Stator modal and vibration test of HEC 600 MW turbine generator

Yao Dakun\ Qudazhuang 2(1. Harbin Institute of Electric Machinery, Harbin 150040, China; 2 Harbin Power Equipment Co., Ltd., Harbin 150040, China) Abstract*: Introduces the stator modal and vibration performance of 600MW turbogenerator manufactured by Harbin Electric Power. Experimental Research. The elliptical intrinsic residual stress of the stator, the vibration amplitude of the stand and the bearing seat, and the vibration isolation system of the stator frame are given, which can be used for 600MW turbo generator operation and the design and manufacture of large turbine generator sets. .

Foreword With the vigorous development of China's electric power industry, the single-capacity children of thermal power units are increasing, and thermal power construction is gradually transitioning to a new situation with domestically-produced 600 MW units. W. This article describes the HEC 600 MW turbine generator manufactured by Harbin Electric. Stator modal and vibration test conditions for 600 MW turbine generator operation and design and manufacture of large turbine generator sets.

During the operation of the turbo-generator, the stator will be subjected to the magnetic pull of the rotor to generate a forced vibration with twice the system frequency. For a generator with a system frequency of 50 Hz, this excitation frequency is 100 Hz and is elliptically distributed in the circumferential direction. . If the natural frequency of the stator elliptical mode is equal to or close to 1Hz, the machine base may resonate, resulting in great vibration, affecting the normal operation of the unit, or even accidents.

We obtained the experimental modal parameters of the stator of the HEC 600 MW turbogenerator by experiments, and examined the dynamic characteristics of the stator, and corrected the finite element calculation method.

Whether the design of the unit is reasonable or not is ultimately assessed through on-site operation. On-site vibration measurement and analysis are the ultimate criteria for assessing mechanical performance. Through type testing, we simulated various stress conditions actually operated on the site, and conducted tests and analysis to predict the vibration conditions of the power plant. Because the in-plant test vibration estimation is conservative, the type test is sufficient to represent the operation status of the power plant.

The vertical spring plate is used for vibration isolation between the stator core and the base of the HEC600MW turbine generator, and its vibration isolation effect is directly related to the life and normal operation of the base. The vertical spring plate structure is different from the conventional horizontal elastic positioning bars, and the measured vibration isolation coefficient of the spring plate is determined through actual measurement to ensure the safe operation of the unit. At the same time, it is provided for the design and calculation of the vibration isolation structure of the larger capacity unit in the future.

1 Unit main parameters Maximum continuous output 654 MW Rated power factor 0.9 2 Research content 2.1 Transverse test The stator modal test is performed on the assembly test platform, which is exactly the same with the unit in the running state of the power plant. The modal parameters of the test reflect the actual operation of the unit. Dynamic characteristics.

2.2 Iron core, machine base, bearing seat The vibration of the vibration measuring base and bearing seat is required by the national standard, and it is also the monitoring parameter of power plant operation. We strictly perform the vibration test and analysis of the stand in accordance with national standards and factory standards.

2.3 Vibration isolation coefficient of spring plate The type of vibration test of the stator core and frame is used to determine the vibration isolation coefficient of the spring plate.

3 Test Methods and Principles 3.1 Stator Transverse Test This test uses a hammer test method. The hammer is used to carry out vibration on the stator frame, and the excitation force and acceleration response are measured simultaneously. The force signal and response signal are recorded by the tape drive and then sent to the person. The structural dynamic analyzer performs Fourier transform on the force signal and the response signal to obtain the frequency response function of each point, and the modal parameters of the system are obtained after the frequency response function is fitted to the curve.

When the system motion differential equation only discusses the viscous damping, the transfer function of the displacement X(/) external force F(/) is W? The transfer function force represents a unit external force acting at the y point, and the response caused at point i. The resulting expression shows that the denominator of the transfer function obtained is the same at any point in the machine. Because it is not related to the excitation point, it is only related to the frequency and damping ratio. The molecules are related to the modal values ​​of modal stiffness, mass, excitation and response points. Therefore, the natural frequency and damping ratio can be obtained by using one transfer function; in order to find the vibration mode, one row or one column of the transfer function matrix is ​​required.

From Equation (4), we can see that in order to obtain the transfer function between the heart points, only the excitation force (single-point excitation) is measured at the y-point, and the response of the point can be found by the definition of the vibration mode. It can be seen that it is not an absolute quantity (referring to a unit), but only represents the relative relationship between the points and is a dimensionless quantity.

Therefore, it is usually regularized at a reference point (a diagonal component in the transfer function matrix) to be a. The value itself is a relative amount. If we now use a) regularization with a reference point of 1, when the reference point is /, the transfer function for Z measurement can be obtained by I...|. 1, then we can obtain another generation transfer function, The vibration mode can be calculated by multiplying all the components of the transfer function matrix to obtain the dynamic characteristics of the mechanical object.

When measuring a row, the response point is fixed at /, and the excitation point is moved from 1 to m. Conversely, when measuring a column, fixing the excitation point and moving the response point in turn can also be obtained. Vibration mode.

3.2 Vibration measurement (3) Acquire the vibration signal of the measured part with an acceleration, velocity or displacement sensor, pass a preamplifier into a tape drive or a digital vector filter, and perform spectrum analysis with a dynamic signal analyzer.

In general, the vibration signal can be written as the rate of steady-state acceleration; the second is the ith harmonic amplitude; a, the third harmonic phase angle.

Performs two integrations of equation (5) to obtain the signal corresponding to the displacement. In the unit operation, the base is mainly affected by 50Hz power frequency interference and 100Hz frequency multiplication interference. The other harmonic vibration amplitude is very small. Can be ignored. Therefore, the main research frequency of 50 and 100Hz vibration, through the frequency spectrum analysis obtained 50Hz and 100Hz acceleration vibration amplitude, by the formula (6) obtained at the corresponding frequency displacement amplitude. Or, the collected acceleration signal can be directly integrated numerically to obtain the vibration displacement; the integration can also be accomplished with a charge amplifier with two integrations.

3.3 Spring plate vibration isolation coefficient The spring plate is an elastic element that connects the iron core and the base. Its function is to reduce the vibration and weaken the vibration of the iron core on the base. Because the iron core is mainly oscillated by 100 Hz electromagnetic force, the spring plate mainly isolates the 100 Hz vibration of the iron core, and the vibration isolation effect is determined by the vibration isolation coefficient K.

The 100Hz amplitude of the iron core is measured by the single-point excitation method of the hammer test by the modal test of the formula (4). The 24 points of the stator frame are arranged along the circumference of the axial center to measure the response. The excitation point is selected at the top of the circle.

The vibration test point arrangement is as shown respectively.

5 Analysis of test results The natural frequency of the elliptical mode shape of the stator obtained by modal fitting is 123 Hz. The natural frequency of the elliptical mode is avoided to avoid the requirement of electromagnetic frequency of 10%.

As can be seen from the vibration amplitude and frequency of the stand in Table 1, when the no-load and steady-state short-circuit conditions, the maximum amplitude of the pass-through frequency of the measuring point No. 11 on the base is 21.5jun, and the maximum amplitude of the measuring point No. 2 is 7jun, which meets the design. Claim. Other measuring points have smaller amplitude.

Table 2 shows the vibration amplitude of the bearing seat. The vibration of the excitation bearing seat is slightly larger than that of the steam end. The amplitude of the horizontal direction of the bearing is 8 and 21 jun, respectively, which are lower than the national standard 30 jun and also lower than the standard of excellence of the company. The maximum amplitude of axial vibration is 17jun, which is far below the national standard. 38 It can be known from the radial vibration of table 3 and base. In the rated no-load conditions, the average amplitude of 100Hz amplitude of two cores is 18.5jim. The average amplitude of the 100 Hz amplitude of the four measuring points is 2.2 jtm, and the vibration isolation coefficient of the elastic positioning ribs is 8.4. 6 Summary The natural frequency of the elliptical modal stator coil of the HEC 600MW turbo-generator stator is 123 Hz, avoiding 100 Hz electromagnetic force frequency enough. Far, indicating that the power design of the unit is reasonable, the unit will not generate large vibration when the unit is running.

The amplitude of stator vibration of HEC600MW turbine generator fully complies with national standards, which can ensure the long-term safe operation of the unit.

The test method of stator modal and vibration performance of turbo-generator described in this paper is applicable to the evaluation and evaluation of generator vibration performance by new type test and field test.

Table 1 Sets the condition of peak amplitude and enthalpy rate of the air-conditioning and dead-line road conditions. No-load steady-state short-circuit condition l./N é“Ž rate through-pass frequency table 2 Rated speed conditions, stand and bearing seat vibration value And frequency pm steam end bearing seat excitation end bearing seat horizontally and vertically axially straightened axially Table 3 rated no-load working conditions, core, frame radial vibration 100Hz peak-to-peak Cheng Zhaochang. Mechanical vibration. Beijing: Mechanical Industry Press, 1982. Frame Core

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