ARMATURE REACTION IN D.C.MACHINES PDF

Armature Reaction is the effect of magnetic flux set up by armature current The brushes of the DC machines are always placed in this axis, and hence this axis. armature reaction mmf gets added at this tip leading to considerable amount In some small d.c. machines the brushes are shifted from the position of the mag-. Commutation problem is not the only problem in DC machines. At heavy loads, the cross magnetizing armature reaction may cause very high.

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The armature reaction changes the distribution of the magnetic field, which affects the operation of the machine. Retrieved from ” https: Copper reactiln wiring enhances electrical efficiencies due to its higher electrical conductivity.

Armature Reaction in DC machines |

Brushes are always placed along the MNA because reversal of current in the armature conductors takes place along this axis. There are two kinds of magnetic fluxes acting in DC Generator; the first one is because of the stator poles called main flux, while the second one is because of the current flowing in the armature called armature flux.

So, when applying a produced by conductor is against the main field at lower side torque, loading on electrical side should reflect as load of the conductor while it adding with the main field at upper torque, such that the prime mover should supply extra torque side of the conductor.

So this amplitude keeps varying then the resultant could be in any direction depending upon the amount of load current as shown in Fig.

Armature Reaction in DC machines

The following figure shows: In a DC machinetwo kinds of magnetic fluxes are present; ‘armature flux’ and ‘main field flux’. Due to current the comes out to electrical domain. This results an armature current flux directed along the brush axis and causes cross magnetization of the main field. Fig 8 Resultant flux due to interaction between two fluxes Now the flux created by armature current is in the upward direction and the direction of north-south pole flux is right angle to this flux. Due to saturation in the pole shoe, the increase in flux density may be less than the reduction in the flux density in remaining section of the pole shoe.

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GNA Geometrical Neutral Armwture may be defined as the axis which is perpendicular to the stator field axis. Timeline of the electric motor Ball bearing motor Barlow’s wheel Lynch motor Mendocino motor Mouse mill motor. Alternator Electric generator Inchworm motor.

Armature (electrical)

This can be easily understand from the load characteristics of DC Generator, which is shown below. In an induction generatorgenerated power is drawn from the stator. Compensating windings major drawbacks: The MMF flux is uniformly distributed along the magnetic axis. If the brushes were contacting commutator segments outside the neutral plane, they would short-circuit “live” coils and cause arcing and loss of power. In other projects Wikimedia Commons.

Now the machine has two fluxes, i. Remember me on this computer. Since an armature is wound with coils of wire, a magnetic field is set up in the armature whenever a current flows in the coils.

In large machines subject to heavy overloads or plugging In small motors subject to sudden reversal and high acceleration. These are two principal methods by which the effect of armature reaction is overcome.

The armature flux is produced by the current induces in the armature conductors while the field pole flux is induced because reation the main field poles. Obviously it is help in commutation as the inter polar winding gets relieved from its duty to compensate for the armature mmf under the pole arc.

Armature Reaction in a DC Generator – its Effect – Circuit Globe

AC asynchronous induction IM. Now a resultant flux is known and therefore orthogonal to the plane is this and these would be neutral zone which is shown in Fig. Armature wiring is made from copper or aluminum. The field this comes out as the induced voltage.

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And this effect is as much important to note as the armature losses and other constant loses like windage and iron losses, because all of them consequently gives us a decreased emf. The brushes of the DC machines are always placed in this axis, and hence this axis is d.c.mavhines the axis of commutation. Armature reaction drop is the effect of a magnetic field on the distribution of the flux under main poles of a generator.

You enjoy this post: In the armature, an electromotive force is created by the relative motion of the armature and the field.

The second role is to generate an electromotive force EMF. The cross magnetizing armature reaction effect is mainly caused by armature conductors which are located under the pole arc.

Compensating Winding Commutation problem is not the only problem in DC machines. Now, when the machine is loaded, the armature flux is directed along the inter polar axis the axis in between the magnetic poles and is triangular in wave shape. Thus as the load increases the armature reaction losses increases and hence rexction efficiency of the Generator decreases. This paper also simplifies the logic related to armature reaction and gives the effective way to overcome the problem created due to armature reaction.

Fig 3 Lorentz force law So the field on the bottom side of the conductor is tried to oppose the main field and field becomes weak while the Fig 1 a Magnetic Flux lines of north-south pole, upper field becomes stronger because of adding.