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Short-time thermal transient identification method was successfully adopted to evaluate the winding thermal parameters of induction motors for industry applications. In this work, the modeling approach and the identification methodology are extended to the more sophisticated case of multiple three-phase machines. The generalized model takes into consideration the mutual heat exchange between the windings as well as the possible causes of temperature mismatch. A complete procedure to evaluate the parameters of the modified model is provided, supported by experimental validation on a 7.5 kW machine with two three-phase windings in contact at slot level. The method covers any type of multiple three-phase machines, whatever the thermal promiscuity of the winding sets: From deep coupling as the ones presented, to the case where only the end-turns are in contact, to the completely decoupled case. The proposed technique can be useful for the machine design and for real-time temperature monitoring during operation.

The present work describes a lumped parameter approach for the filling analysis of engine lubrication systems. Filling analyses are typically carried out by means of multi-phase 3-D CFD models but, despite allowing detailed and reliable results, they require very demanding computational capabilities. Based on these premises, the authors present a modelling procedure to address the topic by means of a lumped parameter approach. By introducing a detailed modelling technique, the proposed method offers the possibility to reproduce not only the common and simple elements such as pipes and bends, but also permits the discretization of complex three-dimensional fluid domains. The proposed approach has been applied to the lubrication system of a heavy-duty V6 engine: since long stop intervals are planned during the engine lifetime, the filling time of the system plays a fundamental role. The analysis has been run with the obtained 0-D model, simulating at different lubricant temperature. The predictive capabilities of the numerical model are presented in terms of flow pattern and filling time of the circuit branches. The simulation has also been performed by means of a 3-D CFD model, providing the possibility of a result comparison: since this methodology is nowadays considered the state of the art for this kind of analyses, the results are taken as reference to evaluate the capabilities of the proposed 0-D approach. The comparative analysis concerns both the overall distribution of the lubricant over time, and the local phenomena. The differences in terms of computational effort are considered as well, to assess the approximation of the lumped parameter approach with respect to the complex but more accurate three-dimensional models. The results highlight the accuracy of the methodology on the estimation of the filling time. Moreover, the proposed procedure reveals great advantages in terms of computational effort.

Some specific application fields of electric motors, such as food and beverage applications, require highly demanding hygiene procedures that involve a highly aggressive environment for the motor, including frequent high pressure and high temperature washing with water or more aggressive detergents. Specific materials and protection features are used in motors to better withstand such environment; however, these have an impact on performance and lead to oversized machines. This paper describes some solutions and their impact on performance, with specific focus on the thermal properties of the analyzed machine.

[EN] Non-conventional thermal zones are low-cost and ecology friendly alternatives to the housing needs of populations in various situations, such as surviving natural disasters or addressing homelessness. However, it is necessary to guarantee thermal comfort for occupants, while aiming to minimize energy consumption and wastage in refrigeration systems. To reduce the cooling requirements in non-conventional thermal zones it is necessary to model the structure and analyze the principal factors contributing to internal temperature. In this paper, a geodesic dome is modellingusing the lumped parameter technique. This structure is composed of a wooden skeleton and wooden floor, with a canvas surface as its exterior. The mathematical model was tuned using experimental data, and its parameters were classified using Monte Carlo sensitivity analysis. The mathematical model was used to evaluate the impact on internal temperature and occupants' comfort when two strategies are considered. The results obtained indicatee internal temperature reductions down to a range of 7% to 11%; this result is reflected directly in the energy used to refrigerate the thermal zone, contributing to the objective of providing houses with lower energy consumption., This work was supported by RTI2018-102256-B-I00 of MINECO/FEDER.

Purpose The purpose of this paper is to propose a new simplified numerical model, based on a very compact semi-empirical formulation, able to simulate the fluid dynamics behaviors of an electrohydraulic servovalve taking into account several effects due to valve geometry (e.g. flow leakage between spool and sleeve) and operating conditions (e.g. variable supply pressure or water hammer). Design/methodology/approach The proposed model simulates the valve performance through a simplified representation, deriving from the linearized approach based on pressure and flow gains, but able to evaluate the mutual interaction between boundary conditions, pressure saturation and leak assessment. Its performance was evaluated comparing with other fluid dynamics numerical models (a detailed physics-based high-fidelity one and other simplified models available in the literature). Findings Although still showing some limitations attributable to its simplified formulation, the proposed model overcomes several deficiencies typical of the most common fluid dynamic models available in the literature, describing the water hammer and the nonlinear dependence of the delivery differential pressure with the spool displacement. Originality/value Although still based on a simplified formulation with reduced computational costs, the proposed model introduces a new nonlinear approach that, approximating with suitable precision the pressure-flow fluid dynamic characteristic of a servovalve, overcomes the shortcomings typical of such models.

An active air thrust bearing controlled by an Arduino board and digital valves is described. A numerical model for the complete system is developed to design the control and perform a sensitivity analysis based on geometric parameters such as the conductance of the valves. Model validation is based on experimental open-loop and closed-loop tests. The purpose of the model is to determine the range of force and air gap height in which the pad can be controlled.

This paper presents the validation of a first-order winding thermal model in machine operative conditions. The proposed model can be used in motor control strategies for the winding temperature prediction during transient overload, or vice versa , for the prediction of the maximum time duration of the overload maintaining the winding temperature within the limit imposed by the class of insulation. The thermal model has been validated using two different electrical machines. The first one is a 10-kW automotive starter-generator prototype for mini-hybrid powertrain equipped with distributed bar windings, while the second one is a 2.2 kW total enclosed fan cooled industrial induction motor equipped with conventional stranded wire windings. Depending on the application for both machines, a short-duty transient operation in overload conditions could be required. In particular, the automotive starter-generator must accomplish engine cranking and torque assistance during the vehicle acceleration and braking, while the industrial induction machine could operate in intermittent service in overload conditions when used in machine tool applications. As a consequence, an accurate stator winding temperature prediction is mandatory to fully exploit the machine performance. For both motors, the thermal model parameters have been evaluated by fast experimental approach, and, subsequently, the model has been validated during operative overload conditions.

Highly detailed computer models are required for design and development of modern flight control systems, capable of emulating with high accuracy the behaviour of on-board equipment. At the same time, different simplified models are needed, specifically intended for operations such as the optimization of preliminary design and the development of diagnostic or prognostic strategies. These simplified models are required to combine sufficient levels of accuracy and reliability with reduced computational costs, to minimize the computational burden associated with prognostic and optimization algorithms. In this work, we focus on electro-hydraulic actuators, since they are critical subsystems in terms of safety and availability of the aircraft. Advanced monitoring and prognostic algorithms require new numerical models, combining an acceptable computational effort with a satisfying ability to simulate their performance and dynamics. To this purpose, this paper proposes a new simplified numerical model of the servovalve fluid-dynamic behaviour. This numerical algorithm, based on a very compact semi-empirical formulation, is intended to take into account in a simplified but sufficiently accurate way several typical effects related to the SV spool geometry and the operating conditions. To evaluate the approximations introduced by this model into a system-level simulation, it has been integrated into a dedicated numerical model simulating a simple electrohydraulic on-board actuator, and compared with a higher fidelity servovalve model.

Because of their low friction and wear, aerostatic pads are widely in many high precision applications, e.g., linear slides, coordinate measuring machines and medical equipment. However, especially grooved aerostatic pads can be unstable under certain operating conditions. This paper presents a lumped parameter model to study the static and the dynamic performance of a rectangular grooved aerostatic pad. The theoretical results are compared with the experimental ones.

Some specific applications fields of electric motors, such as Food and Beverage (F&B) applications, require highly demanding hygiene procedures that involve a highly aggressive environment for the motor, including e.g. frequent high pressure and high temperature washing with water or more aggressive detergents. Specific materials and protection features are used in motors to better withstand such environment, however these have an impact on performance and lead to oversized machines. This paper describes some solutions and their impact on performance, with specific focus on the thermal properties of the analyzed machine.

The article gives a general description of the SIMCO calculation code designed to simulate thermohydraulic and physico-chemical processes in containments of nuclear power facilities. The authors present a calculation technique based on a physico-mathematical model in lumped parameters. As a numerical solution method, the modified semi-implicit SIMPLER procedure is used. The code was examined using analytical and qualitative tests. A comparison of the numerical and analytical solutions showed good agreement. The code was verified using the experimental data obtained at the NUPEC installation (Japan). Based on the results of testing and verification, it was concluded that, in general, physico-mathematical code models adequately describe the processes of heat/mass transfer in the containment. Therefore, this SIMCO code version can be used to analyze the totality of thermophysical and physico-chemical processes in nuclear power facilities with containments, including the transfer of hydrogen/steam/air mixtures.

Short-time thermal transient identification method was successfully adopted to evaluate the slot thermal parameters of induction motors for industry applications. In this work, the modeling approach and the identification methodology are extended to the more sophisticated case of multiple three-phase machines. The generalized model takes into consideration the mutual heat exchange between the windings as well as the possible causes of temperature mismatch. A complete procedure to evaluate the parameters of the modified model is provided, supported by experimental validation on a 7.5 kW machine with two three-phase winding in contact at slot level. The method covers any type of multiple three-phase machines, whatever the thermal promiscuity of the winding sets: from deep coupling as the ones presented, to the case where only the end-turns are in contact, to the completely decoupled case. The proposed technique can be useful for the machine design and for real-time temperature monitoring during operation.

In the last years the use of high temperature low sag conductors has become more and more frequent in electric power system. Such conductors have an inner layer in polymeric and/or fibre material, with reduced thermal coefficient and weight with respect to conventional ones. For this reason, under short circuit conditions they can experience large displacements due to the electromagnetic forces induced by the fault currents. Such displacements can influence phase-to-ground or phase-to-phase clearances, thus reducing the system security. In this paper, a possible way to model the dynamic electromechanical behaviour of overhead electric power lines conductors is presented and discussed, using lumped parameter models implemented through Modelica language.