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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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They have the polarity of succeeding pole coming next in sequence of rotation in d.c.machinew action and proceeding which has passed behind in rotation sequence pole in motor action. Power Factor Correction Equipment: Inter polar windings are always kept in series with armature, so inter polar winding carries the armature current; therefore works satisfactorily irrespective of load, the direction of rotation or the mode of operation.

Home Electrical machines Power system Contact electricaleasy. The field this comes out as the induced voltage. So therefore this flux which is created due to the load Because when the brushes are passing over that coil there is current of armature current flowing in and going to cause a a current flowing through that and there is an inductive problem.

Armature (electrical) – Wikipedia

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. Consequently, the coil under this tip may develop induced voltage high enough to cause a flash over between the associated adjacent commutator segments particularly, because this coil is physically close to the commutation zone at the brushes where the air temperature might be already high due to commutation process.

Reaaction you like to know more about DC Zrmature So, the neutral zone can set at orthogonal to the main flux. Due to motion of coil, current induced in the conductors of the d.c.macchines which flow through the brushes d.c.machones to the external circuit.

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 be referred to as armatures. 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.

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Armature Reaction in DC Machine

The problems such as high circulating current, poor commutation and sparking may occur at brush contact due to armature reaction. Leave a Reply Cancel reply Your email address will not be published.

Now flux is produced due to the armature current and this flux always going to resction this direction whatever may the position be of will resultant voltage being induced in the coil. Thus in this case compensation windings are installed in slots of the poles faces of main field poles. Skip to main content.

In a “wave” winding, there are only two paths, d.c.mmachines there are as many coils in series as half the number of poles. If the load varies to a marked degree, the neutral plane will shift proportionately, and the brushes will not be the correct position rewction all times. In view of this, brush shift is limited only to very small machines. Hence, the conductor on both the sides combines their MMF in such a way so that their flux goes downward direction.

So at this new point it avoids the circulating current and also decreases the sparking. This phenomenon is thus known as the demagnetizing effect of cross magnetizing armature reaction, which is further compensated by the use of compensating windings.

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. The first method is to shift the position of the brushes so that they reation in the neutral plane when the generator is producing its normal load current. What is D.c.mschines and Trailing Pole tip?

Consider, no current is flowing in the armature conductors and only the field winding is energized as shown in the first figure of the above image. The tip of the pole from where the armature conductors come into influence is called leading tip and the other tip opposite in direction reactiom it will be the trailing tip.

This can be easily understand from the load characteristics of Reacion Generator, which is shown below.

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Since inter poles are connected in series with armature, the change in direction of current in armature changes direction of inter pole. Compensating windings major drawbacks: The armature conductors combine their MMF for generating the fluxes through the armature in the downward direction.

Click here to armqture up. The armature interacts with the magnetic field magnetic flux in the air-gap; the field component can comprise either permanent magnets, or electromagnets formed by a conducting coil, such as another armature i.

Armature Reaction in DC Machine

Therefore the brushes cannot be dynamically positioned as the load arkature changes. The content on this website is copyrighted and may not be reproduced. The base of the inter poles is made wider to avoid saturation and to improve d.c.,achines. Brush Shift A natural solution to the problem appears to shift the brushes along the direction of rotation in generator action and against the direction of rotation in motor action, this would result into a reduction in air gap flux.

Although distinctly separate these two sets of terminology are frequently used interchangeably or in combinations that include one mechanical term and one electrical term. The first is to carry current crossing the field, thus creating shaft torque in a rotating machine un force in a linear machine.

Remember me on this computer. 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.

Armature Reaction in a DC Generator

The word armature was first used in its electrical sense, i. On another side also have a flux distribution or field distribution so a flux lines is in form of ring by the right hand rule and in anti-clockwise direction. This problem is more acute while the load is decreasing in generating action and increasing in motor action as then, the induced e. The conductor on the right-hand sides is also combining their MMF for producing the flux in the downwards direction.