Superconducting Generators

Presented B y

Sajeesh Jos Parakkal

MTI-Thrissur

Reg.No.89035078

SUPERCONDUCTING GENERATORS

SUPERCONDUCTING ELECTRIC MACHINESSuperconductivity is the property of having zero electrical resistance.Are electromechanical systems that rely on the use of one or more superconducting elements. Since superconductors have no DC resistance, they typically have greater efficiency.

THE MOST IMPORTANT PARAMETER

The generation of a very high magnetic field that is not possible in a conventional machine.Since superconductors only have zero resistance under a certain superconducting transition temperature,Tc that is hundreds of degrees lower than room temperature

HISTORY

DC homopolar machines are among the oldest electric machines. Michael Faraday made one in 1831. Superconducting DC homopolar machines use superconductors in their stationary field windings and normal conductors in their rotating pickup winding

HISTORYIn 2005 the General Atomics company received a contract for the creation of a large low speed superconducting homopolar motor for ship propulsion.Superconducting homopolar generators have been considered as pulsed power sources for laser weapon systems.

SUPERCONDUCTING GENERATOR

SUPERCONDUCTING GENERATOR

The higher current density achievable in many superconducting materials tends to make them smaller compared with non-superconducting machines with the same power density.

These machines employed LTS wire made up of a niobium-titanium (NbTi) alloy.

SUPERCONDUCTING GENERATOR

High-temperature superconductors become superconducting at more easily obtainable liquid nitrogen temperatures.

HTS-based motors and generators will be smaller, lighter, more efficient, and less expensive to manufacture and operate than conventional machines.

HTS WIRE STATUS

High temperature superconductor bismuth strontium calcium copper oxide (BSCCO-2223) manufactured commercially by American superconductor (AMSC).

It is able to carry more than 140-times the electrical current of copper wire of the same cross section, and is robust enough to meet commercial requirements

HTS WIRE

HTS WIRE STATUS However, a newer yttrium barium copper oxide (YBCO) superconductor has been developed Yttrium barium copper oxide, often abbreviated YBCO, is a crystalline chemical compound with the formula YBa2Cu3O7-x. This material, a famous "high-temperature superconductor",

HTS MACHINES The major components of a rotating machine employing HTS winding

Only the field winding employs HTS cooled with a cryocooler subsystem to about 35-40K The cryocooler modules are located in a stationary frame and a gas, such as helium, is employed to cool components on the rotor.

HTS MACHINES

CROSS-SECTION OF SUPERCONDUCTING GENERATOR.

CONCEPTIONAL FIGURE FOR SELF-PUMPING EFFECT.

SUPERCONDUCTING GENERATORS

Superconducting Generators offer increased electrical efficiency, reduced size, increased system stability, and higher generation voltages.

Unlike a conventional generator winding where the core has iron teeth and the armature coils are disposed in slots, the winding in a superconducting generator sits in an “air-gap” between the rotor and an iron flux shield. For the 300 MVA superconducting generator, the six armature coils were pancake wound and were interleaved together in a spiral configuration.

The overall armature winding and flux shield were very orthotropic in their material properties.

Stress and displacement of the armature winding and flux shield were calculated using finite element analysis for steady state and transient electromagnetic and thermal loads.

COMPARED WITH A CONVENTIONAL CONDUCTOR MACHINE

Superconducting electric machines typically have the following advantages:Reduced resistive losses but only in the rotor electromagnet.Reduced size and weight per power capacity without considering the refrigeration equipment.

There are also the following disadvantages:The cost, size, weight, and complications of the cooling system.A sudden decrease or elimination of motor or generator action if the superconductors leave their superconductive state.A greater tendency for rotor speed instability. A superconducting rotor does not have the inherent damping of a conventional rotor. Its speed may hunt or oscillate around its synchronous speed.

CONCLUSIONA well-designed superconducting generator can represent a beautifuloptimization between competing and often conflicting electrical, economic, thermal,reliability, and mechanical requirements.

Basically thermal performance improvesas the operating temperature is increased, and electrical performance is decreased.

Electrical system stability and power density is increased at the expense of mechanicalstrength and vibration tolerance

ANY QUESTIONS???

REFERENCES[1] J. H. Parker, Jr. and M. P. Krefta, “The Intrinsic Magneto-Resistance of CryogenicJoints,” IEEE Transactions on Applied Superconductivity, Vol. 7, Part 1, pages 820-823,June 1997.[2] Z.J.J. Stekly, H.H. Woodson, A.M. Hatch, L.O. Hoppie, and E. Halas. IEEE

Transactions on Power Apparatus and Systems Vol. 85, p. 274 (1966).[3] P. Thullen, J.C. Dudley, D.L. Green, J.L. Smith, H.H. Woodson, IEEE Transactions onPower Apparatus and Systems Vol. 90, p. 611 (1971).