Search

In today’s large ships a wide use is made of hydraulic machinery to actuate high-torque low-speed onboard loads like rudders, stabilizing fins and bow thrusters. Such mechanical drives are very cumbersome and suffer from serious maintenance and reliability issues. In this paper, a novel all-electric direct-drive oil-free drive solution is proposed based on an inverter-fed permanent magnet linear synchronous motor (PMLSM). The PMLSM is coupled to shipboard rotary loads through an innovative kinematic chain, consisting of a tiller and a prismatic-rotoidal joint, that performs force to torque conversion. The advantages of the PMLSM solution are presented in the paper in terms of compactness, robustness, reliability, efficiency and maintenance. Furthermore, the design optimization of a technology demonstrator which is presently under construction is addressed.

Slotless Surface Permanent Magnet (SPM) machines are used is some applications where the torque ripple and / or the additional losses due to slotting need to be eliminated. These machines have a geometric structure allowing for an accurate analytical solution for the magnetic fields, which is desirable especially for optimization purposes. This paper derives an analytical formula for the flux density in the stator core of slotless SPM machines during no-load operation. The derived formula is assessed by comparison with Finite Element (FE) analysis. It is shown how it can be used for the computation of no-load core losses including rotational eddy current effects. The method proposed can be naturally extended to determine the core field due to armature reaction as well.

A split-phase machine is a special electric machine whose stator winding is split into multiple (N) three-phase sets. The possibility to supply it through N independent inverters makes it attractive especially when high power and reliability are required. So far, the dq0 refeence frame representation, originally introduced for three-phase machines, has been applied in detail to split-phase configurations in the N=2 case only. In this paper, the extension to an arbitrary number of stator sets is investigated from an equivalent circuit representation viewpoint. The equivalent circuit topologies proposed in this paper to represent a split-phase machine with N three-phase sets is directly derived from the theory presented in Part I. In particular, it will be stressed that as long as N is equal to 1 or 2, dq equivalent circuits remain decoupled as known from the literature, otherwise for N higher than or equal to 3, dq cross couplings must be taken into account in the equivalent circuit representation.

Surface Permanent Magnet (SPM) machines with slotless stator design are used is some applications where torque pulsations and/or the additional losses due to slotting effects need to be eliminated. These machines have a geometric structure allowing for an accurate analytical solution for the magnetic fields, which is desirable especially for optimization purposes. This paper derives a compact but exact analytical formula for the load torque computation in slotless SPM machines. The formula has the advantage of well highlighting the dependence of the load torque from machine construction details. It can be therefore useful in the design and dimensioning stage as a fast alternative to time-consuming Finite Element (FE) analysis.

One of the most common issues in permanent magnet motors for automotive applications is to improve their capability of operating over very wide speed ranges. For this purposes, various motor design techniques have been proposed in the literature. After a brief review of these techniques, the paper presents an idea for improving the flux weakening capability of permanent-magnet reluctance-assisted motors. The idea is based on using an auxiliary field circuit embedded in flux barriers and used to partly demagnetize the motor above the base speed. The field circuit is fed by a brushless permanent-magnet exciter and a diode rectifier. While at low speed the field is not energized, it automatically activates above the base speed by means of a centrifugal switch. As discussed in the paper, the auxiliary field current increases linearly with the speed so as to progressively reduce motor flux with a consequent beneficial reduction in the current to be fed by the inverter for flux regulation.

A split-phase machine is a special electric machine whose stator winding is split into multiple (N) three-phase sets. The possibility to supply it through N independent inverters makes it attractive especially when high power and reliability are required. So far, the dq0 refeence frame representation, originally introduced for three-phase machines, has been applied in detail to split-phase configurations in the N=2 case only. In this paper, the extension to an arbitrary number of stator sets is investigated from an analytical viewpoint. In particular, the paper shows that when N exceeds two, the d-axis and q-axis stator voltage equations are no more decoupled, in general, as it happens for N=1 and N=2. Such d-q cross-coupling is explained in terms of mutual leakage inductances, regardless of possible rotor saliencies and magnetic saturation. The implications of these results in terms of equivalent circuit representation will be presented in a companion paper (Part II).

The use of electric drives for large ship propulsion is a spreading trend in today’s marine industry thanks to the benefits it brings not only in dynamic performance and noise reduction but also from an environmental and energy-saving viewpoint. In fact, using electric motors enables to operate on-board prime movers (diesel engines above all) close to their maximum efficiency point, thus significantly reducing fuel consumption and polluting emissions. The paper presents an overview of state-of-the-art high-power electric propulsion drives used on large ships, with particular regard to cruise liners, mega-yachts and naval vessels.

Modeling and Simulation of Multiphase Machines in the Matlab/Simulink Environment