Alternator Write the facility of rotating the field and name the prime movers used in Alternator keeping the definition and identity and working of Alternator machine.

 

Definition and Identity: Alternator is a machine or electrical device that produces voltage of varying quality. Both D.C generator and Alternator produce alternating voltage within them. D, C In generator, unidirectional voltage is brought out with the help of commutator and brush, but in alternator, alternating voltage is brought out with the help of slipring. As in D, C Generator, Armature is rotated by keeping the Field fixed, in Alternator just opposite, the Armature is kept fixed by rotating the Field.This method is used in almost all alternators to get several benefits. The direction and speed of this rotation must be kept at a predetermined decision so that the frequency produced is the same everywhere. This frequency is directly dependent on the rotation and the phase sequence depends on the direction of rotation. It is also called Synchronouse generator as it has to be kept at a certain speed all the time. (adsbygoogle = window.adsbygoogle |Operation: Alternator operation is same as D, C Generator. Because Alternating Voltage is generated inside both, in case of Alternator, this alternating voltage is brought out directly with the help of slip ring.

E.M.F equation of alternator : Here it should be remembered that the Volta produced in case of alternator will be known as phase voltage.

Alternator voltage regulation method: Voltage regulation can be determined by different methods, they are as follows: Synchronous impedance or E.M.F method (b) Magnetomotive force or ampere turn method. (c) Zero power factor or Pottier method. (d) Old AIEE method. (adsbygoogle = window.adsbygoogle || []).push({}); In this method the voltage drop across the synchronous impedance is determined.Synchronous impedance includes armature effective resistance, leakage reactance, armature magnet reaction etc. For effective resistance the voltage drop is in the same direction as the current. For synchronous reactance the voltage drop is 90° leading to the current. Vector diagram is drawn for pf lagging as a result. And no load voltage can be easily extracted from it.

Write the advantages of rotating the field while keeping the armature fixed in the alternator: Armature winding is much more complex than field winding, so it is much easier and safer to use this complex winding in a fixed coil than in a rotating body. Armature winding requires a lot of atomic conductors and thus becomes quite heavy and the cost of winding by the prime mover is high. It is more convenient to use the heavy weight winding on a fixed body.

Alternator voltage is usually very high. Insulating this high voltage in the rotating pill is a more complicated task. By making the winding large enough in the fixed frame, cooling can be done easily and the air movement is facilitated. The weight can be reduced by using a spider in the structure of the rotor, thus reducing the cost of the prime mover.

Name the prime movers used in Alternator. Answer: 1) Diesel Engine 2) Steam Engine Gas Engine 4) Hydraulic Turbine

Go Next Page