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 direction of current induces in the conductor is afmature by the Fleming right-hand rule. 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 armature field is produced by the armature conductors when current flows through them.

Coils of the winding are distributed over the entire surface of the air gap, which may be the rotor or the stator of the machine. They have the polarity of succeeding pole coming next in sequence of rotation in generator action and proceeding which has passed behind in rotation sequence pole in motor action.

Armature Reaction in DC machines

Thus the compensating winding produces flux, which is completely opposite and equal in magnitude to the armature flux, hence both cancel the effect of each other and thus armature reaction is completely neutralized. In other projects Wikimedia Commons. Besides this the distortion of main field can be prevented by cancelling the effects of the flux produced by the armature current. For example, in the above figure if the motor rotates clockwise, then for North Pole, the lower tip is leading tip and for South Pole upper tip is leading tip.

Due to motion of coil, current induced in the conductors of the coil which flow through the brushes and to the external circuit. This is because the direction of armature reaction mmf is in the inter polar axis.

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The north-south poles and conductors are in circular armature. Retrieved from ” https: This is because commutation occurs at the coils located on the brushes only, and the coil undergoing commutation comes under the influence of the alternate pole changes its location from north to south pole or vice versa. The flux is flowing in upward direction as shown in Fig. MNA Magnetic Neutral Axis may be defined as the axis along which no emf is generated in the armature conductors as they move parallel to the flux lines.

For this reason it is desirable to incorporate a corrective system into the generator design. Now two small poles are placed in between the north-south poles known as commutated poles. As armature reaction effects are not good for normal operation of DC Machine both generator and motor.

Armature Reaction in DC machines |

Thus as the load increases the armature reaction losses increases and hence the efficiency of the Generator decreases. Alternator Electric generator Inchworm motor. Now flux is produced due to the armature current and this flux always going to in this direction whatever may the position be of will resultant voltage being induced in the coil.

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

Doubly-fed Linear Servomotor Stepper Traction. The effect of the armature field is to distort the generator field and shift the neutral plane. 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.

Remember me on this computer. The armature must carry currentso it is always a conductor or a conductive coil, oriented normal to both the field and to armsture direction of motion, torque rotating machineor force linear machine.

So this would be the resultant flux direction. Now let us look at the effect of this armature reaction.

American Society of Power Engineers. The base of the inter poles is made wider to avoid saturation and to improve response.

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In other words, the armature reaction represents the impact of the armature flux on the main field flux. Larger generators require the use of interpoles. The following figure shows: The brushes of the DC machines are always placed in this axis, and hence this axis is called the axis of commutation. AC asynchronous induction IM. Direction of load current equivalent flux in this direction which is shown in Fig.

This would start from the center of pole as the coil below it possesses the maximum inductance. Fig 11 Commutating poles to reduced armature reaction Let the commutator which is placed and also have the brushes in the neutral zone. And this armature flux which is created due to the reactance in the coil because of the coil is inductive in nature armature current flowing in the conductor is called as it is trying to suddenly break current in the coil, a huge spark armature reaction which is shown in Fig.

Power Factor Armatre Depth. Copper armature wiring enhances electrical efficiencies due to its higher electrical conductivity. Now, the In D. C machine shaft energy coming from mechanical conductor is placed in magnetic field and let the current domain goes into the magnetic domain, and then finally flowing through it as shown in figure Circuit D.c.machhines All about Electrical and Electronics.

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. By means of the brushes and magnetic field is produced around the conductor.

Would you like to know more about DC Generator? When the field flux enters into the armature, they may get distorted.