INTRODUCTION The higher current density achievable in many

superconducting materials tends to make them smaller compared with non-superconducting machines with the same power density.

The advent HTS has created an opportunity for quantum leap in technology

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

The complexity and cost of the refrigeration equipment, and the challenging nature of thermal isolation systems that are necessary for allowing LTS materials to operate at an ultra-low 4K, have made rotating machine applications a prohibitive concept.

American Superconductor Corporation (AMSC) has built and tested a 5000 hp, 1800-RPM motor for industrial market.

Conductivity of hts is (10)6 greater than copper wire. Current density is ten times larger than in copper winding.

SUPERMACHINE TOPOLOGY

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. The stator winding employs conventional copper winding but with a few differences. The stator winding is not used in conventional iron core teeth because they saturate due to high magnetic field imposed by the HTS winding.

 LITZ WIRE

Litz wire is a type of cable used in electronics to carry alternating current.The wire is designed to reduce the:- (i)skin effect (ii)proximity effect

Superconducting generators and motors

Why ?

Superconducting generators and motors

Losses in conventional and superconducting designs

Superconducting generators and motors

LTS (Low Temperature Superconductivity) has not been successful in electric power applications

•low reliability•high cost•difficult technology

Impact of HTS (High Temperature Superconductivity)

•better thermal stability

•cheaper cooling•improved reliability

Superconducting generators and motors

All conceptual HTS designs and small demonstartors use BSCCO tapes at temperatures between 20K and 30K

•at 30K critical fields and currents order of magnitude better than at 78K

•it is possible to have a core-less design

But !!!

•liquid neon or helium gas needed

•increased cost and complexity of refrigeration plant

•reduced thermodynamic efficiency

•worse reliability and higher maintenance requirements

Machine DesignStator

An existing 100kVA stator with 48 slots and a balanced 2-pole 3-phase winding has been usedThe pitch of the stator coils ensures that the winding produces very little 7th harmonic fieldHigher order fields are reduced significantly by the distribution of the phase conductors throughout each phase beltThe primary concern is the 5th harmonic

Rotor and field winding The rotor is made of 9% nickel steel The core is formed by thirteen plates of various shapes and sizes The HTS rotor winding is made of silver clad BSCCO-2223 tapes10 identical coils and each coil has 40 turns

Each superconducting coil is separated by the flux diverters

Machine Design

Rotor

Flux Diverters

HTS field winding

Stator

Stator winding

3D Modelling and Analysis

3D Modelling and Analysis

0.03%0.0001420.003444-0.002175190.02%0.0000770.000535-0.008446170.11%0.0005280.0092600.003801150.09%0.000400-0.003893-0.007908130.41%0.0018950.0052460.032844110.59%0.002736-0.023096-0.01316490.18%0.000823-0.002635-0.04462871.46%0.006747-0.038555-0.03499950.47%0.0021810.081732-0.0088973100%0.4606890.7581380.6076581

% harmonic voltage

contribution

Actual harmonic

Winding factor

Sine Harmonic magnitude

Space harmonic

order

-0.1

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 30 60 90 120 150 180

1

3

5

7

9

1-19

2D

Angle (deg)

Flux density (T)

Field Optimisation

However mechanical constraint allowed only slight improvement.

To reduce the 5th harmonic, the gap density is reduced at an angle where the 5th harmonic contribution is positive.

(1) Sink the bolts deeper into the core.Two methods: (2) Reduce the width as shown in the

diagram.

The total rms harmonic voltage improved from 1.46% to 1.35% and the 5th harmonic reduced to 0.55%.

ADVANTAGE:-• Reduced resistive losses but only in the rotor electromagnet.• Reduced size and weight per power capacity without considering the refrigeration equipment • Lower operating costs • Less vibration and noise • Smaller size and weight

DISADVANTAGE:-• Motor bearings need to be able to withstand cold or need to be insulated from the cold rotor. • The cost, size, weight and complications of the cooling system.

SUPERGENERATOR

The SuperGenerator consist of 3 parts:-1) rotor2) rotor cooling 3)Stator

SUPERGENERATOR

Physically, this generator is expected to be about half (1/2) the length and two-thirds (2/3) the diameter of a conventional machine.

This generator has a low synchronous reactance of 0.28 pu but the transient and sub-transients reactances are similar to those of conventional machines.

The overall efficiency of the generator is 98.6% which is retained down to 1/3rd of the rated load.

The cryogenic cooling system power consumption is merely 2% of the total losses in the machine.

SuperGenerator produces nearly clean AC voltage in the stator winding.

Both rotor and stator windings generate minimal harmonics.The field winding produces 2% of 5th harmonic voltage in

stator winding; all other harmonics are negligible.

SUPERDRIVE FOR SHIP PROPULSION

The 25 MW, 120-RPM HTS SuperDrive motor It is 2.65 m in diameter and 2.08 m long. It weighs 60 k-kg and generates structure borne noise of 48 dB at full-

speed. The motor employs a 6.6 kV stator winding that is cooled with freshwater. The HTS rotor winding is cooled by off-the-shelf cryocoolers positioned in

the stationary reference frame – a defective cooler could be replaced in less than 30minutes without having to stop the motor.

The motor has an overall efficiency of 97% at full speed and 99% at 1/3rd full-speed.

CONCLUSIONS

small size and weight will translate to lower cost.HTS windings operating at an easily attainable

temperature level (~35K), and cooled with low cost and dependable off-the-shelf refrigerators, will result in the fielding of highly reliable.

high performance, sufficiently robust, and affordable.HTS SuperMachines will be more compact, lighter,

and more efficient than the conventional machines.

Thank you

ANY QUERIES

SUBMITTED BY-SHASHI LAL COLLEGE –KRUPAJAL ENGINEERING

COLLEGEBBSR