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What are the effect of armature reaction in DC machine and how the armature reaction is minimise?
Wiki User
∙ 11y ago
Armature reaction is the interaction between the magnetic flux produced by armature current and that of the main magnetic field in an electric motor or generator.
Wiki User
∙ 11y ago
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What is armature reaction in dc motor?
Armature reaction is effect of armature flux on main field flux. Basically there are two windings in a dc motor - Armature winding (on stator) and field winding (on rotor). When we excite the field winding, it produces a flux which links with the armature. This causes an emf and hence a current in the armature. This current in armature produces another flux which lags the main flux. This is referred to as armature reaction. It has two effects on the machine: 1. Demagnetising effect: It reduces the strength of the main flux. 2. Crossmagnetising effect: Its effect is that it bends/distortes the the main flux line along the conductor
What is the excitation system in a generator used for?
The excitation system is used to control the excitation of the rotating field in the armature. By increasing the armature current, it in turn increases the magnetic flux in the armature coil. This has the effect of increasing the voltage output of the generator. By lowering the armature current this in turn lowers the generator output voltage. The generator's voltage regulator automatically adjusts the output voltage continuously as the applied load on the generator changes.
What is the Significance of back emf in dc motor?
Fig. (4.3)ZN/60 A) is large and hence the motor will draw less armature current and vice-versa.4.4 Significance of Back E.M.F.The presence of back e.m.f. makes the d.c. motor a self-regulating machine i.e.,it makes the motor to draw as much armature current as is just sufficient todevelop the torque required by the load.Armature current,abaREVI−=(i) When the motor is running on no load, small torque is required toovercome the friction and windage losses. Therefore, the armaturecurrent Iais small and the back e.m.f. is nearly equal to the appliedvoltage.(ii) If the motor is suddenly loaded, the first effect is to cause the armature toslow down. Therefore, the speed at which the armature conductors movethrough the field is reduced and hence the back e.m.f. Ebfalls. Thedecreased back e.m.f. allows a larger current to flow through thearmature and larger current means increased driving torque. Thus, thedriving torque increases as the motor slows down. The motor will stopslowing down when the armature current is just sufficient to produce theincreased torque required by the load.(iii) If the load on the motor is decreased, the driving torque is momentarilyin excess of the requirement so that armature is accelerated. As thearmature speed increases, the back e.m.f. Ebalso increases and causesthe armature current Iato decrease. The motor will stop acceleratingwhen the armature current is just sufficient to produce the reduced torquerequired by the load.It follows, therefore, that back e.m.f. in a d.c. motor regulates the flow of armature current i.e., it automatically changes the armature current to meet theload requirement
What are the effect of hunting in synchronous motor?
1.it can lead to loss of synchronism. 2.the machine losses increases 3.temperature of the machine rises . 4.it can increases the possibility of resonance.
What is difference between stab shunt dc motor and shunt dc motor?
A series motor respond by decreasing its speed with small increase in current for a given load torque. A shunt motor holds its speed nearly constant with large increase in input current for same amount of load torque
What is armature reactions in a synchronous machine?
Armature reaction is the effect of armature flux on the flux generated by the fied windings.Cross magnetisation and Demagnetising are its consequences.
What is armature reaction in dc motor?
Armature reaction is effect of armature flux on main field flux. Basically there are two windings in a dc motor - Armature winding (on stator) and field winding (on rotor). When we excite the field winding, it produces a flux which links with the armature. This causes an emf and hence a current in the armature. This current in armature produces another flux which lags the main flux. This is referred to as armature reaction. It has two effects on the machine: 1. Demagnetising effect: It reduces the strength of the main flux. 2. Crossmagnetising effect: Its effect is that it bends/distortes the the main flux line along the conductor
Why are the compensating winding used in dc motor?
compensating winding is used for equal load sharing of two generators running in parallel. while interpole winding is used to minimise the effect of armature reaction by supporting the main field.
How does voltage commutation work in DC machine?
In voltage commutation process, the introduction of interpoles between main poles compensate armature mmf and reduces the effect of armature reaction.
What is armature reaction in dc machines?
The armature reaction is the interaction between armature flux and field flux when current is introduced to a dc motor. It results in a cross-magnetizing effect and a demagnetizing effect.
What are compensating winding?
compensating windings are used to overcome armature reaction
How you can reduce the effect of armature reaction?
by using capacitor
What is mean by armature reaction?
armature reaction means when load is added to the armature then current is passed through armature conductors then in armature creates flux. It is demagnetize and cross magnetize the main field flux. in other ward it is effect of armature field on main field.
What is the purpose of Inter-pole fitted in a DC generator?
to chancel the effect of the armature reaction.
What is the use of interpoles in dc machine?
Interpoles are similar to the main field poles and located on the yoke between the main field poles. They have windings in series with the armature winding. Interpoles have the function of reducing the armature reaction effect in the commutating zone. They eliminate the need to shift the brush assembly.
What effect does raising the temperature of a chemical reaction?
2SO2(g) + O2(g) 2SO3(g)-The reverse reaction is favored.
Remedies for Armature reaction?
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. This field is at right angles to the generator field, and is called cross magnetization of the armature. The effect of the armature field is to distort the generator field and shift the neutral plane. The neutral plane is the position where the armature windings are moving parallel to the magnetic flux lines. This effect is known as armature reaction and is proportional to the current flowing in the armature coils. The brushes of a generator must be set in the neutral plane; that is, they must contact segments of the commutator that are connected to armature coils having no induced emf. If the brushes were contacting commutator segments outside the neutral plane, they would short-circuit "live" coils and cause arcing and loss of power. Armature reaction causes the neutral plane to shift in the direction of rotation, and if the brushes are in the neutral plane at no load, that is, when no armature current is flowing, they will not be in the neutral plane when armature current is flowing. For this reason it is desirable to incorporate a corrective system into the generator design. These are two principal methods by which the effect of armature reaction is overcome. The first method is to shift the position of the brushes so that they are in the neutral plane when the generator is producing its normal load current. in the other method, special field poles, called interpoles, are installed in the generator to counteract the effect of armature reaction. The brush-setting method is satisfactory in installations in which the generator operates under a fairly constant load. If the load varies to a marked degree, the neutral plane will shift proportionately, and the brushes will not be in the correct position at all times. The brush-setting method is the most common means of correcting for armature reaction in small generators (those producing approximately 1000 W or less). Larger generators require the use of interpoles.
