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An air-core strip-type high-voltage pulse transformer (HVPT) features a relatively simple structure in terms of design and fabrication. However, this HVPT requires considerable attention to prevent dielectric breakdown between the conductor windings. Because each spiral winding must be very thin, the field enhancement at the edges of the windings is very high. Therefore, it is important to develop proper methods to reduce the field enhancement factor and to prevent the dielectric breakdown at the winding edges. In this paper, in order to minimize the field enhancement, the proposed HVPT winding edges were folded, and each winding width was designed to decrease gradually to form a reverse trapezoid. These windings were insulated by multilayer insulators arranged in a specific manner. The requirement specifications are a maximum input voltage of 50 kV and an output voltage of 400 kV. This paper describes a design process and an electric field analysis to reduce the field enhancement. The simulation and experimental results confirmed the validity of the fabricated HVPT. The dielectric breakdown strength was tested up to 467 kV. [ABSTRACT FROM PUBLISHER]

The pulse transformer is used in many applications to provide high-voltage pulses. In order to obtain high and narrow output pulses, it is necessary to reduce the leakage inductance of the pulse transformer. The circuit of a high-voltage power supply is analyzed and simulated to study the effect of the leakage inductance on the pulse waveform. Afterwards, the winding structure is analyzed. Three transformer models were built based on the asymmetric parallel winding, the traditional parallel winding, and the taper winding. Their leakage inductances and parasitic capacitances are calculated and compared. The 3-D finite element simulation is adopted to compute the leakage inductance precisely. The simulation results demonstrate that the asymmetric parallel winding in this paper reduces the leakage inductance effectively with small parasitic capacitances. In addition, using the asymmetric parallel winding, a pulse transformer prototype is manufactured and tested. The experimental results verify the accuracy of the simulation method and the feasibility of the asymmetric parallel winding. [ABSTRACT FROM PUBLISHER]

This paper presents a novel brushless doubly-fed pulsed alternator (BDPA) in the direct-drive power supply system for high-energy pulsed lasers. There are two sets of stator winding which are embedded in the stator slots of BDPA. One is called power winding and another is called control winding. The rotor winding is short circuit. Because there is no brush, compared with the compensated pulsed alternator, BDPA has higher reliability and can run at higher speeds to get higher energy-storing density. Besides, when the system works on the state of continuous multiple pulses, with a decrease of speed, the BDPA can maintain the frequency and voltage of the power winding constant basically. In this paper, the design procedure of BDPA is proposed according to the requirement of the high-energy pulsed lasers. Utilizing the finite-element model of the alternator, we can analyze the electromagnetic properties and calculate inductance parameters of the BDPA to verify the design scheme. Meanwhile, the simulation model of the direct-drive power supply system is established in MATLAB/Simulink to analyze the output performance of the flashlamp load. The simulation results confirmed the feasibility of design scheme of BDPA for the system. [ABSTRACT FROM PUBLISHER]

This paper presents a novel three-coil reconnection electromagnetic launcher (TCREL). Analytical calculations and simulation results indicated that not only does this model possess a higher structural strength, but also the launching efficiency is improved effectively compared with that of the traditional reconnection electromagnetic launcher (REL). In addition, take the TCREL model as an independent module; a toroidal REL (TREL) model can be obtained after several modules are uniformly placed and fixed around the circumference. The TREL model can reduce the magnetic flux leakage among driving coils, and further improves the launching efficiency. To verify the conceptual feasibility, two-stage TCREL and REL models were built and tested. The experiments demonstrate that the TCREL model possesses better launching performance than does the REL model; the former can obtain the desired launching efficiency of 15.818% but the latter only 8.248% in the contrast experiment. The experimental results are also in accordance with the simulation results. [ABSTRACT FROM AUTHOR]

With the quick development of electromagnetic propulsion systems, permanent magnet linear synchronous motors (PMLSMs) have been the focus of research for high-performance propulsion systems. Compared with traditional windings, two ring windings with novel structures and better performance for PMLSMs are proposed: the single-layer ring windings are suitable for high-power systems; the double-layer ring windings can be adopted in low fluctuation systems. This paper first analyzes the electromagnetic parameters of the ring windings based on the equivalent magnetizing current method to verify the availabilities of ring windings. The main parameters of two ring windings are compared to achieve the optimization guides. Then, the magnetic fields and thrust characteristics of ring windings and traditional lap windings are analyzed by the finite-element method, and the independent magnetic field of ring winding ends is verified. And then a prototype motor with double-layer ring windings was manufactured and experimentally tested, the measurement data were matched with the theoretical calculations. The results illustrate that the PMLSM with ring windings has higher thrust density and lower thrust ripple, ring winding structure is more suitable for electromagnetic propulsion systems. [ABSTRACT FROM PUBLISHER]

In switching power supplies, the transformer leakage inductance (TLI) is of considerable practical significance. Ordered winding is the certain assumption in previously reported works for the calculation of the TLI value. However, disordered windings are usually unavoidable in practice and their effect on the value of the TLI is considerable. The problem becomes more complex when the number of winding turns increases. In this paper, the effect of winding disorder on the TLI value is investigated. In disordered wrapping, the winding turns arrangement (WTA) of each produced transformer is different from the others. Thus, each produced transformer has an exclusive TLI value in a disordered wrapping. Moreover, the number of possible WTAs is high, especially in transformers with a large number of winding turns. The proposed method utilizes an analytical tool for estimating the distribution of the TLI values for all of the possible WTAs. This estimation is carried out based on the limited number of the WTAs. The required number of WTAs is calculated and the validity of the proposed method is checked with Kolmogorov–Smirnov theorem. The TLI value is calculated by means of the stored magnetic energy in different parts of the transformer using the magnetomotive force variation method. Finite element simulation and experimental results are presented to show the effects of disorder on the TLI value and the validity of the proposed analytical method. [ABSTRACT FROM AUTHOR]

This paper presents a new method to calculate stray capacitance of coil turns of magneto flux cumulative generator. The proposed method depends on the coil geometrical properties. The presented analysis in this paper is based on the calculation of capacitance between two adjacent turns and capacitance between the coil turns and the central cylindrical liner of the generator for a single-layer coil with N series turns having an integrated round cross section. Moreover, the effects of the insulating coating of winding, winding pitch, distance of coil turns to the central cylindrical liner on the stray capacitance, and the sensitivity analysis of effective parameters in the creation of stray capacitance between coil turns and also between coil turns and the central cylindrical liner are considered in this paper. Simulation results show that the proposed method is very useful for the designing geometrical structure of the magneto cumulative generator coil. [ABSTRACT FROM AUTHOR]

The poloidal field (PF) coils are one main subsystem of the ITER magnets. The PF6 coil is being manufactured by the Institute of Plasma Physics, Chinese Academy of Sciences (ASIPP) as per the PF coils cooperation agreement between ASIPP and Fusion for Energy. The ITER PF6 winding pack is composed by stacking nine double pancakes. Dummy double pancake fabrication aims to fully qualify the critical fabrication processes, before series production. This paper describes ITER PF6 dummy double pancake winding process and results, which was performed with a “two-in hand” configuration. Conductors were wound sequentially in the following steps: despooling, straightening, ultrasonic cleaning, sandblasting, bending, and turn insulation wrapping until deposition on the winding table. Joggle bending, helium inlet manufacturing, and tail assembly were also carried out during winding. The dummy double pancake winding was finally completed with the qualification requirements well met, which demonstrated good synchronization of the control system, fine conductor positioning accuracy, tight radial buildup, and so on. [ABSTRACT FROM AUTHOR]

Compulsator is a specially designed generator capable of delivering high current pulses to a low-impedance load, such as the electromagnetic railgun. In order to increase the tip speed of the rotor, advanced composite materials have been used in the recent compulsator prototype, which is mentioned as air core instead of the traditional iron core. For typical air-core compulsators, there are no slots and steel teeth to place the armature windings due to the nonmachinability of composite materials. Therefore, concentric windings in racetrack style are often adopted instead of traditional lap winding in most cases, since it is more convenient to be fixed by composite materials. However, overlap occurs at the end winding part for multiphase compulsators, which are not easy to be formed during the manufacture process. In this paper, a fractional slot multiphase air-core compulsator with concentrated windings is proposed and analyzed. The main advantage of fractional slot configuration is that it can offer a concentrated winding structure under certain conditions, which means each coil only spans one “tooth,” and will not cause any intersection between each phase at the end winding. Two referenced fractional slot air-core compulsators with two phases, six poles, and four “slots” or eight “slots” (q = 1/3 and q = 2/3, q is the “slot” per pole per phase) are analyzed and compared with the performance of a traditional integral slot machine. The results indicated that the output voltage and self-excitation performance of a fractional slot compulsator can reach the same level with an integral slot one, and the discharging performance can reach an acceptable level. Thus, the fractional slot multiphase concept can be further used to improve the manufacture process of the winding in the future. [ABSTRACT FROM PUBLISHER]

Compulsators are popular choices for high-end railgun power supplies. In order to maximize energy stores and power densities, compulsators are designed as an air-core prototype. However, new problems have also been brought out by the new structure. Due to the poor thermal conductivity of composite materials and the high field current needed to maintain the magnetic potential, one of the principal limiting factors for achieving continuous discharges is the high winding temperature rise. In this paper, on the basis of electromagnetic analysis, the losses of the coils and compensating shield could be calculated first, and then, a transient 3-D finite-element thermal analysis was performed for both the stator and rotor. Finally, for the purpose of stabilizing the hottest spot temperature of the coils at a given level, an active cooling system has been designed and simulated. The presented method can be applied to other compulsators having the same thermal issues. [ABSTRACT FROM AUTHOR]

The replacement of steam catapults with electromagnetic ones is becoming an overwhelming trend in aircraft launch systems. Recently, the double-sided linear launcher has attracted more and more attention from researchers. This paper presents the design and analysis of the moving-magnet-type permanent-magnet linear synchronous motor (PMLSM). The thrust density is the most important indicator for a powerful motor, so an analytical expression of the thrust-density coefficient is derived from basic electromagnetic force laws. Based on the analytical results, the thrust and the thrust ripple are analyzed using the finite element method in different conditions. In order to modularize easily, the ring windings have been applied in the double-sided PMLSM, and then, the design features and parameter optimization of the windings are discussed. This paper can provide references to select the suitable type of motor for the launch systems and accomplish the fundamental work for the design of a prototype. [ABSTRACT FROM AUTHOR]

The technical solution of Unmanned Aerial Vehicle (UAV) has the following features: good controllability; simple thrust control; high precision; long operating life; low cost; strong adaptability, repeatability, maneuverability, and imperceptibility. So the UAV has widespread application prospects. The position sensor of the mover of UAV linear electromagnetic ejection is the key component of control system. It has a direct influence on performance, structure, and reliability of the system. As the sensors such as linear photoelectric encoder and magnetic encoder are not able to meet the demand of high speed control, the paper develops the research on the detection methods of the mover position. First, the paper presents a detection method of mover position based on sliding mode observer. Due to the flicker problem of sliding mode observer, the paper then proposes a detection method based on state observer, and the method can result in smooth detected position of the mover. Finally, the simulated results of the ejection verify the validity of the proposed method. [ABSTRACT FROM AUTHOR]

The superconducting toroidal field (TF) coils composed of a winding pack (WP) without radial plates, encapsulated in a steel casing, are currently being studied in the framework of the EUROfusion work package magnets (WPMAG). The ENEA (Italian National Agency for New Technologies, Energy and Sustainable Economic Development) 2014 TF WP design consists of graded (Nb3Sn + NbTi), double-layer wound rectangular cable-in-conduit conductors, for which the operational as well as accidental transients must be carefully investigated. This paper presents the analysis of the quench propagation inside the TF WP proposed in 2014 by ENEA using the state-of-the-art thermal-hydraulic code 4C. Different locations are considered for the quench initiation: 1) at the maximum temperature margin \Delta T\mathrm {mar}^{\mathrm {max}} , resulting in the most severe hotspot condition and 2) at the minimum temperature margin \Delta T\mathrm {mar}^{\mathrm {min}} , to analyze the most probable event. The evolution of voltage, normal zone, hotspot temperature, and maximum pressure in the TF WP is computed comparing the results from the two cases, highlighting the role of heat diffusion inside the TF WP. [ABSTRACT FROM AUTHOR]

High synchronization accuracy can be obtained when saturable pulse transformer (SPT) with multisecondary windings is employed in the technology of multipulses synchronization. LC generator based on multisecondary windings SPT is presented in this paper. The operation principle of the proposed LC generator is introduced. Three important requirements for voltage multiplication are analyzed and simulated. Experimental studies are carried out, and the results show that: when the primary energy storage capacitor is charged to 335 V, the output voltage of the system can reach up to 48.2 kV. The voltage multiplication ratio is 2.9. It means that the output voltage is 2.9 times larger than the charging voltage on single main energy storage capacitor. The step up ratio of the whole generator is 143.9. The voltage multiplication ratio increases with the increase of the charging voltage. The generator is suitable to operate at high voltage situation. [ABSTRACT FROM AUTHOR]

The balanced winding displaced in the cavity, the magnet provides the possibility for obtaining the stronger magnet field without enhancing mechanical stresses in the conductors. The model of such a system is the single-turn magnet with an additional triple-thread spiral winding. The equilibrium condition with respect to the radial force takes place at definite values of the axial current and pitch of the turns. In order to decrease the transverse field provoking the azimuthal force, the correction system in the form of cylindrical conductors with slits has been used. The discharging of the end part of the additional winding from the axial force is achieved using the flat concentrators of the flux. [ABSTRACT FROM PUBLISHER]

Longitudinal end-effects seriously affect the electromagnetic performance of linear motor especially for large volume devices such as electromagnetic launchers. So, the purpose of this paper is to study longitudinal end-effects in a permanent magnet (PM) slotless linear launcher and proposes some measures for improvement. The longitudinal end-effects induced by finite length of PM mover can give rise to two mechanisms, uneven airgap magnetic field and partial saturation. The splitting edge magnets method is used to improve the uniformity of flux distribution, and it is also beneficial for enhancing thrust. In addition, we focus on asymmetrical phase characteristics stemming from finite stator part with distributed windings. Its influence on thrust and thrust ripple are investigated based on symmetrical component and energy method. The comprehensive analyses are established to aid initial design and assessment of performance for PM slotless linear launcher. [ABSTRACT FROM PUBLISHER]

This paper presents the investigation of a novel capacitor-charging power supply through inertial energy storage of a homopolar inductor alternator (HIA). The structure of a new 18/16-pole HIA is proposed, and we introduce the theory and advantages of HIA. The characteristics of the static magnetic field distributions are calculated by finite-element analysis, and a basic mathematic model of HIA is set up. We propose an efficient and stable capacitor-charging circuit topology to meet the requirements of this system. A functional model of the key device, namely, IGCT, is also established. Finally, we verify its feasibility and advantages through analysis of the system simulation. [ABSTRACT FROM AUTHOR]

A preliminary design scheme of a model-scale compulsator, which is the heart of the railgun pulse-power system, is provided in this paper. The model-scale air-core compulsator, which can provide considerable energy, power density, and energy density, is the best choice for pulse-power supply of a railgun system equipped to an amphibious assault vehicle. To allow rapid sizing of compulsator systems, it is necessary to present the main first-stage design process which can be used to design systems for advanced applications. Three main aspects during the design of a model-scale compulsator are necessarily presented in this paper: the simulation and calculations of air-core electromagnetic field; the evaluation of extremely high forces imposed during the discharge; and the choice of cooling method of the windings due to the large level of armature current and excitation current. The topology of the model-scale compulsator is chosen. The compulsator has no concrete compensation component, and the excitation winding does the excitation and compensation simultaneously. The design of the model-scale is based on research of a small-scale air-core principle prototype. The feasibility of the technique and machining is also demonstrated. In addition, the main auxiliary components, such as the high-temperature superconducting magnetic bearing and the high-speed brush slip-ring mechanism, are discussed according to the operating conditions. [ABSTRACT FROM AUTHOR]

Since permanent magnet linear synchronous motor (PMLSM) has a bright future in electromagnetic launch (EML), moving-magnet PMLSM with multisegment primary is a potential choice. To overcome the end effect in the junctions of armature units, three different ring windings are proposed for the multisegment primary of PMLSM: slotted ring windings, slotless ring windings, and quasi-sinusoidal ring windings. They are designed for various demands of EML, regarding the load levels and force fluctuations. Auxiliary iron yokes are designed to reduce the mover weights, and also help restrain the end effect. PMLSM with slotted ring windings has a higher thrust for heavy load EML. PMLSM with slotless ring windings eliminates the cogging effect, while PMLSM with quasi-sinusoidal ring windings has very low thrust ripple; they aim to launch the light aircraft and run smooth. Structure designs of these motors are introduced; motor models and parameter optimizations are accomplished by finite-element method (FEM). Then, performance advantages of the proposed motors are investigated by comparisons of common PMLSMs. At last, the prototypes are manufactured and tested to validate the feasibilities of ring winding motors with auxiliary iron yokes. The results prove that the proposed motors can effectively satisfy the requirements of EML. [ABSTRACT FROM PUBLISHER]

A slide-contact type linear electromagnetic catapult (SCLEMC) is investigated in this paper. The structure model of SCLEMC is proposed and its working principle and commutation process are analyzed. The thrust model of the SCLEMC is presented. The thrust characteristic of the SCLEMC is researched by means of the method of finite element analysis. The influences of the driving current and the gap between the mover and the stator on the thrust characteristic of the SCLEMC are analyzed. Research shows that the scheme of the SCLEMC is feasible and that the SCLEMC has high efficiency. The commutation process can be automatically realized through three brushes, which can avoid the complex drive and control system. The commutation voltage of commutation turns is not high under the condition of low speed, which does not damage the stator winding and the brushes. The value of the driving current has an important influence on the thrust characteristic of the SCLEMC. The thrust acting on the mover increases with the increase of driving current. [ABSTRACT FROM PUBLISHER]

A sectioned-winding permanent-magnet linear synchronous motor (SW-PMLSM) is proposed in this paper, whose iron core is continuous, whereas winding is divided. The model of the SW-PMLSM is derived after the section structure and the winding distribution are introduced. The basic theory and implementation of the current error vector-based predictive control (CEVPC) and space-vector pulse-width modulation deadbeat-predictive control (SVPWM-DBPC) are proposed. The moving stroke of the SW-PMLSM is divided into five zones according to the position of the secondary, and the implementations for both control methods are investigated in the five zones. Simulation results of both control methods validate the excellent dynamic performance and show that the SVPWM-DBPC is better than the CEVPC. [ABSTRACT FROM PUBLISHER]

The high-speed metal jet generated by the high explosive antitank method to damage the armor vehicles and tanks. The penetration capacity of the high-speed metal jet is proportional to the effective length of the metal jet. In order to improve the effective length of the metal jet, an electromagnetic enhancing system is put forward, and its principle is introduced. The time sequence of the high-speed metal jet and the pulsed magnetic field is analyzed, and the determination method of the time sequence is obtained. Furthermore, the simulation model of the electromagnetic enhancing system is established based on finite element method, and the distribution characteristics of the discharge current, magnetic field, and the electromagnetic force are obtained. Finally, an experiment system of the electromagnetic enhancing system is built and some verification experiments are carried out. With the analysis and the experiments, the conclusions as follows can be drawn: the high-speed metal jet will be reshaped with the effect of the axial pulsed magnetic field, and the effective length will be improved. Furthermore, the optimal time sequence is that when the central sections of the metal jet and magnetic field coil coincide, the discharge current of the magnetic field coil just reaches its peak point. [ABSTRACT FROM AUTHOR]

This paper describes the design and implementation of a prototype 30-kW (or 30-kJ/s) pulsed-power supply for capacitor charging. The system operates at 200-kHz maximum switching frequency, which is considerably higher than the conventional practice at this power level, leading to smaller passive components. A high power density of 143 \W/in^3 is achieved with the converter operating at a high ambient temperature of 65 ^\circ\C with 90 ^\circ\C cooling oil, by utilizing various technologies on topology, control, devices, passives, and thermal management. The experimental results demonstrate that the converter meets the performance requirements while achieving a high power density. [ABSTRACT FROM AUTHOR]

This paper investigates the thrust characteristics of the transverse flux tubular linear machine, including theoretical analysis and numerical calculation. The influence of structure parameters on the thrust force and cogging force characteristics is analyzed in detail. Special attention is paid to the length of stator segment, air-gap length, and pole-arc coefficient. The analysis results provide a foundation for the optimum design of electromagnetic launcher. [ABSTRACT FROM AUTHOR]

Some intriguing advantages of permanent-magnet linear synchronous machines (PMLSMs), such as simple structure, high thrust, high efficiency, ease of maintenance, and controller feedback, make it possible to take the place of steam catapults in the future. The conventional PMLSM is renowned for its simple structure and high efficiency, whereby the high reactive power resulted from great leakage inductances during the long stator. Thus, great concern is paid to the section structure of the PMLSM. A sectioned permanent-magnet linear synchronous machine (SPMLSM) used in the EMALS is introduced in this paper, whose stator core is continuous but the armature winding is divided into two sectioned parts. First, the electromagnetic fields of the SPMLSM are investigated analytically. Then, the fields are computed by the finite-element method (FEM) and measured experimentally. Not only are the self-inductances and mutual inductances in one section studied but also the mutual inductances between the two sections. These inductances are then calculated by the FEM and measured experimentally. Good correlation among the results was obtained by these three methods. [ABSTRACT FROM AUTHOR]

As the exploitation of astrospace deepens, many new types of space-based electromagnetic launchers (EMLs) have aroused wide attention and discussions. Compared with traditional slotted electromagnetic linear launchers, a slotless-plate permanent-magnet linear synchronous motor can easily meet demands such as flexible structure, light weight, and high control precision for space use. This paper analyzes the magnetic field of the slotless inverted- U structure based on the equivalent-magnetizing-current method. The validity of this technique for integral-slot configuration is confirmed with finite-element analysis. Then, the influence of the main design parameters is investigated, and design optimization guides are established for the selection of the key design parameters. To reach the suitable air-gap flux density here, some new constructional optimization details are discussed. Design optimization is also performed to fulfill enough thrust for the EML system. [ABSTRACT FROM AUTHOR]

Compulsator is the best pulse power supply of electromagnetic gun, into which the energy storage, electromechanical energy conversion, and pulse shaping are integrated. Due to the unique machine configuration, nature of pulse power generation, and potentially large impulse forces and torques, the mechanical analysis of compulsator is essential and different from that of the traditional electrical machine. Based on the iron-core and air-core prototypes, mechanical analysis of iron-core and air-core compulsators was presented in this paper. Although the mechanical analysis theoretical bases of iron-core and air-core compulsator topologies are the same, the analysis processes are different. In the iron-core passive compulsator, the compensation conductive shield was assembled by a thermal shrink fit. The compensation conductive shield would be separated from the rotor as the rotating speed increased above critical speed. Therefore, the critical speed and reasonable value of interference fit were calculated. In the air-core passive compulsator, the compensation aluminum shield was epoxy bonded to the carbon fiber banding, because the elevated temperature about a few hundred degrees centigrade of thermal shrink fit requirement would result in a breakdown of carbon fiber epoxy resin banding. The bonding strength was evaluated, then the reasonable epoxy resin system was chosen, and safe layer thickness was calculated. Due to the large discharge pulse current, the pulsed tangential and radial forces applied to the rotor and armature windings in the stator were also analyzed for iron-core and air-core compulsators. The prototypes operated safely and smoothly, and the design and calculation results were validated. [ABSTRACT FROM AUTHOR]

In order to develop and verify the key manufacturing technologies of the large Nb3Sn superconducting magnet, the central solenoid model coil (CSMC) for China Fusion Engineering Test Reactor is being developed in the Institute of Plasma Physics, Chinese Academy of Sciences (ASIPP), Hefei, China. The design value of the highest magnetic field for CSMC is 12 T, which is made of Nb3Sn and NbTi hybrid superconducting magnets. The key structural parameters of all windings have been determined by the electromagnetic design and optimization of the coil. All the windings of CSMC are a kind of pancake coil wound one in hand by cable-in-conduit conductor; each winding is composed of pancakes (concentric circular turns with turn transitions), pancake joggles, and upper and lower leads. The winding design has been finished including the winding direction analysis, the key bending segments geometry of turn transitions, pancake joggles, and leads transitions. Besides, the new winding production line has come into use and some key forming trials have been conducted. [ABSTRACT FROM AUTHOR]

We present the detailed design, simulation, and fabrication of a hybrid excitation passive compensated pulsed alternator (HEPCPA). The HEPCPA design offers long-lifetime stable operation over a broad range of operating conditions. The stator uses a two-winding design. A slotless armature winding is epoxy bonded on the inner ring of the stator core, and the electrical-excitation winding is embedded in the middle slot of the stator core. The second electrical-excitation winding is used to expand the acceptable range of operating conditions. We explore the magnetic flux density distributions under permanent-magnetic excitation. In addition, we examine two types of electrical excitation. We then calculate the eddy current density distribution in the compensation shield. We discuss conditions for the safe operation of the permanent magnet. We present fabrication techniques for the slotless armature winding. We discuss our experimental results showing enhanced magnetic and electrical field activity. The experimental results show agreement with the simulation. [ABSTRACT FROM PUBLISHER]