Armature reaction in dc machine pdf

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Armature Reaction: The effect of magnetic field set up by armature current on the distribution of flux under main poles of a generator. The armature magnetic field has two effects: (i) It demagnetises or weakens the main flux and (ii) It cross-magnetises or distorts it. If the machine has a pole arc to pole pitch ratio of then 70% of the armature reaction mmf gets added at this tip leading to considerable amount of saturation under full load conditions. The flux distribution also is shown in Fig. This is obtained by multiplying mmf and permeance waves point by . Armature reaction. The armature flux superimposes with the main field flux and, hence, disturbs the main field flux (as shown in third figure the of above image). This effect is called as armature reaction in DC machines. The armature reaction in a dc generator is explained as below, Consider no current in armature conductors, then MNA coincides with GNA.. Now, when current start flowing through the armature conductors, due to the combined action of main flux and armature flux the MNA get shifted from GNA.. In case of a generator, the M.N.A. is shifted in the direction of rotation of the nikeairmaxoutlet.us: Electrical Engineer. Armature Reaction. So far we have assumed that the only flux acting in a d.c. machine is that due to the main poles called main flux. However, current flowing through armature conductors also creates a magnetic flux (called armature flux) that distorts and weakens the flux coming from the poles.

The armature of the machine rotates clockwise. Which we indicate in the figure by the cross sign. For the same reason, at that instant, the current in the conductors in front of S pole will be in the outward direction. That indicates in the figure by dot sign. Now by considering the direction of current in the conductors, we can illustrate the flux produced surround the armature conductors. By applying the Right-Hand Thumb Rule, we can draw the direction of circular flux lines of the conductors. Armature Reaction In DC Machines Recieve ebook biografi iwan fals updates Via Email! Home Electrical machines Power system Ask a question Contact electricaleasy. In armature reaction in dc machine pdf DC machinetwo kinds of magnetic fluxes are present; 'armature flux' and 'main field flux'. The effect of armature flux on the main field flux is called as armature reaction. There is an axis or, you may say, a plane along which armature conductors move parallel to the flux lines and, hence, they do not cut the flux lines while on that plane. MNA Magnetic Neutral Axis may be defined as the axis along which no emf is generated in the armature conductors as they move parallel dcc the flux lines.

Armature Reaction: The effect of magnetic field set up by armature current on the . the currents induced in armature conductors of a d.c. generator are. In some small d.c. machines the brushes are shifted from the position of the mag- . The third effect of the armature reaction mmf distorting the flux density is. of armature flux on the main field flux is known as armature reaction. Armature reaction effects the normal operation of DC Generator in many ways. It actually. In a DC machine, two kinds of magnetic fluxes are present; 'armature flux' and ' main field flux'. The effect of armature flux on the main field flux is called as. compensated du to nonlinearity. ⇒ flux and e.m.f. reduction (+ augm. pmag). e.m.f. with load. 1. and 2. armature reaction. DC machines.

armature reaction in dc machine pdf Search inside document. Then the only flux that would exist is the north-south pole flux and this would still the orthogonal plane armature reaction in dc machine pdf would still into arature neutral zone. The field this comes out as the induced voltage. Dhimmar3, Jay A. GNA Geometrical Neutral Axis may be defined as the axis which is perpendicular to the stator field axis. This happens when machines running at no-load condition. more information meherbaniyan veer karaoke s Armature reaction also occurs in a DC motor just like armature reaction in DC Generator. This is expected because when current flows through the armature conductors of a DC motor, it produces flux (armature flux) which lets on the flux produced by the main Author: Electrical Engineer. Armature Reaction in a Synchronous Machine. The effect of Armature (stator) flux on the flux produced by the rotor field poles is called Armature Reaction. When the current flows through the armature winding of the an alternator, a flux is produced by the resulting MMF. This armature flux reacts with the main pole flux. Oct 04,  · How to Reduce the effects of armature reaction? Remedies to armature reaction effect: The following methods are used in order to reduce the effect of armature reaction. The armature reaction causes the distortion in main field flux. This can be reduced if the reluctance of the path of the cross-magnetising field is increased.

To browse Academia. Skip to main content. Log In Sign Up. Download Free PDF. Free PDF. Download PDF Package. Premium PDF Package. This paper. A short summary of this paper. Solanki1, Nirav J. Patel2, Nikunj J. Dhimmar3, Jay A. The problems such as high circulating current, poor commutation and sparking may occur at brush contact due to armature reaction.

This paper also simplifies the logic related to armature reaction and gives the effective way to overcome the problem created due to armature reaction. 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 Due to current the comes out to electrical domain. By means of the brushes and magnetic field is produced around the conductor.

The field this comes out as the induced voltage. 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 it rotates with same rpm and as a result getting the same induced emf [1] [2] [3]. 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. Now upper field is acting like a rubber band, so it is trying to push the conductor in downward direction as shown in Fig.

On the left hand side of neutral zone, the flux is creating rings around conductors because there is current flowing within this loops and the direction is in clockwise which is given by the right hand rule. 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. These two fluxes are not going to contribute the neutral axis conductor placed at the centre. Now, inside the centre of armature of machine because of all the fluxes are pointing up, it means there is an effective flux which is pointing in upward direction.

The flux is flowing in upward direction as shown in Fig. 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]. Armature reaction is an undesirable effect that should be overcome in DC machine. In operation of DC Generator there is a flux between north-south poles and there is a coil in armature.

Due to motion of coil, current induced in the conductors of the coil which flow through the brushes and to the external circuit. But, due to current flowing in the conductor of coil, there will be a field around it, now this field is going to interact with the main flux field of the north south magnetic poles which has been applied. Field created by conductor will distort the main field. Now in neutral zone which supposed to be as zero field zone where no induced voltage coil can exist, so no current flow though the armature conductors.

Now let us look at the effect of this armature reaction. The north-south poles and conductors are in circular armature. The orthogonal plane is supposed to be Fig 7 Main pole flux and flux due to armature current the neutral zone where no induced voltage and thereby no induced current because at this point flux is equal to zero in There are two fluxes present in DC machine, the flux due to that direction.

Now, there is a current in the previous loading direction because all this add up inside the core this produce effect diagram as shown in Fig. Direction of load current equivalent flux in this direction which is shown in Fig.

In flows through the conductor is shown in Fig. Because the load current is varying quantity which means the flux due to armature current which indicating orthogonal to the north-south flux the amplitude keeps varying.

So this amplitude keeps varying then the resultant could be in any direction depending upon the amount of load current as shown in Fig. So orthogonal to that only will be the neutral zone. So, the neutral zone has much higher band of angle in which it can exist at various load current. Therefore the brushes cannot be dynamically positioned as the load current changes. 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.

As shown in Fig. So this would be the resultant flux direction. 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 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. Due to this armature current will short circuit the coil and produce huge Fig 10 Armature Reaction short circuit circulating current and therefore I2R losses produced in armature winding and also results in sparking.

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. 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.

So, due to these problems like circulating current which itself heat up the winding and the other one is 3. So, the neutral zone can set at orthogonal to the main flux. 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.

The direction of rotation is consider as anti-clockwise. So neutral zone has shifted in the direction of rotation therefore brushes has been place in this new neutral zone.

So at this new point it avoids the circulating current and also decreases the sparking. Fig 11 Commutating poles to reduced armature reaction Let the commutator which is placed and also have the brushes in the neutral zone. Now two small poles are placed in between the north-south poles known as commutated poles. And the negative terminal brush is connected to winding which is wound over There are many problems like high circulating current, poor this small pole and it is connected to negative terminal.

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. So in flows from this commutated pole windings. Jones, So there are three [2] P. Fitzgerald, Charles Kingsley, Jr. Stephen D. Jones Then the only flux that would exist is the north-south pole flux and this would still the orthogonal plane and would still into the neutral zone. This means the flux due to armature current or in fact the armature reaction is now zero.

There by still maintaining the same neutral zone position and thereby do not shift position of the brush and the brushes can still stand same position and the voltages induced in the coil at the neutral zone to still the zero and therefore no short circulating current and therefore also no sparking or arcing when the commutator segment are passing over the brushes at that point that is the neutral zone [1] [3] [5].

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IJRET: International Journal of Research in Engineering and Technology eISSN: | pISSN: CONCEPT OF ARMATURE REACTION IN DC. So far we have assumed that the only flux acting in a d.c. machine is that due to The phenomenon of armature reaction in a d.c. generator is shown in Fig. (). Armature reaction in DC machines. • If the magnetic field windings of a dc machine are connected to a power supply and the rotor of the machine is turned by an. Armature Reaction. Introduction. In a d.c. generator, the purpose of field winding is to produce magnetic field (called main flux) whereas the. The effect is the same for both lap- and wave-wound machines. In a machine called the amplidyne, the armature reaction is utilised but in the d.c. generator ( and.

this Armature reaction in dc machine pdf

Armature Reaction: The effect of magnetic field set up by armature current on Commutation: the currents induced in armature conductors of a d.c. generator. IJRET: International Journal of Research in Engineering and Technology eISSN: | pISSN: CONCEPT OF ARMATURE REACTION IN DC. Armature Reaction in a DC Generator. Definition: The armature reaction simply shows the effect of armature field on the main field. In other words, the armature. Armature Reaction in DC machines. by Kiran Daware DC Machines. In a DC machine, two kinds of magnetic fluxes are present; 'armature flux' and 'main field flux'. Armature reaction effects the normal operation of DC Generator in many ways. It actually decreases the main flux by. 10% which results the generated emf to fall. The armature reaction is the effect of the armature flux on the main flux. In case of a DC motor the resultant flux is strengthened at the leading. The armature flux distorts and weakens the main flux posing problems for the proper operation of the d.c. generator. The action of armature flux. The armature flux distorts and weakens the main flux posing problems for the proper operation of the d.c. nikeairmaxoutlet.us action of armature flux on the main flux is. Armature Reaction and Commutation. Introduction. In a d.c. generator, the purpose of field winding is to produce magnetic field. (called main flux) whereas the.Compensating Windings: These are used for large direct current machines which are subjected to large fluctuations in load i.e. rolling mill motors and turbo-generators etc. Their function is to neutralize the cross magnetizing effect of armature reaction. In the absence of compensating windings, the flux will be suddenly shifting backward and. This paper gives the brief introduction about armature reaction. The problems such as high circulating current, poor commutation and sparking may occur at brush contact due to armature reaction. This paper also simplifies the logic related to. Armature reaction effects the normal operation of DC Generator in many ways. It actually decreases the main flux by 10% which results the generated emf to fall with the increase in load current. Thus as the load increases the armature reaction losses increases and hence the efficiency of the Generator decreases. This can be easily understand from. DC MACHINES • In DC machines, the field winding is wound onto the stator, while the armature winding is located on the rotor. • Current is supplied to the rotating armature winding through Commutator Segments. • Each commutator segment (also located on the rotor) is connected to an armature winding coil. DC machines II. The phenomena of armature reaction and commutation III. Characteristics of generators and parallel operation of generators IV. Methods for speed control of DC motors and applications of DC motors V. Various types of losses that occur in DC machines and how to calculate efficiency VI. Testing of DC motors. Armature reaction Y(Ia)=y(Ia)+RaIa Total armature reaction Compensating winding disadvantages: •for a single value of I a •shift direction dependson rotation direction •shift direction dependson operating mode (generatoror motor) Shift of the brushesw.r.t. neutralaxis Reductionof the armature reaction DC machines. Sep 01,  · To illustrate the armature reaction, let us consider a two pole dc machine. The armature of the machine rotates clockwise. Hence, as per Fleming’s rule, at any instant, the current in the conductors in front of N pole will be in the inward direction. Which . Although DC is not widely used by consumers, DC machines have played a major role in industry over the years. FE: elevators use DC machines. DC MACHINE: DC machine operates as the result of the interaction of rotating coils with a stationary magnetic field. The rotor contains the armature winding -a number of coils mounted in lots on the rotor.

armature reaction in dc machine pdf