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The on-going electrification transportation system revolution has already started and the continuous evolution of power electronics allows new and more reliable system layouts and control strategies to be investigated. Mainly, this revolution is driven by increased reliability levels. Since multi-three phase motors are fault tolerant by definition, they are a very good candidate for more reliable...
All Electric Ships (AESs) are becoming a standard for what it concerns large ships with large power requirements (for both propulsion and onboard loads). At present, the design of shipboard complex power system (namely the IPS — Integrated Power System) is done through a well-proven process, relying on historical data and trial-and-error procedures developed in nearly 30 years of design experience...
Nowadays, the Medium Voltage Direct Current (MVDC) technology represents a new possibility to renew the shipboard power system of large All Electric Ships (e.g. cruise liners or military vessels.). This new concept is capable of achieving valued advantages, such as simplified system integration, modularity and system efficiency, together with an expected reduction of the space devoted to technical...
At the present days, the AC motors is an industrial standard, not only in high power constant speed applications, but also in the medium and low power range. With the diffusion of induction motors some crucial problems emerged: (i) to control the AC drive in order to achieve high dynamic performances; (ii) to monitor the induction motor, with the aim to detect the most common faults. Several types...
The increasing complexity of ship's Integrated Power Systems (IPSs) led to the need of a review of conventional design process. Moreover, several stakeholders influence ship design, each of them aiming to protect its own interests, in particular when responsibility of accidents has to be defined. Dependability could be the tool to modify conventional design, transforming it into a dependability oriented...
Dependability has only recently become a unified theory, developing its own taxonomy, lexicon and methods. This newly formed discipline now regroups concepts defined and developed within international rules corpus in different areas of engineering, such as: aerospace, automotive, computing, etc. Applications to marine sector are, at present, partial, lacking in terms of systematic approach and limited...
DC distribution is being considered as an attractive alternative to its traditional AC counterpart in many fields of applications and, in particular, for shipboard power systems. The adoption of a DC distribution network makes it possible and sometimes necessary to radically revise the technology of the generation systems in many regards. Not only frequency-related constraints are removed, allowing...
In many applications, electric machines are designed for operation over a wide speed range and require important flux weakening capabilities at high speeds. This paper presents and innovative rotor mechanical design that endows an interior permanent magnet (IPM) machine with an intrinsic capability of reducing its own rotor flux at high speeds. Unlike most state-of-the-art flux-weakening techniques,...
A promising solution to improve tomorrow's all-electric ship onboard power system design and performance relies on moving from 50-Hz or 60-Hz AC distribution to a Medium-Voltage DC (MVDC) grid. This paper provides a review of presently-available and under-development technologies for electric generators to be used in perspective MVDC shipboard systems. The inspiring reason for the survey lies in the...
The vector approach in either stationary or synchronous plane is commonly used for the analysis of the AC drives like induction and PM brushless AC drives whilst it has been hardly ever used for the PM brushless DC (BLDC) drives. A possible reason is that they require injection of square-wave currents into the motor phases, which are non-sinusoidal in nature. Recently, the PM BLDC drives have been...
The degree of complexity of Integrated Power Systems (IPS) for All Electric Ships (AESs) points out the need to review the design process from a dependability perspective. This paper suggests the application of dependability concepts and definitions to accomplish to requirements set by recent rules and regulations in the field of threat levels for shipboard electrical equipment. Guidelines about 1)...
Permanent-magnet synchronous motors are widely used in vehicular traction applications due to their high efficiency and torque density. A critical point of their operation is the flux weakening needed at high speed, which usually implies injecting a d-axis demagnetizing current by the inverter. This paper presents a critical survey of the alternative approaches found in the literature and patent databases...
Vehicular traction motors are usually designed to operate over a wide speed range and require important flux weakening capabilities at high speeds. This paper presents and innovative design intended to endow an interior permanent magnet (IPM) motor with an intrinsic capability of reducing its own rotor flux at high speeds. The design does not involve any additional current source nor control systems...
DC distribution is an attractive solution for onboard integrated power systems of new-generation all-electric ships, especially thanks to the benefits it offers in terms of reducing generation system size, weight and power consumption. Technologies have already been implemented in full-scale prototypes based on synchronous generators feeding the DC grid through rectifiers. In these proven solutions,...
In this paper two possible design alternatives are investigated for a high-power synchronous motor propulsion drive employing two voltage-source inverters for motor supply. The two arrangements are compared based on their steady-state behavior in both normal and faulty conditions (i.e. with one out-of-service inverter), predicted by time-stepping finite-element simulations. Simulation results found...
The paper presents the activities ongoing in the framework of a two-year Italian National Research Project aimed at developing a distributed Driving and Steering (DaS) system for Electric Vehicles (EVs). The system is built up around an actuation module embedding a rotary-linear motor and including a power converter and a local Electronic Control Unit (ECU) to supply and control the motor. The actuation...
Split-phase synchronous motors equipped with multiple-stator three-phase windings, each supplied by a load-commutated inverter, play an important role in today's very high power electrical-drive applications. A criticality of these systems is the possibility that commutations occur in different motor windings simultaneously. The resulting electromagnetic transient depends on the magnetic coupling...
Z-source inverters (ZSIs) supply AC loads from a DC source and boost the voltage of the DC source in a single stage. Such an ability is much needed in electric vehicles where the rated voltage of the traction motors is usually higher than the voltage generated by the onboard DC sources. Being the technological trend in the traction drives directed toward the employment of PM brushless motors, the...
In today's electrical drives, the use of more than three-phases to implement the electrical machine stator winding is a frequently adopted provision to enhance system power rating and fault tolerance. In VSI-fed electrical machines, multi-phase windings are adopted in both their symmetrical structures (with n equally distributed phases, supplied by a single n-phase inverter) and in their multiple...
The paper presents a small-signal stability analysis of voltage control systems employed onboard all-electric cruise liners. To realize the stability analysis, a model of shipboard power station voltage control system has been determined, moving from dynamic models of alternators, voltage regulators and loads. Reduced order models of alternators have been utilized, to simplify at best the analysis...
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