Tag Archives: nikola tesla

A brilliant 100-year-old Nikola Tesla invention is just beginning to make sense

Credit: Public Domain.

Eccentric scientist and inventor extraordinaire Nikola Tesla is known for developing the basis for AC electric power that, today, most of the planet uses. But the Serbian-American inventor, who emigrated to New York City in 1884, held nearly 300 patents for items such as motors, radios, remote controls, X-rays, neon signs, and many other marvelous gadgets and gizmos.

Many of these inventions are still in use today or have heavily influenced modern technology in some way. But one of Tesla’s lesser-known patents, a macrofluidic valve, is only recently being recognized for its genius and worth.

The scientist patented his “valvular conduit”, also known as a “Tesla valve”, in 1920. It is essentially a one-way fluid valve with no moving parts consisting of a pipe with an intricate series of diverting teardrop-shaped loops. The design is such that water can easily flow through in one direction, but when the direction is reversed, the flow is almost totally blocked, or so the initial patent stated.

In a new study, the physics of the Tesla valve was revisited by researchers at New York University who built a 30-centimeter-long replica following Tesla’s original plan. They then performed a series of experiments and measured flow in both directions at different values for pressure.

“It’s remarkable that this 100-year-old invention is still not completely understood and may be useful in modern technologies in ways not yet considered,” explains Leif Ristroph, an associate professor in New York University’s Courant Institute of Mathematical Sciences and the paper’s senior author. “While Tesla is known as a wizard of electric currents and electrical circuits, his lesser-known work to control flows or fluid currents was truly ahead of its time.”

Although Tesla claimed that his valve would make fluid flow 200 times slower in one direction than the other, the researchers’ replica only cut the flow by half.

Comparison of flows in the reverse direction (right to left) at three different speeds. The water current is visualized with green and blue dyes, showing that the flows are increasingly disrupted at higher speeds. Credit: NYU’s Applied Mathematics Laboratory.

However, the researchers learned that the Tesla valve is more sophisticated than initially thought. At low flow rates, there is hardly any difference between forward and reverse flows. But above a certain threshold, the valve abruptly “turned on” like a switch and significantly resisted reverse flow.

“Crucially, this turn-on comes with the generation of turbulent flows in the reverse direction, which ‘plug’ the pipe with vortices and disrupting currents,” explains Ristroph. “Moreover, the turbulence appears at far lower flow rates than have ever previously been observed for pipes of more standard shapes–up to 20 times lower speed than conventional turbulence in a cylindrical pipe or tube. This shows the power it has to control flows, which could be used in many applications.”

What’s more, the valve controls the reverse flow even better when the flow isn’t steady. If the flow comes in pulses or oscillations, the device will smoothen the fluid flow, making the device ideal for use in high-vibration environments. This is remarkably similar to how AC-DC converters transform alternating current to direct current.

“We think this is what Tesla had in mind for the device since he was thinking about analogous operations with electrical currents,” observes Ristroph. “He in fact is most famous for inventing the AC motor as well as an AC-DC converter.”

Although the constricting effect of the valve is much lower than Tesla claimed more than a century ago, the design is still useful. It has no moving parts, unlike other valves that need springs and other parts that require regular maintenance and replacements. Ristroph and colleagues imagine a number of applications where the Tesla valve could prove useful, such as harnessing vibrations in engines to pump fuel, lubricants, and other fluids.

One of the original Tesla Electric Motors from 1888 which is today the main power of for industry and household appliances. Credit: Wkimedia Commons

Who invented the induction motor

The induction motor is one of the most important inventions in modern history. It turned the wheels of progress at a new speed and officially kicked off the second industrial revolution by drastically improving energy generation efficiency and making the long-distance distribution of electricity possible. Today, not only do the machines turn on the lights in your home but also power many mechanical gadgets people take for granted, from vacuum cleaners and electric toothbrushes to that classy Tesla Motors Model S.

 One of the original Tesla Electric Motors from 1888 which is today the main power of for industry and household appliances. Credit: Wkimedia Commons

One of the original Tesla Electric Motors from 1888. To this day, this design is the main power generator for industry and household appliances. Credit: Wikimedia Commons

The first induction motor was invented by the famed Nikola Tesla in 1887 at his workshop on 89 Liberty Street, New York. This gifted inventor is said to have had a vision of his A-C motor one sunny day in Budapest, 1882, while reciting stanzas from Goethe’s Faust.

“At that age, I knew entire books by heart, word for word. One of these was Goethe’s ‘Faust’. The sun was just setting and reminded me of the glorious passage, ‘Sie ruckt und weicht, der Tag ist uberlebt, Dort eilt sie hin und fordert neues Leben. Oh, da kein Flugel mich vom Boden hebt Ihr nach und immer nach zu streben! Ein schöner Traum indessen sie entweicht, Ach, au des Geistes Flügeln wird so leicht Kein körperlicher Flügel sich gesellen!’ As I uttered these inspiring words the idea came like a flash of lightening and in an instant the truth was revealed. I drew with a stick on the sand, the diagram shown six years later in my address before the American Institute of Electrical Engineers, and my companion understood them perfectly.

The images I saw were wonderfully sharp and clear and had the solidity of metal and stone, so much so that I told him, ‘See my motor here; watch me reverse it.’ I cannot begin to describe my emotions. Pygmalion seeing his statue come to life could not have been more deeply moved. A thousand secrets of nature which I might have stumbled upon accidentally, I would have given for that one which I had wrested from her against all odds and at the peril of my existence…”

In the summer of 1883, while in Paris, Tesla built his first actual induction motor and saw it run. Tesla sailed for America in 1884, arriving in New York, with four cents in his pocket, a few of his own poems, and calculations for a flying machine. After a few odd jobs, he got employed by Thomas Edison who tasked him with improving the dynamo for his DC motor. Neither Edison nor Edison’s investors were interested in Tesla’s plans for alternating current.

[panel style=”panel-primary” title=”How a DC motor works” footer=””]In a direct current motor, a magnet that supplies a magnetic field is fixed in place and forms the outside, static part of the motor. This is called the stator. A coil of wire is suspended between the poles of the magnet and hooked to a direct current power source, like a battery. The current running through the wire produces a temporary magnetic field (it’s an electromagnet), which repels the field from the permanent magnet causing the wire to flip over.

Normally, the wire would stop after one turn and flip back again, however, a key component called a commutator reverses the current every time the wire flips. This way, the wire can keep rotating in the same direction for as long as the current keeps flowing.

The DC engine was conceived by Michael Faraday in the 1820s and was turned into a practical invention a decade later by William Sturgeon. [/panel]

After a fight with the American inventor, Tesla left Edison’s lab and partnered with George Westinghouse in 1888 to whom he sold the patent for Tesla’s polyphase alternating current technology. Their partnership became very lucrative, winning numerous contracts, including one that supplied the Chicago World’s Fair of 1893 with electricity.

However, the AC motor’s first big break came when Tesla’s polyphase alternating current design was chosen to harness the power of Niagara Falls that same year.

Since his childhood, Tesla himself had dreamed of harnessing the power of the great natural wonder. In his autobiography “My inventions” he told:

“In the schoolroom there were a few mechanical models which interested me and turned my attention to water turbines”.

After hearing a description of the great Niagara Falls:

“I pictured in my imagination a big wheel run by the Falls.”

He proclaimed to his uncle that one day “he would go to America and carry out this scheme.”

US patent 382,279 Electro magnetic motor granted to Nikola Tesla in 1888.

US patent 382,279 for an Electro magnetic motor granted to Nikola Tesla in 1888.

Despite Edison’s propaganda aimed at discrediting Tesla as an inventor and alternative current as a viable tech — things like public demonstrations in which animals were brutally electrocuted with AC — Tesla’s designs followed the natural course of progress. As DC current travels through transmission lines, the accumulated resistance in the wires greatly reduces the electrical power supplied to the consumer.  AC, on the other hand, does not suffer the same loss and is able to travel great distances with far less loss of potential. Alternative current can also have its voltage increased or decreased by transformers, so electricity can be produced at high power at generating stations then reduced right at the point of local distribution.

[panel style=”panel-success” title=”How an AC motor works” footer=””]Alternative current reverses its direction about 50 times a second (~50 Hz), so an electric motor needs a radically different design from the DC motor.

In an AC motor, the stator is comprised of a ring of electromagnet pairs which produce a rotating magnetic field. Unlike a DC motor where the power is sent to the inner rotor, in an AC motor the power is coupled to these electromagnets to induce the field. The brilliant trick lies in energizing the electromagnets at a time, in pairs. When one pair is fully active, the other is completely shut down.


When the coils are energized, they produce a magnetic field that induces an electric current in the rotor, which is an electrical conductor, per Faraday’s law. The new current produces its own magnetic field which tries to oppose the field that produced it in the first place, per Lenz’s law. This game of catch between the two magnetic fields is what ultimately turns the rotor. [/panel]

In the 20th century, electrical power distribution witnessed a massive expansion all over the world. In the first decade of the century, for instance, a generating unit with a capacity of 25,000 kilowatts was considered large. But by 1930, the largest unit in the United States had a capacity of 208,000 kilowatts, with pressures exceeding 1,200 pounds per square inch. Driven by the economy of scale, the price per kilowatt-hour of electricity dramatically plunged which eventually helped electrify the whole nation. And with so much energy at our disposal all of a sudden, the world was ready to bloom technologically.