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In a dc generator brushes are placed in which side to avoid armature reaction?
Wiki User
∙ 15y ago
along the M.N.A axis along the M.N.A axis
Wiki User
∙ 15y ago
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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.
How is an alternating current produced?
EMF is induced in a coil when it is rotated in magnetic field. The magnetic field is obtained in the space between N Pole and S Pole of a magnet. coil is kept on shaft and it is rotated. To take out the current from the coil, two slip rings made of brass are kept on the shaft. The slip rings are insulated from each other and from the shaft. Carbon brushes are placed on the slip ring. EMF is available across these brushes. Load is connected across the brushes. This is called single phase type alternator or AC Generator. In practice three phase type alternator is used. In alternator, used in power stations, armature is kept stationary and field is rotated.
Why are brushes staggered in dc motor?
To avoid sparking they need to be placed at zero point
What special instrument is placed inside the heart and used as impulse generator to make it function normally?
The special instrument that is placed in the heart and used as a impulse generator is called pacemaker. The pacemaker helps the heart to make it fuction normally....
How do you define the synchronous generator capability limiters?
SYNCHRONOUS GENERATOR CAPABILITY LIMITTsynchronous generator capability limiters are as follows 1.MVA or armature current limit of generator: this depends on the cooling system of generator so that temperature rise in generator is limited to safe value.depending on cooling system effectiveness and temperature limit for the insulation used in generator, MVA limit is decided.2.MW limit: this is determined by the power output capacity of prime mover to which generator is connected.3.rotor angle limit: this is related to stability of generator which is synchronised to the grid.ideally this could be 90 degree, but in practice this is limited to70 degree so as to have better stability margin in transient and dynamic condition.the generator falls out of synchronism in trasient condition if rotor angle is close to 90 degree.4. rotor current limit: the field winding placed on rotor has got limited current carrying capacity, beyond which it may burn .so this limit is used.all these limitters make capability curve of g generator within which the generators operates safelyr. k.niranjanemail id: rkniranjan@yahoo.com
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.
Why is brushes placed at MNA in a dc generator?
to avoid sparking ,since their is no e.m.f induced in magnetic neutral axis.
Define the brush on a dc motor?
The brush is actually a piece of carbon placed on the rotating commutator of the motor. it will be in pairs. Since the armature shaft rotates but gets the continuity through these brushes.
Answering Which one is a separately excited generator - ac generator or dc generator?
Excitation is the phenomenon by which you control the excitation of field winding of a generator. In DC generator field winding is placed on stator and this field winding can be self excited or seperately excited depending upon the type on generator used. AC generators can also be self excited or seperately excited type but field winding is placed on rotor nad armature winding on stator.
What is an armature made of?
The armature is the part of an electric generator or motor that contains the main current-carrying winding. It usually consists of a coil of copper wire that is wound around an iron or steel core. The coil and core are placed in a magnetic field, which is produced by one or more permanent magnets or electromagnets.
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 are the parts of an alternator?
In an alternator, there are two main parts, one is stationary part and other is rotating part. Field winding may be placed on fixed part(stator) as in case of DC generator and on rotating part(rotor) as in case of AC genarators. Armature winding may be placed on rotating part(rotor) in case of DC generator and on stationary part (stator) in case of AC generator. In AC generators, for all practical purposes you have rotating filed system.
How is an alternating current produced?
EMF is induced in a coil when it is rotated in magnetic field. The magnetic field is obtained in the space between N Pole and S Pole of a magnet. coil is kept on shaft and it is rotated. To take out the current from the coil, two slip rings made of brass are kept on the shaft. The slip rings are insulated from each other and from the shaft. Carbon brushes are placed on the slip ring. EMF is available across these brushes. Load is connected across the brushes. This is called single phase type alternator or AC Generator. In practice three phase type alternator is used. In alternator, used in power stations, armature is kept stationary and field is rotated.
Why are the brushes of a dc machine always placed at the neutral points?
The function of brush is to collect current from rotating commutator and supplies the current to external stationary load. The brushes of a DC machine are placed at neutral points because the current in the rotating part drops to zero at the neutral point. If brushes are placed in location other than the neutral points, then the current may be switched off and it causes magnetic field and it may also create voltage spikes and arc at brushes.
Why are brushes staggered in dc motor?
To avoid sparking they need to be placed at zero point
Where does one place the emergency generator?
An emergency generator is a type of machine that helps generate emergency electricity. Most emergency generators are gas powered. Therefore, they should be placed in a well-ventilated area. Usually, they are placed on a back porch or in a garage. They should not be placed inside a home.
What special instrument is placed inside the heart and used as impulse generator to make it function normally?
The special instrument that is placed in the heart and used as a impulse generator is called pacemaker. The pacemaker helps the heart to make it fuction normally....
