SU983899A2 - Electric machine stator - Google Patents

Description

(5 STATOR ELECTRIC MACHINE

The invention relates to electric machines of alternating current / in particular, to powerful turbo-generators, characterized by the electromagnetic and thermal loads of the end elements of the stator.

According to the main author. St. 930497 is a known stator of an electrical machine, comprising a laminated magnetic circuit, a winding, a pressure plate and an electrically conductive screen located on the side surfaces of the plate facing the magnetic conductor and the frontal part of the winding, and on its inner cylindrical surface tl.

This design removes tangential currents, concentrating on the cylindrical surface of the screen, from the dentate zone of the extreme packages of the magnetic circuit. The stator is in the back area of the magnetic line, where the electromagnetic field is weak. This reduces the magnetic flux, reducing the jagged zone of the packages of the magnetic circuit. However, due to the large splash of the screen surface facing the frontal part of the winding, eddy currents of very large values in this section of the screen, which freely flow onto the cylindrical surface of the screen, i.e. in the area of the screen, the blicker located to the dentate zone of the extreme packages. These currents, although they dissolve into an array of screen area, located by the magnetic conductor and plate, on the cylindrical surface will still be significant. They are powerful secondary sources of 10 fields, which unfavorably affect extreme packages, causing additional losses and heat, thereby limiting the permissible load of the turbogenerators and reducing the reliability of their operation.

The aim of the invention is to improve the performance characteristics by increasing the efficiency of shielding from the magnetic fluxes of the dispersion and reducing the heating of the dentate zone of the extreme stator packets.

 The goal is achieved by the fact that in the stator design of an electric machine, an alternating current with a laminated magnetic core, a winding, a pressure plate and an electrically conductive screen located on the sides of the plate surface and on its internal cylindrical surface

30 screen located between the stove /

and the frontal part of the winding is made of at least two separate parts mated to each other, along the surfaces of rotation, and the mating point on the outer surface of the screen facing the frontal part of the winding are located on the area bounded by half of the radial screen size and measured from the interface of two winding layers of size D C (1-у-) sinp, where C is the length of the concave section of the frontal part of the stator winding J ft - the angle of the bend of this section, up to half the radial size H of the screen area located in front of the plate. The size corresponds to the location on the surface of the projection screen of the center of gravity of the axial-radial currents of the winding frontal part, which are located close to the screen. In the Location zone on the surface of the projection screen of the center of gravity, there are eddy currents and their lines change directions, if the influence of the edge effects is excluded. This determines the choice of articulation points of the individual parts of the screen.

If the forming surfaces of the opposition vary according to the linear law r f (Z), then in the coordinate system orfz, in which the coordinate surface is from сов coincidence. with the side surface srfpaHa facing the frontal part of the winding, forming a curve expressed as

g ztgoC + A + B, where - | - oL -f-, O B

A is the radius of the cylindrical interface between the two layers of the winding; In place of articulation on the outer

surface of the screen. At the same time, an electrical insulating layer is placed between the individual parts of the screen, the screen and the plate.

This design prevents the currents from flowing from the side surface, where they are maximal, to a cylindrical surface that is close to the teeth of the outer zone of the packages. The eddy currents are closed in separate parts of the ec: wound and are more evenly distributed in the radial direction. The articulation of the two parts of the screen through the insulating layer over the surface, for example conical (), reduces the penetration of the magnetic flux into the slab at the joints.

The proposed stator design of an AC electric machine is more reliable, and its load capacity will increase due to a decrease in tangential currents on the cylindrical surface of the screen located near the dentate zone.

extreme packets, reducing locale. losses, radial temperature gradients and local overheating of the extreme stator and screen packets.

FIG. 1 depicts the proposed

stator of an electric machine of alternating current, face part; Fig. 2 is the same longitudinal section / in Fig. 3 screen, an example of a specific embodiment / in Fig. 4 - compositing: full screen; on

5 of FIG. 5 is a monolithic screen; in FIG. 8, curves showing the effectiveness of the composite screen.

The stator of the electric machine contains a certified magnetic circuit 1, a winding 2, a pressure plate 3, an electrically conductive screen 4 (Fig. 1). Screen 4 consists of three sections 5-7, covering the side surfaces of the plate and its cylindrical surface. Section 5, located between the plate 3 and the frontal part of the winding 2, the radial size of which is equal to H, is made of two or more parts. In the joints of individual parts of the site

n 7 of the screen, between screen 4 and plate 3

placed electrical insulation layer 8 i The interface of two

parts of the screen is the surface

rotation. with an envelope having the form

 arbitrary curve (Fig. 3).

In the coordinate system in which the coordinate surface og is aligned with the side surface of the screen facing the frontal part of the winding 2, the resultant can be expressed,

0 for example, g 2tgot. + A + B 1fig.1). The angle d varies from -2 to (Fig. 2), A the radius of the interface between the two layers of the winding (Fig. 1). The size B varies in the range from 5 2

The expression C (1--) s5np, where

С - length of the OTorHyTOiTo section of the lobo / howl part of the winding 2 / fi- angle of the limb

H

of this section, up to - - half of the radial size of section 5 of the screen. The interface of the two parts of the screen 4 is tapered when, and when ot O. is cylindrical. In the latter case, parts of the screen section 5 have 5 kind of cylindrical rings (disks). At ot / 0 drives have sloping ends.

In the areas of the screen and plates on which they are electrically insulated, channel cooling can be provided to improve cooling, if the insulation is made in the form of gaskets. These areas can also be electrically insulated using spacers between the screen and the stove to form ventilation ducts. . When an electric AC machine is operating, the magnetic flux of the bottom of winding 2 induces eddy currents in screen 4, plate 3 and extreme packages of magnetic circuit 1. Since the frontal part of winding 2 with current is close to screen 4 and the side surface area of screen 4 facing side of the winding is very significant, then significant and variable magnetic flux penetrating this surface. As a result, eddy currents flow through the array of section 5 of the screen, reaching large values. In the case of a monolithic screen, eddy currents flow from screen 4, located on the outer side surface of plate 3, into the array of screen b and concentrate near the edge of screen 4 on the inner cylindrical surface close to the toothed zone. If the section 5 of the screen is composite, some parts of which are articulated through the electrically insulating layer 8, then the indicated flow of currents from the array of section 5 to the array of section 6 does not take place, as there is no current flowing through the plate array due to the presence of layer 8. Same electromagnet The interaction takes place when using screens with several components. Since separate parts of screen 4 are articulated through rotational surfaces with an arbitrary forming curve, for example, through conical surfaces, the magnetic flux cannot freely penetrate into the massif of plate 3. Reduction of tangential currents in the massif of the screen area b, removal of the main current contours from the tooth zone leads to a decrease in the magnetic flux penetrating the surface of this zone, losses and heating in it. In addition, there is an alignment of the temperature of the extreme packages of the stator and the screen. All this favorably distinguishes the proposed / design of the known. The technical and economic effect of introducing the proposed design in AC generators with a capacity of 500 MW and above is achieved by increasing the load capacity (extension of the load range, power output) and increasing the reliability of the machines. Since the use of a composite screen in the proposed stator design reduces the axial o component of the magnetic induction in the dentate zone of the extreme packages, local heating of these elements is thus reduced. It is known that heating the bottom zone of the groove in the outer packages limits the permissible load of the generators in under-excited and asynchronous move Therefore, the use of the proposed stator design will increase the load capacity and reliability of the machines. Indeed, this is confirmed by experimental data on the current density L in screen 4 (Fig. 6-8), and obtained on the physical model of the end zone of the turbo-generator with the 500 MW screening DLI for two options of screens 4: monolithic (Fig. 5) on the plate surface facing frontal part, and composite (Fig. 4), in which parts 5 and b are not in contact with each other. The current density (Figs. 6-8) is presented depending on the point on the screen, located at a distance of ji (i. 2, 3) from the end of the screen, Ha — the starting point of each 1 is shown (Fig. 4 and 5). If the screen 4 is monolithic, then the currents in the screen freely flow from the electrically conductive part 5 to part b and the current density is concentrated at the edge of part b (Fig. 7) near the tooth zone of the outermost stator packets. If screen 4 is composite, then in part b of the screen the current density decreases and is evenly distributed (Fig. B) as a result of the effect of proximity of the two parts 5 and b of the screen. The total current in part b of the composite screen will be reduced by 2.2 times compared with the version of the monolithic screen. The magnetic flux permeating the dentate zone of the outermost packets is reduced. In this case, the axial component at the surface is. Teeth zone reduced by 30%. If the location of the partition of the screen 4 is moved away in the direction o1. |, Or such divisions are somewhat exceeded, then the maximum current density in part 5 will decrease (Fig. 8) and it will be distributed more evenly. If the axial component of the induction of the magnetic field, caused by the scattering of the frontal part of the stator winding, decreases by 30%, then in different load modes of the turbogenerator, taking into account the flow of bulging from the gap, the maximum loss and heating is reduced by no less than 10%. This ensures the economic effect of the implementation of the proposed design on a 500 MW turbo-generator only due to the expansion of the load diagram of at least 150 thousand rubles. per year for one turbogenerator, if accepted, that the turbogenerator operates in the peak load mode for 300 hours per year. The reduction of the radiative component of the temperature gradients in the extreme packets and the screen leads to a decrease in their vibration and noise, which provides a social effect.

Claims (2)

1. The stator of an electric machine according to ed. St. 930497, about tl and h and rout and with the fact that in order to improve performance, the screen area located between the plate and the fishing part of the winding is made of at least two separate parts mated to one another with the surface meters of rotation, and the interface points on the outer surface of the screen facing the frontal winding are located on a section bounded by half of the radial size of the screen and measured from the interface of two layers of a winding of size D C (1-) sin, where C is the length of the bent portion of the frontal part of the stator winding; ft corner of the limb of this site. 2. The stator according to claim 1, distinguishes between the box and the fact that an electrical insulating layer is placed between the plate, the screen and its individual parts. Sources of information taken into account in the examination 1. USSR author's certificate No. 930497, cl. H 02 K 1/12, H 02 K 3/42, 1980. & r I-j fftttt nineteen F 9.v