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In this article, a new low-cost small-scale three-phase brushless motor topology is proposed. This is a new topology for self-excitation of brushless wound rotor synchronous motor investigated initially for rated speed. For brushless excitation, the stator is designed to contain two windings, namely, three-phase armature winding and exciter winding. The rotor consists of two windings, that is, harmonic winding and field winding, and a diode rectifier. An inverter feeds the three-phase armature winding which is connected in series through an uncontrolled three-phase rectifier to a single exciter winding. When the current is supplied from the inverter, both the armature and exciter windings are energized eventually producing a flux in the air gap. Since the flux produced by the exciter winding is not synchronized with the field winding, it produces a harmonic to be intercepted by the harmonic winding on the rotor. Eventually, the voltage produced in the harmonic winding is used to feed dc current to the field winding for brushless operation. The results obtained by 2-D finite-element analysis (FEA) validate the brushless operation of the motor. The proposed motor is analyzed basically for topology verification with the FEA results. Since the topology can be verified, further effort can be put to investigate such low-cost topologies for brushless wound rotor synchronous motor. It can be an alternative to a costly permanent magnet synchronous motor for specific applications.

This paper proposes and analyzes the design philosophies of the single-phase main exciter (ME) for an aircraft wound-rotor synchronous machine and investigates its operating characteristics in both generating and starting modes. The fundamental structure and starting–generating system are discussed. The load features of single-phase ME are summarized. The ME has the characteristics of linear current amplifier and approximately constant current source the generating mode, which can be used in the wide range of working temperature. Detailed waveforms and finite-element analysis verify that excitation current $I_{\mathrm {ef}}$ is almost irrelevant to speed but in direct proportion to frequency in the starting mode. Besides, simulated data indicate that the energy transferring efficiency between ME stator and rotor can reach about 55% by the single-phase ac excitation method. Finally, the experimental verification is carried out, and the simulated and experimental data and waveforms of single-phase ME agree well with each other.

For testing a conductive pipeline, remote field eddy current testing (RFECT) is used, which is composed of solenoidal exciter coil and receiving sensor coils. In RFECT, there is remote field zone where the eddy current distributions are concentrated on the external surface of the pipe wall. Therefore, it is possible to detect a defect that occurs on the external surface of the pipe wall even if the receiving coils are located inside the pipe. From the measured coil signals, it is necessary to decompose background offset and predict the pattern of defect signal in order to estimate the defect size for the maintenance of underground pipelines eventually. In the process, the amplitude variations of the induced magnetic field at sensor coils are closely related to defect depth. Therefore, it is important to analyze and eliminate distortions of measured RFECT signals. This paper analyzes the effects of the induced magnetic field on the sensing signals with respect to different depth sizes in the RFECT system. The amplitude and the distribution pattern of defect signals are computed by a 3-D finite-element method and the method to eliminate the signal distortions caused by induced magnetic fields are presented. Simulated results in this paper agreed well with measuring ones.

In this paper, a new shaded-pole main exciter (ME) with additional short-circuited coils for aircraft three-stage starter–generator (SG) is proposed and investigated. The basic structure, winding configurations, operating principle, and start system structure of the presented shaded-pole ME are illustrated in detail. The comparative study between the original ME and the shaded-pole ME with respect to the starting mode performances is conducted by 2-D finite-element method (FEM). A prototype SG with original ME has been developed, and the experimental results are essentially consistent with the simulation results by the FEM utilized in the predictions in this paper. Simulation data and waveforms verify that the proposed shaded-pole ME is a good candidate for aircraft machines to satisfy the dual function of starter and generator.

In general, the brushless wound rotor hybrid excitation synchronous generator (HESG) needs a separate exciter. In this paper, a novel integrated brushless excitation HESG (IBE HESG) is developed by integrating the excitation section into the iron core of wound rotor HESG. Compared with the conventional brushless excitation method, the axial length of the IBE HESG is shorter and the original topology of the wound rotor generator is not changed. The excitation section has two sets of windings: stator excitation windings and rotor armature windings. The stator excitation windings are installed in the stator slots evenly. The static excitation field is established by the dc excitation current of the stator excitation windings. The rotor armature windings are buried in the rotor armature slots around the rotor. The static excitation field induces a voltage in the three-phase rotor armature windings and supplies the dc current to the rotor excitation windings through a rotating rectifier on the rotor. The magnetic field distribution is analyzed by the frozen permeability method to decouple the multimagnetic circuits. Also, the influencing factors of excitation efficiency are studied and the parameters of the IBE HESG are obtained to achieve a reasonable excitation characteristic. Finally, the theoretical analysis is confirmed by the experiments on a 1.5 kVA/50 Hz prototype generator. The results show that the output power can be regulated over a wide range.

A two-stage brushless excitation method for hybrid excitation synchronous generators (HESGs) is proposed in this paper. Comparing with the traditional three-stage brushless excitation method, the auxiliary exciter is eliminated. The complete self-excitation is realized. As the main generator of two-stage brushless generation system, a tangential/radial HESG (T/R-HESG) is studied. The exciter is designed for T/R-HESG. The design steps are given. The operation modes of rotating rectifier are analyzed. A 1.5 kVA prototype of a two-stage brushless excitation generation system is made to verify the theoretical design. The measured results agree well with the theoretical design and finite element analysis. It shows that the design of exciter is correct and the two-stage brushless excitation method is feasible.

This paper deals with a design of the exciter which is a self-magnetizing apparatus of a written-pole motor (WPM). For a given rotor of 0.2 hp WPM, the pole shape and winding specifications of the exciter which is driven by a general voltage are optimally designed. Then, with consideration of hysteresis characteristics of a magnetic layer, the magnetization waveform is investigated with Preisach model. To validate the results calculated in design and analysis, the experimental test is carried out and comprehensive test results are suggested.

This paper deals with the shape design of the excitation unit of a magnetic induction tomography (MIT) system by means of a procedure of multiobjective design. As a result of the proposed method, a set of optimal geometries of the basic excitation structure was found.

This paper describes the use of an artificial intelligence-electromagnetic modeling approach for the performance prediction of stand alone synchronous generators during no break power transfer (NBPT) operating conditions. This approach uses radial basis networks (RBNs), which have the advantage of not being locked into local minima as could do feedforward neural networks. The RBNs are simply linear function approximators that use radial basis functions which are powerful techniques for interpolation in multidimensional space. The RBN is used to evaluate the stresses accompanying this mode of operation which may result in the failure of the diodes in the rotating rectifier bridge of the generator brushless field exciter. The modeling approach is applied in a case study of two standalone synchronous generators system for aerospace applications. This study resulted in the prediction of the system performance characteristics including the peak currents and reverse voltages of the rotating diodes. The simulation results were validated by comparison to experimental data

We present a semianalytical method for calculating the electromagnetic field distribution in a multilayer slab conductor. This is a very advanced and comprehensive method because there is no limitation for the shape of the exciter and the number of layers (i.e., an exciter of any arbitrary shape and at any distance near the surface of a multilayer conductor with a large number of layers can be modeled). We solve the Helmholtz equation in three dimensions by separation of variables. We develop a two-dimensional fast Fourier transform (FFT) integral model and use exponential functions in the third dimension. We solve this integral model analytically and numerically by using the custom matrix form AX = B and a system of algebraic equations, respectively. To verify this method, we solve a simple example problem both by the new method and a finite-element method (FEM) program. The results are in good agreement with each other.

This paper explains the progress in designing a shielded encircling remote-field eddy-current (RFEC) probe to inspect nuclear fuel rods and investigates resulting signal characteristics. To force electromagnetic energy from the encircling exciter coil to penetrate into the rod, the exciter coil is shielded outside. The effects of the shielding and operating frequency are studied by finite-element analysis and the location for the sensor coil is decided. The sensor coil is also shielded to prevent direct influence from exciter fields. The totally shielded probe dramatically improves signal characteristics. Numerical modeling with the designed probe shows that the phase signal is almost equally sensitive to inner- and outer-diameter defects and there is a linear relationship between phase signal strength and defect depth, which are typical characteristics of RFEC signal.

The Remote Field Eddy Current (RFEC) technique uses an internal probe to inspect conducting tubes nondestructively. A coaxial solenoidal exciter, energized with low frequency AC, and detector coils near the inside of the pipe wall are separated by about two pipe diameters to obtain through wall transmission and equal sensitivity to defects on the outside or inside of the pipe wall. Calculation methods are outlined and the voltage plane polar plot signal representation for defect measurement is described. Slit defect interactions in ferromagnetic and non-ferromagnetic tubes are discussed. Defect-induced anomalous fields are interpreted in terms of anomalous source eddy current and missing magnetization defect models. The use of computer animations to represent the time variations of high resolution field measurements and calculations is described.

In the course of the Austrian development program for superconducting generators, upgrading of the field winding was undertaken. While the first exciter winding in the main sections was a copper dummy winding, the next step was a fully superconducting field winding with 150% of the ampere turns of the preceding winding. This superconducting winding occupies only a very small part of the available cross section of the rotor. In an upgraded modification, a field winding was designed, manufactured and tested which fully occupies the available space. This exciter winding, its principal features, the trial manufacturing, and some fabrication problems due to the stiffness of the NbTi conductor are described. The test rig for the individual modules of the field winding and the test procedure which each coil has to pass is outlined. Test results of different element coils are reported. >

Synchronous machines with permanent magnet excitation can be designed for high power densities and low losses. This paper initially provides an overview of various machine concepts. Constructions with flux concentration and others with air gap oriented magnets are described. A comparison provides dimensioning rules for designs with minimal amounts of permanent magnetic material. On the basis of this, measures are outlined which improve the thrust density and further reduce the losses. These are: 1. design of machine and current inverter with more than three independent phases to achieve a square wave shape for the field and current; 2. employment of appropriately laminated poles to reduce the armature reaction in conjunction with measures which increase flux concentration. The effectiveness of these measures is demonstrated with the use of an example. For a current loading of 100 kA/m, a mean force density of 100 kN/m2is attainable. In conclusion, a machine concept is described which allows control of the exciter field from the armature, thus enabling a more flexible adaptation to the drive requirements.

A superconductive field winding subsystem has been developed for a 3000 hp homopolar motor for a model ship propulsion system. This subsystem includes a large NbTi superconductive coil mounted in a cryostat designed to withstand relatively severe environmental conditions expected during the ship-board tests planned by the Navy. Other components are a 2.5 kVA exciter for energizing the windings, an instrumentation console for monitoring system operation and a transfer line to permit operation with batch quantities of liquid helium. An overall description of the design and construction of the individual components in the system is presented along with a summary of preliminary component test results.