Effect of Rotor Interturn Short circuit degree and position on Stator Circulating Current inside Parallel Branches in Generators

The isolated dc–dc converters with primary-side phase shifting (PPS) provides severely narrow soft-switching range for main devices in the primary side leg of full bridge converter. The leakage inductance of the high frequency transformer should be large enough for providing the energy needed for soft switching operations and also the idling power loss due to circulating current in the converter legs under large phase-shift angle, which makes reduction of conversion efficiency and complicated in designing the parameters of transformer. Furthermore, the turn-off diode commutations in the output-side rectifier are performed by hard-switching mode. To overcome all these drawbacks, a secondary side phase shifting (SPS) technique has been developed for two-level isolated DC-DC converter. This scheme provides wider soft switching range and reduced power loss due to elimination of circulating current in the primary side of high frequency transformer. In addition, SPS control also provide no reverse recovery current in diodes and hence no power losses in the secondary rectifier circuit. The control switches operate under soft switching even under rated load and short circuit conditions.

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Calculation of the circulating current and short- circuit impedance of a 3000kVA HTS transformer with split types of windings

10.1109/icems12746.2007.4412333 ◽

2007 ◽

Author(s):

Bingruo Xie ◽

Xiaosong Li ◽

Qiaofu Chen ◽

Yu Zhang ◽

Jin Wang

Keyword(s):

Short Circuit ◽

Circulating Current ◽

Circuit Impedance

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Analysis of Turbo-Generator Circulating Current Between Stator Winding Parallel-Connected Branches Under Fault Conditions

ASME 2005 Power Conference ◽

10.1115/pwr2005-50046 ◽

2005 ◽

Author(s):

Shuting Wan ◽

Heming Li ◽

Yonggang Li ◽

Fanchao Meng

Keyword(s):

Second Harmonic ◽

Short Circuit ◽

Air Gap ◽

Normal Operation ◽

Magnetic Flux Density ◽

Stator Winding ◽

Magnetomotive Force ◽

Circulating Current ◽

Turbo Generator ◽

Rotor Winding

Firstly analyzes the generator parameters of air-gap magnetomotive force, magnetic permeability, magnetic flux density, the stator winding parallel-connected branches electromotive force distribution, and gets voltage difference and circulating current expressions between stator winding parallel-connected branches. Secondly, through analyzing the parameters changing on normal operation and fault condition, the circulating current characteristics are given based on the expressions, which are that hasn’t the circulating current when generator operates normally, and second harmonic circulating current will increase when the rotor winding inter-turn short circuit fault has happened, and fundamental circulating current will increase when stator winding inter-turn short circuit or air-gap eccentricity fault has happened. Considering that different fault has different circulating current characteristic, the generator fault diagnosis method based on circulating current was developed. Finally practically acquires SDF-9 generator data on the fault, the results of verification show that analysis is correct.

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Investigation on Stator Circulating Current Characteristics of Turbogenerators under Air Gap Eccentricity and Rotor Short-circuit Composite Faults

Electric Power Components and Systems ◽

10.1080/15325000903571525 ◽

2010 ◽

Vol 38 (8) ◽

pp. 900-917 ◽

Cited By ~ 8

Author(s):

Shuting Wan ◽

Yuling He ◽

Guiji Tang ◽

Yonggang Li

Keyword(s):

Short Circuit ◽

Air Gap ◽

Circulating Current ◽

Current Characteristics

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Structural Imperfections in thin Oxide Films Formed on Some Fe- and Ni-Base Alloys

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100069545 ◽

1970 ◽

Vol 28 ◽

pp. 510-511

Author(s):

L. P. Lemaire ◽

D. E. Fornwalt ◽

F. S. Pettit ◽

B. H. Kear

Keyword(s):

Oxide Scale ◽

Oxidation Process ◽

Short Circuit ◽

Protective Oxide ◽

Protective Oxide Scale ◽

Thin Oxide Films ◽

Diffusion Paths ◽

Oxidation Resistant ◽

Structural Imperfections ◽

Short Circuit Diffusion

Oxidation resistant alloys depend on the formation of a continuous layer of protective oxide scale during the oxidation process. The initial stages of oxidation of multi-component alloys can be quite complex, since numerous metal oxides can be formed. For oxidation resistance, the composition is adjusted so that selective oxidation occurs of that element whose oxide affords the most protection. Ideally, the protective oxide scale should be i) structurally perfect, so as to avoid short-circuit diffusion paths, and ii) strongly adherent to the alloy substrate, which minimizes spalling in response to thermal cycling. Small concentrations (∼ 0.1%) of certain reactive elements, such as yttrium, markedly improve the adherence of oxide scales in many alloy systems.

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