A transformer supplying an arc furnace has to deliver unusually high currents over a wide range of voltage. Power ratings between 50 and 100 MVA are quite common now with the secondary currents of more than 50 kA. Furnace transformers have special features for handling very high currents compared to conventional transformers. Since the LV […]
Duties of rectifier transformers serving special industrial loads are more stringent than conventional transformers. Electrical energy in the form of direct current is required in electrolytic processes used in aluminum smelters and chemical plants (producing chlorine, soda, etc.). Various methods used for converting AC into DC in earlier days included use of motor-generator sets, rotary
Hysteresis and eddy current losses together constitute the no-load loss according to the classical theory. The loss due to the no-load current flowing in the primary winding is negligible. Also, at the rated flux density condition on no-load, since most of the flux is confined to the core, negligible losses are produced in the structural
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Hydropower, or hydroelectric power, is the most common and least expensive source of renewable electricity. Hydropower technologies have a long history of use because of their many benefits, including high availability and lack of emissions. Hydropower is fueled by water, so it is a clean fuel source. Hydropower technologies use flowing water to create energy
Tides are the daily swells and sags of ocean waters relative to coastlines due to the gravitational pull of the moon and the sun. Although the moon is much smaller in mass than the sun, it exerts a larger gravitational force because of its relative proximity to earth. This force of attraction causes the oceans
Wind energy technologies use the energy in the wind as the source for generating electricity, charging batteries, pumping water, grinding grain, and so on. Most wind energy technologies can be used as stand-alone applications, connected to a utility power grid. For utility-scale sources of wind energy, a large number of turbines are usually built close
Solar energy technologies produce electricity from the energy of the sun. Small solar energy systems can provide electricity for homes, businesses, and remote power needs. Larger solar energy systems can produce more electricity and feed the electric power system. The block diagram of a solar energy system is shown in Figure 1. The system consists
Reverse Recovery Characteristics of Power Diode Ideally, a diode should have no reverse recovery time. However, the manufacturing cost of such a diode may increase. In many applications, the effects of reverse recovery time is not significant, and inexpensive diodes can be used. Depending on the recovery characteristics and manufacturing techniques, the power diodes can
Lightning or surge arresters serve the same purpose on an electric circuit or line as a safety valve on a boiler. A safety valve on a boiler relieves a high pressure by allowing steam to blow off until the high pressure is reduced to normal, at which time the safety valve closes again and is
The base speed listed on a DC motor’s nameplate is an indication of how fast the motor will run with rated armature voltage and rated load amperes at rated field current. DC motors can be operated below base speed by reducing the amount of voltage applied to the armature and above base speed by reducing