RU2510564C1 - Method of impregnating coils of electrical machines - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: method of impregnating the multi-winding coil of an electrical machine involves feeding to the front parts of the coil a thin jet of a impregnating composition from a nozzle to the heated front part of the coil and rotating the jet along the front part of the coil. Before impregnation, fine ferromagnetic filler, which is pre-disintegrated, is added to the impregnating composition. The impregnating composition is mixed with the ground ferromagnetic filler; the obtained mixture is stirred and poured into the impregnating apparatus. Before impregnation, coil data are used to calculate the maximum mass of the impregnating composition m_im, which can be accommodated in the cavities of each of the same-type coils during impregnation. An electrode is inserted into the nozzle and potential is applied across the electrode. The process of impregnating each of same-type coils is then carried out. During the impregnation process, particles of the impregnating mixture of the compound with fine ferromagnetic powder are electrostatically charged. A jet is formed. Final compounding of the impregnating mixture that has penetrated the coil is then carried out.

EFFECT: method increases the impregnation coefficient of the coils by 1,55 times on average and improves stability thereof from coil to coil.

1 tbl

Description

The invention relates to electrical engineering and can be used, for example, in the production of stators of electrical machines.

A known method of impregnating the windings of electrical machines, in which the winding and impregnating composition is heated to the impregnation temperature, immersed one of the frontal parts of the winding in the impregnating composition and after the appearance of the impregnating composition on the other frontal part of the winding, remove the winding from the composition, rotate it 180 ° around its vertical axis and dry it in this position [1]. A distinctive feature of the method is that the frontal part of the winding immersed in the impregnating composition is mounted on the conductive element, and an electrode is connected to the non-immersed frontal part of the winding and a potential difference is created between the electrode and the conductive element.

The disadvantage of this method is that the coefficient of impregnation of the windings K _ol impregnated with the specified method does not exceed 0.24, this indicates that 76% of the cavities of the winding are not filled with an impregnating composition.

Closest to the claimed method is a method of impregnating a multi-turn winding of an electric machine, described in [2]. The prototype method consists in applying a stream of impregnating composition to the frontal parts of the winding, and simultaneously vibrating the windings on the vibration stand, the vibration frequency being cyclically changed continuously from minimum to maximum values.

The disadvantages of the prototype method are: low coefficient of impregnation K _ol not exceeding 0.36, instability of the values of K _ol from winding to winding, due to the lack of control of impregnation during its conduct, and leakage of the impregnating composition from the winding during drying. In addition, the impregnation by the method of the prototype does not effectively eliminate the defect in the coil insulation of the winding, and slightly increases the thermal conductivity of the winding, which reduces its operational reliability.

The objective of the invention is to reduce the variation in the values of the coefficient of impregnation K _CR from winding to winding and increase its value, as well as improving the efficiency of impregnation.

где х, y - координаты горизонтальной плоскости лобовой части обмотки, R - средний радиус лобовой части обмотки, L - ширина лобовой части обмотки, k - количество колебаний, совершаемых струей поперек лобовой части обмотки при одном обороте вращающегося магнитного поля, w - угловая скорость вращения вращающегося магнитного поля, t - время, при этом угловую скорость вращения магнитного поля задают в диапазоне (1<w<3) об/мин, а количество колебаний, совершаемых струей поперек лобовой части задают в диапазоне 10<k<12. В процессе пропитки постоянно взвешивают весоизмерительным преобразователем массу пропиточной смеси m_c, проникшую в полости и капилляры каждой пропитываемой обмотки, и при достижении равенства массы пропиточной смеси m_c в пропитываемой обмотке и массы m_пр пропиточной смеси, которую можно разместить в полостях однотипных обмоток в процессе пропитки, прекращают полив компаунда на верхнюю лобовую часть обмотки. Провода обмотки отсоединяют от земли, и через них к обмотке вновь подводят греющий ток, которым разогревают обмотку до температуры (160-165)°С и при этой температуре осуществляют окончательное компаундирование проникшей в обмотку пропиточной смеси.The technical result is achieved by the fact that in the method of impregnating a multi-turn winding of an electric machine, which includes applying a thin stream of impregnating composition from the nozzle to the frontal parts of the winding, to the heated frontal part of the winding, and turning the stream along the frontal part of the winding, additionally, before impregnation, the impregnation composition is added finely divided ferromagnetic filler, which is pre-disintegrated to a size d _fer <10 μm. The impregnating composition is mixed with crushed ferromagnetic filler in the ratio of wt.%: (10 ÷ 15) ferromagnetic particles, (90 ÷ 85) of the impregnating composition, the resulting mixture is thoroughly mixed, and it is poured into the impregnation unit. In this case, before the impregnation, the ultimate mass of the impregnation mixture m _pr , which can be placed in the cavities of each of the same type of windings during the impregnation, is calculated before winding. This mass m _{pr is set} in the load transducer, after which the impregnated winding with a magnetic core is mounted on the load cells of the load transducer and weighed together with the magnetic core. The measured weight of the non-impregnated winding with a magnetic core is taken as a zero count, for which purpose the weight reading of the impregnated winding with a magnetic core is reset to zero. Then, heating current is supplied to it through the output wires of the winding, by which the winding is heated to a temperature of (80 ÷ 90) ° С, after which the heating current is disconnected from the winding, and the impregnated winding wire is grounded. An electrode is introduced into the nozzle and a potential is applied to it, the absolute value of which, relative to the grounded wire of the winding, lies in the range (2 ÷ 5) kV, and the process of impregnation of each of the same type of windings is carried out. In the process of impregnation, the particles of the impregnating mixture of the compound with finely dispersed ferromagnetic powder are electrostatically charged by passing the particles of the impregnating mixture along the said electrode. A jet is formed by passing electrostatically charged particles of the indicated impregnating mixture through the nozzle; at the exit from the nozzle, the jet is bent and rotated. In order to rotate the jet along the frontal part of the winding at the exit from the nozzle, the jet is affected by a rotating electromagnetic field, the intensity of which is directed perpendicular to the axis of the jet. The amplitude of the mentioned magnetic field strength is changed according to a harmonic law, ensuring that the end of the impregnation mixture jet falling on the heated frontal part of the winding describes the trajectory $$x^2+y^2=R^2+\frac{L^2}{\mathrm{four}}+RL\left[\cos \left(kwt\right)\right],$$

where x, y are the coordinates of the horizontal plane of the frontal part of the winding, R is the average radius of the frontal part of the winding, L is the width of the frontal part of the winding, k is the number of oscillations made by the jet across the frontal part of the winding for one revolution of the rotating magnetic field, w is the angular velocity of rotation of a rotating magnetic field, t is time, while the angular velocity of rotation of the magnetic field is set in the range (1 <w <3) rpm, and the number of oscillations made by the jet across the frontal part is set in the range 10 <k <12. In the process of impregnation, the weight of the impregnation mixture m _c penetrated into the cavities and capillaries of each impregnated winding is constantly weighed by the weighing transducer, and when the mass of the impregnation mixture m _c in the impregnated winding and the mass m _{pr of the} impregnation mixture, which can be placed in the cavities of the same type of windings in the process, are reached impregnations, stop watering the compound on the upper frontal part of the winding. The wires of the winding are disconnected from the ground, and through them the heating current is again supplied to the winding, with which the winding is heated to a temperature of (160-165) ° С and at this temperature the final compounding of the impregnating mixture penetrating the winding is carried out.

Figure 1 shows a diagram of the technological process of impregnation according to the claimed method. Figure 2 schematically shows the trajectory of the jet along the frontal part of the winding.

Figure 1 introduced the following notation: 1 - stream impregnating composition; 2 - nozzle; 3 - upper frontal part of the winding; 4 - impregnating composition; 5 - button; 6 - control unit; 7 - lower frontal part; 8, 9 - strain gauges; 10 - thermometer; 11 - high voltage source; 12 - load transducer; 13 - three-phase voltage; 14, 15, 16 - electromagnetic coils; 17 - high voltage electrode; 18 is a magnetic core.

The invention consists in the following.

The impregnation of the windings by the traditional jet-drop method involves feeding a thin stream of impregnating composition from the nozzle to the heated frontal part of the winding and in rotation of the impregnated winding under the impregnating composition impinging stream. The disadvantages of this technology are that for its implementation it is necessary to have electromechanical devices with which it is necessary to rotate the impregnated winding under the impregnating composition falling on its frontal parts. These electromechanical rotation devices are energy-consuming, and create noises around themselves that are dangerous to people. Another significant drawback of this traditional technology is that the impregnating compounds have a relatively low thermal conductivity, therefore, heat removal from the winding during its operation as a part of electric motors is difficult, which reduces the reliability of the products with the winding. Another drawback of traditional technology is that during the drying (compounding) of the impregnating composition in the winding, it, in the initial period of heating, sharply decreases its viscosity and begins to flow out intensively from the winding cavities. This leads to a decrease in the coefficient of impregnation of the winding, which characterizes the degree of saturation of the inter-turn and casing cavities of the winding with an impregnating composition. In turn, a decrease in the impregnation coefficient leads to a deterioration in the thermal and mechanical properties of the winding, as well as to a decrease in the probability of concealment of defects in the coil and case insulation of the windings. All this greatly reduces the reliability and durability of the windings.

To eliminate all these disadvantages, the present invention is directed. Let's consider, due to what operations the set technical task is solved.

The first difference of the proposed method from the traditional technology and the prototype method is that before impregnation, finely dispersed ferromagnetic filler is added to the impregnating composition, using nickel-zinc ferrite powder having a high specific resistance of at least (10 ⁵ -10 ¹³ ) Ohm × m, whose thermal conductivity is higher than the thermal conductivity of the impregnating compound, which is pre-disintegrated to a grain size of not more than 10 μm (d _fer <10 μm). The impregnating composition is mixed with the crushed ferromagnetic filler in the ratio of wt.%: (10 ÷ 15)% ferromagnetic particles, (90 ÷ 85)% of the impregnating composition, the resulting mixture is thoroughly mixed, and it is poured into the impregnation unit.

This operation is necessary in order to achieve the following goals without reducing the electrical insulation and technological properties of the impregnating composition:

1 - increase the thermal conductivity of the impregnating composition;

2 - to give the ability to control the jets of the impregnating composition using magnetic fields (bending, rotation and vibration of the jet);

3 - use the magnetic properties of the impregnating composition to prevent it from flowing out of the winding during drying after impregnation.

The insulating properties of the impregnating composition are maintained due to the fact that the particles of the ferromagnetic nickel-zinc powder have a high resistivity comparable with the resistivity of the impregnating compound.

The technological properties of the impregnating composition (viscosity, temperature and compounding time, etc.) are maintained due to the fact that the grain size of nickel - zinc powder should be no more than 10 microns. This value can be justified by the following estimates.

The fill factor of the wire groove winding KZ for most stators of the electric motors of the windings is in the range of 0.6-0.8. The slot fill factor with a wire is usually specified in the design documentation of a particular type of electric motor and is equal to

KZ = nS _pp / S _groove ,

where n is the number of conductors in the groove, S _CR is the cross-sectional area of the wire, S _groove is the free cross-sectional area of the groove.

Since the fill factor of the winding groove with the wire K ₃ in the winding usually lies in the range of 0.6-0.8, the interturn cavity of the winding accounts for a fraction of 0.2-0.3 of the groove area.

The inter-turn cavities are capillaries, and their number in the groove can be taken equal to the number of conductors m in the groove. In this regard, the average diametrical size of the inter-turn cavity (capillary) d _floor will also be (0.2-0.3) of the wire diameter d _pr , i.e. d _floor = (0.2-0.3) d _ave

The selected grain size of the nickel-zinc powder should be such that it can be used when impregnating any windings, including the windings of electric motors made of a relatively thin wire. The drip-jet method of impregnation is used only for large-scale electric machines with a center height of, as a rule, more than 200 mm. The diameters d _for used winding wires, for windings with the mentioned center heights, are usually greater than 0.5 mm. Therefore, for the minimum size of the diameter of the wire, windings impregnated with the jet method, you can take the diameter of the wire d _pp = 0.5 mm. Then, with the densest filling of the groove with the wire Kz = 0.8, the diametrical size of the inter-turn cavity will be equal to

. $$d_{P\mathrm{about}l}=0.2d_{PR}=0.2\times 0.5=0.1mm(\mathrm{one})$$

.

To nickel - zinc particles loosely held in cavities interturn necessary that the grain size d _fer nickel-zinc particles much smaller than the diameter d interturn _floor cavities. This condition is satisfied when the inequality d _φep << d _floor , or, based on the expression (1)

. $$d_{feR}<<0.1mm(2)$$

.

Inequality (2) is reliably satisfied if the diameter of the nickel-zinc particles is at least not less than an order of magnitude smaller than 0.1 mm, i.e., the size of the ferromagnetic particles must satisfy the inequality

. $$d_{feR.}\le 0.01mm(3)$$

.

In other words, the grain size of nickel-zinc ferrite should be no more than 10 microns.

Since the heat sink from the winding is better, the higher is its equivalent thermal conductivity, which largely depends on the thermal conductivity of the impregnating composition.

The thermal conductivity of the impregnating composition is increased due to the fact that the thermal conductivity of nickel-zinc particles (λ _n = 1.08 W / m × K) is greater than the thermal conductivity of the compound (λ _n = 0.28 W / m × K), and the mixture of the composition of the impregnating composition of the mentioned components has a higher thermal conductivity than the thermal conductivity of the impregnating compound.

The addition of nickel-zinc powder to the impregnating compound imparts electromagnetic properties to the jet of this compound, which makes it possible to control this jet using electromagnetic fields: bend it, rotate a curved stream, vibrate with a stream, which greatly contributes to the simplification and increase of the efficiency of the impregnation technology, since allows you to get rid of impregnation of energy-intensive electromechanical, noisy devices.

If, after the winding is impregnated with the said composite impregnating composition, the current is passed through the winding wire, then under the influence of the magnetic field of the said current, nickel-zinc particles are reoriented in the inter-turn cavities, and they are grouped in such a way that they create a kind of electromagnetic shutter in the inter-turn capillaries, and the impregnation flows out The mixture from the winding instantly ceases. This allows, in the process of compounding and drying the impregnating composition in the winding after its impregnation, to completely preserve the entire impregnating composition that got into it during the impregnation process. Due to the preservation of the impregnating composition in the winding, it is possible to significantly increase the impregnation coefficients of the windings, increase the stability of the values of the mentioned coefficients, and, as a result, increase the reliability of the windings.

The next distinguishing feature of the proposed method is that previously, before impregnation, according to the winding data, the ultimate mass of the impregnation mixture m _{c is} calculated, which can be placed in the cavities of each of the same type of windings during the impregnation process. This mass m _{cc is set} in the load transducer, after which the impregnated winding with a magnetic core is mounted on the load cells of the load transducer. It is weighed together with the magnetic core, and the measured weight of the non-impregnated winding with a magnetic core is taken as a zero count, for which purpose the weight reading of the non-impregnated winding with a magnetic core is reset to zero.

This operation is necessary in order to control the technological operation of the impregnation. Consider this distinguishing feature in more detail. When impregnating the windings in accordance with the traditional technology and with the impregnation technology according to the prototype method, only the impregnation modes are controlled: the preheating temperature of the winding wire, the impregnation time, temperature conditions and the final drying time of the windings. The main parameter of impregnation is the degree of saturation of the windings with an impregnating composition (impregnation coefficient), which determines the quality of the indicated impregnation operation, is not controlled during its implementation. This leads to the fact that at the end of the impregnation operation, due to fluctuations in the impregnation modes, changes in the properties of the impregnation composition, variation in the parameters of the wire and magnetic core, change in the winding modes, etc., the impregnation coefficient from one type of winding to the other has a large spread. In other words, the lack of proper control of the impregnation coefficient directly during the impregnation operation leads to a large spread in the quality of the windings, and as a result, to a large spread in the indicators of their operational reliability. The inventive method proposes to eliminate this drawback and to control the coefficient of impregnation directly during its implementation. The coefficient of impregnation K _ppi is determined by the formula

$${\mathrm{TO}}_{PRi}=\frac{m_i}{m_0},\text{(four)}$$

where m ₀ is the ultimate mass of the impregnating composition that can be placed in the cavities of the winding when they are 100% filled with a dry impregnating composition

$$m_0=d_c{\text{V}}_{\text{0}}=d_c{\text{Sl}}_{\text{w}}(\mathrm{one}-\frac{p}{\mathrm{four}}Ks)\times \frac{p}{2}\text{(5)}$$

where d _c is the density of the dry residue of the impregnating composition; V ₀ is the volume of air cavities in the non-impregnated winding; S is the free cross-sectional area of the groove; l _w is the average length of the coil in the winding; p is the number of grooves into which the controlled part of the winding is poured; KZ - the fill factor of the groove with the wire.

In order to control the impregnation by the coefficient of impregnation, proceed as follows. Based on the winding data of the impregnated type of windings, the limiting mass of the impregnating composition m _{0 is} calculated by the formula (5).

The value of V ₀ in expression (5) is calculated according to the formula given in [3]:

$${\text{V}}_{\text{0}}={\text{Sl}}_{\text{w}}(\mathrm{one}-\frac{p}{\mathrm{four}}Ks)\times \frac{p}{2}\text{, (6)}$$

Since the impregnation of the winding interturn cavity filled with liquid impregnating composition whose density d _f is different from the density of a dried residue of d _c, the impregnating mixture and the mass m _0zh that can be placed in the cavities of each of the windings of the same type in the process of impregnation, should be calculated from the formula

$$m_0{}_{\mathrm{well}}=d_{\mathrm{well}}{\text{V}}_{\text{0}}=d_{\mathrm{well}}{\text{Sl}}_{\text{w}}(\mathrm{one}-\frac{p}{\mathrm{four}}Ks)\times \frac{p}{2}\text{(7)}$$

In the process of impregnation, the impregnating composition not only penetrates into the cavity of the winding, but also flows from it; therefore, it is not possible to achieve 100% filling of the winding cavities with a liquid impregnating composition during jet impregnation. When impregnated, a certain dynamic equilibrium occurs between the penetrating in the cavity of the winding and the impregnating composition resulting from it. This dynamic equilibrium depends on the chemical composition of the impregnating mixture, its temperature, viscosity, winding data and a number of other parameters. The experiments showed that the mass of liquid impregnating composition that can actually be filled in the cavity of the winding when dynamic equilibrium is reached is

$$m_c=\left(0.85-0.90\right)m_{0\mathrm{well}}^{}\text{. (8)}$$

The mass m _c calculated by formula (8) is set in a load transducer, after which each unimpregnated winding with a magnetic core is installed on the load cells of the load transducer, weighed together with the magnetic core, and the measured weight of the unimpregnated winding with a magnetic core is taken as a zero count, for which in the load transducer, the weight indications of the non-impregnated magnetic core winding are reset to zero.

The weighing operation before impregnation of each winding with a magnetic core and the acceptance of the obtained weight of each non-impregnated winding with a magnetic core for zero counting is carried out for the following reasons. As mentioned above, the main parameter determining the quality of the impregnation is the impregnation coefficient, which characterizes the degree of saturation of the inter-turn cavities in the winding by the impregnating composition. Since the maximum mass of the impregnating composition m _c that can be placed in the inter-turn cavities of the winding is almost an order of magnitude less than the weight of the magnetic core with the winding, it is quite difficult to accurately determine this mass against the background of the whole product as a whole, especially since the spread in the weight of the magnetic core with the winding from one product of the same type to another, it is large enough, and if you do not take the weight of each controlled impregnated winding together with a magnetic core for a zero count, this will complicate the control of impregnation, since for each bmotki need to install a different weight limit impregnated windings at which the impregnation process can stop. Zeroing allows you to set the same weight gain m _c for each impregnated winding, regardless of what weight variations have impregnated windings with a magnetic core. In addition, the absence of zeroing and the acceptance of the weight of the impregnated winding with a magnetic core for a zero count can lead to even greater errors in controlling the mass of the impregnating composition penetrating the winding against the background of the weight of the whole product. The control process of the mentioned mass of the impregnating composition is greatly simplified if we take for zero reference the initial weight of each non-impregnated winding with a magnetic core.

The next distinguishing feature of the claimed invention is that through the leads of the winding wires a heating current is supplied to it, it is heated to a temperature of (80 ÷ 90) ° C, and then the heating current is turned off. The impregnated winding wire is earthed. An electrode is introduced into the nozzle, to which a potential is supplied, the absolute value of which, relative to the grounded winding wire, lies in the range (2 ÷ 5) kV. After that, the process of impregnation of each of the same type of windings is carried out, for which the particles of the impregnating mixture of the compound with the finely divided ferromagnetic filler are electrostatically charged by passing the particles of the impregnating mixture along the said electrode. A stream is formed by passing electrostatically charged particles of said impregnation mixture through a nozzle.

The operation of heating the windings to a temperature of (80 ÷ 90) ° C is carried out in order to improve the penetration of the impregnating composition in the cavity of the winding. Improving the penetration of the impregnating composition in the cavity of the winding is achieved due to the fact that the viscosity of the impregnating composition at a temperature of (80 ÷ 90) ° C decreases sharply, and it penetrates the winding cavity easier and faster.

The heating current is disconnected from the winding wire before impregnation because the said current flowing through the winding wires creates a magnetic field around them, and since the impregnating mixture is given magnetic properties, the magnetic field flowing through the current winding wires prevents the penetration of the impregnating mixture into cavity of the winding, and instead of impregnating the windings, only the enveloping of the impregnating surface of the frontal part of the winding occurs.

Grounding the winding wire, introducing an electrode to the nozzle, to which a potential is supplied, the absolute value of which is relative to the grounded winding wire, lies in the range (2 ÷ 5) kV, it is necessary for the impregnation mixture particles to be electrostatically charged. This charging of the particles of the impregnating mixture is carried out by an induction method [4], due to the contact of the particles of the impregnating composition with a high-voltage electrode. Charging the particles of the impregnating composition has two goals: firstly, the electrostatically charged stream of the impregnating composition becomes more controlled and it is easier to bend, rotate and vibrate under the influence of an electromagnetic field than without electrostatic charging, using only the magnetic properties of the impregnating composition. Secondly, electrostatically charged particles of the impregnating composition, flowing through the cavity of the winding, more effectively interact with the surface of the bare wire in the defective places of insulation of the winding wires, which contributes to a more effective hiding by the film of the impregnating composition of these mentioned defective places. This, in turn, leads to an increase in the quality of the windings and to an increase in their indicators of reliability and durability.

The choice of the potential value on the electrode in the range (2 ÷ 5) kV is due to the following considerations. The efficiency of electrostatic charging of the particles of the impregnating composition is higher, the greater the potential at the high-voltage electrode with which these particles come into contact. However, if a potential higher than 5 kV is applied to the high-voltage electrode, this can lead to breakdown of the gap between the electrode and the winding, which can cause a number of undesirable consequences.

When the potential on the electrode is less than 2 kV, the efficiency of electrostatic charging of a part of the impregnating mixture decreases sharply, which reduces the efficiency of impregnation.

где х, y - координаты горизонтальной плоскости лобовой части обмотки, R - средний радиус лобовой части обмотки, L - ширина лобовой части обмотки, k - количество колебаний, совершаемых струей поперек лобовой части обмотки при одном обороте вращающегося магнитного поля, w - угловая скорость вращения вращающегося магнитного поля, t - время, при этом угловую скорость вращения магнитного поля задают в диапазоне (1<w<3) об/мин, а количество колебаний, совершаемых струей поперек лобовой части задают в диапазоне 10<k<12.The next distinguishing feature of the proposed method is that when impregnating for rotation of the jet along the frontal part of the winding at the exit of the nozzle, the jet is affected by a rotating electromagnetic field, the intensity of which is directed perpendicular to the axis of the jet, and the amplitude of the mentioned magnetic field is changed in harmonic law, achieving so that the end of the jet of impregnating mixture falling on the heated frontal part of the winding describes the trajectory $$x^2+y^2=R^2+\frac{L^2}{\mathrm{four}}+RL\left[\cos \left(kwt\right)\right],$$

where x, y are the coordinates of the horizontal plane of the frontal part of the winding, R is the average radius of the frontal part of the winding, L is the width of the frontal part of the winding, k is the number of oscillations made by the jet across the frontal part of the winding for one revolution of the rotating magnetic field, w is the angular velocity of rotation of a rotating magnetic field, t is time, while the angular velocity of rotation of the magnetic field is set in the range (1 <w <3) rpm, and the number of oscillations made by the jet across the frontal part is set in the range 10 <k <12.

This operation has several purposes. Firstly, under the influence of a rotating magnetic field, the intensity of which is directed perpendicular to the axis of the jet at any time, the impregnating composition stream bends and rotates in a bent state, providing watering of one of the frontal parts of the impregnated winding. This makes it possible to exclude from the impregnation process energy-consuming, noisy, unreliable electromechanical units of the impregnating installation that rotate the magnetic core together with the impregnated winding, under the impregnating composition stream falling on the front part of the winding. Secondly, the mentioned law of change of a rotating electromagnetic field provides a more uniform watering of the frontal part of the impregnated winding than can be done using electromechanical rotational devices.

Consider this process in more detail. We will consider the frontal part of the winding in the XY plane (see figure 2). If we denote by R the radius of the circle passing through the middle of the frontal part of the winding, and through the L-width of the frontal part of the winding, then, in order for the end of the falling jet of impregnating composition to describe the trajectory of the middle circle of the frontal part of the winding, it is necessary that the x and y coordinates of the falling stream impregnating composition changed by law:

. $$x=R\text{sin (wt)}\text{, y}=\text{R cos (wt) (9)}$$

.

We square the left and right sides of expressions (9) and, adding them, we obtain the equation of a circle

. $$x^2+{\mathrm{at}}^2=R^2\text{(10)}$$

.

Therefore, if the rotating electromagnetic field is changed according to the harmonic law described by equations (9), then we can provide watering of the frontal part of the winding only along the average circumference of the radius R of the frontal part. Such a law of rotation of the jet will not allow for uniform watering of the entire frontal part of the impregnated winding, which can lead to a decrease in the efficiency of impregnation. In order to provide more uniform watering of the frontal part of the winding, the curved stream of impregnating composition not only needs to be rotated along the middle circumference of its frontal part, but also vibrated by this jet across the frontal part of the winding. In this case, the amplitude of the vibration of the stream should not exceed half the width of the frontal part L. Since if the amplitude of the vibration of the stream is greater than L / 2, the impregnating composition stream will go beyond the frontal part and fill the magnetic core, which will lead to the necessity of cleaning the said core from the impregnating composition adhering to it, and in addition, this will lead to unjustified costs of the impregnating composition. However, the amplitude of the vibration of the jet should not be significantly less than the value of L / 2, as this reduces the uniformity of irrigation of the impregnating composition of the frontal part of the winding. Therefore, such a vibration of the jet will be optimal at which the amplitude of the vibrations is equal to L / 2.

For the rotation of the jet and its simultaneous vibration across the frontal part to occur, it is necessary that the electromagnetic field of the impregnating composition acting on the jet change according to the law:

. $$x=R\sin (wt)+\frac{L}{2}+\sin (kwt);y=R\cos (wt)+\frac{L}{2}\cos (kwt);\text{(eleven)}$$

.

Squaring the left and right sides of expressions (11) in a square, we obtain

$$x^2=R^2{\sin }^{2}wt+RL\sin (wt)\sin (kwt)+\frac{L^2}{\mathrm{four}}{\sin }^2(kwt);\text{(12)}$$

$$y^2=R^2{\cos }^{2}wt+RL\cos (wt)\cos (kwt)+\frac{L^2}{\mathrm{four}}{\cos }^2(kwt);\text{(13)}$$

Add the left and right sides of expressions (12) and (13), we obtain.

$$\begin{array}{l}{x}^2+y^2=R^2{\sin }^{2}wt+\frac{L^2}{\mathrm{four}}{\sin }^2(kwt)+R^2\cos wt+\frac{{\text{L}}^{\text{2}}}{\text{four}}{\cos }^2\left(kwt\right)+RL\left[\sin (wt)\sin (kwt)+\cos (wt)\cos (kwt)\right]\\ =R^2+\frac{L^2}{\mathrm{four}}+RL\left[\sin (wt)\sin (kwt)+\cos (wt)\cos (kwt)\right]=R^2+\frac{L^2}{\mathrm{four}}+RL\left[\cos (wt-kwt)\right]=R^2\\ +\frac{L^2}{\mathrm{four}}+RL\left[\cos wt(\mathrm{one}-k)\right]\text{( fourteen)}\end{array}$$

In order to ensure uniform watering of the frontal part of the winding with a jet of impregnating composition, it is necessary that for one revolution of the jet along the frontal part of the winding, vibrational vibrations of the jet should be made, and this should be significantly greater than 1. Since k >> 1, we can write :

. $$x^2+y^2=R^2+\frac{{\text{L}}^{\text{2}}}{\text{four}}+RL\left\{\cos \left[wt(\mathrm{one}-k)\right]\right\}=R^2+\frac{L^2}{\mathrm{four}}+RL\left[\cos (kwt)\right]\text{(fifteen)}$$

.

Thus, the electromagnetic field acting on the stream of impregnating composition must change according to the law:

. $$x^2+y^2=R^2+\frac{L^2}{\mathrm{four}}+RL\left[\cos (kwt)\right]\text{(16)}$$

.

The angular velocity w of rotation of the jet is determined based on the following conditions. On the one hand, the angular velocity should be so slow enough that the varnish that has fallen on the surface of the frontal part during one revolution of the jet has time to soak from the surface of the frontal part into the pores and capillaries of the winding. On the other hand, the greater the angular velocity of the winding, the faster the impregnation of the winding can be completed; these two conditions are satisfied by an angular velocity lying in the range (1 <w <3) rpm.

The vibration frequency of the impregnating composition jet is determined by the value of k in expression (16). When choosing the quantity k, one should proceed from the following considerations. The greater k, the higher the frequency of vibrations and the higher the uniformity of watering the frontal part of the winding with an impregnating composition. However, due to the large inertia of the jet at high values of k, the jet may not have time to react to changes in the magnetic field, which can lead to a decrease in the amplitude of vibrations, and as a result of this, worsen the uniformity of irrigation with the impregnating composition of the frontal part of the winding. It was found that the optimal value of k satisfying the above requirements should lie in the range 10 <k <12.

The next distinguishing feature of the proposed method is the constant weighing, in the process of impregnation of the mass of the impregnating mixture m _i , penetrated into the cavities and capillaries of each i-th impregnated winding, by a weight measuring transducer, and when the mass of the impregnating mixture m _c in the impregnated winding and the mass m _{c of the} impregnating mass are equal the mixture, which can be placed in the cavities of the same type of windings during the impregnation process, stop watering the compound on the upper frontal part of the winding.

This operation in the inventive method is necessary in order, firstly, to continuously monitor the most important indicator of the quality of impregnation - the gain of the impregnating composition in each winding, which determines the impregnation coefficient, and secondly, in order to ensure stable and the maximum possible with this method of impregnation, the coefficient of impregnation.

After the impregnation operation is completed, the winding wires are disconnected from the ground, and a heating current is supplied again to the winding, the winding is heated to (160-165) ° C, and the final compounding of the impregnating mixture penetrating the winding is carried out.

The operation of disconnecting the wire from the ground and supplying a heating current to it is necessary in order, firstly, to prevent the impregnation mixture from flowing out of the winding, and secondly, to heat the winding to a temperature of (160-165) ° C. The process of leakage of the impregnating composition from the cavities of the winding stops immediately after the heating current is applied to the winding wire, for the reason indicated above.

Heating the winding to a temperature of (160-165) ° C is necessary, in accordance with the established technological regulations, for compounding the impregnating mixture.

The indicated temperature range is due to the fact that solvent-based thermosetting compositions introduced into the winding using the jet method have been widely used recently. The time for the technological process when using modern solvent-free thermoset compositions is determined by the duration of heating of the winding to a given temperature, as well as by the polymerization rate of the composition, which, as a rule, quickly polymerizes. For the polymerization of the impregnating composition, the current method of heating the windings is mainly used, which dramatically reduces the duration and complexity of the processes. In automatic plants of various types for impregnation with solvent-free compositions, impregnation and drying are usually carried out in 15-18 minutes.

The impregnation according to the claimed method can be carried out on the device shown in figure 1. The device operates as follows. In the initial state, the high-voltage source 11 and the electromagnetic coils 14, 15, 16 are turned off. High voltage electrode 17 does not receive high voltage. Impregnating composition 4 from the nozzle 2 is not received. The impregnated winding, poured into the grooves of the magnetic core 18, is mounted on the load cells 8 and 9 and weighed, and the measured weight is taken as a zero report. The estimated weight of the impregnating composition m _{c is} entered into the memory of the control unit 6. Contacts KM2.2, KM2.3, KM2.4 are normally open. By pressing the button 5, the control unit 6 is started, and a magnetic starter is activated in it, which closes the contact KM2.1, connecting a three-phase voltage to the winding wires. The non-impregnated winding begins to warm up, and the temperature of the winding is continuously measured by a temperature meter 10. When the winding temperature reaches a preset value lying in the range of 80-90 ° C, the control unit issues a command by which contact KM2.1 opens, disconnecting the winding from the three-phase voltage, and the contacts KM2.2, KM2.3, KM2.4 are closed, connecting the wires of the winding to the ground. At the same time, by command from the control unit 6, contact K1.1 and contact KM1.1 are closed, including the high-voltage source 11, and supplying voltage to the coils 14, 15, 16, creating a rotating magnetic field. The high voltage electrode 17 from the high voltage source 11 is supplied with a given high voltage potential lying in the range of 2-5 kV. The particles of the impregnating composition, in contact with the high-voltage electrode 17 are electrostatically charged, and, leaving the nozzle 2, are converted into an electrostatically charged stream 1 of the impregnating composition. The impregnating composition jet, in addition to the electrostatic charge, also has magnetic properties due to the introduction of ferromagnetic nickel-zinc particles into the impregnating composition. Due to the electrostatic charging of the jet and its magnetic properties, it, passing in the magnetic field of coils 14, 15, 16, changing according to the law described by expression (16), bends, and rotates along the radius R in a bent state (see Fig. 2, A), making transverse vibrations along the frontal part 3 of the winding with an amplitude of L / 2 (see figure 2, B). The winding is impregnated. Its weight gain is continuously measured in the weight measuring transducer 12 and its value is transmitted to the control unit 6. When the gain value of m _c is reached, a command is generated in the control unit by which contacts K 1.1, KM1.1, KM2.2, KM2.3, KM2 open .4, and the KM2.1 contacts close. On this command, the high-voltage source 11 and the electromagnetic coils 14, 15, 16 are turned off. The impregnating composition ceases to flow from the nozzle 2 to the frontal part 3 of the winding. The three-phase voltage is reconnected to the wires of the winding and the current heating the winding begins to flow through them. The leakage of the impregnating composition from the winding through the frontal part 6 is stopped. The process of heating the winding to the compounding temperature of the impregnating composition, which lies in the range (160-165) ° C, begins. When the specified temperature is reached, within a specified time of 4-5 minutes, the impregnating compound is compounding and forms a command to the control unit 6, by which the entire impregnation unit comes to its original state. An example of a specific implementation.

According to the prototype method and the claimed method, they were soaked in 5 windings of 4A112M4 series electric motors. The impregnation of all five windings according to the prototype method was carried out by KP-34 compound. The impregnation according to the claimed method was carried out by an impregnating composition with the addition of a finely divided ferromagnetic filler, which was taken as a nickel-zinc ferrite brand 400 NN, which was previously disintegrated to a particle size of 5-10 microns. The impregnating composition was mixed with ground ferromagnetic filler in the ratio of wt.%: 10% ferromagnetic particles, 90% of the impregnating composition. Using the winding data of the 4A112M electric motor (groove area S _p -8.8 × 10 ^-6 m ² ; winding half-turn length l _w = 0.572 m; groove fill factor Кз = 0.678; number of grooves in the stator p = 36) the cavity volume V _{0 was} calculated in the winding, according to the formula (6)

$$V_0=S{l}_w(\mathrm{one}-\frac{p}{\mathrm{four}}Ks)\times \frac{p}{2}=S{l}_w(\mathrm{one}-\frac{p}{\mathrm{four}}\mathrm{TO}s)\times \frac{p}{2}=8.8\times {10}^{-5}\times 0.572(\mathrm{one}-0.53223)\times \mathrm{eighteen}=\mathrm{0,00042382}{m}^3.$$

By formula (7), the limiting mass of liquid impregnating composition m _{0zh was determined} , which can be placed in the cavities of the winding

m _0zh = d _w V ₀ = 0.00042382 × 1570 = 0.665 kg, where d _w = 1570 kg / m ³ .

The value of m _{c was} calculated by the formula (8), taking a coefficient of 0.9.

m _c = 0.9 m _0zh = 0.665 × 0.9 = 0.599 g.

This mass m _{c was} stored in the memory of the control unit 5.

Impregnation by the present method was carried out on the installation shown in figure 1. The impregnation process according to the claimed method is described above, when considering the operation of the device. Preheating of all windings before impregnation was carried out to a temperature of 90 ° C. In the inventive method, the angular velocity of rotation of the magnetic field was equal to w = 3 rpm, and the number of oscillations k made by the jet across the frontal part was set equal to k = 12. The compounding temperature of the impregnating composition in all windings was maintained equal to 162 ° C.

Upon completion of the impregnation, the impregnation coefficient of each of the windings was determined. The results of monitoring the coefficients of impregnation are shown in table 1.

Table 1 Impregnation Coefficients According to the prototype method According to the claimed method No. CRC No. CRC one 0.28 one 0.48 2 0.34 2 0.48 3 0.33 3 0.48 four 0.26 four 0.47 5 0.35 5 0.47 KPR cf. = 0.31 5 KPR cf. = 0.48

As follows from table 1, the claimed method in comparison with the prototype method allows an average of 1.55 times increase the coefficient of impregnation of the windings, and significantly increase the stability of their values from winding to winding.

Information sources

1. A.S. No. 1820453 (USSR). The method of capillary impregnation of the windings of electric machines / G.V. Smirnov. - Publ. in the BI, 06/07/93. Bull. No. 21.

2. USSR No. 1312692. The method of impregnation of a multi-turn electric machine ”/ Smirnov G.V., Khabarov M.V., Eleushov A.D. - Publ. 05/23/87. Bull. No. 19. (prototype).

3. G.V. Smirnov. Reliability of insulation of windings of electrical products. - Tomsk: Publishing house Tom. Univ., 1990, p. 96, formula 3.3.

4. Electrical reference book. In 3 volumes T. 3. Book 2. The use of electrical energy / Under the total. ed. professors MPEI V.G. Gerasimova, P.G. Grudinsky, L.A. Zhukova et al. - 6th ed., Rev. and add. - M.: Energoizdat, 1982, p. 228.

Claims (1)

The method of jet impregnation of the windings of electric machines, which consists in feeding a thin stream of impregnating composition from the nozzle to the heated frontal part of the winding and in rotating the jet along the frontal part of the winding, characterized in that finely dispersed ferromagnetic filler is added to the impregnation compound before it is disintegrated to a size that is not more than 10 microns, the impregnating composition is mixed with ground ferromagnetic filler in the ratio, wt.%: (10 ÷ 5) ferromagnetic particles, (90 ÷ 85) impregnating composition, alternating ivayut resulting mixture and pour it into the impregnating unit, wherein the pre-before impregnation calculated limit weight impregnating mixture m, _etc., which can be placed in the cavities of each of identical windings during impregnation, set this mass m _forth in the weighing transducer then impregnated winding with the magnetic core is installed on the load cells of the load transducer, weighed together with the magnetic core, and the measured weight of the impregnated winding with the magnetic core they’ll be taken for a zero count, for which purpose, in a weight measuring transducer, the weight of the impregnated winding with a magnetic core is zeroed, then a heating current is supplied to it through the output terminals of the winding wire, which is heated to a temperature of 80 ÷ 90 ° C, after which the heating current is disconnected from the winding, and the impregnated winding wire is grounded, an electrode is inserted into the nozzle and a potential is applied to it, the absolute value of which, relative to the grounded winding wire, lies in the range (2 ÷ 5) kV, and the impregnation process of each of windings of the same type, while in the process of impregnation, the particles of the impregnating mixture of the compound with finely dispersed ferromagnetic powder are electrostatically charged, by passing the particles of the impregnating mixture along the said electrode, a jet is formed by passing electrostatically charged particles of the specified impregnating mixture through the nozzle, and the jet is bent and rotated at the exit of the nozzle moreover, to rotate the jet along the frontal part of the winding, the jet is affected by a rotating electromagnetic field, the intensity of which is directed perpendicular is parallel to the axis of the jet, and the amplitude of the mentioned magnetic field strength is changed according to a harmonic law, ensuring that the end of the jet of impregnating mixture falling on the heated frontal part of the winding is described $$x^2+y^2=R+\frac{L^2}{\mathrm{four}}+RL\left[\cos \left(kwt\right)\right]$$

where x, y are the coordinates of the horizontal plane of the frontal part of the winding, R is the average radius of the frontal part of the winding, L is the width of the frontal part of the winding, k is the number of oscillations made by the jet across the frontal part of the winding for one revolution of the rotating magnetic field, w is the angular velocity rotation of a rotating magnetic field, t is time, while the angular velocity of rotation w of the magnetic field is set in the range (1 ÷ 3) rpm, and the number of oscillations k made by the jet across the frontal part is set in the range (10 ÷ 12), while in the process of impregnation but weighed weighing transducer mass of the impregnating mixture of m _c, penetrating into the cavities and capillaries each impregnated winding and on reaching equality mass impregnating mixture of m _c to be impregnated winding and mass m _pr impregnating mixture, which can be placed in cavities of the same type of winding in the process of impregnation is stopped watering the compound on the upper frontal part of the winding, the winding wires are disconnected from the ground, and through them the heating current is again supplied to the winding, with which the winding is heated to a temperature of 160-165 ° C, and with the above temperature, the final compounding of the impregnation mixture penetrating the winding is carried out.

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