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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So, for a given rating of machine, a wave winding is more suitable for large currents and low voltages. In other words, the armature reaction represents the impact of the armature flux on the main field flux. This is because the direction of armature reaction mmf is in the inter polar axis.

Armature Reaction in DC Machine

The first is to carry current crossing the field, thus creating shaft torque in a rotating machine or force in a linear machine. The armature flux is produced by the current induces in the armature conductors while the field pole flux is induced because of the main field poles.

If the motion is reversed in case of generatorthe tips is interchanged. The distortion increases the density of the flux in the upper pole tip of N-pole and the lower pole tip of the south pole. Newer Post Older Post Home.

Armature Reaction in DC Machine

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. Why not share it? The brushes of a generator must be set in the neutral reactiion that is, they must contact segments of the commutator that are connected to armature coils having no induced emf.

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Armature Reaction in DC machines |

The pole piece of a permanent magnet or electromagnet and the moving, iron part of a solenoidespecially if the latter acts as a switch or relaymay also d.c.machones referred to as armatures.

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So this leads to the following equivalent representation like north-south poles Fig 5 Direction of current in armature, main pole flux and and the circular armature and was supposed to be a neutral neutral axis zone where no flux [1] [3]. Recieve free updates Via Email! The second role is to generate an electromotive force EMF.

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.

This can be achieved by installing commutating poles in between two consecutive main poles. Due to motion of coil, current induced in the conductors of the coil which flow through the brushes and to the external circuit. Armature reaction is essential in amplidyne rotating amplifiers. Thus, no sparking takes place. As armature reaction effects are not good for normal operation of DC Machine both generator and motor. Windings are held in slots in the rotor or armature covered by stator magnets.

Because of this one major problem that the brushes which were supposed to be located at in the neutral zone because in neutral zone there is no voltage induced in the coil there is no brush short circuit at the point and there is no problem there is no huge circulating current.

Now two small poles are placed in between the north-south poles known as commutated poles. In electrical engineeringan armature is the power-producing component of an electric machine.

This would start from the center of pole as the coil below it possesses the maximum inductance. The base of the inter poles is made wider to avoid saturation and to improve response. Retrieved from ” https: You enjoy this post: Now let us look at the effect of this armature reaction. Would you like to know more about DC Generator?

The armature must carry currentso it is always a conductor or a conductive coil, oriented normal to both the field and to the direction of motion, torque rotating machineor force linear machine. Connects Facebook Youtube Arrmature.

The magnetic neutral axis armatjre poles is always perpendicular to the axis of the resultant flux. The MMF flux is uniformly distributed along the magnetic axis. When the machine is used as a generator, the armature EMF drives the armature current, and the shaft’s movement is converted to electrical power. Compensating Winding Commutation problem is not the only problem armahure DC machines.

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The armatufe of the armature field is to distort the generator field and shift the neutral plane. The magnetic axis means the centre line between the north and south pole. So in flows from this commutated pole windings. However for a constant load current, the rotation of brush hanger mechanism find the correct neutral zone position and then good commutation is possible to achieve. Skip to main content.

Armature wiring is made from copper or aluminum. So, commutation, and sparking may occur due to armature the current which flows from external load circuit is also reaction which affects the performance of the machine.

Armature Reaction in DC machines

Help Center Find new research papers in: Overall flux is less than the field flux because saturation occur at the pole tip B of the field pole due to higher field flux, thus increase in the flux at pole tip B is less than the decrease in the flux at pole tip A.

Inter poles are made narrower to ensure that they influence only the coil undergoing commutation and its effect does not spread to the other coils. Although distinctly separate these two sets of terminology are frequently used interchangeably or in combinations that include one mechanical term and one electrical term.

If the reaxtion remain at their previous positions, then back emf in case of motor or generated e. The armature reaction is the effect of the armature flux on the main flux. This page was last edited on 2 Decemberat Retrieved July 17, The following figure shows: Armafure no load connected to the generator, the armature current becomes zero.

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