made of electrical steel. The air gap reduces the magnetic permeability, therefore, in the presence of a constant component of the current, the magnetic circuit is not magnetized to saturation.

The constant value of the measurement error is compensated by electronic methods. However, due to the nonlinearity of the magnetization curve (the dependence of magnetic induction on the magnitude of the magnetic field strength), the measurement error after such compensation will depend on the magnitude of the DC component of the current. If these fluctuations in error do not exceed the values allowed for a measuring transformer of a certain accuracy class, then we can assume that the transformer fits into this accuracy class also in the presence of a constant current component. Thus, the magnetic core of the measuring transformer operating with a constant component must have a high linearity of the magnetization curve. The nonlinearity of the magnetization curve can be characterized by the ratio Cmax / Cn, where Cmax is the maximum relative magnetic permeability, and c is the initial relative magnetic permeability. The closer this ratio is to unity, the higher the linearity of the magnetization curve.

In the table. Table 1 shows the values of the angular error 5, deg, depending on the ratio Cmah / Tsn9 In table. Figure 2 shows the limits of permissible angular error at rated current (in the region of maximum magnetic permeability) depending on the accuracy class of the measuring transformer. From a comparison of the data it follows that in order to obtain an accuracy class of 1, it is necessary that in the magnetic material of the magnetic circuit the ratio Tssch / Tsn does not exceed 1.15.

Table 1.

The degree of linearity of the magnetization curve is closely related to the magnitude of the magnetic anisotropy constant Kc induced during thermomagnetic processing in a transverse magnetic field. In this case, the higher the value of Kc, the closer the ratio Cm / Tsn to unity.

To obtain a magnetic circuit with a high degree of linearity of the magnetization curve, it is proposed to use an alloy with an amorphous structure in which the iron content is in the range of 1.65-5 at%. This allows you to maintain a high level of magnetic induction of saturation. The total amount of iron and manganese should be 4-8 at%, so that the saturation magnetostriction is close to zero. To increase the induced magnetic anisotropy constant, the silicon content should be in the range of 28 at%. Silicon and boron in total should be 16-24 at% to maintain a sufficiently high saturation magnetic induction.

A magnetic core made of an amorphous ribbon of the proposed chemical composition has magnetostriction close to zero and a high constant of induced magnetic anisotropy KU. These factors reduce the sensitivity of the magnetic properties of the magnetic circuit to compressive stresses, which makes it possible to apply a coating of polymer materials on top of the magnetic circuit without noticeable deterioration of its magnetic properties.

Thus, we propose a transformer consisting of a magnetic circuit and several windings inductively connected to the magnetic circuit, characterized in that the magnetic circuit is made of a tape made of an amorphous alloy containing components in the following ratio, at%: iron 1.65-5, the amount of iron and manganese 4-8, silicon 2-8, the sum of silicon and boron is 16-24, cobalt is the rest, while in the magnetic circuit the ratio / Tsn is less than 1.15, where imax is the maximum relative magnetic permeability, Tsn is the initial relative magnetic permeability.

FIG. 1. Cross section of a current transformer. 1 - magnetic circuit, 2 insulating coating, 3 - secondary winding of the transformer, 4 primary winding of the transformer.

Examples. In an induction vacuum furnace, cobalt-based alloys containing iron, manganese, silicon and boron were smelted. The melt was cast on the Sirius 150 / 0.02M installation. The thickness of the obtained amorphous tape was 25-30 microns. The tape was wound into toroidal magnetic cores with an outer diameter of 25 mm, an inner diameter of 20 mm, and a height of 10 mm. After that, the magnetic cores were annealed at the optimum temperature. During annealing and cooling, the magnetic cores were in a transverse or longitudinal magnetic field. After annealing everything

the magnetic cores were coated with a 0.4 mm thick polypropylene film. Table 3 presents the chemical composition of the prepared alloys and the results of magnetic measurements of the ratio Ctah / | n after annealing in a transverse magnetic field.

A secondary winding of 2500 turns of wire with a diameter of 0.16 mm was wound on a magnetic circuit having the chemical composition of alloy No. 4. The primary winding was a bus, that is, it had one turn. The secondary winding was connected to an active load of 56 ohms. The angular error measurements were carried out in the range of variation of the direct current from 0.5 to 60 A. The oscillation of the angular error at constant current did not exceed ± 1 deg. Therefore, the transformer can be attributed to class 2 accuracy.

SOURCES OF INFORMATION

1.Natent of Russia 2041513, H01F1 / 04, С22С19.07, 1995.

2.Afanasyev A.A., Adonyev V.M., Kibel V.M., Orphan I.M., Stogniy B.S. Current transformers. M.: Energoatomizdat, 1980, p. 124.

Table 3.

Claims (1)

A transformer consisting of a magnetic circuit and of several windings inductively coupled to a magnetic circuit, characterized in that the magnetic circuit is made of a tape made of an amorphous alloy containing components in the following ratio, at.%:
Iron - 1.65-5
The amount of iron and manganese - 4-8
Silicon - 2-8
The sum of silicon and boron is 16-24
Cobalt - Else
in the magnetic circuit, the ratio μ _max / μ _{n is} less than 1.15, where μ _max is the maximum relative magnetic permeability, μ _n is the initial relative magnetic permeability.