Calculation method for stress and strain of magnetic pole lead of hydro-generator

Abstract

The invention relates to the technical field of hydro-generators, and particularly discloses a hydro-generator magnetic pole lead stress-strain calculation method, which comprises the following steps of: 1, selecting half of a single magnetic pole in the height direction of the magnetic pole as a simulation object and a geometric model according to the geometric structure of a generator rotor and the periodic symmetry of a load; 2, applying a rotation speed to the global overall rectangular coordinate system, and applying a corresponding pre-tightening force to a fastening bolt of the magnetic pole lead seat; according to the method, the influence of peripheral parts of the magnetic pole lead on the magnetic pole lead, especially the huge influence of tangential overturning and axial lifting of the magnetic pole lead caused by tangential and axial small deformation of a magnetic pole yoke and a coil, on the magnetic pole lead is fully considered, and the real stress-strain state of the magnetic pole lead can be quickly simulated at the initial stage of design; the calculation precision is improved, the design period is shortened, the stress-strain state of the magnetic pole lead is accurately calculated, and safe, stable and reliable operation of the water-turbine generator set is ensured.

Description

Technical Field

[0001] The present invention belongs to the technical field of hydro-generators, and particularly relates to a calculation method for the stress and strain of the pole leads of a hydro-generator. Background Art

[0002] A hydro-generator is an energy conversion device that converts the potential energy and kinetic energy of water into electrical energy. With the increasing unit capacity, gradually increasing speed, and gradually increasing radial size of the unit, this series of increases in production and efficiency directly leads to a very large radial size of the peripheral components of the generator. The pole leads are located on the outer diameter side of the generator rotor components, and the material is copper. Copper has excellent electrical conductivity and thermal conductivity, excellent ductility and plastic forming ability, is easy to process, is also corrosion-resistant and has stable chemical properties, making it the best choice for pole lead materials. However, the mechanical properties of copper are poor, the tensile strength is very low, only two or three hundred megapascals, and there is no obvious yield strength. Due to the increase in the unit speed and diameter, the linear velocity of the pole leads reaches extremely high values, easily generating high stress on the pole leads and causing fractures. With the accumulation of operation time, many accidents have occurred to the pole leads, bringing great economic losses to the owners.

[0003] The current calculation method for pole leads overly simplifies the actual complex structure, only considering the pole leads within the minimum geometric period range, and not considering the influence of the deformation of the pole yoke itself on the pole leads. This overly simplified method only considers the main pure radial deformation of the pole leads, ignoring the tangential flipping and axial lifting of the leads, resulting in a smaller numerical value of the stress and strain of the pole leads obtained by simulation.

[0004] The present invention mainly solves the deficiencies of the existing simulation method for the pole leads of the generator rotor, comprehensively considers the displacement constraint effect generated by the deformation of surrounding components such as poles, yokes, and coils on the pole leads, can reflect the comprehensive effect of the pole leads under their own centrifugal force and the displacement constraints of surrounding components, and truly reflects the stress and deformation conditions of the pole leads under various working conditions, thereby providing important verification and optimization guidance for the design.

[0005] Therefore, how to effectively estimate the true stress and strain state of the pole leads of the generator rotor during the design stage of the unit and estimate the number of life cycles during which it can operate safely has become an urgent issue to be solved. It is necessary to adopt a method that is more in line with the actual state to calculate the stress and strain state of the pole leads, thereby providing important verification and optimization guidance for the design. Therefore, a calculation method for the stress and strain of the pole leads of a hydro-generator is proposed. Summary of the Invention

[0006] The purpose of the present invention is to provide a calculation method for the stress and strain of the pole leads of a hydro-generator to solve the problems raised in the above background art.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] A calculation method for the stress and strain of the pole lead of a hydrogenerator, comprising the following steps:

[0009] Step 1: According to the geometric structure of the generator rotor and the periodic symmetry of the load, select half of a single pole in the pole height direction as the simulation object and the geometric model;

[0010] Step 2: Apply the rotational speed in the global overall rectangular coordinate system, apply the corresponding pre-tightening force to the fastening bolts of the pole lead seat, and apply the magnetic pulling force on the iron core, ignoring the influence of torque;

[0011] Step 3: Use the large general finite element simulation software ANSYS for calculation, which can accelerate convergence and improve the calculation accuracy. Set multiple sub-steps in the analysis settings, consider the geometric large deformation non-linearity, consider the weak spring, use the direct solution method, which can reduce the computer time, and allocate more computer cores for a single analysis task;

[0012] Step 4: View the calculation results, determine the overall deformation diagram of the generator rotor and the deformation diagrams of the three components of X, Y, and Z, and focus on determining the radial deformation, tangential deformation, axial deformation, equivalent stress, and equivalent strain of the pole lead.

[0013] Preferably, the geometric model includes a pole lead, a lead seat and fastening bolts, a pole iron core, a pole end plate, a yoke, a coil, a side plate, an insulating plate, a hoop, and an iron flange. The friction coefficient between each component is 0.1-0.15, which can establish an accurate contact relationship between complex components, especially establish a frictionless contact between the coil and the surrounding components to simulate the circumferential expansion of the coil.

[0014] Preferably, there is a frictionless contact between the coil and the surrounding components.

[0015] Preferably, multiple sub-steps are set in the analysis settings, the direct solution method is used, and more computer cores are allocated for a single analysis task.

[0016] Preferably, the hoop is welded on the iron core and the iron flange. ]>

[0017] Compared with the prior art, the beneficial effects of the present invention are:

[0018] The present invention fully considers the influence of the components around the pole lead on the pole lead. In particular, the small tangential and axial deformations of the pole yoke and the coil have a huge impact on the tangential flipping and axial lifting of the pole lead. It can quickly simulate the true stress and strain state of the pole lead in the initial design stage, improve the calculation accuracy, shorten the design cycle, accurately calculate the stress and strain state of the pole lead, and ensure the safe, stable and reliable operation of the hydro-generator set. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a structural diagram of the present invention;

[0020] Figure 2 is a stress wire diagram of the hydro-generator of the present invention.

[0021] In the figure: 1, yoke; 2, lead seat; 3, fastening bolt; 4, coil; 5, iron flange; 6, insulating plate; 7, pole end plate; 8, pole core; 9, hoop. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0023] Step 1: According to the geometric structure and periodic symmetry of the generator rotor, half of a single pole in the pole height direction is selected as the simulation object and geometric model. The geometric model includes the pole lead, lead seat 2 and fastening bolt 3, pole core 8, pole end plate 7, yoke 1, coil 4, side plate, insulating plate 6, hoop 9 and iron flange 5. Contact relationships are established between the mutually contacting components, and the friction coefficient between each component is 0.1 - 0.15, and the friction coefficient between the coil 4 and the surrounding components is 0. The hoop 9 is welded to the iron core and the iron flange 5;

[0024] Furthermore, contact nonlinearity is fully considered here, and symmetric constraints are applied on each cross-section to simulate the characteristics of the entire rotor. Corresponding material properties are assigned to each component, especially copper materials and insulating materials, and anisotropic material properties are assigned to the iron core material, fully considering its elastic properties in three directions, because radial deformation, tangential deformation and axial deformation all have a huge impact on the pole lead;

[0025] Furthermore, material nonlinearity is fully considered here. High-order solid elements are selected to divide the mesh, and corresponding element sizes are assigned to the overall components. In particular, a finer mesh size is assigned to the pole leads because stress is very sensitive to the mesh. A finer mesh can obtain more accurate stress calculation results, and the mesh independence is considered.

[0026] Step 2: Apply the rotational speed in the global rectangular coordinate system, apply the corresponding pre-tightening force to the fastening bolts 3 of the pole lead base, and apply the magnetic tensile force on the iron core, ignoring the influence of torque.

[0027] Step 3: Use the large general-purpose finite element simulation software ANSYS for calculation, which can accelerate convergence and improve calculation accuracy. Set multiple sub-steps in the analysis settings, consider large geometric deformations, consider weak springs, use the direct solution method, and allocate more computer cores for a single analysis task.

[0028] Step 4: Check the calculation results, determine the overall deformation diagram of the generator rotor, the deformation diagrams of the three XYZ components, and particularly determine the radial deformation, tangential deformation, axial deformation and other equivalent stresses and equivalent strains of the pole leads.

[0029] After calculation, the vast majority of the displacement components of the generator rotor model are radial. Compared with the radial deformation, there are also tangential and axial components. As the size of the unit increases and the linear velocity at the outer lead of the rotor increases, the proportion of the tangential and axial displacement components will also become larger and larger, and the influence on the pole leads will also be greater. Therefore, when calculating the pole leads, we cannot only consider the leads themselves and thus ignore the influence of the deformation of the pole yoke 1 and the coil 4 on the leads. After calculation, it can be seen that the stress level of the pole leads is very high, resulting in a large strain.

[0030] In summary, the present invention fully considers the influence of the components around the pole leads on the pole leads, especially the huge influence of the small tangential and axial deformations of the pole yoke 1 and the coil 4 on the tangential flipping and axial lifting of the pole leads. It can quickly simulate the true stress and strain state of the pole leads at the initial design stage, improve the calculation accuracy, shorten the design cycle, accurately calculate the stress and strain state of the pole leads, and ensure the safe, stable and reliable operation of the hydro-generator unit.

[0031] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A calculation method for the stress and strain of the pole lead of a hydrogenerator, characterized in that It includes the following steps: Step 1: According to the geometric structure of the generator rotor and the periodic symmetry of the load, select half of a single pole in the pole height direction as the simulation object and geometric model; Step 2: Apply a rotational speed in the global overall rectangular coordinate system, apply a corresponding pre-tightening force to the clamping bolts 3 of the pole leads, and apply a magnetic tensile force on the iron core to ignore the influence of torque; Step 3: Use the large general-purpose finite element simulation software ANSYS for calculation, which can accelerate convergence and improve calculation accuracy, set multiple sub-steps in the analysis settings, use the direct solution method, can reduce the computer time, and allocate more computer cores for a single analysis task; Step 4: View the calculation results to determine the overall deformation diagram of the generator rotor and the deformation diagrams of the three XYZ components.

2. The calculation method of the stress and strain of the pole lead of a hydrogenerator according to claim 1, characterized in that: The geometric model includes pole leads, lead seats (2) and clamping bolts (3), pole iron cores (8), magnetic end plates (7), yokes (1), coils (4), side plates, insulating plates (6), hoops (9) and iron flanges (5), and the friction coefficient between each component is 0.1 - 0.

15.

3. A calculation method for the stress and strain of the pole lead of a hydrogenerator according to claim 2, characterized in that: There is a frictionless contact between the coil (4) and the surrounding components.

4. A calculation method for the stress and strain of the pole lead of a hydrogenerator according to claim 1, characterized in that: Multiple sub-steps are set in the analysis settings.

5. The calculation method of the stress and strain of the pole lead of a hydrogenerator according to claim 2, characterized in that: The hoop (9) is welded to the iron core and the iron flange (5).

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