What is trapped field magnet

Currently in the U.S., ferromagnetic materials (permanently magnetized materials) are often costly to obtain because they are supplied from foreign countries.  Center researchers are searching for alternative materials with the potential to produce higher magnetic fields to enable revolutionary motor and generator designs. The science begins with high temperature superconducting (HTS) materials such as yttrium barium copper oxide (YBCO).  HTS implies the material becomes superconductive at the boiling temperature of liquid nitrogen (77 K).  If pucks of these materials are first cryogenically cooled using liquid nitrogen and then exposed to a pulsed magnetic field, a field is trapped on each puck, hence the name Trapped Field Magnet (TFM).

CEM's technical approach:

Working in collaboration with researchers specializing in the creation of YBCO crystalline pucks from University of Houston and nuclear engineers from Texas A&M, CEM’s engineers are trying to incorporate these HTS YBCO pucks into innovative new designs.  Typical applications that attempt to leverage HTS materials, do so using thin wire made from the HTS materials.  This wire is difficult & costly to manufacture and is ultimately quite fragile.  Alternatively, designs that utilize HTS pucks should be less expensive and more robust.  CEM engineers are combining years of expertise in the design of rotating machines and generators to come up with innovative new designs that are smaller, lighter, and more powerful than their predecessors!

There are two primary research challenges being addressed at UT.  The first, is to determine cost effective ways to magnetize the pucks onsite in a large motor generator.  There are obvious manufacturing advantages to site magnetization, but it must be done in a way that is both practical and nearly transparent to the user.  The second, is to achieve adequate thermal insulation on the generator to maintain cryogenic cooling without compromising the electromagnetic performance of the motor or generator.

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Technical Advantage

Numerous applications are require more power these days.  However, these applications often don’t allow much if any more room for expanding the size or weight of the machine delivering the power.  The next generation of military vehicles will require more power to run onboard weapons and supporting equipment, but have little to no room to budge on size or weight design parameters.  The Air Force predicts the next generation of fighter jets will have twice the power and thermal requirements of current fighter jets like the F-22.  The U.S. Navy plans to make all electric ships a reality by 2012.  This means all mechanisms currently driven by hydraulic or pneumatic controls will be driven by distributed electrical power.  CEM’s HTS motor design can help the military meet the power demands of next generation vehicles, as the current design delivers up to 50% more power for the same package size versus conventional motors.  Put another way, HTS motors can deliver the same power as a conventional permanent magnet motor in a smaller & lighter package.

Future Applications

Wind Turbine Generators - Direct drive wind generator systems utilizing HTS materials instead of conventional materials for the generator’s stator are expected to be much smaller, lighter and more efficient than conventional generators and gearboxes. Resulting in a lighter suspended tower weight and a lower cost of wind generated electricity, particularly for offshore wind farms.

Portable Power – Islanding of power for military base security and emergency response requires lighter weight and more portable power generators that can be airlifted easily into an effected area.  When power was desperately needed at the nuclear plant in Japan and all roads into the plant were obstructed, one possible solution would have been to airlift in power units.

Texas A&M University of Houston

Mr. Jon Hahne

Mr. Jon Hahne

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