What is armature reaction? Explain briefly the cross magnetizing and de-magnetizing effect of a loaded generator

Armature reaction: The current flow in the armature conductors of a dynamo has an important and undesirable effect upon the dynamo’s operation. The current in the armature produces a flux and it is the interaction between this flux and the field flux that is called armature reaction.

Cross magnetizing and demagnetizing effect: The effects of the armature flux my be analyzed by considering the flux to consists of two components that are at right angle to each other as shown in fig. One component is at right angle to the field, and because this component crosses the main –field flux, it is known as the cross –magnetizing component of the armature flux. The second component is in the same plane as the main field flux . The direction of this component is opposite to the direction of the main field flux, with the result the it tends to reduce the effect of the main field flux. This component of the armature flux , is known as demagnetizing component of the armature flux.

Elimination: A method to reduce the armature flux on large machines is by the use of compensating windings .These windings are placed in the pole faces of the field pole can run parallel to the armature conductors. A connection is made from one of the brushes to one end of this winding, so that current from the armature must first pass through this winding before going to the load. The direction of current through the winding is opposite to that of the current in the armature conductors under the pole. The location of the compensating winding and of the connection of the winding is shown in fig. indicates that the current in the armature conductors located under the north pole carry current away from the observer , therefore the direction of current following in the part of the compensating windings situated in the north pole is toward the observer. The direction of flux due to the current in the armature conductor shown in fig. will be from the brush to the bottom brush. Since the current in the compensating winding is opposite in direction to the current in the armature conductors, the flux product by the current in the compensating winding will be opposite in direction to the armature flux. The compensating flux , being opposite in direction to the armature flux, tends to cancel the armature flux. If the armature current increases, the compensating current increases, so that the armature flux is cancel for all load conditions.

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How to Calculate Heat Rate of Generator Engine?

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Packing, Seals and Gaskets

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Why a dc generator fails to build up voltage?

How can the problem be remedied : No residual magnetism, reversed field connection and high resistance of field circuit are responsible for the failure of build up process of a dc generator. The factors are explained below: No residual magnetism: For the starting build up process requires some residual magnetism in the magnetic circuit then no voltage will be generated that can produce current flow through field circuit. Reversed field connection: The voltage induced inside the coil of field circuit due to residual magnetism that can permit the flow of current. For the following direction of this flux will be created and the direction of this flux will be same direction as the residual flux. If the field connections are reversed the lines of flux produced by current flow will oppose the residual flux, as a result generate voltage will decrease rather than increase. So voltage build up process failed. Field circuit resistance too high: A field

what is the difference between long shunt and short shunt dc generator?

How do they differ from normal generator? Draw their V-I characteristics and explain them? In short shunt connection the shunt field is connected directly across the armature terminals and the armature connection equals the sum of the shunt field current plus the load current . In this instance the load current flow s through the series field winding so that the load current and series field current are one and same. In long shunt connection the voltage across the shunt field is the same as the terminal voltage of the generator and current in the armature will be the current in the series field. The armature current equals the shunt field current plus the load current. A shunt generator has the field circuit connected directly across the armature. As more devices connected in parallel the load on the generator increases that the generator current increases which results decrease in terminal voltage of the generator.

Therbligs and Basic 17 motion name of therblig

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Various Methods of Drawing Flow Nets

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Which type of Battery connection Series or Parallel Connection is used for Diesel Generator?

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what is PIV drive? Why is PIV drive more effective than any other system of drive?

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What are the main components of Automobile?

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“Equalizer connection is needed in lap winding armature but not in wave winding “ why ?

The equivalent circuit of a four point – pole dynamo with a simplex winding. The voltage induced in each path is assumed to both to be same and should be if the reluctance of each magnetic path is the same, so that the lines of flux cut by each inductor of each path are the same. However wear of the bearings or deflection of the armature shaft may cause the armature to be closer to some poles and farther from others, thus changing the length of the air gap, and therefore the reluctance of the magnetic circuits of the poles is not identical. This factors cause the voltage in the materials making up the magnetic circuit. These factors cause the voltage in each parallel path differ, and the unequal voltages in turn cause flow of a circulating current through the windings and brushes , undue heating of the armature and waste the power. To reduce the circulating current, points on the winding which should be at the same potentials are brought to the same potentials by connecting

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