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This paper proposes a novel high-temperature superconducting stator-excited axial-flux magnetic gear (HTS-SEAFMG) for the high-torque transmitting system. The proposed magnetic gear combines the merits of both HTS-excitation and stator-excitation. By using the HTS-excitation, a high air-gap flux density can be easily obtained, thus achieving the high torque density. The HTS-excitation windings are placed on the stator with a static seal of cooling Dewar which greatly reduces the manufacturing difficulty and the cost of refrigeration system compared with the dynamic seal. Thanks to the stator-excitation pattern, both the high-speed rotor and the low-speed rotor comprise only iron, thus contributing to the high mechanical reliability. The axially sandwich structure can also simplify its assembly in the high torque transmission applications. The dimensional parameter optimization and the electromagnetic performance evaluation are conducted by using the finite element method, respectively. The results show that the torque density of the proposed HTS-SEAFMG can reach 123 kNm/m3. Theoretical analysis and results are both given to verify the feasibility of the proposed HTS magnetic gear design.

This paper proposes a new 12-slot/10-pole high-temperature superconducting excitation claw-pole doubly-salient (HTS-CPDS) machine with a single HTS-excitation unit using stationary seal cooling. The key advantage of adopting claw-pole structure is that a ring-shaped HTS-excitation coil can be easily wound and artfully placed in the claw-pole cavity to realize the design of single excitation unit, and thus the cooling Dewar design for stationary seal is easily implemented. Also, due to using HTS-excitation, the air-gap flux can be flexibly regulated by changing the HTS current, thus keeping a constant amplitude of phase back-EMF under different rotor speeds. The cooling Dewar construction and the key parameter optimization are illustrated in detail. And compared to a counterpart employing the discrete racetrack HTS coils, the proposed machine can significantly reduce the HTS wire consumption and electromagnetic stress to a certain extent, thus cutting the cost and improving the anti-quench ability. By using the finite element analysis (FEA), the machine electromagnetic performances are evaluated, and its validity is verified.

This paper proposes a high temperature superconducting (HTS) double stator machine (HTS-DSM), based on the magnetic field modulation principle. In the proposed HTS-DSM, the HTS field winding and the copper armature winding are separately located on the two stators, so that it overcomes the drawbacks caused by the coupling device for cryogenic transfer, the torque tube, the carbon brushes, and slip rings in the conventional HTS synchronous machines with the rotating field winding, bringing the merits of high reliability and low maintenance cost. Moreover, a method of amounting a ferromagnetic ring outside the HTS field winding is also proposed to reduce the negative effects of the armature reaction field on the HTS field winding, since the alternating current (AC) losses induced by the armature reaction field easily cause the quench of the HTS field winding. Totally four different topologies are proposed, and the operation principle of the HTS-DSMs is analyzed based on the magnetic field modulation principle. Then the design and optimization of the HTS-DSM is discussed in detail to present the main design parameters of the four topologies. Finally, the performance of the four different topologies are compared by the finite element analysis, the results reveal that the HTS-DSM with modular dewar and iron-teeth inner stator exhibits the merits of higher power density.

This paper proposes a novel high-temperature super-conducting (HTS) claw-pole vernier machine, which combines the merits of stator HTS-excitation machine with the “magnetic gearing effect” designed for direct-drive applications. The key is to adopt claw-pole stator structure to realize the multi-pole pattern using single HTS-excitation unit with stationary seal, thus greatly simplifying the cooling Dewar architecture as well as improving the structural compactness. Moreover, the armature windings are wound around the split-teeth which are set on the surface of claw poles to achieve the physical separation from the HTS-excitation coil, thus reducing their space conflicts and impact with each other. The operation principle analysis and the initial machine design are conducted in details. By using the three-dimensional finite element analysis, the machine performances are evaluated, and its validity is verified.

This paper proposes a new high-temperature super-conducting (HTS) linear flux-controllable doubly salient machine for high-power long-stator applications, which incorporates the merits of both the HTS-excitation machine and the primary-excitation linear machine. The key is to adopt the modular mover to obtain the phase symmetric magnetic circuit as well as effectively reduce the cogging force due to module complementary effect, while the HTS-excitation windings and armature windings are physically separated to reduce space conflicts between each other and easily implement static seals of cooling Dewar. Also, the air-gap field can be flexibly regulated by changing the HTS-excitation current, thus facilitating to extend the operating speed range. The operation principle analysis, cooling Dewar design, and key parameters determination are conducted in detail. By using the finite-element analysis, the machine performances with emphasis on flux-controllable features are analyzed to verify its validity.

This paper proposes and analyzes a novel high-temperature superconducting (HTS) flux-switching transverse-flux (HTS-FSTF) machine with partitioned stator, which keeps the merits of stator-excitation HTS machine with static seals. The key is to adopt the axial partitioned stator structure to realize the independent partition arrangement of armature windings and HTS-excitation windings, as well as artfully place the flux barrier between them to minimize the impact of armature field on the critical field state of the HTS excitation. Moreover, by using the split-pole design, only a single ring-shaped HTS-excitation coil is employed, thus, easily implementing static seals of simple cooling Dewar pattern to improve the refrigeration system reliability and reduce costs. The operation principle based on the transverse-flux path analysis and the cooling Dewar design are described in details. Also, by using the three-dimensional finite-element analysis, the electromagnetic performances of the proposed machine are investigated, and its validity is verified.

This paper proposes a new high-temperature superconductor (HTS) dual-rotor flux-switching machine for direct-drive wind energy conversion. The key is to adopt dual-rotor structure to improve utilizations of the HTS excitation field and the machine space, thus achieving a high power density. Also, the HTS excitation can easily achieve flexible flux regulation to keep armature voltage constant under time-varying wind speeds. The operation principle, with emphasis on the effect of relative position of both rotors on the magnetic circuits, is described in details. And the initial machine design, especially the split ratio optimization, has been done. By using the finite element analysis, the machine performances are analyzed, and its validity is verified.

This paper proposes a new stator high-temperature superconducting (HTS) field-modulated machine with the merit of high torque density for direct-drive applications, which incorporates the attractive features of both stator excitation HTS machine and field-modulated machine. The key is to artfully place the HTS windings on the stator to implement static seals as well as utilizing the “magnetic gearing effect” to achieve high torque capability. Based on the geometry of the fabricated double-layer Dewar assembly for cooling the HTS excitation coil, the proposed machine is initially designed. By using the finite element analysis (FEA), the machine performances are analyzed, and its validity is verified

This paper proposes and develops a new kind of cryogenic cooling system for high-temperature superconducting (HTS) flux-switching (FS) machine using stationary seal for its cooling Dewar. Test results show that this cryogenic cooling system can offer the cryogenic operating environment around 63 k for the racetrack-shaped HTS field coils. Based on the proposed cryogenic cooling system, a new HTS-FS machine with segmented rotor is proposed. By using the finite element analysis, the machine performance is analyzed accordingly. Hence, the electromagnetic characteristics of the proposed machine are verified.

The superconducting machines are more and more attractive due to the advantages of high power density and high efficiency, in which the superconductor is adopted to be excitation windings, armature windings, and flux leakage shielding bulks, respectively. In this paper, a new linear stator permanent-magnet (PM) vernier high-temperature superconductor (LSPMV-HTS) machine is developed for the direct drive system. A double-sided design and inner-translator arrangement are adopted in the LSPMV-HTS machine in which both PMs and armature windings are placed on the stator, whereas the translator is designed as an iron core with salient teeth on the two sides and the HTS bulks are inset between every two adjacent salient teeth. Due to the flux leakage shielding of the HTS bulks, the power density of the machine can be improved effectively. The mathematical model of the LSPMV-HTS machine is derived based on the finite-element method results. Based on using the FEM, the theoretical analysis results are verified.

This paper proposes a new high-temperature superconductor (HTS) axial-field flux-switching machine with the merit of high power density for wind energy conversion. The key is to introduce a kind of modular racetrack cooling Dewar with static seals to replace the one with dynamic seals used in the conventional rotor excitation HTS machine. Also, the effects of rotor relative positions of the proposed machine on the back electromotive force are discussed. By using finite-element analysis, the machine performances are analyzed. Hence, the validity of the proposed machine is verified.

This paper proposes a linear doubly-salient high-temperature superconductor (HTS) machine for wave energy conversion, which is composed of a tubular stator and a tubular translator. Since the translator is a simple iron core with salient poles, it is so robust that it can be directly coupled with the reciprocating buoy. The stator consists of an iron core with salient poles, DC HTS field windings and 3-phase HTS concentrated armature windings. By using the finite element analysis, the proposed machine is quantitatively compared with its permanent magnet and copper-winding counterparts. Hence, it validates that its performance, especially the power density, can be improved greatly.

This paper proposes a new kind of racetrack-shaped high-temperature superconducting (HTS) magnet for a stator field-excitation HTS machine, for the purpose of implementing stationary seal at the cooling Dewar. The key is to introduce a vacuum sandwich-structure into the proposed racetrack-shaped Dewars so that the operation temperature of field-excitation windings can be regulated at 63 K. The method of reducing pressure by vacuuming is applied accordingly to decrease the temperature of cryogenic liquid nitrogen to ensure the cooling effect. The test results show that all the fabricated racetrack HTS magnets can operate at HTS state when the excitation current reaches 40 A. Hence, the proposed racetrack HTS magnet is experimentally verified.

In this paper, an 8-pole/12-slot high-speed superconducting bearingless machine is proposed for flywheel energy storage systems. The proposed machine adopts a homopolar configuration: the rotor only consists of iron lamination with eight salient iron poles and the 12-slot stator accommodates all three groups of windings: the high temperature superconducting (HTS) field winding; the armature winding; and the suspension winding. With the HTS field winding, eight iron poles in the rotor are magnetized as 4-pole-pair electromagnets. Also, by adjusting the dc current in the HTS field winding, the air-gap flux can be controlled flexibly. By deploying the suspension winding which shares the same slot with the armature winding, a two-degree-of-freedom suspension force can be generated for bearingless operation.

This paper proposes a new high-temperature superconductor (HTS) flux-switching machine with the merit of high power density for the direct-drive wind energy conversion system. The key is to introduce HTS windings to replace permanent magnet material in the flux-switching permanent magnet machine. Also, the use of HTS field excitation windings can easily achieve constant output armature voltage under time-varying wind speeds. By using the finite element analysis, the machine performances are analyzed. Hence, the validity of the proposed machine is verified.