BALL BEARING 6L8796 - Caterpillar

An alternating current generator is often referred to as an alternator. This name is used to prevent confusing A.C. generators with D.C. generators. A simple, non technical discussion of alternating currents and generators cannot be very comprehensive, but it is hoped that generator behavior can be made to seem reasonable in the non-rigorous explanations that follow. It may be necessary to read this material several times for complete understanding.If an electrical conductor (a wire) is passed sideways through a magnetic field, a voltage is generated in it. If a circuit including this conductor is completed, the generated voltage will cause a current to flow. As soon as current flow is established, force is required to move the conductor through the magnetic field. Electrical power is then developed from the mechanical work done during such movement. This is an generator in its simplest form (Illustration 1).Conversely, if some outside source of voltage causes a current to flow through a conductor placed in a magnetic field, force is required to restrain the conductor from moving. If the conductor is permitted to move against a lesser force, mechanical work is done. This is the simplest form of a motor.
Illustration 1 g01059078
An generator in its simplest formIllustration 1 is a cutaway view of an generator. In a generator, the magnetic field is established by causing direct current to flow through coil A wound on part of the iron structure of the magnetic path – usually, in the larger machines, on the rotating field or "rotor" B. The direct current is generated by the belt driven D.C. exciter F and is supplied to the rotor through brushes bearing on slip rings G. Since voltage is generated whether the conductor moves across the magnetic field or the field across the conductor, the rotor moves the magnetic field across armature conductor C located in the stator D. Amortisseur bars E in the rotor pole faces have several functions, one of which is to improve the wave shape of the output voltage. This generator has an integral static voltage regulator H. Voltage regulators will be discussed later. Illustration 3 shows a simplified schematic of the generator pictured in Illustration 2.
Illustration 2 g01059080
Cut away view of an generator with a belt driven D.C. exciter.
Illustration 3 g01059081
Schematic of an generator with a belt driven D.C. exciter.When alternate north and south magnetic poles pass a conductor in the stator, as represented in Illustration 4, the direction of the voltage reverses periodically and an alternating voltage is generated.
Illustration 4 g01059083
Schematic of an generator which will produce three-phase current.
Illustration 5 g01059084
Actual plot of the three-phase current.The voltage will rise to a maximum value in one direction, decrease through zero to a like maximum in the other direction, and then rise through zero to a maximum in the initial direction. This is represented in Illustration 5. The variation of voltage from one maximum point to the next maximum point in the same direction constitutes a cycle. Most generators are designed and the speed of rotation so chosen