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World-record high temperature superconductor

 

Since the discovery of superconductivity in 1911, scientists have gradually raised the temperature of the superconducting transition to industry-friendly values. Now the unusual materials to move from the laboratory into everyday life. For example, a warship with a superconducting motor or City Electric on superconductors.
It looks pure fantasy, but a reality right before our eyes. If the first scientists to observe the effects of superconductivity at temperatures just above absolute zero, but now the numbers look much more attractive. But a world record high temperature superconductor says later, but let’s sees what we promise to practice the ability of some materials conduct electricity with zero electrical resistance.
There cannot do without the story of the achievements of American Superconductor. Recently it has developed industrial production of superconducting cables for power networks.

According to BBC News, a short section of cable American Superconductor, which can carry 150 times more current than copper wire of the same size, are already working in Columbus (Columbus), Ohio. And soon in order to enter 800-meter power cable, also from American Superconductor, which will participate in the transfer of loads in the power system of the island of Long Island (New York).

The new cables work at liquid nitrogen temperature, which makes them attractive for industrial applications. After cryogenic system using liquid nitrogen for a long time familiar and widely distributed. For this revolution can only adjust cooling liquid nitrogen long enough energy networks, which is a problem. But doable.
However, superconductors that operate at lower temperatures, it turns out, can also find its niche in the art. We’re not talking about just a single product and exotic applications, such as large particle accelerators and tokomaks. Of superconductors, for example, you can make the windings of large electric motors.

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Such an interesting topic and now occupies American Superconductor. Back in 2003, the company has built and tested a prototype 5-megawatt electric motor for high-temperature superconductors (called HTS motor, synchronous, AC). And now, in collaboration with Northrop Grumman, she built for the U.S. Navy real-engine monster.

36.5 HTS motor has a shaft power of 36.5 megawatts (49,000 horsepower), developed at 120 rpm (corresponding to a monstrous torque may find themselves).
In the rotor windings are used here and BSCCO superconductors Bi-2223 (oxide complex composition based on bismuth), which operate at a temperature of 35-40 degrees Kelvin. They are cooled by helium gas, supplied through the hollow shaft to the rotor machine.

The stator winding of the motor is not superconducting – it is made of copper and has a simple liquid cooling. However, it also differs from the conventional coil motors. For example, inside it is not the usual iron core. Heavy duty rotor field and so perfectly “saturates” stator, through which, by the way, passed a very small fraction of the total current consumed by this giant.

HTS motor is specifically designed for U.S. Navy ships the next generation, which is designed for all-electric propulsion system. HTS motor efficiency at full power exceeds 97%, and one-third of the load at all close to 99%.

Note some types of conventional electric motors can also show efficiency of about 95-97%. What’s the difference? The fact that such a high performance they give is not the entire range of engine speed and load, and in many modes of motion “fail” to more modest values ​​efficiency is about 85-88%.

Superconducting same motor show such a decent performance from 5% of the maximum speed up to their maximum speed.

Thus, at low loads HTS motor, resulting in the ship’s propeller, saves a ship more than 10% of the fuel burned in the gas turbine generators or diesel generators, or 10% of the input of the ship’s electrical power network, if the vessel – Nuclear power plant. Add that up in a sound performance HTS motor is included in the energy consumption of cryogenic cooling system.

However, the main advantage of their marine motors American Superconductor said even efficiency and small size and weight. Capacity of 36.5 MW model weighs 69 tons and has a thickness of 3.4 meters, width of 4.6 meters, a height of 4.1 meters. The traditional “copper” motor with the same output parameters would have a lot of 200-300 tons, and dimensions are about twice as much.

For medium-sized vessel that difference is not a trifle. Reducing the size of the engine room, you can pay for extra volume of cargo, passengers or ammunition (in the case of a military ship). And the weight savings in the 130-230 tons can be spent on something useful.

In addition, HTS motor is much quieter than conventional motor of the same power. Thus, according to the company, the 25-megawatt 60-ton version of HTS motor is noisy at full speed with a force of 48 decibels – louder than a desktop computer.
MRI scanners with superconducting coils cooled by liquid helium, long no one is surprised. They work in many major hospitals.

Now here on the stage serial superconducting cables and wires under helium gas and the same liquid nitrogen. Benefit of the American engineers was able to solve the problem brittle superconducting materials. New guides are a series of subtle (in nanometers) layers of superconductors, deposited on a thin (in millimeter) metal substrates. Are obtained in veins that can easily bend, just as is the case with an optical fiber, although it is made of glass.

What’s next? Recently found new superconductors with even more amazing properties. For example, a complex structure on the basis of mercury, which has a transition temperature to the superconducting state at 134 degrees Kelvin (minus 139 Celsius).

“When we applied to the material pressure, raised the transition temperature to 164 Kelvin (minus 109 Celsius) – a record,” – said the author of the opening of Professor Paul Chu (Paul Chu) of the University of Houston (University of Houston). Chu, note the first to find the materials, which stepped on the transition temperature of the bar at 77 Kelvin (boiling point of nitrogen at atmospheric pressure). He discovered compounds that become superconducting at 93 Kelvin. And now we see the impressive numbers 164.
Let go of the practical application of the mercury is still very far, though, the discovery is encouraging. May soon establish a more convenient and perfect superconductor?
“There are no limitations in principle we do not see” – he says Dennis Newns (Dennis Newns) and Chiang Tsuey (Chang Tsuei) of IBM, published their work on the mechanism of high-temperature superconductivity in the journal Nature Physics.
The authors of the study say that the existence of superconductors remains so even at room temperature, from the point of view of physics possible. It remains only to find them.