Analysis on the Causes of Large Fluctuation of Auxiliary 6kV Busbar Voltage

2021 ◽  
Keyword(s):  
Large Fluctuation

Numerical Simulation on Rupture Behavior and Selection of Safety Membranes

2014 ◽  
Author(s):  
Chen Sheng ◽  
Zhang Jian ◽  
Xiaodong Yu
Keyword(s):  
Present Theory ◽  
Large Fluctuation ◽  
Surge Tank ◽  
Small Hydropower ◽  
Weak Points ◽  
Maximum Water ◽  
Safety Operation ◽  
Hydropower Stations ◽  
Selection Of ◽  
Rupture Behavior

This present study deals with a new mechanical device consisting of a set of safety membranes, which has been successfully applied in several middle and small hydropower stations in China instead of a surge tank. Safety membranes are installed on the penstock near the powerhouse as controlled weak points. When the pressure caused by load rejection rises to the preset explosive value, one or more membranes rupture, protecting the penstock and the unit from damage. The device is simple, reliable and economical. The method of characteristics is employed to establish numerical model of safety membranes to simulate their rupture behavior, which is then introduced to investigate how to determine the number and diameter of membranes from two aspects, large fluctuation and hydraulic disturbance. The results show that the diameter of the membranes depends on the negative pressure along pipeline under hydraulic disturbance while the number of the membrane depends on the maximum water hammer pressure under large fluctuation during load rejection of the unit. The conclusion of membrane selection can perfect the present theory of safety membranes, and provide the theoretical guidance and practical basis for membrane device design and safety operation.

The Instantaneous Efficiency of Epicyclic Gears in Flight Control Systems

2011 ◽  
Vol 133 (5) ◽  
Author(s):  
Anngwo Wang ◽  
Seth Gitnes ◽  
Lotfi El-Bayoumy
Keyword(s):  
Control Systems ◽  
Flight Control ◽  
The Sun ◽  
Large Fluctuation ◽  
Planetary Gears ◽  
Average Efficiency ◽  
Rotary Actuator ◽  
Epicyclic Gear ◽  
Gear Trains

The instantaneous efficiency of an epicyclic gear rotary actuator is an important factor in sizing flight control systems where compound epicyclic gear trains are typically used. The efficiency variation can be smooth or fluctuating depending on the combination and timing of the teeth of ring, planet, and sun gears. In this paper, the instantaneous efficiency characteristics of synchronous and nonsynchronous actuators under forward-driving with opposing load and reverse-driving with aiding load are investigated. The emphasis will be on instantaneous, rather than average efficiency of gears. Several gear arrangements are considered: external and internal gears, simple planetary gears and compound planetary gears. Efficiency will be discussed considering not only the geometry of the mating gears, but also the relative phasing of the planet gears relative to the sun and ring gears. Synchronous compound epicyclic gears are shown to have large fluctuation in their instantaneous efficiency. When reverse-driving efficiency falls below 0%, the unit cannot be back-driven and will chatter. Nonsynchronous compound gears have a smaller variation in instantaneous efficiency. However, extra care must be taken in timing the compound planet gears, as well as clocking position of compound planet gears relative to ring gears and the sun gear.

scholarly journals Effect of Mechanism Error on Input Torque of Scroll Compressor

2013 ◽  
Vol 2013 ◽  
pp. 1-5
Author(s):  
Man Zhao ◽  
Shurong Yu ◽  
Chao Li ◽  
Yang Yu
Keyword(s):  
Adverse Effect ◽  
Rotational Speed ◽  
Fundamental Principle ◽  
Friction Loss ◽  
Machining Accuracy ◽  
Large Fluctuation ◽  
Connecting Rod ◽  
Scroll Compressor ◽  
Calculation Results ◽  
Input Torque

Based on the fundamental principle of plane four-bar mechanism, the force on the equivalent parallel four-bar mechanism was analyzed for scroll compressor with mini-crank antirotation, and the formula of input torque was proposed. The change of input torque caused by the mechanism size error was analyzed and verified with an example. The calculation results show that the mechanism size error will cause large fluctuation in input torque at the drive rod and connecting rod collinear and the fluctuation extreme value increases with rotational speed. Decreasing of the crankshaft eccentricity errors is helpful for reducing the effects of dimension error on input torque but will increase the friction loss of orbiting and fixed scroll wrap. The influence of size error should be considered in design in order to select suitable machining accuracy and reduce the adverse effect caused by size error.

SU-FF-T-91: Unusually Large Fluctuation of Monitor Unit (MU) Efficiency in Large-Field IMRT Plans Using Sliding-Window Technique

2005 ◽  
Vol 32 (6Part7) ◽  
pp. 1970-1970
Author(s):  
H Song ◽  
Z Chen ◽  
Y Fan ◽  
J Deng ◽  
M Ahmad ◽  
...  
Keyword(s):  
Sliding Window ◽  
Large Field ◽  
Monitor Unit ◽  
Large Fluctuation ◽  
Window Technique

General discussion

1990 ◽  
Vol 330 (1615) ◽  
pp. 679-681
Keyword(s):  
Environmental Changes ◽  
Mean Field ◽  
Climatic Changes ◽  
Archaeological Record ◽  
Large Fluctuation ◽  
Axis Of Rotation ◽  
The Mean ◽  
Earth’S Climate ◽  
Newcastle Upon Tyne ◽  
Interesting Analogy

S. K. Runcorn, F. R. S. ( University of Newcastle upon Tyne, U. K. ). In examining whether there is evidence in the records of the Earth’s climate for small variations with periods of about 200 years, the geophysicists suppose that the large fluctuation from year to year (of which we are very conscious) due to the instabilities of the atmosphere-ocean system may average out over long periods so as to reveal shorter-period changes in solar activity. There is an interesting analogy with the Earth’s magnetic field, which varies considerably on a shorter timescale, yet over longer time spans the mean field is exactly that of a dipole aligned along the axis of rotation. Can we tell, from the archaeological record, whether climatic changes, resulting for instance in the migration of peoples, are short lived, or whether they might be produced by longer-term environmental changes?

ANALYSIS OF THE FLOW IN A SEDIMENT BYPASS TUNNEL WITH A LARGE FLUCTUATION IN SEDIMENT LOADING

2004 ◽  
Vol 48 ◽  
pp. 1129-1134
Author(s):  
Akihiko NAKAKAYA ◽  
Yuji OMOTO ◽  
Chihiro YOIDA
Keyword(s):  
Sediment Loading ◽  
Large Fluctuation

Research of Simulation Model for Non-Linear Turbine Regulating System

2011 ◽  
Vol 354-355 ◽  
pp. 569-574 ◽  
Author(s):  
Mei Feng Sun ◽  
Rui Lian Wang ◽  
Jia Wang ◽  
Jing Bin Lu
Keyword(s):  
Mathematical Model ◽  
Simulation Model ◽  
Transition Process ◽  
Hydraulic Turbine ◽  
Large Fluctuation ◽  
Transfer Coefficients ◽  
Operating Condition ◽  
Hydro Turbine ◽  
Governing System ◽  
The Mathematical Model

In the large fluctuation transition process of hydropower unit, hydraulic turbine operating condition changes drastically, following the change, hydraulic-turbine transfer coefficients also change drastically, thus the mathematical model of hydro-turbine governing system is nonlinear. This paper establishes simulation model of large fluctuation transition process in SIMULINK software, puts forward a method of establishing simulation model of nonlinear hydro-turbine governing system.

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