RU2249899C1 - Method for diagnosing interference fit of end-winding retaining rings on electrical machine rotor barrel - Google Patents

Abstract

FIELD: electromechanical engineering; checking shrink fit of rotor end-winding retaining rings of large electrical machines such as turbogenerators.

SUBSTANCE: proposed method for diagnosing interference fit of end-winding retaining rings on rotor barrel of electrical machine that has rotor barrel with head part and butt-end part, winding, and retaining ring includes evaluation of change in interference fit at point of installation of end-winding retaining ring or insufficient negative allowance by comparison measurements of linear dimensions in end-winding retaining assembly prior to placing electrical machine in operation, in the course of operation, and during next scheduled outage. Change in interference fir or insufficient negative allowance is evaluated by change in eccentricity of this retaining ring in sectional area of its mating with thrust ring by comparison measurement of difference in radial clearances between inner bore of thrust ring (or outer cylindrical surface of retaining ring) and outer cylindrical surface of rotor barrel head part; insufficient negative allowance is found by change in eccentricity Δε using equation Δε = ε _end - ε _st = (δ $\genfrac{}{}{0ex}{}{\text{1}}{\text{end}}$ - (δ $\genfrac{}{}{0ex}{}{\text{11}}{\text{end}}$ )/2 - (δ $\genfrac{}{}{0ex}{}{\text{1}}{\text{st}}$ - (δ $\genfrac{}{}{0ex}{}{\text{11}}{\text{st}}$ )/2, where ε _end and ε _st are eccentricities measured, respectively, during scheduled outage of turbogenerator (index "end") compared with measurements made earlier (index "st"), mm; δ ¹ δ ¹¹ is, respectively, mean value of clearances between inner bore of thrust ring (or outer cylindrical surface of end-winding retaining ring) and rotor shaft measured in diametrically opposite points with rotor shaft turned through 180 deg.

EFFECT: ability of diagnosing interference fit in end-winding retaining assembly without its disassembly.

2 cl, 2 dwg

Description

The invention relates to the technology of electrical engineering, in particular to control the values of the interference fit of the hot fit of the retaining rings of the rotors of large electrical machines, for example, turbogenerators.

A known method of measuring interference in the retaining unit [1], which requires complete disassembly of the retaining unit, measuring the diameters of the mating parts and comparing the results with factory sizes. The method is very laborious, and is not always feasible according to the operating conditions of the turbogenerator and economic opportunities.

The closest analogue is the prototype of the invention is a patent [2], the implementation of which provides the opportunity to diagnose the state of the interference fit in the retaining unit of the rotor of an electric machine without disassembling it. A method for diagnosing the condition of landing interference fit includes assessing the change in interference at the seats of the retaining ring on the barrel of the rotor and the centering ring, and the change in interference is determined by comparative measurements of the diameter of the retaining ring at the place of its landing before the turbogenerator is put into operation and after it is stopped.

However, this diagnostic method is not able to detect the weakening of the landing interference during operation of the electric machine, for example, in the abnormal modes of its operation, if this interference is restored after stopping. In addition, in this way it is impossible to assess the adequacy of the normative, for example, the magnitude of the seating interference fit of the retaining ring on the rotor barrel, established by the manufacturer.

The technical result to which this invention is directed is to diagnose the state of the interference fit in the retainer assembly without disassembling it, including fixing an unacceptable change in the interference fit of the retaining ring during operation of the electric machine, as well as its insufficient value, which is especially important for brace assemblies of cantilever design ( figure 1).

Figures 1 and 2 show the construction of a retaining assembly of such a design with a retaining ring (1), cantilevered, cantilevered on the end part (2) of the rotor barrel (3). It is well known that the most mechanically loaded node of the turbogenerator is the retainer assembly that holds the frontal parts of the winding (4), mounted on the rotating barrel of the rotor in the radial direction from the action of centrifugal forces due to the retaining ring and in the axial direction from the action of forces arising from thermal expanding the rotor winding using a snap ring (5).

The coupling parts of the retaining unit is carried out by hot landing with an interference fit, the value of which is determined by mechanical calculation. The use of a hot landing is due to the need for a tight connection of the parts of the retaining assembly, primarily at the operating speed.

Violation of the connection density of the parts of the retaining assembly during rotation of the rotor can lead to damage to the joints at the assembly, as well as to displacement of the windings and, as a result, to a deterioration in the vibrational state of the machine.

The latter is most essential for cantilever brace assemblies, when the back of the brace ring (6) is not rigidly centered (with a centering ring) relative to the end part (7) of the rotor barrel.

In the cantilever design of the retainer assembly, the hot fit of the retainer of the retainer ring is intended to secure the retainer ring in the radial and axial direction, which can only be successfully implemented by firmly fitting the retaining ring onto the end part of the rotor barrel with a guaranteed interference fit that does not allow turning this fit into a sliding fit for any , including the abnormal mode of operation of the turbogenerator.

For each rotor, with a certain equilibrium state of the retaining assembly, there is a rotation speed at which the seating interference is weakened so much that the retainer is in a state of unstable equilibrium. With a further increase in speed, the value of the distorted moment will exceed the stabilizing moment from the action of the landing interference and the bandage will begin to warp relative to the initial coaxial position.

The new stable position of the bandage, provided by the equality of the skew band and its holding moments and accompanied by a change in the vibration level of the bearings, can be violated either by an increase in the rotor speed or by a decrease in the compressive force developed by the bandage nose due to a change in the temperature condition of the bandage assembly. In the end, the bandage is locked in a skewed state and maintains this position when the machine stops and during subsequent starts. This process most often occurs when the retaining ring of the retaining ring is weakened on the rotor barrel as a result of wear or permanent deformation of the mating seating surfaces or insufficient initial tightness. It is this manifest defect that the cantilever retaining ring fits on the rotor barrel that can be detected by comparative measurements of the eccentricity of the retaining ring in the initial period of operation of the electric machine and during subsequent scheduled shutdowns.

, определяемого из выражения:.The proposed method for diagnosing the state of the interference fit of the retaining rings on the barrel of the rotor without disassembling the retaining assembly is implemented by comparative measurements of the linear dimensions in the retaining assembly before putting the electric machine into operation, during operation and subsequent scheduled stop with the change in the eccentricity of the position of the retaining ring in its cross section mating with a thrust ring by comparative measurements of the difference in radial clearances between the inner bore of the thrust ring (or uzhnoy cylindrical surface of retaining ring) and the outer cylindrical surface of the end portion of the drum rotor, and attenuation of interference fit is found by changing the eccentricity

defined from the expression :.

where ε _kon and ε _nach are eccentricities, respectively measured during the planned shutdown of the turbogenerator (index “kon”), compared with earlier measurements (index “nach”), mm;

δ ¹ and δ ¹¹ are the average values of the gaps between the inner bore of the thrust ring (outer cylindrical surface of the retaining ring) and the rotor shaft, measured in diametrically opposite places when the rotor shaft is rotated 180 degrees.

The proposed method for diagnosing the state of the seating interference of the retaining ring on the rotor barrel can be preceded, followed by vibration diagnostics of the oscillation of the rotor shaft (thrust bearings) by indicators characterizing the state of landing.

Significant unbalanced forces associated with the appearance of the eccentricity of the retaining assembly relative to the longitudinal axis of the rotor shaft even with a temporary weakening of the interference fit are most often manifested when the turbogenerator is under the greatest load, or in the abnormal mode of its operation, but to fix this surge of vibration displacement of the rotor shaft (pillow bearings) and identify it, as an indicator of the manifested defect of the retaining nodes is difficult. This is due to the numerous manifestations of the instability of the vibrational state of the rotor under the influence of changing conditions of its cooling, heating, winding circuits, as well as contamination of the passage sections of the winding cooling system.

With the greatest degree of probability, the identification and diagnosis of the appeared eccentricity of the retaining assembly can be carried out by a comparative analysis of the vibration displacement vectors of the rotor shaft (thrust bearings) during the start-up of the turbogenerator and its at least short-term stable operation at the nominal rotation speed without excitation of the rotor in order to exclude any influence of thermal , electromagnetic imbalance and other reasons.

So, if, as a result of a weakening of the seating interference from the moment of start-up to the subsequent shutdown of the turbogenerator, a noticeable eccentricity appears on only one retaining ring relative to the longitudinal axis of the rotor shaft or is equally oriented on the retaining rings on both sides of the rotor, one should expect a sharp increase in the vibration vector of the shaft (pillow bearings) at the first critical rotor speed. This vibration displacement vector will increase many times when, according to the strength conditions of the installation places of balancing weights on the thrust ring or fan, the balancing weights balancing the unbalance are regulated and practiced transferring to the middle massive part of the rotor barrel.

If, as a result of the weakening of the seating tension of the retaining rings on the rotor barrel during the operation of the turbogenerator, their eccentricity changes relative to the longitudinal axis of the rotor shaft, with the orientation of the displacement of each of the retaining nodes in a direction close to diametrically opposite, then it should be expected at the nominal rotor speed without excitation of an increase in the skew-symmetric displacement vector of the shaft (thrust bearings).

With this in mind, the use of the proposed method for measuring the eccentricity of the retaining nodes for the diagnosis of the seating interference of the retaining ring on the rotor barrel is recommended to coordinate the diagnostic results with the above indicators of changes in the vibration displacement vectors of the rotor shaft (thrust bearings), and when balancing the rotors, balancing weights should be installed only after eliminating the eccentricity of the retaining ring that arose as a result of a weakening of the interference fit.

Combining these works is quite convenient, since the installation of test weights when balancing the shaft of the rotor of the turbogenerator in its own bearings and diagnostic measurements by the proposed method for assessing changes in seating interference or their insufficiency are carried out in almost the same area near the thrust ring of the retainer assembly.

Sources of information

1. Guide to repair of turbogenerators. / Ed. P.I.Ustinova / M.: Energy. 1978, p. 258.

2. Avrukh V.Yu. and Rostik G.V. Patent for the invention of Russia No. 2145144 "A method for diagnosing the condition of the seating interference of retaining rings on the components of the rotor of an electric machine (options)" 02/09/1999.

Claims (2)

1. A method for diagnosing the interference condition of retaining rings on a rotor barrel of an electric machine containing a rotor barrel with end and end parts, a winding and a thrust ring, including assessing the change in interference at the seat of the retaining ring or its insufficiency by comparatively measuring the linear dimensions in the retaining assembly before starting electric machine in operation, during operation and subsequent scheduled shutdown, characterized in that the change in interference or its insufficiency is produced by the magnitude of the change in excision tricity of the position of the retaining ring in the cross section of its conjugation with the thrust ring by comparative measurements of the difference of the radial gaps between the inner bore of the thrust ring (or the outer cylindrical surface of the retaining ring) and the outer cylindrical surface of the end part of the rotor barrel, and the weakening of the seating interference is found by changing the eccentricity Δε, defined from the expression: Δε = ε _con -ε _nach - (δ $\genfrac{}{}{0ex}{}{\text{one}}{\text{con}}$ -δ $\genfrac{}{}{0ex}{}{\text{eleven}}{\text{con}}$ ) / 2- (δ $\genfrac{}{}{0ex}{}{\text{one}}{\text{beg}}$ -δ $\genfrac{}{}{0ex}{}{\text{eleven}}{\text{beg}}$ ) / 2, where ε _kon and ε _nach are eccentricities, respectively measured during the planned shutdown of the turbogenerator (index “kon”), compared with earlier measurements (index “nach”), mm; δ ¹ and δ ¹¹ are, respectively, the average value of the gaps between the inner bore of the thrust ring (or the outer cylindrical surface of the retaining ring) and the rotor shaft, measured in diametrically opposite places when the rotor shaft is rotated through 180 °. 2. The method according to claim 1, characterized in that it is preceded, accompanied and completed by vibration diagnostics according to indicators characterizing the weakening of the seating interference of the retaining ring on the rotor barrel, including: - growth of the vibration displacement vector of the rotor shaft (thrust bearings) at the first critical speed of rotation - when eccentricity appears on one of the retaining nodes or identically oriented eccentricities on both retaining nodes; - an increase or a significant vector change in the skew-symmetric vibration displacement of the rotor shaft (thrust bearings) of the turbogenerator rotating at a nominal speed without excitation - when eccentricity of retaining elements appears relative to the longitudinal axis of the rotor shaft with the eccentricity of each of them in a direction close to diametrically opposite.

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