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Hydropower and Floods
Published in Saeid Eslamian, Faezeh Eslamian, Flood Handbook, 2022
Sachin Kumar, Aanchal Singh S. Vardhan, Akanksha Singh S. Vardhan, R. K. Saket, D.P. Kothari, Saeid Eslamian
The generator is the part of a power plant that converts rotary motion provided by a turbine into electrical energy, as shown in Figure 5.21. The machine exploits a phenomenon discovered during the 19th century by the English scientist Michael Faraday; when a conductor moves through a magnetic field, a current is generated in the conductor. The earliest devices of this type were called dynamo-electric machines, named by Werner Siemens, the inventor of the first generator, in 1867. This name was soon shortened to the dynamo. A dynamo is a machine that generates a direct current (DC) from mechanical rotation. Later, machines that could provide an alternating current (AC) were designed because it proved easier to distribute over large distances. These AC devices were originally named alternators, but today they are usually called generators. Some small hydropower plants use devices called asynchronous generators. These are very simple generators, sometimes motors run as generators and cannot provide synchronized power.
D
Published in Philip A. Laplante, Comprehensive Dictionary of Electrical Engineering, 2018
dynamical linear stationary discrete-time finite-dimensional system dynamical linear stationary discrete-time finitedimensional system a system described by the linear difference state equation x(k + 1) = Ax(k) + Bu(k) (1) state space X and has infinite number of eigenvalues each of finite multiplicity. The corresponding eigenfunctions may form the basis in the infinitedimensional state space X . It should be stressed that it is possible to consider other types of linear dynamical systems with delays, namely systems with multiple delays, systems with delays in the control or neutral dynamical systems with delayed derivative. dynamo a term used to describe any of a variety of rotating machines that convert mechanical to electrical energy, or less commonly, electrical to mechanical energy. Dynamos typically consist of a stationary structure, called the stator, supporting a rotating element called the rotor. Energy conversion occurs via Faraday induction. A field winding (or in some smaller machines, permanent magnets) is mounted on one of the mechanical structures and produces a magnetic flux. An armature winding is mounted on the other structure, and rotation of the rotor produces relative motion between the field flux and the coils of an armature winding, inducing a Faraday voltage in the armature coil. This Faraday induced voltage is the source of electrical energy at the dynamo output. dynamometer a rotating device used to measure the steady-state torque and power output of rotating machines. Dynamometers generally provide precise control of the load torque applied to a test machine, and power output is determined through precise speed measurements.
Multiplicity in an optimised kinematic dynamo
Published in Geophysical & Astrophysical Fluid Dynamics, 2022
A kinematic dynamo is the simplest system that allows a self-sustaining magnetic field. In this setup, a seed magnetic field is amplified by an electrically conducting fluid that flows according to a prescribed velocity field and becomes sufficiently strong to overcome Ohmic decay as time ; the backreaction from the generated magnetic field on the flow is ignored (Moffatt 1983). Due to the linearity of the induction equation with respect to the magnetic field , for a given flow, the time evolution of can be treated as a linear eigenvalue problem. The magnetic Reynolds number measures the relative strength of the induction effect to magnetic diffusion. For different flows, the efficiency to generate a dynamo at a specific is ranked by the largest real eigenvalue of , while its imaginary part describes the oscillatory frequency.
Evolution of aligned states within nonlinear dynamos
Published in Geophysical & Astrophysical Fluid Dynamics, 2019
In figure 10, I show the average energy and alignment in the final state for . We see that the average energy decreases as and that the flow and magnetic field remain almost perfectly aligned and at equipartition up until . These simulations show that an aligned and equipartition state can be reached even after the introduction of significant time dependence to the forcing. The addition of circular polarisation to the Archontis dynamo results in a decrease in average energy and eventually distortion of the magnetic field structure. Until the dynamo fails at , the states produced by the dynamo have the flow and magnetic field almost perfectly aligned. The simultaneous failure of the alignment and the dynamo show that, for this particular family of forcings, one cannot exist without the other.
Topology of Rayleigh–Bénard convection and magnetoconvection in plane layer
Published in Geophysical & Astrophysical Fluid Dynamics, 2019
Hari Ponnamma Rani, Yadagiri Rameshwar, Jozef Brestenský
One important simplification of dynamo theory, related to the mechanism of the self-consistent hydromagnetic dynamo, is in the study of rotating convection with an a priori given initial magnetic field. Our rotating magnetoconvection (henceforth RMC) simplification is only in the a priori given magnetic field which can evolve in time to be modified possibly for different values in comparison with initially given value (very small in the self-consistent dynamo or large in the so called magnetoconvection dynamo). However, all non-linearities arising in the momentum, heat and magnetic field equations are considered contrary to linear studies of RMC at the onset. Our RMC can mimic the magnetoconvection dynamo conveniently applied to some moons of Jupiter. Thus, henceforth in the present paper dynamo means the magnetoconvection dynamo as well as the self-consistent dynamo.