The history of the transformer. Part 2
Principle of operation of the transformer
In the transformer, the winding from the turns of the wire, connected to the power source and generating a magnetic field, is called the primary winding. Another winding, in which an electromotive force (EMF) arises under the action of this field, is called secondary.
The induction between the primary and secondary windings is mutual, that is, the current flowing in the secondary winding induces the EMF in the primary just like the primary winding induces EMF in the secondary winding. Moreover, since the coils of the primary winding cover their own lines of force, EMF itself arises in them. This phenomenon, called self-induction, is also observed in the secondary winding.
On the phenomenon of mutual induction and self-induction, the action of the transformer is based. For effective operation of this device, it is necessary that there be a connection between its windings and each of them possess high self-induction. These conditions can be satisfied by winding the primary and secondary windings on the iron core as Faraday did in his first experiments.
Iron increases the number of magnetic field lines approximately 10,000 times. The materials possessing this property are said to have a high magnetic permeability. In addition, the iron core localizes the flux of magnetic induction, so that the transformer windings can be spatially separated and still remain inductively coupled.
In an ideal transformer, all lines of force pass through all the turns of both windings, and since a changing magnetic field generates the same EMF in each turn, the total EMF induced in the winding is proportional to the total number of its turns.
If no energy loss occurs in the transformer, the power in the secondary circuit must be equal to the power supplied to the primary winding. In other words, the product of the voltage on the current in the secondary winding should be equal to the product of the voltage and current in the primary.
Thus, the currents turn out to be inversely proportional to the ratio of the voltages in the two windings and, consequently, the ratio of the currents is inversely proportional to the ratio of the number of turns in the windings. Such a calculation of power is valid only if the currents and voltages coincide in phase; The high self-induction condition ensures a negligibly small amount of currents that do not coincide in phase.
Perfect transformer
The ideal transformer represents for electricians a tool similar to the lever in mechanics, but instead of transforming the force and displacement, the transformer converts the voltage and current. Instead of the ratio of the arms of the force, the quantitative characteristic of the transformer is the ratio between the number of turns in its windings.
Of course, there is no ideal transformer, but almost realized devices are very close to ideal. The iron core is an indispensable part of all modern power transformers, and copper due to its low electrical resistance has been and remains the basic material from which the wire for windings is made.
Experiments with "inducers"
After his discovery, Faraday did not go into details of the open phenomenon, believing that his work would be continued by others. However, in reality, it turned out that devices like transformers did not find wide practical application in the next few decades.
Of particular interest were the first experiments with "inductors" consisting of a wire wound on an iron core, in particular, a study of the ability of these devices to generate sparks when the current in the winding was interrupted.
Among the famous scientists involved in this phenomenon was the American Joseph Henry , first secretary and director of the Smithsonian Institution. Subsequently, his unit was named inductance unit.
In these experiments it was found out that the currents circulating in solid metal cores dissipated energy. In order to minimize these so-called eddy currents, the cores were made to be nonconducting in a direction perpendicular to the magnetic lines of the transformer. Now the cores were a "bundle" of isolated iron wires.
Comments
When commenting on, remember that the content and tone of your message can hurt the feelings of real people, show respect and tolerance to your interlocutors even if you do not share their opinion, your behavior in the conditions of freedom of expression and anonymity provided by the Internet, changes Not only virtual, but also the real world. All comments are hidden from the index, spam is controlled.