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A generator in electrical circuit theory is one of two ideal elements: an ideal voltage source, or an ideal current source. [1] These are two of the fundamental elements in circuit theory. Real electrical generators are most commonly modelled as a non-ideal source consisting of a combination of an ideal source and a resistor.
An ideal current source generates a current that is independent of the voltage changes across it. An ideal current source is a mathematical model, which real devices can approach very closely. If the current through an ideal current source can be specified independently of any other variable in a circuit, it is called an independent current source.
The generator is represented by an abstract generator consisting of an ideal voltage source and an internal impedance. The generator's V G {\displaystyle V_{\text{G}}} and R G {\displaystyle R_{\text{G}}} parameters can be determined by measuring the winding resistance (corrected to operating temperature ), and measuring the open-circuit and ...
These are called the "generator-load conventions" [10] [11] [12] which are used in electric power engineering Generator convention - In source components like generators and batteries, the variables V and I are defined according to the active sign convention above; the current variable is defined as entering the negative terminal of the device ...
Since a Van de Graaff generator can supply the same small current at almost any level of electrical potential, it is an example of a nearly ideal current source. The maximal achievable potential is roughly equal to the sphere radius R multiplied by the electric field E max at which corona discharges begin to form within the surrounding gas.
A branch that is already a current source is simply not converted. In the expression above, this is equivalent to replacing the / term in the numerator of the expression above with the current of the current generator, where the kth branch is the branch with the current generator. The parallel conductance of the current source is added to the ...
For instance, one might transform a voltage generator into a current generator using Norton's theorem in order to be able to later combine the internal resistance of the generator with a parallel impedance load. A resistive circuit is a circuit containing only resistors, ideal current sources, and ideal voltage sources.
For a machine using field coils, as is the case in most large generators, the field must be established by a current in order for the generator to produce electricity. Although some of the generator's own output can be used to maintain the field once it starts up, an external source of current is needed for starting the generator.