P. Cancelliere

A Tubular-Generator Drive For Wave Energy Conversion

This paper illustrates the operation of a tubular-machine drive as a linear generator for a heave-buoy wave energy conversion. Linear generators, which are adopted in marine power plants, offer the advantage of generating without introducing any conversion crank gear or hydraulic system. The use of a tubular-machine topology allows the electromagnetic thrust density to be improved. This paper briefly summarizes the principles of marine wave buoy interaction and reports the design analysis and control of a permanent-magnet (PM) synchronous tubular linear machine based on a scaled generator prototype and on a rotating simulation test bench

Modeling and Control of a Zero-Current-Switching DC/AC Current-Source Inverter

Choosing a dc/ac converter is mainly a compromise among three major issues, namely: 1) efficiency; 2) waveform quality; and 3) cost. This paper considers a zero-current-switching (ZCS) current-source inverter (CSI) as a viable choice for many applications. It features low conduction and switching losses, inherent output filtering, capability of withstanding short circuits, and the opportunity to use thyristors. Despite these promising characteristics, this inverter exhibits a nonlinear relationship between the modulation index and the output current. Moreover, the resonant modes that are generated by the load-filter interaction must be damped. Since the previous aspects require a proper control law, a model of the system is very useful for defining and tuning a control structure. Thus, after providing a functional overview of the ZCS dc/ac CSI, this paper formulates a large-signal model and then derives and simplifies the averaged one. Numerical data are used to validate the models that are obtained. An active damping control for a motor drive is defined and tuned by means of the simplified averaged model, and its effectiveness is numerically validated. Experimental results conclude this paper.

Voltage control of current source inverters

The current source inverters may become direct competitors of the voltage source inverters thanks to the voltage control techniques. The paper proposes an improved voltage control technique for current source inverters, that chooses the current vectors relying on bang-bang controllers. This technique is compared to a well-established one using current space vector modulation and synchronous-frame proportional and integral controllers. The presented controller is explained and validated by means of off-line as well as real time simulations and experimental tests. The numerical results prove that the proposed control technique produces less distorted voltage waveforms in terms of total harmonic distortion and spectrum. According to the real-time simulations performed the proposed control technique is computationally less expensive than the benchmark. Finally, the experimental results obtained confirm the feasibility of the proposal.

Analytical formulation of the no-load magnetic field in IPM tubular machines with translator eccentricity

The design of electrical machines requires a suitable procedure in order to highlight the main machine parameters. Among them, the knowledge of the no load magnetic field as a function of the main geometry machine parameters helps designers in formulating optimal design choices. Inevitably, tubular machines are subject to eccentricity of the mover, therefore a non uniform distribution of the no load magnetic field in the air-gap arises. This yields attractive radial forces that must be taken into account in the choice of the bearings. This paper illustrates an analytical formulation of the no load magnetic field distribution in tubular IPM machines with translator eccentricity in order to facilitate the computation of the radial forces

Selecting the electromagnetic actuator of the ELT primary mirror

The segmented, adaptive primary mirror of the ELT is the most delicate optical component of the telescope. Its full-adaptive operational modes require an high bandwidth actuation system, able to provide large and precise stroke motions. As the core component of the actuation system hardware, the electromagnetic device has to be accurately designed. This paper depicts the preliminary electromagnetic study of the actuator. After a discussion of the chosen concept, the design process and the computational approach are illustrated. The goal of the study is the definition of the basic geometrical and physical parameters which allow the minimization of the power dissipated to deliver the proper actuation force, in order to reduce the local overheating in the telescope optical path.

Soft switching current source inverter with modified space vector modulation and active damping for an axial flux in-wheel motor with fractional slot winding

The paper presents a power supply for an axial flux in-wheel motor with a fractional number of slots per pole and per phase. A soft switching ZCS current source inverter is adopted in order to improve machine and converter efficiency. The chosen topology allows direct motoring and regenerating operation directly from the battery. The paper improves the converter analysis and deals about modulation and control. Moreover, the paper summarizes the machine construction, and it investigates the whole drive performances by means of numerical simulations.

Analytical Formulation of Radial Magnetic Forces in PM Linear Tubular Machines with Translator Eccentricity

Due to mechanical couplings, permanent magnet tubular linear machines are subject to eccentricity of the mover and hence to a non uniform circumferential distribution of the no load magnetic field in the air-gap. The intensity of radial forces arising thereof is such that it must be taken into account both for flexion analysis and for choice of bearings. This paper illustrates an analytical formulation of the no load magnetic field distribution in tubular IPM machines with translator eccentricity in order to facilitate the computation of the radial forces. Measurements on two prototypes in a test rig illustrate the validity of the approach.

A Fractional Slot Axial Flux PM Direct Drive

The paper deals with an axial-flux PM synchronous motor (AFPMSM) for a direct wheel drive. Its main feature is the armature winding of the fractional slots type. The choice of a concentrated non-overlapping winding allows a large number of pole pairs to be designed. The paper is aimed at emphasizing the special features of the whole motor drive. Therefore, both machine and control design aspects are targeted. Encoder-less operation of the drive is particularly critical. A vector control scheme is illustrated. A sliding-mode rotor flux estimation scheme is investigated. Its performances are experimentally compared to the encoder operation

SelfDrive: fully integrated solution for DC PM motors

PM brushless motors with trapezoidal EMF are perhaps today the most used motors for low-cost applications. An increasing number of solutions is aimed to reduce control electronics in this kind of motor in order to reduce total size. The paper shows an application in which virtually all power and signal electronic components are placed in the same chassis as the motor. Particularly, Hall switches are placed inside motor slots, to provide adequate slot switching. The motor is thereby capable to be self commutated, just like an ideal DC machine. The reduced dimensions of the whole drive allows a suitable application of such a solution in a different field of application as robotics, automotive and so on. The placement of components inside the motor obviously poses some electrical, magnetic and thermal problems that are approached in the paper by means of finite element modelling and experimental tests.

SelfDrive: a high-integration self-commutated DC brushless smart motor

The paper discusses some results obtained on a very low-cost fully integrated fractional horsepower DCPM brushless motor. The main feature of the motor is the absence of both an encoder and of any command logic. The correct phase switching is, in fact, given by proximity sensors integrated in the slot openings. To evaluate the feasibility of the approach, extensive FEM simulations have been performed. The proposed motor drive system has been assembled and tested in the laboratory for its performances. Some experimental results are illustrated.