A gas turbine engine includes a fan section, a gear arrangement configured to drive the fan section, a compressor section and a turbine section. The compressor section includes a low pressure compressor section and a high pressure compressor section. The turbine section is configured to drive compressor section and the gear arrangement. An overall pressure ratio, which is provided by a combination of a pressure ratio across said low pressure compressor section and a pressure ratio across said high pressure compressor section, is greater than about 35. The pressure ratio across the low pressure compressor section is between about 3 and about 8 whereas the pressure ratio across the high pressure compressor section is between about 7 and about 15.

Gas turbine engine compressor arrangement

This paper introduces a novel topology for generating a spatial third-harmonic current component to excite the rotor field winding of a wound rotor synchronous machine to achieve brushless operation. In this topology, each of the three-phase windings on the stator is connected with a switch in parallel. In particular, two antiparallel thyristors are used to switch during positive and negative half cycles. Two windings are mounted on the rotor of the machine: 1) the harmonic winding and 2) the field winding. Zero-sequence currents are generated, when the switches are closed near zero crossing for a short time interval. Consecutive operation of the switches creates an additional spatial third-harmonic current pulsating in the stator winding. The number of poles of the stator winding and the field winding is the same (four-poles in this case) to intercept the torque generation component of the air-gap flux, whereas, the number of poles of the harmonic windings is adjusted (12-poles in this case) to intercept the harmonic component of the air-gap flux and develop voltage across the harmonic windings. Harmonic voltage is rectified through a rotating rectifier to feed dc current to the field windings. Results verify the proposed topology simulated by a 2-D finite-element method.

Novel Brushless Wound Rotor Synchronous Machine With Zero-Sequence Third-Harmonic Field Excitation

WFSM are included in the majority of large power generating units and special high-power motor drives, due to their high efficiency, flexible field excitation and intrinsic flux weakening capability. Moreover, they are employed in a wide range of high-end solutions in the low-to-medium power range. This contribution presents a comprehensive survey of classical and modern methods and technologies for excitation systems (ESs) of (WFSMs). The work covers the fundamental theory, typical de-excitation methods and all the modern excitation equipment topologies in detail. It also includes a description of the state-of-the-art and the latest trends in the ESs of wound-field synchronous motors and generators. The purpose of the paper is to provide a useful and up-to-date reference for practitioners and researchers in the field.

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Excitation System Technologies for Wound-Field Synchronous Machines: Survey of Solutions and Evolving Trends

A gas turbine engine includes a fan shaft and a support which supports the fan shaft. The support defines at least one of a support transverse and a support lateral stiffness. A gear system drives the fan shaft. A flexible support at least partially supports the gear system, and defines at least one of a flexible support transverse and a flexible support lateral stiffness with respect to at least one of the support transverse and the support lateral stiffness. An input to the gear system defines at least one of an input transverse and an input lateral stiffness with respect to at least one of the support transverse and the support lateral stiffness. A method of designing a gas turbine engine is also disclosed.

Flexible support structure for a geared architecture gas turbine engine

Permanent magnet synchronous machines (PMSMs) utilize permanent magnets to generate the rotor flux needed to produce torque. They are ideal for high-accuracy fixed-speed drives. But rise in the price of rare earth magnet caused by its scarcity is a key consideration while developing such kind of machines. In this situation, wound rotor synchronous machines (WRSMs) have benefits compared to PMSMs as it does not need magnetic material and can be operated in a wide range of speeds [1]. In a WRSMs field windings are used, which is supplied with a DC current that generates the rotor flux. DC current can be applied to the rotor winding either using the brush and slip-ring structure or brushless excitation method. The brushes and slip rings have losses and maintenance issues, so they are used for small synchronous machines. For brushless excitation, additional (auxiliary) stator windings are used to excite the rotor field winding. Several patents are granted according to this excitation method [2]-[4]. The conventional method faces issues, since both the stator windings are located in the same stator core and require a large stator volume for making place for the both windings. Using a single winding in the stator to perform the brushless operation for the WRSMs is presented in [5]. But in that case concentrated windings are used to develop the higher harmonics for the excitation which will result in more losses. Thus a new idea for brushless WRSMs is proposed in which single stator winding is used to excite the rotor as well as generate the fundamental air gap harmonic for electromagnetic torque. A 2D finite element analysis (FEA) have been done to analyze and verify the proposed brushless WRSMs.

Design and Analysis of a Novel Brushless Wound Rotor Synchronous Machine

A novel brushless self-exciting three-phase synchronous generator is proposed. It consists of three-phase armature windings on the stator, one field winding and one exciting winding with five times as many poles as that of the armature winding on the rotor, and a three-phase reactor connected to the terminal of the armature windings. By utilizing the 5th-space harmonic component of armature electromotive force, small voltage regulation for various loads and no oscillatory tension occurring at the rotor shaft were realized. The basic constitution, principle of operations, and exciting characteristics are described. The experimental results obtained from using a trial generator demonstrated its practical usefulness. >

A brushless self-exciting three-phase synchronous generator utilizing the 5th-space harmonic component of magneto motive force through armature currents

On a stator core, there are wound T-connection primary generating windings such that the second and third single-phase windings are respectively arranged at positions electrically orthogonal to the first single-phase winding. The winding number of the first single-phase winding is 31/2 times that of the second single-phase winding or the third single-phase winding. The stator excitation windings are also wound on the stator core, which are connected to the center taps of the primary generating windings through a control rectifier. A plurality of field windings are wound on a rotor core. The field windings are arranged at positions where they are magnetically coupled with both the odd-order spatial higher harmonic components of armature reaction magnetic fields produced by currents flowing in the primary generating windings and the static magnetic fields produced by current flowing in the stator excitation windings. Due to the T-connection primary generating windings, the generator is capable of simultaneously generating not only the three-phase outputs but also the single-phase three-line outputs.

Three-phase brushless self-excited synchronous generator with no rotor excitation windings

On a stator core, there are wound primary generating windings of four (4) poles with a distributed full-pitch winding structure and stator excitation windings with a concentrated full-pitch winding structure, having the number of poles odd-number times the number of poles of the primary generating windings, that is, twelve (12) poles. The primary windings appropriately produce spatial higher harmonic components of the armature reaction magnetic fields. The excitation windings are connected to the center taps of the primary windings through a control rectifier. On a rotor core, six field windings of four poles. The field windings are arranged at positions where they are magnetically coupled with both static magnetic fields produced by the stator excitation windings and odd-order spatial higher harmonic components of armature reaction magnetic fields produced by the currents in the primary generating windings. The field windings are short-circuited by the diodes, respectively. In the brushless self-excited synchronous generator, the number of slots in each of the rotor and stator can be determined irrespective of the order number of the spatial higher harmonic components of the armature reaction magnetic fields. The generator is simple and rigid in its structure.

Three-phase brushless self-excited synchronous generator with no rotor exciting windings

A brushless three-phase synchronous generator includes a stator having primary generating windings and stator excitation windings whose number of poles is odd-number times the number of poles of the primary generating windings. The generator further includes a cylindrical rotor on which a plurality of field windings are wound in a full-pitch concentrated winding form. The plurality of field windings are respectively short-circuited by the corresponding diodes. A plurality of field windings in which voltages of the same phase are induced based on the odd-order spatial higher harmonic magnetic fields are connected in parallel and further connected in parallel to the central field windings which effectively produce primary field magnetic fluxes. A circulating rectifier element is connected in parallel to the central field windings. Improvement in the waveforms of the primary magnetic fields can be achieved and self-excitation in the case where the single-phase loads are connected can be prevented from occurring while magnetic coupling of the rotor field windings to the spatial higher harmonic components of the armature reaction magnetic fields is effectively maintained well.

Brushless three-phase synchronous generator having enhanced rotor field system

A series-exciting device for a synchronous generator characterized in that armature windings at the side of the armature are wound using concentrated full-pitch winding or a winding method similar to the concentrated full-pitch winding; an exciting winding which is magnetically coupled to magnetic poles in a quantity odd times greater than the quantity of the poles of the said armature windings, and a rectifier which converts the electromotive force of the exciting winding into a DC are provided at the side of the field system; and a DC output terminal of the rectifier is connected to a field winding having poles in the same quantity as the quantity of the poles of the said armature windings.

Kenji Inoue

Papers

A brushless self-exciting three-phase synchronous generator utilizing the 5th-space harmonic component of magneto motive force through armature currents

Three-phase brushless self-excited synchronous generator with no rotor excitation windings

Three-phase brushless self-excited synchronous generator with no rotor exciting windings

Brushless three-phase synchronous generator having enhanced rotor field system

Series-exciting device for synchronous generators