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Hydropower
Published in Robert Ehrlich, Harold A. Geller, John R. Cressman, Renewable Energy, 2023
Robert Ehrlich, Harold A. Geller, John R. Cressman
The rotational speeds of hydro turbines tend to be lower than either those of gas or steam turbines, typically being in the range of 60–720 revolutions per minute (rpm), although it is not unusual to have them as high as 1,500 rpm. Recall that the frequency of AC is 60 Hz (in the United States) and 50 Hz (in Europe). Thus, if the hydro turbine is being used to power a generator that produces electricity for the power grid, too low a turbine speed can be a major problem. You might think that a generator producing electricity having a 60 Hz frequency would need to be spinning at 60 revolutions/s = 3,600 rpm, but that assumes that the coil in the generator has just two magnetic poles. If many magnets are used (having a total of p poles), the coil could spin at a slower speed of 7,200/p rpm. However, a generator that is powered by a turbine spinning at only 60 rpm would be problematic since it would need an extremely large number of magnetic poles (120) in order to produce 60 Hz AC.
Wireless Topology for EV Battery Charging
Published in L. Ashok Kumar, S. Albert Alexander, Power Converters for Electric Vehicles, 2020
L. Ashok Kumar, S. Albert Alexander
In an AC-to-DC converter, electric power is transported on wires either as DC flowing in one direction at non-oscillating constant voltage or as an AC flowing backward and forward due to oscillating voltage. AC is the dominant method of transporting power because it offers several advantages over DC, including lower distribution costs and easier conversion among different voltage levels, to the invention of a transformer. AC power that is sent at high voltage over long distances and then converted to a lower voltage is a more efficient and safer source of power in homes. Depending on the location, high voltage can range from 4 up to 765 kV. As a reminder, AC mains in homes range from 110 to 250 V, depending on which part of the world you live it. In the United States, the typical AC main line is 120 V.
Quantum Signals at Microwave Devices
Published in Maged Marghany, Automatic Detection Algorithms of Oil Spill in Radar Images, 2019
where N is numerous of sequence modes s = (n1μ1; n2μ2;……; nNμN) of photon occupancy configuration, and vac stands for “volts of alternating current”. In this view, the Alternating Current (AC) is an electric current which periodically reverses direction. In contrast to Direct Current (DC), which flows only in one direction. The abbreviations AC and DC are often used to mean simply alternating and direct, as when they modify current or voltage. It can be said that the most general wave function of the field of the transmission line(s) is a superposition of all field photon configurations in all the spatiotemporal modes of the lines [38,43]: () |Ψ〉=∑sCs|Ψs〉
Computational-Experimental Framework for Realizing a Novel Apparatus for Supercritical Water by Induction Heating
Published in Heat Transfer Engineering, 2023
Alessandro Montanaro, Luigi Allocca, Stefano Ranieri, Carlo Beatrice
IH consists in inducing electric currents (i.e., eddy currents) in a material to be heated, hereinafter referred to as “workpiece,” placed inside a multiturn coil (hereinafter “induction coil,” or simply “coil”). When an alternating frequency voltage is applied to an induction coil, an AC will begin to flow in the coil circuit, generating a time-varying magnetic field in its surroundings, characterized by the same frequency as the current in the coil (Ampere’s law). As stated by Faraday’s law, this variable magnetic field induces, in turn, eddy currents in the workpiece with the same frequency and opposite direction to the coil current, as shown in Figure 8. When eddy currents flow into the workpiece, the electric power is dissipated due to the Joule effect, producing the heating of the workpiece itself.
Efficiency and Cost Based Multi-optimization and Thermal/Electromagnetic Analyses of 3-Phase Dry-Type Transformer
Published in IETE Journal of Research, 2022
Burak Esenboga, Tugce Demirdelen
In an electric power system, electric energy is converted from one form to another such as converting between the alternating current (AC) to direct current (DC) or changing current, voltage or frequency. Transformers are such devices that convert one AC voltage to another AC voltage level while providing some electrical isolation. They are indispensable components in many energy conversion systems. They make the possible electric conversion at the most economical transformation voltage, power transfer at the most economical transmission voltage. Therefore, transformers are the most important equipment for energy conversion, transmission and distribution and are commonly used for supplying electricity to various residential, industries and hospital usages.
Performance Analysis of Buck-Boost and SEPIC Converter for Commutation Torque Ripple Minimization in BLDC Motors
Published in Electric Power Components and Systems, 2022
Muhammed Reşit Çorapsız, Hakan Kahveci
In Buck-Boost converters, the output voltage may be high or low than the input voltage depending on the duty cycle of the switch in the circuit. The operation of these converters can be likened to the operation of a transformer at AC voltage. Transformers realize power flow by changing current and voltage components in AC. The DC voltage equivalent of this process is DC-DC converters. In Buck-Boost converters, the input voltage and the output voltage are opposite to each other. Equivalent model of the Buck-Boost converter is shown Figure 6 and parameters of Buck-Boost converter is given in Table 1.