Calculation of unbalanced electromagnetic force of a hydro-generating unit
Calculation of Unbalanced Electromagnetic Force of a Hydro-generating Unit in a Journal of Tangshan College Chen Zhengqing Department of Fundamental Research, Tangshan Shang School, Tangshan 063000, Hebei Unbalanced electromagnetic enthalpy and electromagnetic degree were calculated and solved. Practical question on engineering.
The class number. 39 Unbalanced electromagnetic force, also known as unilateral electromagnetic force, results from the electromagnetic action of a generator. It can greatly reduce the dynamic natural frequency of the shaft system, intensify the vibration of the shaft system, and affect the quality of power generation. Because the rotor inevitably has eccentricity, the unbalanced electromagnetic force and the eccentricity are equal to each other. Therefore, the balance electromagnetic force intensifies the eccentricity. As a result, historical hazards will occur. Flashing this, the heart must fully analyze and calculate the balance of the magnetic force in order to achieve control and reduce its purpose.
The unique feature of the transfer of a hydroelectric generator is that all its poles are barely hung on the yoke, which brings certain difficulties to the calculation of the rotor magnetic potential and other related calculations. In this paper, for the rotor and stator calculations of the hydroelectric generating units in the strong stream in Hunan Province, the mathematical expressions of the rotor magnetic potential of the stator magnetic field and the magnetic field energy of the generator air gap under the symmetric steady-state operating conditions are obtained, and the energy is then vibrated. Eccentric displacement seeks partial guidance to obtain unbalanced electromagnetic force and electromagnetic stiffness. In order to obtain the air gap magnetic field energy, it is necessary to first obtain the stator rotor's magnetic potential and air gap permeability. Solve sequentially below.
1 Calculation of the stator rotor's magnetic potential and air-gap permeability The circumstantial hunger of the stator rotor is set to be a double-layer wave winding, and 4 winding-path connections are made. The phase-angle voltage of the winding machine is on a circle of ten circles. The phase sequence distribution is completely symmetrical and the number of stator slots is 720. 1 Because the number of phases is 3, the rotor of the generator has 88 poles, so the number of slots per phase per pole is 24. The windings with a fraction of each pole per phase rather than an integer are called fractional slot windings. The large-capacity, low-speed water turbine generating units all use fractional-slot winding. The advantages of this method are that they can reduce the utilization of the effective material for niobium in the middle of the slot insulation, reduce the volume and weight of the motor, and reduce the manufacturing cost; and weaken the harmonic and magnetic density. The induced harmonic potential makes the potential waveform close to the claw string shape.
1. Calculation of stator single-phase winding magnetic potential Because the unit stator has 720 slots and the rotor pole pair number is 44, the greatest common divisor is 4. According to literature 2, the entire stator slot can be divided into 4 units. The unit occupies 180 slots. Using 180 slots as the dragon cycle, the Fourier series expansion of the magnetic potential of the stator single-phase winding is calculated as 1 stator winding composite magnetic potential. The final result of the phase winding composite magnetic potential is the stator current rms value.
13 Rotor Asynchronous Harmonic Analysis Turn 88 poles evenly on the magnetic pole. In the harmonic analysis of the magnetic field of the rotor, 1 the magnetic pole is expanded in the circumferential direction, and the rotating magnetic potential is every two magnetic poles. In a period of 2 cycles, the rotor magnetic potential is 71 and the excitation current is 17 as the number of turns of the field winding is the electrical angle.
Pilot air gap magnetic permeability type Considering both the salient pole and the eccentricity when the air gap is magnetically guided The following formula 2 Air gap magnetic field energy and unbalanced electromagnetic force calculation In front of the rotor magnetic potential and air gap permeability, are based on static The state is counted separately by the rotor to be small to rotate the rotor magnetic potential. The fundamental phase should lead the stator magnetic potential fundamental phase 729 + electrical angle, where 0 is the power angle, 1 power factor angle, so it should be the front of the 1 Escape the proper replacement with stationary logbook as a reference system.
The rotor magnetic potential in Roundup 3 is to be replaced by Yushimu. Let 19+ be calculated to obtain the FjTCicos air gap permeability.
The formula for calculating the air gap magnetic field energy is 1 in the equation above, where sky is the average radius of the rotor and 1 is the effective length of the rotor as the number of pole pairs. To delete some minor high-order minor terms, the calculation can be obtained through a complex calculation, can be obtained in the rated operating state, into the relevant data, which can be obtained through the calculation, the heart 6.7 = for the rotor shape in the two mutual The amount of vibration in the vertical direction.
Here, the generalized average air gap length. Because the length of the air gap between the rotor and the stator of the salient pole is convex and concave, a generalized average of 6 must first be calculated when using 9 to perform the calculation. The calculation process is as follows.
It is known that the circumferential length of each magnetic pole on the outer circle of the rotor is 0.4381. The circumferential length occupied between the two magnetic poles is 0.154, the maximum gap length between each magnetic pole and the stator is 03, and the minimum air gap length is 03. For 0.02, the average is 0.0251. The length of the four-gap gap between the two magnetic poles is 0.34, but considering that the field winding has a certain space, the actual air gap length can be taken as half of the design air gap length 0.171. . According to the formula, the unbalanced electromagnetic force can be calculated in terms of 1 and 7. The projection in the 7 direction is =6.272, which is the generalized mean air gap.
Using the above formula, when given the eccentricity of the vibration, 7 the unbalanced electromagnetic force is easily solved. For example, engineering regulations stipulate that vibration eccentricity must not be exceeded. Small air gap 1 is said, that is, 2 is the theoretical ten calculation method. It should be taken into account if it is equal to the eccentric mass of additional ton.
The electromagnetic stiffness is defined as the coefficient of the electromagnetic force up to the sub-term in the formula 10, which has the magnetic stiffness and the supporting stiffness of the upper guide bearing. , 1 and the lower bearing bearing stiffness 1.66 into the close. Since this electromagnetic constraint will have a greater impact on the dynamic frequency of the shafting treatment, it can reduce the dynamic natural frequency 4 and it can reduce the dynamic natural frequency 35.3. Several conclusions and suggestions 1. This article gives a simple and easy solution The new method for the electromagnetic force of a hydroelectric generating set can also be obtained by this method.
The resonance stiffness of the two-man rejection waterwheel generator sets will make the dynamic solid-frequency production of the shaft system less colorful than that of humans. After paying the hunger adjustment of this model machine, it can reduce the dynamic paleo frequency 3 pairs. 3. In order to reduce the unbalanced electromagnetic force, the vibration eccentricity and the length of the air gap can be appropriately reduced.
Wang Yihan and so on. Qiangxi Hydropower Station Electromechanical Design. Hydroelectric power, 1994, 5963.
Bai Yannian. Hydrogenerator design and metering 1. Beijing Machinery Industry Press. 198 Niu Xiuyan. Motor elbow. Beijing Metallurgical Industry Press, 1990.169195.
Chen Guiqing. Research on Nonlinear Vibration of Bending and Torsion Excited by Electromagnetic Parameters for Large Hydrogenerator Rotor Shaft Systems
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