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
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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 is a type of cable used in electronics to carry alternating current.
The wire is designed to reduce the:-
Losses in conventional and superconducting designs
LTS (Low Temperature Superconductivity) has not been successful in electric power applications
Impact of HTS (High Temperature Superconductivity)
All conceptual HTS designs and small demonstartors use BSCCO tapes at temperatures between 20K and 30K
An existing 100kVA stator with 48 slots and a balanced 2-pole 3-phase winding has been used
The pitch of the stator coils ensures that the winding produces very little 7th harmonic field
Higher order fields are reduced significantly by the distribution of the phase conductors throughout each phase belt
The 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 tapes
10 identical coils and each coil has 40 turns
Each superconducting coil is separated by the flux diverters
Sine Harmonic magnitude
% harmonic voltage contribution
Flux density (T)
Angle (deg)3D Modelling and Analysis
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.
(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%.
However mechanical constraint allowed only slight improvement.
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.
The SuperGenerator consist of 3 parts:-
2) rotor cooling