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Category: Synchronous Motor

Introduction:-

With the development of the technology and the way in which human labour is getting minimized and the comforts increasing tremendously the use of electrical energy is ever increasing. Basically electric power is the main source of energy for carrying out many functions, as it is a clean and efficient energy source, which can be easily transmitted over long distances. With the availability of Transformer for changing the voltage levels to a very high value (of say 132kV to 400kV) the use of AC power has increased rapidly and the DC power is used only at remote places where AC power cannot be supplied through power lines or cables or for a few social purposes. A synchronous generator is an electrical machine producing alternating emf (Electromotive force or voltage) of constant frequency. In our country the standard commercial frequency of AC supply is 50 Hz. In U.S.A. and a few other countries the frequency is 60Hz. The AC voltages generated may be single phase or 3-phase depending on the power supplied. For low power applications single phase generators are preferable. The basic principles involved in the production of emf and the constructional details of the generators are discussed below.

Generation of E.M.F:-

In 1831 Faraday discovered that an emf can be induced (or generated) due to relative motion between a magnetic field and a conductor of electricity. This voltage was termed as the induced emf since the emf is produced only due to motion between the conductor and the magnetic field without actual physical contact between them. The principle of electromagnetic induction is best understood by referring. The magnetic field is produced by the two fixed poles one being the north pole from which the magnetic flux lines emerge and enter into the other pole known as the south pole. It was found that the magnitude of the voltage induced in the conductor is proportional to the rate of change of flux lines linking the conductor.

Interconnected Synchronous Generators

Interconnected Synchronous Generators

The study of interconnection of several synchronous generators is important because of the following main reasons: 1. Since the demand of electricity varies during a day, also during the various seasons in a year, a modern power station employs two or more units so that one or more alternators can supply power efficiently according to the need. Installation of a single generator of capacity equal to the installed capacity of a station will be uneconomic, as such a generator will…

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Parallel Operation Of Two Generators

Parallel Operation Of Two Generators

When two synchronous generators are connected in parallel, they have an inherent tendency to remain in step, on account of the changes produced in their armature currents by a divergence of phase. Consider identical machines 1 and 2, in parallel and working on to the same load. With respect to the load, their e.m.fs are normally in phase: with respect to the local circuit formed by the two armature windings, however, their e.m.fs are in phase-opposition. Suppose there to be…

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Synchronous Generator Operation

Synchronous Generator Operation

Cylindrical Rotor Machine:-   The synchronous generator, under the assumption of constant synchronous reactance, may be considered as representable by an equivalent circuit comprising an ideal winding in which an e.m.f. Et proportional to the field excitation is developed, the winding being connected to the terminals of the machine through a resistance ra and reactance  (Xl + Xa) = Xs all per phase. The principal characteristics of the synchronous generator will be obtained qualitatively from this circuit. Generator Load Characteristics:- Consider…

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Armature Winding

Armature Winding

Winding Types:- Concentrated three-phase,half-coil wave winding with one slot per phase(one coil side per slot and instantaneous polarity and phase relation of coils). A three phase winding, in extremely simplified form. The start and finish of all the coils in phase A are designated, respectively, as SA and FA. Phase A is shown as a solid line in the figure, phase B as a dashed line, and phase C as a dotted line. Note that each winding does not start…

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Synchronous Machines

Synchronous Machines

Introduction:- With the development of the technology and the way in which human labour is getting minimized and the comforts increasing tremendously the use of electrical energy is ever increasing. Basically electric power is the main source of energy for carrying out many functions, as it is a clean and efficient energy source, which can be easily transmitted over long distances. With the availability of Transformer for changing the voltage levels to a very high value (of say 132kV to…

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