Damping and screening in the synchronous superconducting generator

Lawrenson, P.J.; Miller, T.J.E.; Stephenson, J.M.; Ula, A.H.M.S.

doi:10.1049/piee.1976.0172

Cited by 44 publications

(14 citation statements)

References 2 publications

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“…The rotor screening system, consisting of the outer rotor and the radiation screen, presents an intriguing problem in the design of superconducting machines as it must carry the full short-circuit force whilst maximising natural damping of rotor-hunting oscillations and minimising flux-density variations at the superconductor. Such a design requirement can be met by using a double-rotor construction [3][4][5][6]. In this the outer rotor is designed to withstand 95% of the short-circuit forces, to screen armature negativesequence fluxes and reduce substantially the flux-density variations at 50 Hz seen by the radiation screen during a fault.…”

Section: List Of Symbolsmentioning

confidence: 99%

“…In earlier work Lawrenson et al, [5] using an eigenvalue technique, and Bumby [3], using transient rotor angle results, demonstrated that an outer rotor time constant of typically 0.1 to 0.3 s was required, depending on generator parameters, to achieve maximum damping of rotor hunting oscillations. Damping of rotor hunting oscillations was also shown to increase as the coupling between the outer rotor and radiation screen decreased.…”

Section: Rotor Hunting Oscillationsmentioning

confidence: 99%

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Superconducting AC generator with a magnetic steel outer rotor

Bumby¹

1981

IEE Proc. C Gener. Transm. Distrib. UK

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The specific power output per unit length of large superconducting AC generators is limited by the material properties, of the outer rotor. By manufacturing this component from a high strength magnetic steel, such as is used in. conventional turbogenerator rotors, the diameter of this component can be increased producing an increase in the specific power output. This paper demonstrates the feasibility of using a magnetic outer rotor and shows that advantages are to be gained in respect of generator systems performance and ease of manufacture as well as improved specific power output. List of symbolsA = electric loading, A/m A z = axial component of vector potential B o = flux density at axial centre of air-cored superconducting AC generator, T. B o = /JL 0 K O / 2 B r = radial component flux density, T H r -radial component magnetic, field, A/m HQ = tangential component magnetic field, A/m K o = superconducting field winding linear current density, A/m L'a = subtransient inductance, H L s = synchronous; inductance of generator with magnetic outer rotor, H L so = synchronous inductance of generator with nonmagnetic outer rotor, H P = power output, W R = winding resistance, O, T ph = number of turns in series/phase ki = magnetic outer rotor factor k w= winding factor k r = radial flux density environmental screen factor k e = trangential flux density environmental screen factor / = generator length, m n =• generator speed, rev/s r -radius of field point, m ri = inner radius outer rotor, m r 2 = outer radius outer rotor, m r D -mean radius outer rotor, m r 0 = mean radius superconducting field winding, m r s = mean radius armature windings, m r x = inner radius environmental screen, m t = winding thickness, m 6 = circumfrential position, rad Hi = incremental permeability H o = permeability of free space H/m H r = relative permeability p = resistivity, flm a o.2 = 0.2% (300K) proof stress of inner rotor N/mm 2 i// = internal power factor angle, rad

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Section: List Of Symbolsmentioning

confidence: 99%

Section: Rotor Hunting Oscillationsmentioning

confidence: 99%

Superconducting AC generator with a magnetic steel outer rotor

Bumby¹

1981

IEE Proc. C Gener. Transm. Distrib. UK

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“…However, the exciter loop of the SCG with very long field winding time constant of about 750 s and the shielding effect of the two rotor screens rules out the option of controlling through the exciter by adding the supplementary signal to damp the oscillations [5].…”

Section: Introductionmentioning

confidence: 99%

Adaptive damping controller for a superconducting generator

Paul¹,

Malik

2014

2014 6th IEEE Power India International Conference (PIICON)

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Due to the long field time-constant and the shielding effect of the double rotor screen, it is not effective to control a superconducting generator (SCG) through the generator excitation system. A possibility, considered here, is to control the SCG through an electrohydraulic governor as its time-constant is much less than that of the field winding. An adaptive power system stabilizer for an SCG based on the pole-shift linear feedback control algorithm and acting through the SCG electro-hydraulic governor has been designed and applied to a single SCGinfinite-bus power system driven by a three stage turbine that includes a re-heater. The turbine is controlled by an electrohydraulic governor. A third order autoregressive moving average (ARMA) model is used to represent the plant that can be controlled by an adaptive pole-shift controller through the electro-hydraulic governor.

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“…In previous works, the rotor screen was studied mainly under transient conditions, especially short-circuit faults [5]. It required the screen to offer adequate shielding performances, as well as to damp the oscillations sufficiently after a severe disturbance.…”

Section: Introductionmentioning

confidence: 99%

Analysis on the Performances of a Rotor Screen for a 12 MW Superconducting Direct-Drive Wind Generator

Liu

Zhu

et al. 2014

IEEE Trans. Appl. Supercond.

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A rotor screen, usually called the damper and made of magnetic or conductive materials, is located in a superconducting (SC) wind generator between SC field coils in a rotor and copper windings in a stator. The detailed analysis of the rotor screen is needed for the growing interest in SC wind generators. The rotor screen can isolate the SC field coils from ac magnetic fields produced by the stator. As the outer closure of the rotor, it should withstand the maximum forces in fault conditions. Moreover, its thickness should not be too large. Otherwise, it would increase the effective electromagnetic gap of the generator, resulting in more SC wires. In this paper, the rotor screen of a 12 MW SC direct-drive wind generator with an air-cored rotor is analyzed based on the 2-D finite element (2D FE) method. Electromagnetic performances of rotor screens with different thicknesses under the rated load state are studied after the short-circuit analysis. Then mechanical performances are analyzed under the maximum forces of fault condition.

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Damping and screening in the synchronous superconducting generator

Cited by 44 publications

References 2 publications

Superconducting AC generator with a magnetic steel outer rotor

Superconducting AC generator with a magnetic steel outer rotor

Adaptive damping controller for a superconducting generator

Analysis on the Performances of a Rotor Screen for a 12 MW Superconducting Direct-Drive Wind Generator

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