Transient Torsional Vibration of Steam Turbine and Generator Shafts due to High Speed Reclosing of Electric Power Lines

1976 ◽  
Vol 98 (3) ◽  
pp. 968-979 ◽  
Author(s):  
A. Hizume
Keyword(s):  
Electric Power ◽  
Steam Turbine ◽  
Torsional Vibration ◽  
High Speed ◽  
Elastic Limit ◽  
Power Lines ◽  
Transient Vibration ◽  
First Approximation ◽  
Three Phase ◽  
Large Response

Transient torsional vibration induced on modern large turbine and generator shafts by high-speed reclosing is investigated qualitatively and quantitatively, assuming linearity and no damping as the first approximation. The effect of repeated impositions is analyzed both for sinusoidal torque fluctuation and for stepwise torque fluctuation. It is shown that the danger of high-speed reclosing is attributable to repetitive imposition (as many as four times); furthermore, the severity of transient vibration is decisively influenced by the timing of repeated impositions. The effect of three-phase high-speed reclosing on a typical 600MW machine is calculated both by computer and by modal analysis. The large response predicted, which is far beyond the elastic limit, is possible to be induced under actually feasible timing. Absolutely safe three-phase high-speed reclosing could not be achieved by strengthening the shaft because the strengthened shaft becomes sensitive to sinusoidal torque fluctuation.

A Simple Inverter-Motor System to Improve Energy Consumption and Maximum Torque

2012 ◽  
Author(s):  
Tohru Watanabe ◽  
Yukishige Fujita ◽  
Mikio Totani
Keyword(s):  
Energy Consumption ◽  
High Speed ◽  
Motor System ◽  
Power Lines ◽  
Maximum Torque ◽  
Coil Current ◽  
Ac Motor ◽  
Three Phase ◽  
Constant Strength ◽  
Precise Constant

A new inverter-AC motor system having four power source lines, which can control each coil current independently, is compared to an ordinary inverter-AC motor system using a Y-type coil connection and three power lines. In this paper, three-phase rectangular-type currents are generated by the inverter made of simple ICs. In a previous paper[1], similar comparison experiments were executed using a high-speed DSP board. The board can calculate the three-phase currents to generate a rotating, resultant, magnetic flux with a precise constant strength and phase. It was verified by experiments that an energy consumption of 15% can be saved by using the proposed independent, motor-coil currents. However, it requires high speed and high cost DSP or CPU. In this paper, it is verified by using a new inverter-AC motor system that an energy consumption of 15% can be saved, and also the maximum torque increases 10%.

Direct Current Deadbeat Predictive Controller for BLDC Motor Using Single DC-Link Current Sensor

2020 ◽  
Vol 38 (8A) ◽  
pp. 1187-1199
Author(s):  
Qaed M. Ali ◽  
Mohammed M. Ezzalden
Keyword(s):  
Control System ◽  
High Speed ◽  
Fast Response ◽  
Bldc Motor ◽  
Current Controller ◽  
Three Phase ◽  
Predictive Controller ◽  
Two Phases ◽  
Dc Current ◽  
Three Phase Inverter

BLDC motors are characterized by electronic commutation, which is performed by using an electric three-phase inverter. The direct control system of the BLDC motor consists of double loops; including the inner-loop for current regulating and outer-loop for speed control. The operation of the current controller requires feedback of motor currents; the conventional current controller uses two current sensors on the ac side of the inverter to measure the currents of two phases, while the third current would be accordingly calculated. These two sensors should have the same characteristics, to achieve balanced current measurements. It should be noted that the sensitivity of these sensors changes with time. In the case of one sensor fails, both of them must be replaced. To overcome this problem, it is preferable to use one sensor instead of two. The proposed control system is based on a deadbeat predictive controller, which is used to regulate the DC current of the BLDC motor. Such a controller can be considered as digital controller mode, which has fast response, high precision and can be easily implemented with microprocessor. The proposed control system has been simulated using Matlab software, and the system is tested at a different operating condition such as low speed and high speed.

scholarly journals Optimization of Air Gap Length and Capacitive Auxiliary Winding in Three-Phase Induction Motors Based on a Genetic Algorithm

Energies ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4407
Author(s):  
Mbika Muteba
Keyword(s):  
Genetic Algorithm ◽  
Design Process ◽  
Power Factor ◽  
High Speed ◽  
High Efficiency ◽  
Air Gap ◽  
Element Analysis ◽  
Three Phase ◽  
High Torque ◽  
Cage Induction Motor

There is a necessity to design a three-phase squirrel cage induction motor (SCIM) for high-speed applications with a larger air gap length in order to limit the distortion of air gap flux density, the thermal expansion of stator and rotor teeth, centrifugal forces, and the magnetic pull. To that effect, a larger air gap length lowers the power factor, efficiency, and torque density of a three-phase SCIM. This should inform motor design engineers to take special care during the design process of a three-phase SCIM by selecting an air gap length that will provide optimal performance. This paper presents an approach that would assist with the selection of an optimal air gap length (OAL) and optimal capacitive auxiliary stator winding (OCASW) configuration for a high torque per ampere (TPA) three-phase SCIM. A genetic algorithm (GA) assisted by finite element analysis (FEA) is used in the design process to determine the OAL and OCASW required to obtain a high torque per ampere without compromising the merit of achieving an excellent power factor and high efficiency for a three-phase SCIM. The performance of the optimized three-phase SCIM is compared to unoptimized machines. The results obtained from FEA are validated through experimental measurements. Owing to the penalty functions related to the value of objective and constraint functions introduced in the genetic algorithm model, both the FEA and experimental results provide evidence that an enhanced torque per ampere three-phase SCIM can be realized for a large OAL and OCASW with high efficiency and an excellent power factor in different working conditions.

Power Flow Calculation Realization in Software for Grids with Four-Phase Power Lines

2014 ◽  
Vol 698 ◽  
pp. 694-698 ◽  
Author(s):  
Dmitry I. Bliznyuk ◽  
Pavel Y. Bannykh ◽  
Alexandra I. Khalyasmaa
Keyword(s):  
Steady State ◽  
Power Flow ◽  
Calculation Model ◽  
Power Lines ◽  
Power Flow Calculation ◽  
Steady State Analysis ◽  
Flow Calculation ◽  
Analysis Methods ◽  
Electrical Grids ◽  
Three Phase

The paper is devoted to the problem of power flow calculation and steady state analysis methods adaptation for four-phase electrical grids. These methods are based on developed models of four-phase power lines and phase convering transformers. The basis of research is nodal voltages equations for three-phase, four-phase and mixed (combined by three-and four-phase elements) grids. Algorithm of four-phfase elements parameters automized adaptation for power flow calculation model of "RastrWin" software have been developed.

Paper 23: The Collision of Drops with Dry and Wet Surfaces in an Air Atmosphere

1969 ◽  
Vol 184 (7) ◽  
pp. 57-63
Author(s):  
G. J. Parker ◽  
E. Bruen
Keyword(s):  
Steam Turbine ◽  
High Speed ◽  
Size Range ◽  
Drop Surface ◽  
Wet Steam ◽  
Air Atmosphere ◽  
Made In

This paper describes an investigation into the behaviour of drops which impinge upon dry and wet surfaces. This is of particular interest in the context of the wet steam turbine. Two approaches have been made in the studies; these are: (1) Drops were made to impinge normally on to various types of dry, stationary surfaces. The drops were in the size range 300–1500 μm diameter with velocities of 2–9 m/s. (2) Drops were made to impinge on to surfaces moving with considerable velocity at right angles to the motion of the drop. Surface velocities ranged up to 45 m/s. The latter study is of direct interest for the splashing of drops on turbine casings at small glancing angles, as occurs near drainage belts. Analysis of the mechanisms involved is made from the records of high-speed ciné photography.

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