RU1810850C - Induction-type transducer for magnetic measurements in air gap of asynchronous machine - Google Patents

Abstract

The invention relates to the field of measurement technology and can be used. In particular, magnetic measurements were made in an inhomogeneous magnetic field of interference, complex in the nature of spatial distribution, which occurs in the air gap of asynchronous machines with bevel slopes operating under load. The essence of the invention is that the induction transducer for magnetic measurements in the air gap of an asynchronous machine has an inductor whose active side, with a length corresponding to 0.5-1.0 of the length of the steel package of the machine, has a bevel of 100-180 electrical degrees relative to the generatrix the steel package of the machine in the opposite direction to the bevel of the rotor grooves and is located symmetrically with respect to the center of the steel package, the measuring device. 5 ill. Yo

Description

The invention relates to the field of measurement technology and can be used, in particular, for magnetic measurements in an inhomogeneous, complex spatial distribution pattern interference field occurring in the air gap of asynchronous machines with bevel slopes operating under load.

The purpose of the invention is to increase the reliability of a measuring induction transducer during magnetic measurements in the air gap of asynchronous machines with bevel grooves operating under load.

To achieve this, the induction transducer for magnetic measurements in the air gap of an asynchronous machine, containing a small-coil inductor without a ferromagnetic core, has an active side length corresponding to 0.5-1.0 the length of the machine steel package, the active sides of the coil have a bevel of 100-180 electric

degrees relative to the generatrix of the steel package of the machine in the opposite direction to the bevel of the grooves of the rotor of the machine and are located symmetrically relative to the center of the package of steel.

At the same time, in the slip zone S SHOM, the readings of the measuring device should be increased 1.06 times, in the slip zone 0 S SHOM, the measurement result should be increased 1 / KSC times, where S is the current slip value, SHOM is the slip value corresponding to the nominal at the moment of the machine, KSK is the bevel coefficient of the active sides of the induction converter, determined by the formula known for plane-parallel magnetic fields (e.g. 3, p. 47):

00

about

00

ate about

TO"

sin 0.5 D

0

Here, D is the slope of the active sides of the induction converter, relative to the generatrix of the steel package of the machine, expressed in electrical degrees.

1 is a drawing of an induction converter. Here 1 is an induction converter coil; 2,3 - respectively, the stator and rotor grooves; 4 - measuring device (millivoltmeter); I is the length of the steel package of the machine; - the bevel value of the active sides of the induction transducer relative to the forming steel package of the machine.

Figure 2 shows the half-waves characteristic of different slip values S of the resulting magnetic field in the air gap of an asynchronous machine with bevel grooves.

Fig. 3 shows the polygons of the EMF EI of elementary sections of the conductor located along the axis of the machine, and the resulting vector. The EMF of this conductor Epr induced by the resulting magnetic field in the air gap asyn-. a chronic machine with slanting slots a) S 0, b) S 1.

Figure 4-presents the results of the analysis of the coefficient Ksk. taking into account the decrease in the magnitude of the EMF induced by the resulting magnetic field in the active side of the induction transducer when its position changes in the resulting magnetic field of the machine.

Figure 4, a displays the analysis method; with a change in the value (3c of the active side, its length always corresponds to the length of the steel package of the machine (1,2,3,4 are the successive positions of the active side). In Fig. 4, and the value of / 3Ск is the bevel value of the grooves of the machine, But is the intensity of the resulting magnetic field (the half-wave axis is indicated in zone S 5: 8cr), where 5cr is the slip corresponding to the critical (maximum) moment. In Fig. 4,6, the curve is defined for the Na / F ratio (here Hi, J2 are the magnetic stator strength, respectively , rotor), equal to 0.99 at / 3sk 36 electric degrees, curve -x- - for On / Hi

- 0.99 at 144 email hail., crooked

-O- for Н2 / Н1 0.8 36 electric degrees, curve f- for Na / Ж 0.8 at / Зек 144 electric degrees, curve - for Na / Ж 0.

Fig. 5 shows the methodology and experimental results of the developed induction measuring transducer. Here 1, 2, 3, 4, 5, b are the numbers of induction measuring transducers having different values (Fig. 5, a) and the corresponding EMF at the output of the induction measuring transducer in the 3 0 mode (Fig. 5, b), c mode 5 1 (figure 5, c).

We will consider the claimed technical solution using magnetic measurements as an example.

in the air gap of an induction motor with bevel grooves A02-31-4 (bevel grooves on the rotor, Na / F ratio in zone S SKp is 0.95-0.97). The length of the active side of the measuring induction transducer is chosen according to the length of the steel packet of the machine (I 88 mm). The width of the induction converter, in accordance with existing recommendations, we will choose equal pole division (t 87.9 mm). Based on the claimed range of / 8C, we choose the average value of the slope of the active sides of the converter equal to 140 electric degrees. Given that the air gap

0 motor A02-31-4 is 0.35 mm; a single-coil induction converter coil without a ferromagnetic core will be made with a PEL wire of 0.06 mm diameter. Glue

5, the induction converter to the surface of the stator steel from the side of the air gap is symmetrical with respect to the center of the steel package (Fig. 1). In engine operating modes corresponding to sliding

0 S SHOM, the readings of the measuring device (millivoltmeter) increase 1.06 times, which determines an error level of less than 4%, with sliding О SS SHOM, i.e. when the field in its characteristics

5 close to the plane-parallel readings of the millivoltmeter increase, in accordance with existing recommendations, by 1 / Ksk times.

In the case under consideration, we determine KSK by the well-known formula;

v sin 0.5 D: sin 70 ° „. ,, Ksk 0.5 & --W ° 77

Then we increase the millivoltmeter reading by 1 / KSk 1: 0.77 1.3 times, which provides a level of measurement error of less than 1%.,

The increase in the sensitivity of the measuring induction transducer during magnetic measurements in the air gap of asynchronous machines with bevel grooves operating under load is based on

next.

Figure 2 shows the half-waves of the resulting magnetic field in the air gap of an asynchronous machine with a bevel grooves operating under load, which are characteristic of those considered in

Fig. 2 of the machine slip values (e.g., 4-6). From the data of Fig. 2 it follows that in the slip range S 2: SHOM, the resulting magnetic field should be considered inhomogeneous, complex in character of spatial distribution. For magnetic measurements in such fields, point-sized induction transducers should be used in order. to reduce the measurement to the definition of induction at one point (for example, 2, etc.).

A finite-size induction transducer cannot be used for magnetic measurements in the resulting magnetic field occurring in the air gap of an asynchronous machine in a large slip region. We subdivide the conductor located along the axis of the machine into n elementary sections, within which we can neglect the mutual beveling of the elementary section of the conductor and the wave front of the resulting magnetic field in the region of large glides. The EMF of the conductor EPR is determined for any slip by the geometric sum of the vectors of the EMF EI of the elementary sections. Fig. 3 shows the determination of the resulting EMF of the same conductor for S 0 (plane-parallel resulting magnetic field) and S 1 (the largest redistribution of the resulting magnetic field in space) .

The constructed EMF polygons are characteristic of the considered slides of asynchronous machines with bevel grooves (e.g., 6).

From the data of Fig. 3, it follows that the cause of a sharp decrease in the efficiency of the interaction of the conductor with the resulting magnetic field in the air gap of the asynchronous machine with a bevel groove (loss of sensitivity by the measuring induction transducer) in the region of large slides is the deformation (kink) of the polygon EMF EI, as a result of which EMF the ESR conductor (EMF at the output of the induction converter) can be reduced several times and for this reason may not correspond to the magnetic field data. Physically, this phenomenon is due to the fact that in the slip zone S SHOM, which corresponds to the ratio of the field strengths of the rotor and stator Н2 / Ж 0.8 in asynchronous machines, the bevel of the grooves leads, in accordance with the data of Fig. 2, to a large deformation of the wavefront shape resulting magnetic field

and redistributing the energy of the field along the wave front.

In accordance with others., For taking into account the EMF of the conductor induced by the resulting magnetic field taking place in the air gap of an asynchronous machine with a bevel slope, a coefficient is introduced

10

Ksk - V-. I lEil

(1)

when etrm for Fig.Z, and the coefficient "with w 1,

for fig.Z, b Ksk 0.4.

In the resulting magnetic field, which takes place in the air gap of an asynchronous machine with bevel grooves when sliding 5 1, the conductor (active

side of the measuring induction transducer) into rotation around the center of the steel package of the machine, dividing the length of the conductor in half, while in each position of the conductor its length should

correspond to the length of the steel package of the machine (figure 4, a). In each separately taken position of the conductor, we will determine the coefficient Ksk from (1), using the procedure described in 6. For this, we will consider the position in which the axis of the conductor coincides with the axis of the stator slots (, 0).

We shall consider positive the values of / 3c, which occur when the conductor rotates from its initial position in the direction opposite to the bevel of the rotor grooves (when the stator grooves are bevelled, the relative bevel of the rotor grooves relative to the stator grooves), and negative when rotated in the opposite direction.

The results of the analysis are shown in Fig. 4, b. It is known that the degree of redistribution of the resulting magnetic field in the air gap of the machine depends on the magnitude of the ratio of the magnetic field strengths of the rotor (H2) of the source (HO. Moreover, for the SHOM range: Ј S 1, the ratio H2 / HI lies in the range 0.8 H2 / Hi 0.99. Therefore, the data of Fig. 4,6

correspond to precisely these extreme values of Ha / Hi. The data for H2 / Hi 0 are also given, which corresponds to SHOM S 0. In addition, the degree of redistribution of the magnetic field is in the air

the clearance of the machine depends on the value of the bevel angle of its grooves. Fig. 4,6 shows data for / Zek 36 electric degrees. (average value for asynchronous machines) and J 144 degrees. (Is extremely large) ..

From the data of Fig. 4,6 it follows that, by rotating the conductor (turning around the center of the steel package of the machine, the active sides of the measuring induction transducer in accordance with Fig. 4, and in the resulting magnetic field taking place in the air gap of the asynchronous machine when sliding S 5: SHOM, you can determine the position of the conductor (the active sides of the transducers) at which the KSK of the conductor (the sensitivity of the induction transducer will increase several times (for example, for H2 / Hi 0.99 - six times). it is possible to carry out in the direction of oblique oblique rotor grooves (relative to the stator) to a value fie equal to 180 electrical degrees (for Na / F 0.99). Physically, this is explained by the fact that the axis of the half-wave of the resulting magnetic field in zone S SHOM is oriented to the generatrix of the steel package of the machine at the same angle and therefore rotating the conductor and positioning it at an angle of + pc 180 electric degrees, we thereby place it parallel to the wave front of the resulting magnetic field. In this case, to increase the sensitivity of the induction converter, the bevel of the active sides of its coil (the direction of rotation of the conductor in Fig. 4, a) should be performed in the direction that the rotor grooves are inverse to the stator grooves / since

in this direction the axis of the half-wave of the resulting magnetic field is always located (Fig. 2). The value of Н2 / Ж 0.99 at S 2: SHOM almost never takes place in asynchronous machines (this is the limit value) and, therefore,. 180 electric city is the ultimate value. Usually in asynchronous machines with bevel slopes at S SHOM, there is H2 / Hi 0.97, which determines the value of KSK of the beveled active side of the coil close to 0.9, and therefore, beveling the active sides of the induction converter in the opposite direction to the bevel of the rotor slots in In S 2: SHOM mode, we will go from measuring the information of a finite-size transducer to measurements in inhomogeneous magnetic fields with complex distribution patterns in space with sufficient accuracy for practical fields.

From Fig. 4,6 it follows that even with small values of H2 / Hi, the bevel of the active sides of the induction converter allows to very significantly increase its sensitivity and at the same time the necessary level

-

5 10 15 20 25 30

35

40

45

fifty

fic can be reduced up to 100 electric degrees, although the previous value of / s is 180 electric degrees. gives a satisfactory result, physically the possibility of a significant increase in KSK in the Н2 / Нч zone of 0.80 with significantly lower x / 3s compared to the zone of Н2 / Н1 values is explained by the fact that lower redistribution corresponds to lower values of H2 / Hi in the space of the resulting magnetic field.

From 1 it is known that for current teslameters being designed, the level of error in magnetic measurements is 5% (in this case, the fields are simple in spatial distribution). As follows from Fig. 4, in zone S 5: SHOM, in order to reach an error level not exceeding 5% (relative error), the measurement result should be increased 1.06 times.

It follows from the foregoing that in asynchronous machines with bevel bevels in the slip zone S SHOM, the bevel value of the active sides of the induction transducer is necessary to increase the sensitivity of the induction transducer during magnetic measurements in the resulting magnetic field that takes place in the air gap of the machine, it is determined by the range 100- 180 degrees, with lower values being selected for machines with a small level of Ng / Hi, in the considered slip zone, higher values of / s for machines with H2 / Hi - 1. Induction converter l should become symmetrically positioned relative to the package center machine and a bevel its active side is performed in the direction opposite the bevel grooves of the rotor relative to the stator grooves (Figure 1). The measurement result should be increased 1.06 times.

 In the slip range 0 S SHOM, one should use the technique usually adopted for a plane-parallel field, i.e. the measurement result should be increased by Ksk times, where in accordance with 3,

Ksk

sin 0.5 / ss

0.5 D:

In electric machines, we are talking about the mutual beveling of the grooves of the stator and rotor windings. Therefore, beveling is sometimes performed on the stator. In all cases, we are talking about the beveling of the grooves of the active sides of the converter in the direction opposite to the beveling of the rotor grooves relative to the stator grooves.

In FIG. 1 graphically reflects the developed technical solution for increasing the sensitivity of a measuring induction transducer intended for magnetic measurements in the air gap of asynchronous machines with bevel grooves.

An experimental study of the claimed technical solution showed that even in low-power asynchronous machines, the induction converter can be made single-turn, and the amplification of the output signal is not required. This is explained by the topic. that in the developed solution, the length of the active side of the induction converter is many times greater than the length of the active side of the point induction converter.

The active sides of a full induction converter can either correspond to the total length of the steel package of the machine, or be less than it. The range of rational values of the length of the active side of the converter corresponds to 0,, 0 I, since the execution of the active side of the converter with a length corresponding to less than 0.51 will require the use of additional converters.

The width of the induction converter is selected based on existing recommendations close to the pole division of the machine.

The results of experimental verification of the developed method are presented in Fig. 5l. Fig. 5a shows a diagram of the experiment, the essence of which was that in the air gap of an asynchronous machine with a bevel grooves there were six flat single-turn measuring induction transducers of the same width. In this case; converter No. 4 is equal to zero, No. 3 is 60 electric grad., No. 2 - D: 120 electric grad., No. 1 - 180 electric. city., -60 email. city., N; 6 - 120 electric city

In the 5 0 mode (Fig. 5, b), the largest value of the EMF, in accordance with the existing concepts, is measured by converter No. 4 (0).

In mode S 1 (Fig. 5, c) in the studied machine with a low level of the ratio On / F, the largest EMF value is already measured not by converter 4, but by converter Ns 2 (g 120 electric degrees), which fully corresponds to the theoretical results analysis.

The developed invention is a solution to an urgent problem since:

1. Asynchronous electric machines with bevel grooves form the basis of the fleet of electric machines in our country and abroad,

2. Magnetic measurements in the air gap of such machines are necessary not only for their experimental investigation, but, no less important, they are necessary in microprocessor systems for vector control of asynchronous electric drives. (Eg), Vector control of many systems is based on direct measurement of the magnitude of the magnetic flow in the air gap of asynchronous electric the engine, while it is necessary with a high degree of accuracy to judge by magnetic measurements the magnitude of the magnetic flux for any slip. As noted above, this can be done in engines with a bevel grooves or using a large number of point induction converters, the output signal of which must be amplified and integrated (for this you need the appropriate number of amplifiers, integrators, or sequentially switching the converters to the input of one amplifier, etc. etc., then analysis of the data, their summation, etc., which makes the control system cumbersome, reduces its speed and accuracy). The proposed solution allows you to do with one, finite size, low-turn converter, which does not require amplification of the output signal,

. Advantages of the developed solution:

1. When measuring in inhomogeneous, complex distribution of magnetic fields occurring in the air gap of asynchronous machines with bevel grooves, instead of a large number of point, multi-turn ones requiring amplification of the output signal of induction converters, one converter can be used, of a simple design, not requiring amplification of the output signal, which greatly simplifies and accelerates the technology of magnetic measurements, increases the reliability of the induction converter.

2. Can be used in all slip ranges.

3. The induction converter used is flat, low-turn, of finite dimensions, which simplifies its manufacturing technology.

All of the above allows us to conclude that the developed technical solution allows to increase the sensitivity of the induction converter, simplify and reduce the cost of the technology. Magnetic measurements in the air gap of asynchronous machines with bevel grooves,

Formula Induction transducer for magnetic measurements in the air aazor of an asynchronous machine, comprising an inductor, characterized in that

that, in order to increase the reliability of the induction converter, the active side of the coil with a length corresponding to 0.5-1.0 of the length of the steel package of the machine has a bevel of 100-180 electric degrees relative to the generatrix of the steel package of the machine in the direction opposite to the direction of the bevel of the grooves rotor relative to the grooves of the stator, and is located symmetrically relative to the center of the package of steel.

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, and with $ 6 J / /