RU2268517C1 - Inductive coil for electromagnetic-acoustic transformer - Google Patents

Abstract

FIELD: electro-mechanical equipment engineering, in particular, engineering and production of electromagnetic-acoustic transformers.

SUBSTANCE: during determining of primary constructive and electric parameters, shape of inductive coil is taken into consideration.

EFFECT: increased quality of inductive coil for electromagnetic-acoustic transformer.

7 dwg

Description

The invention relates to ultrasonic non-destructive testing of materials and products.

Known electromagnetic-acoustic transducer containing at least two inductors located in layers by stacking one on the other with a shift in the direction of the winding and made by one wire and laid close to each other, and the turns of the sections of one inductor are located between the turns of the sections of the other inductors, and the ends are bent [1].

The disadvantage of the known coils is the presence of bent ends that do not allow to place them as close to the surface of the concentrators and the complexity of manufacturing.

Known electromagnetic-acoustic transducer (hereinafter, EMAT), equipped with hubs and at least three flat coils, each coil made in the form of at least two identical, single-row spiral-shaped windings. The ratio of the area described around the coil of the circle to the area of the upper base of the concentrator satisfies the ratio: 3 <S _ok / S _VK <40, where S _ok is the area of the circle described around the coil; S _VK - the area of the upper base of the concentrator [2].

A disadvantage of the known inductor is the lack of indications of the main structural, technological and electrical parameters that do not allow to take into account the design and technological features in the manufacture of the inductance by printing or by hand. This drawback in practice leads to the impossibility of high-quality manufacture of inductors for EMAT.

The aim of the invention is to improve the quality of the inductance coil for EMAT by determining its main structural and electrical parameters depending on the shape dictated by the characteristics of the characteristics of the acoustic field in the control object.

This goal is achieved by the fact that the inductance coil of an ultrasonic transducer on a dielectric board, single-layer or multi-layer, containing one or several sections, made by hand or by printing, for example, from foil polyimide, is made in the form of two symmetrical ellipsoidal petals with a working area width C, satisfying the ratio: 1 <C <25 (mm) and the length of the working area D, satisfying the ratio: 3 <D <40 (mm), with the number of turns W, satisfying the ratio: 5 <W <100, with a step t satisfying the corresponding Ocean: 0,15 <t <1,2 (mm), or in the form of a regular polygon with a working zone parameters satisfying the relations:

1.5 <C <20 (mm); 2.5 <D <25 (mm); 10 <W <100; 0.05 <t <1.8 (mm),

or in the form of two symmetrically located ellipses with the parameters of the working area satisfying the relations:

1.5 <C <25 (mm); 3 <D <35 (mm); 10 <W <130; 0.15 <t <1.8 (mm),

or in the form of a paired ellipsoidal inductor with the parameters of the working zone, satisfying the relations:

1.5 <C <30 (mm); 4 <D <30 (mm); 10 <W <130; 0.15 <t <1.8 (mm),

or in the form of a figured multilayer coil with the parameters of the working zone that satisfies the relations:

1.5 <C <35 (mm); 3 <D <35 (mm); 10 <W <130; 0.05 <t <2.9,

while the inductance L and the resistance R of the coils of these forms must respectively satisfy the relations:

coils with elliptical petals - 4 <L <35 (μH); 1.5 <R <100 (Ohms); polygonal coils - 5 <L <35 (μH); 1 <R <100 (Ohms); two symmetrical coils ellipses 6 <L <30 (μH); 1.5 <R <100 (Ohms), twin elliptical coils 4 <L <30 (μH); 1 <R <100 (Ohms), curly multilayer coils 4 <L <40 (μH); 1.5 <R <100 (Ohms),

in multilayer coils, the turns of one layer are located in the gap between the turns of another layer without overlapping, on one or on the opposite sides of the coil and are connected in series with each other using metallized holes, and the transition from one layer to another is made through 2-3 turns, a paired ellipsoid coil the inductance is made of two autonomous sections located on the board in the same plane, or one below the other on different sides of the same board, with the possibility of collaboration on any of the above Connections and location.

The proposed inductors are the main element of the EMAT and are designed to excite and receive a transverse ultrasonic wave in the control object. The main characteristics of the printing coils are divided into two interconnected groups of parameters:

1 - structural and technological,

2 - electric.

The structural and technological parameters include:

1. The width of the working area in mm - C.

2. The length of the working area in mm - D.

3. The step of the conductors in the working area of the coil in microns - t.

4. The number of turns - W.

5. The base material of the foil dielectric. Electrical parameters include:

1. Inductance of the coil in μH - L.

2. The active resistance of the coil in ohms is R.

An important structural parameter of the coil is the size of the working area, which determines the characteristics of the acoustic field in the test object, the type and size of the detected defects, and the EMAT control zone. Such parameters as step t of conductors, technological standards of execution, number of turns W are directly related to the size of the working area. Accordingly, the electrical parameters change from the ratios of the structural and technological parameters. The main electrical parameter of the coil is the inductance value. This parameter is selected based on the operating frequency of the converter, and the operating frequency depends on the characteristics of the intended control object. The length of the EMAT control zone depends on the length of the working zone D. With an increase in the length of the working zone, its area also increases, decreasing the dynamic range of the EMAT, so the choice of the design of the coil for each particular case is a compromise between the EMAT sensitivity to defects and the control density.

In practice, when designing coils at the initial stage, they are set by the dimensions of the working zone of the coil and the operating frequency, then the structural and technological parameters are selected. When designing coils with small dimensions of the working zone, in order to obtain the necessary characteristics in terms of the number of turns (the efficiency of the coil’s reception and inductance depends on this parameter), a multilayer coil design is used. With this design, the coil turns are located in several layers and are connected in series with each other using metallized holes.

Multilayer coils have certain features of the execution of inter-turn transitions and the arrangement of turns in different layers in relation to each other:

To obtain small values of the inter-turn voltage gradient, the transition to another layer of conductors is carried out through several turns (usually 2-3 turns).

That is - in 1 layer, 2 turns are made, the transition through a metallized hole into 2 layers, the next 2 turns, the transition to 1 layer. Thus, we obtain the inter-turn voltage gradient the same as with the arrangement of the turns in a single-layer coil. Structurally, the coils in one layer of the coil are located in the gap between the coils of another layer, without overlapping.

It is also possible to design coils on different sides of the same board. The coils are located one below the other and can have both the same and different parameters. This method of execution provides the ability to use coils in several modes:

1. Separate mode - each coil operates independently.

2. Parallel connection of coils - both coils work as one element.

3. Series connection - both coils work as one element.

Another important feature of the design is the foil dielectric used for the manufacture of the coil. When the electrodynamic effect is manifested during the operation of the EMAT (coil coils mechanically interact with the base material), resonant oscillations can occur in the base material, which is reflected in the RFX converter. To eliminate this effect, film materials with the smallest possible thickness and stiffness were used as the basis for the coil - polyimide (TU 16-503.208-81 grades PF-1, PF-2) or lavsan (TU 2296-003-11436290-98 ELIFOMA BRANDS -LFR).

Figure 1 shows an inductor in the form of two symmetric ellipsoidal petals (shape "butterfly");

figure 2 and figure 3 shows the inductor in the form of regular polygons;

figure 4 shows the inductor in the form of two symmetrically located ellipses;

figure 5 and figure 6 shows a curly multilayer inductor;

7 shows a paired ellipsoidal inductor.

ее динамический диапазон (меньше чувствительность к дефектам с малой площадью отражающей поверхности), соответственно, чем меньше площадь рабочей зоны катушки, тем больше ее динамический диапазон (больше чувствительность к дефектам с малой площадью отражающей поверхности).When choosing specific structural and electrical parameters of the coil, one should be guided by the following regularity common to all its versions: the larger the area of the working zone of the coil (CD), the

its dynamic range (less sensitivity to defects with a small area of the reflecting surface), respectively, the smaller the area of the working zone of the coil, the greater its dynamic range (more sensitivity to defects with a small area of the reflecting surface).

Information sources

1. RF patent No. 2206888. Bull. No. 17, 2003.

2. RF patent №2219539. Bull. No. 35, 2003.

Claims (1)

The inductance coil of an ultrasonic transducer on a dielectric board, single-layer or multi-layer, containing one or more sections, characterized in that the inductance coil, made by hand or printed by, for example, foil polyimide, is made in the form of two symmetrical ellipsoidal petals with a working area width C satisfying the ratio 1 <C <25 (mm), and the length of the working area D, satisfying the ratio 3 <D <40 (mm), with the number of turns W satisfying the ratio 5 <W <100, with a step t, satisfying they relation 0,15 <t <1,2 (mm), or in the form of a regular polygon with a working zone parameters satisfying the relations: 1.5 <C <20 (mm); 2.5 <B <25 (mm); 10 <W <100; 0.05 <t <1.8 (mm), or in the form of two symmetrically located ellipses with the parameters of the working area satisfying the relations: 1.5 <C <25 (mm); 3 <D <35 (mm); 10 <W <130; 0.15 <t <1.8 (mm), or in the form of a paired ellipsoidal inductor with the parameters of the working zone, satisfying the relations: 1.5 <C <30 (mm); 4 <D <30 (mm); 10 <W <130; 0.15 <t <1.8 (mm), or in the form of a figured multilayer coil with the parameters of the working zone that satisfies the relations: 1.5 <C <35 (mm); 3 <D <35 (mm); 10 <W <130; 0.05 <t <2.9, while the inductance L and the resistance R of the coils of these forms must respectively satisfy the relations: a coil with ellipsoidal petals - 4 <L <35 (μH); 1.5 <R <100 (Ohms); polygonal coil - 5 <L <35 (μH); 1 <R <100 (Ohms); a coil in the form of two symmetric ellipses 6 <L <30 (μH); 1.5 <R <100 (Ohms); paired ellipsoid coil 4 <L <30 (μH); 1 <R <100 (Ohms), shaped multilayer coil 4 <L <40 (μH); 1.5 <R <100 (Ohms), in multilayer coils, the turns of one layer are located in the gap between the turns of another layer without overlapping, on one or on opposite sides of the coil and are connected in series with each other using metallized holes, and the transition from one layer to another is made through 2-3 turns, a paired ellipsoid coil the inductance is made of two autonomous sections located on the board in the same plane, or one below the other on different sides of the same board, with the possibility of collaboration on any of the above Connections and location.

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