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Short-circuit - analysis and calculation
... to solve a short – circuit ratios in the power system according to Standard IEC 60909. One of the main subject is describing short-circuit current in system with currents without attenuation alternating component and short-circuit current in system with currents with attenuation alternating componen ...
... to solve a short – circuit ratios in the power system according to Standard IEC 60909. One of the main subject is describing short-circuit current in system with currents without attenuation alternating component and short-circuit current in system with currents with attenuation alternating componen ...
Electricity - nvpsp52009
... from the power source to the electrical appliance that needs to be powered. ...
... from the power source to the electrical appliance that needs to be powered. ...
Another Intro to EIS
... Use the Fourier transform and inverse Fourier transform to switch between the domains. The common term, FFT, refers to a fast, computerized implementation of the Fourier transform. Detailed discussion of these transforms is beyond the scope of this manual. Several of the references given at the end ...
... Use the Fourier transform and inverse Fourier transform to switch between the domains. The common term, FFT, refers to a fast, computerized implementation of the Fourier transform. Detailed discussion of these transforms is beyond the scope of this manual. Several of the references given at the end ...
Crystal radio
A crystal radio receiver, also called a crystal set or cat's whisker receiver, is a very simple radio receiver, popular in the early days of radio. It needs no other power source but that received solely from the power of radio waves received by a wire antenna. It gets its name from its most important component, known as a crystal detector, originally made from a piece of crystalline mineral such as galena. This component is now called a diode.Crystal radios are the simplest type of radio receiver and can be made with a few inexpensive parts, such as a wire for an antenna, a coil of copper wire for adjustment, a capacitor, a crystal detector, and earphones. They are distinct from ordinary radios as they are passive receivers, while other radios use a separate source of electric power such as a battery or the mains power to amplify the weak radio signal so as to make it louder. Thus, crystal sets produce rather weak sound and must be listened to with sensitive earphones, and can only receive stations within a limited range.The rectifying property of crystals was discovered in 1874 by Karl Ferdinand Braun, and crystal detectors were developed and applied to radio receivers in 1904 by Jagadish Chandra Bose, G. W. Pickard and others.Crystal radios were the first widely used type of radio receiver, and the main type used during the wireless telegraphy era. Sold and homemade by the millions, the inexpensive and reliable crystal radio was a major driving force in the introduction of radio to the public, contributing to the development of radio as an entertainment medium around 1920.After about 1920, crystal sets were superseded by the first amplifying receivers, which used vacuum tubes (Audions), and became obsolete for commercial use. They, however, continued to be built by hobbyists, youth groups, and the Boy Scouts as a way of learning about the technology of radio. Today they are still sold as educational devices, and there are groups of enthusiasts devoted to their construction who hold competitions comparing the performance of their home-built designs.Crystal radios receive amplitude modulated (AM) signals, and can be designed to receive almost any radio frequency band, but most receive the AM broadcast band. A few receive shortwave bands, but strong signals are required. The first crystal sets received wireless telegraphy signals broadcast by spark-gap transmitters at frequencies as low as 20 kHz.