Today Tesla's transformer is called a high-frequency high-voltage resonant transformer, and many examples of striking implementations of this unusual device can be found on the network. A coil without a ferromagnetic core, consisting of many turns of thin wire, topped with a torus, emits real lightning, impressing the amazed onlookers. But does everyone remember how and why this amazing device was originally created?
The history of this invention begins at the end of the 19th century, when the brilliant experimental scientist Nikola Tesla, working in the United States, only set himself the task of learning how to transmit electrical energy over long distances without wires.
It is hardly possible to indicate the exact year when exactly this idea came to the scientist, but it is known that on May 20, 1891, Nikola Tesla delivered a detailed lecture at Columbia University, where he presented his ideas to the staff of the American Institute of Electrical Engineers, and illustrated something. showing visual experiments.
The purpose of the first demonstrations was to show a new way of obtaining light through the use of currents of high frequency and high voltage for this, and also to reveal the features of these currents. For the sake of fairness, we note that modern energy-saving fluorescent lamps work precisely on the principle that Tesla proposed to obtain light.
The final theory regarding the wireless transmission of electrical energy was emerging gradually, the scientist spent several years of his life perfecting his technology, experimenting a lot and painstakingly improving each element of the circuit, he developed breakers, invented durable high-voltage capacitors, invented and modified circuit controllers, but so I could not bring my plan to life on the scale in which I wanted.
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However, the theory has reached us. Nikola Tesla's diaries, articles, patents and lectures are available, in which you can find the initial details regarding this technology. The principle of operation of a resonant transformer can be found by reading, for example, Nikola Tesla's patents # 787412 or # 649621, already available on the network today.
If you try to briefly understand how the Tesla transformer works, consider its structure and principle of operation, then there is nothing complicated.
The secondary winding of the transformer is made of an insulated wire (for example, from enamel wire), which is laid turn to turn in one layer on a hollow cylindrical frame, the ratio of the frame height to its diameter is usually taken equal from 6 to 1 to 4 to 1.
After winding, the secondary winding is coated with epoxy or varnish. The primary winding is made of a wire of relatively large cross-section, it usually contains from 2 to 10 turns, and fits into the shape of a flat spiral, or is wound like a secondary one - on a cylindrical frame with a diameter slightly larger than that of the secondary.
The height of the primary winding, as a rule, does not exceed 1/5 of the height of the secondary. A toroid is connected to the upper terminal of the secondary winding, and its lower terminal is grounded. Next, we will consider everything in more detail.
For example: the secondary winding is wound on a frame with a diameter of 110 mm, with a PETV-2 enamel wire with a diameter of 0.5 mm, and contains 1200 turns, thus its height is equal to about 62 cm, and the length of the wire is about 417 meters. Let the primary winding contain 5 turns of a thick copper tube, wound over a diameter of 23 cm, and has a height of 12 cm.
Next, a toroid is made. Its capacitance, ideally, should be such that the resonant frequency of the secondary circuit (grounded secondary coil together with the toroid and the environment) would correspond to the length of the secondary winding wire so that this length would be equal to a quarter of the wavelength (for our example, the frequency is 180 kHz) …
For an accurate calculation, a special program for calculating Tesla coils, for example VcTesla or inca, can be useful. A high-voltage capacitor is selected to the primary winding, the capacitance of which, together with the inductance of the primary winding, would form an oscillatory circuit, the natural frequency of which would be equal to the resonant frequency of the secondary circuit. Usually they take a capacitor close in capacity, and the tuning is carried out by selecting the turns of the primary winding.
The essence of the Tesla transformer in its canonical form is as follows: the primary circuit capacitor is charged from a suitable high voltage source, then it is connected by a switch to the primary winding, and this is repeated many times per second.
As a result of each switching cycle, damped oscillations occur in the primary circuit. But the primary coil is an inductor for the secondary circuit, therefore electromagnetic oscillations are excited, respectively, in the secondary circuit.
Since the secondary circuit is tuned to resonance with the primary oscillations, then a voltage resonance occurs on the secondary winding, which means that the transformation ratio (the ratio of the turns of the primary winding and the turns of the secondary winding covered by it) must also be multiplied by Q - the quality factor of the secondary circuit, then the value of the real ratio the voltage on the secondary winding to the voltage on the primary.
And since the length of the secondary winding wire is equal to a quarter of the wavelength of the oscillations induced in it, then it is on the toroid that the voltage antinode will be located (and at the grounding point - the current antinode), and it is there that the most effective breakdown can take place.
To power the primary circuit, different circuits are used, from a static spark gap (spark gap) powered by MOTs (MOT is a high-voltage transformer from a microwave oven) to resonant transistor circuits on programmable controllers powered by rectified mains voltage, but the essence remains the same.
Here are the most common types of Tesla coils, depending on how you drive them:
SGTC (SGTTS, Spark Gap Tesla Coil) - Tesla transformer on the spark gap. This is a classic design, a similar scheme was originally used by Tesla himself. An arrester is used here as a switching element. In low-power designs, the arrester consists of two pieces of thick wire spaced at a certain distance, while in more powerful designs, complex rotating arresters using motors are used. Transformers of this type are made if only a long streamer length is required, and efficiency is not important.
VTTC (VTTC, Vacuum Tube Tesla Coil) - Tesla transformer on an electronic tube. A powerful radio tube, for example GU-81, is used here as a switching element. Such transformers can operate continuously and produce rather thick discharges. This type of power supply is most often used to build high-frequency coils, which are called "torches" due to the typical appearance of their streamers.
SSTC (SSTC, Solid State Tesla Coil) is a Tesla transformer in which semiconductors are used as a key element. Usually these are IGBT or MOSFET transistors. This type of transformer can operate in continuous mode. The appearance of streamers created by such a coil can be very different. This type of Tesla transformers is easier to control, for example, you can play music on them.
DRSSTC (DRSSTC, Dual Resonant Solid State Tesla Coil) is a Tesla transformer with two resonant circuits, here semiconductors are used as switches, as in SSTC. DRSSTTS is the most difficult type of Tesla transformers to control and configure.
To obtain a more efficient and effective operation of the Tesla transformer, it is the DRSSTC topology circuits that are used, when a powerful resonance is achieved in the primary circuit itself, and in the secondary one, respectively, a brighter picture, longer and thicker lightning bolts (streamers).
Tesla himself tried as best he could to achieve just such a mode of operation of his transformer, and the beginnings of this idea can be seen in patent No. 568176, where charging chokes are used, Tesla then developed the circuit along this path, that is, he sought to use the primary circuit as efficiently as possible, creating in it resonance. You can read about these experiments of the scientist in his diary (the scientist's notes about the experiments in Colorado Springs, which he conducted from 1899 to 1900, have already been published in printed form).
Speaking about the practical application of the Tesla transformer, one should not limit ourselves only to admiration for the aesthetic nature of the discharges obtained, and treat the device as decorative. The voltage on the secondary winding of the transformer can reach millions of volts, it is, after all, an efficient source of extra high voltage.
Tesla himself developed his system to transmit electricity over long distances without wires, using the conductivity of the upper air layers of the atmosphere. It was assumed the presence of a receiving transformer of a similar design, which would lower the accepted high voltage to an acceptable value for the consumer, you can find out about this by reading Tesla's patent No. 649621.
The nature of the interaction of the Tesla transformer with the environment deserves special attention. The secondary circuit is an open circuit, and the system is thermodynamically by no means isolated, it is not even closed, it is an open system. Modern research in this direction is carried out by many researchers, and the point on this path has not yet been set.
Author: Andrey Povny