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This work shows experimental evidences of abnormal end-ring torsional vibrations in fabricated cage induction motors and their role as root cause of bar breakages. A case-study of cage torsional resonances in railway traction motors is presented, which led to bar breakages with a peculiar failure pattern. A particular cage resonant mode (the second natural mode with both the rings vibrating in phase-opposition with respect to the rotor iron stack) is shown as responsible of excessive bar bending, fatigue, and bar fractures, through direct measurements of ring-stack oscillations in working motors. Cage torsions were excited by large harmonic torques due to inverter supply in the case considered. The mechanism of resonance-induced bar solicitations and fatigue is discussed, and the difference of failure pattern with respect to more common bar breakage mechanisms (overloads, heavy start-ups, etc.) is evidenced. Some theoretical models for modal frequency calculation are presented, which may help to identify the origin of vibrations and the fault root-cause in faulted drives. Dynamic simulations of the drive have been carried out for airgap torque calculation and bar length optimization.

This paper investigates the hydraulic system drive used onboard ships to actuate stabilizing fins. The hydraulic drives are often characterized by low efficiencies, heavy maintenance, frequent oil leaks and large weight and size. To overcome these draw-backs, in this paper a concept design of a full-scale permanent magnet linear synchronous motor directly coupled to the shipboard fin stabilizer, is presented, used as a servo-motor. The innovative electric drive is based on prototype of high thrust linear motor built in a previous research. A complete Simulink model, where electric, mechanical and hydraulic domains can be connected, has been realized. Simulations has been performed to evaluate the hydraulic drive efficiency and in order to assess the servo-assistance capabilities. The results show the feasibility of the proposed solution for a future practical application. This research has been carried out in the framework of the Italian Defence Research National Program for the development of ‘dual use’ technologies.

Alternatives to hydraulic drives used on board ship are under study for the Italian Navy in order to reduce the use of the oil which cause environmental problems and high cost. The hydraulic system drive used onboard ship are affected by low efficiencies and generally require intensive maintenance, very high encumbrance. So that the Italian Navy has commissioned a research project for the construction and installation of an innovative oil-free electric drive based on a permanent magnet linear actuator. The new electric motor is more efficient, fault-tolerant, reduces the encumbrance and ensures a greater control.

Hydraulic drives used on board ship to empower rudders, stabilizing fins, anchor winches, etc., are often characterized by low efficiencies, heavy maintenance, frequent oil leaks and large weight and size. To overcome these drawbacks, oil-free inverter-fed alternative drives can be conceived. In this paper a concept design of a full-scale permanent magnet linear synchronous motor directly coupled to a twin rudder on board ship is presented, used as a servo-motor. The servo-assistance capabilities are simulated and evaluated by using a complete model of the electro-mechanic-hydraulic system in Simulink environment. The results show the effectiveness of the electromagnetic drive servo-assistance. This research has been carried out in the framework of the Italian Defence Research National Program for the development of `dual use' technologies.

The paper focuses on the evaluation of the impact on residential buildings of innovative control logics defined for a rational utilization of the electric loads and air-conditioning systems. The control logics are implementable thanks to a Decision Support and Energy Management Systems developed by the same authors and easily installable in new and still-existing houses. The paper shows how a significant reduction of the primary energy consumption can be obtained by controlling the air-conditioning units together with the other electric loads of the house. After having explained how the control logics operate, a simulation tool is described, developed for a preliminary evaluation of their effects on the energy consumptions of residential buildings in the design stage. An application of the simulation tool on a typical house, considering different scenarios and varying the climatic conditions and the energy performance class of the envelope, is presented. Finally, a measurement campaign on two real existing houses, equipped with the Decision Support and Energy Management System, is described, and the effects of the control logics are assessed. © 2015 Elsevier B.V. All rights reserved.

The use of linear machines (LMs) is increasing in research and industry fields. All kinds of LMs are studied: synchronous, induction, flux switching. Research is leading to overcome the known drawbacks of all these machines. Anyway the use of innovative direct-drive solutions are under study to obtain more efficient energy conversion, such as for marine field. As alternative to classical systems, linear force can be used to obtain a more efficient plant. Hydraulic drives used on board ship to empower rudders, stabilizing fins, anchor winches, etc., are often characterized by low efficiencies, heavy maintenance, frequent oil leaks and large weight and size. To overcome these drawbacks, an oil-free inverter-fed alternative drives can be conceived. In this paper a concept design of full-scale permanent magnet linear synchronous motor directly coupled to a twin rudder on board ship is presented, used as a servo-motor. A complete model of the electro-mechanic-hydraulic system in Simulink environment was built. Several simulations are performed to evaluate the servo-assistance capabilities. The results show the effectiveness of the electromagnetic drive servo-assistance and an increased overall efficiency of the steering gear. This research has been carried out in the framework of the Italian Defence Research National Program for the development of `dual use' technologies.

Hydrostatic drives used on board ships are often characterized by low efficiencies, heavy maintenance, frequent oil leaks and large weight and size. To overcome these drawbacks, oil-free inverter-fed alternative drives can be proposed. This paper analyzes the ship rudder hydraulic drive performances, and a proposal for improvements is shown. A full-scale permanent magnet linear synchronous motor directly coupled to a twin rudder is presented, used as a servo-motor. Both servo-assistance features and performance and efficiency improvements are evaluated by using a complete physical model in Simulink environment.

Use of axial flux machines (AFPMs) is studied in order to obtain a given value of the phase inductance, so as to use flux-weakening techniques. Slotted machines are considered, where the locking bars are made by innovative sinterized magnetic materials. A FEM model developed by the authors is used for the determination of the machine parameters: back EMF, cogging torque, load torque, axial force and inductance. A prototype machine designed and manufactured by the authors is described. The numerical tests are compared to the experimental results, allowing appreciation of the effectiveness of the proposed improvement of the machine configuration and the accuracy of the numerical algorithms.

An axial-flux permanent magnet machine (AFPM) topology with a coreless winding is proposed for generator units required aboard ships, aircraft or hybrid-electric vehicles. In the proposed AFPM configuration, the winding consists of rhomboidal shaped coils encapsulated in fibre-reinforced epoxy resin. The coils have a double-layer arrangement to leave space for a cooling water duct being used to remove heat directly from the interior surface of the winding. The overall machine structure has high compactness and lightness, and because of the lack of the iron core generator operation with power output at 400 Hz can be accomplished with high efficiency and acceptable voltage regulation. The paper discusses the basic design and construction of AFPM generators with coreless winding and experimental results taken from a 16 poles machine prototype rated 70 kW, 3000 rev/min are finally reported.

Axial-flux PM machines are particularly suitable for application in electrical drives devoted to ship propulsion, since they allow the elimination of the large-power gearbox used in conventional systems. In consideration of that, this paper deals with a novel slotless axial-flux PM machine topology which is characterized by the synchronous counterrotation of the two machine rotors. Such a new machine topology can find application in the direct driving of two counterrotating propellers, which may be used in ship propulsion systems to recover energy from the rotational flow of the main propeller slip stream. In this case, the use of an axial-flux machine having counter-rotating rotors allows an improvement in terms of weight and efficiency, since the epicyclic gear otherwise required for the motion reversal can be avoided. The paper discusses the stator winding arrangement which allows the opposite motion of the machine rotors and reports experimental results taken from a small-size machine prototype. >

The design of direct-drive wheel motors must comply with a diameter restriction due to housing the motor in a wheel rim, and must allow the achievement of very high torque density and overload capability. Slotless axial-flux permanent magnet machines (AFPMs) prove to be one of the best candidates for application in electric vehicles as direct-drive wheel motors, as in comparison with conventional machines they allow designs with higher compactness, lightness and efficiency. The paper presents a newly-conceived AFPM which has multi-stage structure and water-cooled ironless stator. In the proposed new machine topology, the space formerly occupied by the toroidal core becomes a water duct, which removes heat directly from the interior surface of the stator winding. The high efficiency of the machine cooling arrangement allows long-term 100% overload operation and great reduction of the machine weight. The multistage structure of the machine is suited to overcome the restriction on the machine diameter and meet the torque required at the wheel shaft. The paper gives guidelines for the design of a multi-stage AFPM with water-cooled ironless stator, and describes characteristics of a two-stage prototype machine rated 220 Nm, 1100 RPM.