LESSON SIX. DYNAMO ELECTRIC MACHINERY.The Dynamo. The Alternator. The Motor.The discovery of the induction of currents in wires by moving them across a magnetic field led to the construction of electrical machines, called dynamos, to generate current in place of batteries.The dynamo is perhaps the most important piece of electrical apparatus there is for it is the source of ninety-nine percent of all the electricity now in use. It is practically necessary in any case where a considerable quantity of electricity is used to have a dynamo on the spot or else bring the currents over a wire from some supply station where dynamos are kept running.The operation of a dynamo is dependent upon current induction. It contains a system of closed conductors revolving in a magnetic field in such a way as to continuously vary the number of lines of force threading among them.FIG. 16. Diagram showing the principle of the Dynamo.FIG. 16. Diagram showing the principle of the Dynamo.The illustration show's the ideal simple dynamo, which consists of a loop of wire arranged to revolve between the poles of a permanent magnet in the direction of the arrow and around a horizontal line as an axis. The lines of magnetic force (represented by the fine straight lines) pass across from N to S as indicated. When in the position shown, the coil of wire encloses the largest possible number of lines of magnetic force. When it has revolved ninety degrees or a quarter of a turn as shown by the dotted lines, the lines of force will be parallel to the plane of the coil and none will pass through. During this quarter of the turn the number of lines of force has been decreasing. During the next quarter of a turn the lines will increase again, but will this time pass through from the opposite side of the loop. This decrease and increase of the number of lines of force passing through the loop generates therein a current of electricity. The same process is repeated during the next half of a revolution. However, since the lines of force flow through from opposite sides of the coil every half revolution, the current reverses twice during the same period.In the illustration the loop is represented as forming a complete closed circuit in itself. In order to draw any current for external use some method of establishing connection to the terminals of the coil must be had. This is furnished by two circular rings calledcollector rings. The little strips of metal or carbon employed to form contact with the rings are called brushes.FIG. 17. Simple Alternator.FIG. 17. Simple Alternator.Such a machine, so equipped will deliver alternating currents and illustrates the principle of the alternating current dynamo oralternator.With the aid of a device called acommutatorand consisting of a ring split in sections as shown in the illustration, all the successive current impulses may be turned in the same direction and the current made direct.In practice many coils of wire wound around an iron core called thearmature, the purpose of which is to concentrate the magnetic lines of force, are made to revolve in a powerfulfieldbetween the poles of adjacent electromagnets. Electromagnets are used because they are capable of producing a stronger magnetic field than magnetized bars of steel. The electromagnets used for this purpose are calledfield magnets. The central iron portion upon which the revolving coils are wound, called thearmature, is usually built up of a number of thin sheets of soft steel called armature disks or laminations.FIG. 18. Simple Dynamo showing Commutator.FIG. 18. Simple Dynamo showing Commutator.The modern armature is very complex. A simple coil such as those shown in Figs. 17 and 18 will not yield a steady current for twice in each revolution the electromotive force dies away to zero. The coils of large dynamos are grouped so that some of them are always active.There are three general methods of supplying current to the held magnets of a dynamo, known as theseries,shuntandcompoundwindings.The series dynamo is arranged so that the coils of the held magnets are in series with those of the armature.In the shunt dynamo, the coils of the held magnet form a shunt to the main circuit and being made of many turns of thin wire, draw off only a small fraction of the whole current.FIG. 19. Diagram of Dynamo Field Windings.FIG. 19. Diagram of Dynamo Field Windings.The compound dynamo is partly excited by shunt coils and partly by series coils.FIG. 20. Motor Generator.FIG. 20. Motor Generator.Each variety of dynamo winding has a certain advantage depending upon the condition of use.In the case of alternating current dynamos, the field magnets are sometimes supplied from a separate dynamo called an "exciter." In other cases the dynamo is provided with two sets of windings, one connected to a commutator producing a direct current which excites the field coils and the other connected to a set of rings and supplying the alternating current.In case a supply of either direct or alternating current is available and it is desirable to change the supply from direct to alternating or vice versa, it may be accomplished by employing a Motor-Generator. A motor-generator consists of an electric motor operating from the source of current supply on hand and driving a dynamo which supplies current of the kind desired.A motor is exactly the reverse of a dynamo. If a current of electricity is passed into a dynamo, the armature will be dragged around by the mutual action of the currents flowing in the copper conductors and the magnetic field in which they lie. Such a device constitutes a motor and may be employed to do useful work.Motors are classified as alternating and direct current machines accordingly as they are built to operate on either kind of current.
LESSON SIX. DYNAMO ELECTRIC MACHINERY.The Dynamo. The Alternator. The Motor.The discovery of the induction of currents in wires by moving them across a magnetic field led to the construction of electrical machines, called dynamos, to generate current in place of batteries.The dynamo is perhaps the most important piece of electrical apparatus there is for it is the source of ninety-nine percent of all the electricity now in use. It is practically necessary in any case where a considerable quantity of electricity is used to have a dynamo on the spot or else bring the currents over a wire from some supply station where dynamos are kept running.The operation of a dynamo is dependent upon current induction. It contains a system of closed conductors revolving in a magnetic field in such a way as to continuously vary the number of lines of force threading among them.FIG. 16. Diagram showing the principle of the Dynamo.FIG. 16. Diagram showing the principle of the Dynamo.The illustration show's the ideal simple dynamo, which consists of a loop of wire arranged to revolve between the poles of a permanent magnet in the direction of the arrow and around a horizontal line as an axis. The lines of magnetic force (represented by the fine straight lines) pass across from N to S as indicated. When in the position shown, the coil of wire encloses the largest possible number of lines of magnetic force. When it has revolved ninety degrees or a quarter of a turn as shown by the dotted lines, the lines of force will be parallel to the plane of the coil and none will pass through. During this quarter of the turn the number of lines of force has been decreasing. During the next quarter of a turn the lines will increase again, but will this time pass through from the opposite side of the loop. This decrease and increase of the number of lines of force passing through the loop generates therein a current of electricity. The same process is repeated during the next half of a revolution. However, since the lines of force flow through from opposite sides of the coil every half revolution, the current reverses twice during the same period.In the illustration the loop is represented as forming a complete closed circuit in itself. In order to draw any current for external use some method of establishing connection to the terminals of the coil must be had. This is furnished by two circular rings calledcollector rings. The little strips of metal or carbon employed to form contact with the rings are called brushes.FIG. 17. Simple Alternator.FIG. 17. Simple Alternator.Such a machine, so equipped will deliver alternating currents and illustrates the principle of the alternating current dynamo oralternator.With the aid of a device called acommutatorand consisting of a ring split in sections as shown in the illustration, all the successive current impulses may be turned in the same direction and the current made direct.In practice many coils of wire wound around an iron core called thearmature, the purpose of which is to concentrate the magnetic lines of force, are made to revolve in a powerfulfieldbetween the poles of adjacent electromagnets. Electromagnets are used because they are capable of producing a stronger magnetic field than magnetized bars of steel. The electromagnets used for this purpose are calledfield magnets. The central iron portion upon which the revolving coils are wound, called thearmature, is usually built up of a number of thin sheets of soft steel called armature disks or laminations.FIG. 18. Simple Dynamo showing Commutator.FIG. 18. Simple Dynamo showing Commutator.The modern armature is very complex. A simple coil such as those shown in Figs. 17 and 18 will not yield a steady current for twice in each revolution the electromotive force dies away to zero. The coils of large dynamos are grouped so that some of them are always active.There are three general methods of supplying current to the held magnets of a dynamo, known as theseries,shuntandcompoundwindings.The series dynamo is arranged so that the coils of the held magnets are in series with those of the armature.In the shunt dynamo, the coils of the held magnet form a shunt to the main circuit and being made of many turns of thin wire, draw off only a small fraction of the whole current.FIG. 19. Diagram of Dynamo Field Windings.FIG. 19. Diagram of Dynamo Field Windings.The compound dynamo is partly excited by shunt coils and partly by series coils.FIG. 20. Motor Generator.FIG. 20. Motor Generator.Each variety of dynamo winding has a certain advantage depending upon the condition of use.In the case of alternating current dynamos, the field magnets are sometimes supplied from a separate dynamo called an "exciter." In other cases the dynamo is provided with two sets of windings, one connected to a commutator producing a direct current which excites the field coils and the other connected to a set of rings and supplying the alternating current.In case a supply of either direct or alternating current is available and it is desirable to change the supply from direct to alternating or vice versa, it may be accomplished by employing a Motor-Generator. A motor-generator consists of an electric motor operating from the source of current supply on hand and driving a dynamo which supplies current of the kind desired.A motor is exactly the reverse of a dynamo. If a current of electricity is passed into a dynamo, the armature will be dragged around by the mutual action of the currents flowing in the copper conductors and the magnetic field in which they lie. Such a device constitutes a motor and may be employed to do useful work.Motors are classified as alternating and direct current machines accordingly as they are built to operate on either kind of current.
LESSON SIX. DYNAMO ELECTRIC MACHINERY.The Dynamo. The Alternator. The Motor.The discovery of the induction of currents in wires by moving them across a magnetic field led to the construction of electrical machines, called dynamos, to generate current in place of batteries.The dynamo is perhaps the most important piece of electrical apparatus there is for it is the source of ninety-nine percent of all the electricity now in use. It is practically necessary in any case where a considerable quantity of electricity is used to have a dynamo on the spot or else bring the currents over a wire from some supply station where dynamos are kept running.The operation of a dynamo is dependent upon current induction. It contains a system of closed conductors revolving in a magnetic field in such a way as to continuously vary the number of lines of force threading among them.FIG. 16. Diagram showing the principle of the Dynamo.FIG. 16. Diagram showing the principle of the Dynamo.The illustration show's the ideal simple dynamo, which consists of a loop of wire arranged to revolve between the poles of a permanent magnet in the direction of the arrow and around a horizontal line as an axis. The lines of magnetic force (represented by the fine straight lines) pass across from N to S as indicated. When in the position shown, the coil of wire encloses the largest possible number of lines of magnetic force. When it has revolved ninety degrees or a quarter of a turn as shown by the dotted lines, the lines of force will be parallel to the plane of the coil and none will pass through. During this quarter of the turn the number of lines of force has been decreasing. During the next quarter of a turn the lines will increase again, but will this time pass through from the opposite side of the loop. This decrease and increase of the number of lines of force passing through the loop generates therein a current of electricity. The same process is repeated during the next half of a revolution. However, since the lines of force flow through from opposite sides of the coil every half revolution, the current reverses twice during the same period.In the illustration the loop is represented as forming a complete closed circuit in itself. In order to draw any current for external use some method of establishing connection to the terminals of the coil must be had. This is furnished by two circular rings calledcollector rings. The little strips of metal or carbon employed to form contact with the rings are called brushes.FIG. 17. Simple Alternator.FIG. 17. Simple Alternator.Such a machine, so equipped will deliver alternating currents and illustrates the principle of the alternating current dynamo oralternator.With the aid of a device called acommutatorand consisting of a ring split in sections as shown in the illustration, all the successive current impulses may be turned in the same direction and the current made direct.In practice many coils of wire wound around an iron core called thearmature, the purpose of which is to concentrate the magnetic lines of force, are made to revolve in a powerfulfieldbetween the poles of adjacent electromagnets. Electromagnets are used because they are capable of producing a stronger magnetic field than magnetized bars of steel. The electromagnets used for this purpose are calledfield magnets. The central iron portion upon which the revolving coils are wound, called thearmature, is usually built up of a number of thin sheets of soft steel called armature disks or laminations.FIG. 18. Simple Dynamo showing Commutator.FIG. 18. Simple Dynamo showing Commutator.The modern armature is very complex. A simple coil such as those shown in Figs. 17 and 18 will not yield a steady current for twice in each revolution the electromotive force dies away to zero. The coils of large dynamos are grouped so that some of them are always active.There are three general methods of supplying current to the held magnets of a dynamo, known as theseries,shuntandcompoundwindings.The series dynamo is arranged so that the coils of the held magnets are in series with those of the armature.In the shunt dynamo, the coils of the held magnet form a shunt to the main circuit and being made of many turns of thin wire, draw off only a small fraction of the whole current.FIG. 19. Diagram of Dynamo Field Windings.FIG. 19. Diagram of Dynamo Field Windings.The compound dynamo is partly excited by shunt coils and partly by series coils.FIG. 20. Motor Generator.FIG. 20. Motor Generator.Each variety of dynamo winding has a certain advantage depending upon the condition of use.In the case of alternating current dynamos, the field magnets are sometimes supplied from a separate dynamo called an "exciter." In other cases the dynamo is provided with two sets of windings, one connected to a commutator producing a direct current which excites the field coils and the other connected to a set of rings and supplying the alternating current.In case a supply of either direct or alternating current is available and it is desirable to change the supply from direct to alternating or vice versa, it may be accomplished by employing a Motor-Generator. A motor-generator consists of an electric motor operating from the source of current supply on hand and driving a dynamo which supplies current of the kind desired.A motor is exactly the reverse of a dynamo. If a current of electricity is passed into a dynamo, the armature will be dragged around by the mutual action of the currents flowing in the copper conductors and the magnetic field in which they lie. Such a device constitutes a motor and may be employed to do useful work.Motors are classified as alternating and direct current machines accordingly as they are built to operate on either kind of current.
The Dynamo. The Alternator. The Motor.
The discovery of the induction of currents in wires by moving them across a magnetic field led to the construction of electrical machines, called dynamos, to generate current in place of batteries.
The dynamo is perhaps the most important piece of electrical apparatus there is for it is the source of ninety-nine percent of all the electricity now in use. It is practically necessary in any case where a considerable quantity of electricity is used to have a dynamo on the spot or else bring the currents over a wire from some supply station where dynamos are kept running.
The operation of a dynamo is dependent upon current induction. It contains a system of closed conductors revolving in a magnetic field in such a way as to continuously vary the number of lines of force threading among them.
FIG. 16. Diagram showing the principle of the Dynamo.FIG. 16. Diagram showing the principle of the Dynamo.
FIG. 16. Diagram showing the principle of the Dynamo.
The illustration show's the ideal simple dynamo, which consists of a loop of wire arranged to revolve between the poles of a permanent magnet in the direction of the arrow and around a horizontal line as an axis. The lines of magnetic force (represented by the fine straight lines) pass across from N to S as indicated. When in the position shown, the coil of wire encloses the largest possible number of lines of magnetic force. When it has revolved ninety degrees or a quarter of a turn as shown by the dotted lines, the lines of force will be parallel to the plane of the coil and none will pass through. During this quarter of the turn the number of lines of force has been decreasing. During the next quarter of a turn the lines will increase again, but will this time pass through from the opposite side of the loop. This decrease and increase of the number of lines of force passing through the loop generates therein a current of electricity. The same process is repeated during the next half of a revolution. However, since the lines of force flow through from opposite sides of the coil every half revolution, the current reverses twice during the same period.
In the illustration the loop is represented as forming a complete closed circuit in itself. In order to draw any current for external use some method of establishing connection to the terminals of the coil must be had. This is furnished by two circular rings calledcollector rings. The little strips of metal or carbon employed to form contact with the rings are called brushes.
FIG. 17. Simple Alternator.FIG. 17. Simple Alternator.
FIG. 17. Simple Alternator.
Such a machine, so equipped will deliver alternating currents and illustrates the principle of the alternating current dynamo oralternator.
With the aid of a device called acommutatorand consisting of a ring split in sections as shown in the illustration, all the successive current impulses may be turned in the same direction and the current made direct.
In practice many coils of wire wound around an iron core called thearmature, the purpose of which is to concentrate the magnetic lines of force, are made to revolve in a powerfulfieldbetween the poles of adjacent electromagnets. Electromagnets are used because they are capable of producing a stronger magnetic field than magnetized bars of steel. The electromagnets used for this purpose are calledfield magnets. The central iron portion upon which the revolving coils are wound, called thearmature, is usually built up of a number of thin sheets of soft steel called armature disks or laminations.
FIG. 18. Simple Dynamo showing Commutator.FIG. 18. Simple Dynamo showing Commutator.
FIG. 18. Simple Dynamo showing Commutator.
The modern armature is very complex. A simple coil such as those shown in Figs. 17 and 18 will not yield a steady current for twice in each revolution the electromotive force dies away to zero. The coils of large dynamos are grouped so that some of them are always active.
There are three general methods of supplying current to the held magnets of a dynamo, known as theseries,shuntandcompoundwindings.
The series dynamo is arranged so that the coils of the held magnets are in series with those of the armature.
In the shunt dynamo, the coils of the held magnet form a shunt to the main circuit and being made of many turns of thin wire, draw off only a small fraction of the whole current.
FIG. 19. Diagram of Dynamo Field Windings.FIG. 19. Diagram of Dynamo Field Windings.
FIG. 19. Diagram of Dynamo Field Windings.
The compound dynamo is partly excited by shunt coils and partly by series coils.
FIG. 20. Motor Generator.FIG. 20. Motor Generator.
FIG. 20. Motor Generator.
Each variety of dynamo winding has a certain advantage depending upon the condition of use.
In the case of alternating current dynamos, the field magnets are sometimes supplied from a separate dynamo called an "exciter." In other cases the dynamo is provided with two sets of windings, one connected to a commutator producing a direct current which excites the field coils and the other connected to a set of rings and supplying the alternating current.
In case a supply of either direct or alternating current is available and it is desirable to change the supply from direct to alternating or vice versa, it may be accomplished by employing a Motor-Generator. A motor-generator consists of an electric motor operating from the source of current supply on hand and driving a dynamo which supplies current of the kind desired.
A motor is exactly the reverse of a dynamo. If a current of electricity is passed into a dynamo, the armature will be dragged around by the mutual action of the currents flowing in the copper conductors and the magnetic field in which they lie. Such a device constitutes a motor and may be employed to do useful work.
Motors are classified as alternating and direct current machines accordingly as they are built to operate on either kind of current.