A. Kladas

• Professor
• Head of Department at National Technical University of Athens

The paper presents the development of a fault tolerant electromechanical elevator monitoring system aiming to achieve high safety during operation. The proposed methodology is based on a particular permanent magnet synchonous motor (PMSM) in conjunction with suitable driver system characteristics enabling improvements in overall system reliability....

This paper investigates effects on permanent magnet motor characteristics of the non-uniform air-gap caused by rotor deformations under high-speed conditions. Particularly, changes in the spatial flux density harmonics, in the flux linkage variations observed in the stator windings and in the electromagnetic torque ripple are evaluated and discusse...

Permanent Magnet Synchronous Motors (PMSM) constitute a continuously expanding technology in recent years applied in many emerging electric drive applications, such as electric vehicles and UAVs, but also in more traditional systems such as elevators, replacing induction motors, as they present high efficiency, high power density and energy saving...

Electric field simulations and measurements under overhead high voltage transmission lines, in the presence of human body, are undertaken in this paper, in an effort to assess improvements in the finite element analysis (FEA) precision achieved by using 3-dimensional representation with respect to 2-dimensional one, enabling appropriate shielding c...

The extreme environmental issues and the resulting need to save energy have turned attention to the electrification of energy applications. One of the key components involved in energy efficiency improvements is the appropriate conception and manufacturing of electric machines. This paper overviews the electromagnetic analysis governing the behavio...

The extreme environmental issues and the resulting needs to save energy have turned the attention to electrification of energy applications. One of the key components involved in energy efficiency improvements is the appropriate conception and manufacturing of electric machines. This paper overviews the electromagnetic analysis governing the behavi...

This paper presents a methodology enabling advanced design of permanent magnet motors constituting a favored choice in electric traction applications, particularly promising in high-speed ranges. Appropriate permanent magnet grade and configuration selection ensuring satisfaction of standard design criteria such as high efficiency and high-power de...

This paper presents the modeling procedure of a particular 3D-printed iron material appropriate for low cost production of cores of actuators, a trend which is recently popular in the research community, with direct interest for the relevant industry. At first, the characteristics of cores manufactured by a commercially available magnetic iron poly...

This paper presents the energy savings achieved by using a particular three-phase permanent-magnet motor drive control strategy in an elevator application. The proposed control methodology, based on a particular variable-amplitude variable-frequency voltage control pattern technique implemented in a permanent-magnet motor, is compared to a standard...

The paper proposes a particular modeling procedure for efficient switching frequency loss consideration in surface mounted permanent magnet rotors in cases of PWM supply. The model is based on 2D finite element analysis combined with circuit equations in the permanent magnet regions enabling end effects consideration associated with the switching f...

In this paper, a particular methodology is introduced based on a coupled 2D FEA and circuit approach for the representation of permanent magnets in electrical machines including eddy current losses due to slot harmonics and switching frequency of PWM inverter supplies. The governing equation is diffusion equation expressed in Cartesian two dimensio...

This paper proposes a computationally efficient thermal study method that substitutes Computational Fluid Dynamics (CFD) with Finite Element Analysis (FEA) involving minimal loss of accuracy and omission of the increased computational load. The suggested technique contributes towards the realization of multiphysics optimization of high-speed electr...

This presentation concerns the energy savings achieved by using a particular three-phase permanent magnet motor drive control strategy in an elevator application. The proposed control methodology, based on a particular variable amplitude variable frequency voltage control pattern of a permanent magnet motor, is compared to a standard induction moto...

The Radio Frequency Quadrupole (RFQ) of the European Spallation Source (ESS), operates at 352.21 MHz with an RF pulse length of 3.2 ms and repetition rate of 14 Hz. The RFQ focuses, bunches and accelerates the 62.5 mA proton beam from 75 keV up to 3.6 MeV. In an effort to study and compare the results from 3D electromagnetic codes, different models...

In this paper, the effect of different magnetic shielding materials for electric car power cables has been studied using Finite Element Analysis (FEA), verified by experimental results. Bearing in mind the complex spectrum modulation, typically using pulse width modulation (PWM), a magnetic field shielding up to 2 kHz is required. Therefore, magnet...

Protection against the electromagnetic fields around high-voltage transmission lines is an issue of great importance, especially in the case of buildings near power lines. Indeed, the developed fields can be harmful for the habitants and electrical/electronic devices, so the implementation of appropriate measures to address the above electromagneti...

The azimuth thruster is widely used in electric propulsion ships due to its excellent performance in contrast to their mechanical counterparts which present an inherent drawback regarding to maintenance needs, high costs and overall system deficiency. At the same time, according to up-to-date manufacturers' reports, permanent magnet motors make azi...

Perovskite Solar Cells (PSCs) are in the forefront of third generation of photovoltaics and gained a lot of attention as a very promising green technology towards direct solar energy conversion to electricity. PSCs are fabricated following solution processed techniques at low temperature and they present high power conversion efficiency exceeding 2...

Permanent magnet motors constitute a favored choice for electric drive applications in high speed ranges due to their increased efficiency, compact rotor structure and relative robustness. The respective design involves analysis of coupled electromagnetic, thermal and mechanical phenomena imposing respective limitations. Direct coupling of such a m...

Photovoltaics (PVs) are among the most promising low-cost energy sources with high possibility of large-scale solar cell manufacturing and production. Perovskite solar cells (PSCs) are considered as the fore front of third generation of PVs. They are fabricated using solution processes and their power conversion efficiency now exceeds 25%, making t...

This paper develops a mixed finite-element, analytical solutions, equivalent surface impedance methodology for the computation of electric and magnetic field distributions near power facilities. The proposed method enables efficient consideration of conductor sag, ground surface irregularities, proximity effects of metallic components such as trans...

The liberalization of electricity market, in conjunction with the actual environmental constraints and previsions, is leading to considerations for combined urban and electricity market developments, promoting, therefore, buildings’ energy autonomy in perspective to transform regional and individual electricity consumers to producer-consumer (prosu...

The more-electric aircraft initiative represents an important technology step-change for the aircraft industry. The reduction of both fuel consumption and environmental impact are leading to alternative solutions for actuating the flight control surfaces. The traditional hydraulic systems, are progressively being replaced with electrically powered...

The objective of this paper is to give an insight about the development of a fuzzy logic efficiency control system which is incorporated to a standard adjustable speed drive control (i.e. Indirect Vector Control) in order to improve the online efficiency in Permanent Magnet Synchronous Motor (PMSM) drives for both transient and steady state operati...

Purpose This paper aims to introduce a computationally efficient hybrid analytical–finite element (FE) methodology for loss evaluation in electric vehicle (EV) permanent magnet (PM) traction motor applications. In this class of problems, eddy current losses in PMs and iron laminations constitute an important part of overall drive losses, representi...

The paper develops analyses electromagnetic compatibility issues in electric vehicles. Particular techniques are developed involving special elements of tubular geometry based on the analytical solution of diffusion equation combined with standard finite elements, for analysis of electromagnetic shielding effectiveness in power cables due to power...

This paper proposes a multi-criteria design optimization methodology for Permanent Magnet (PM) motors used in electric vehicle applications. In the process, an Adaptive Network-Based Fuzzy Inference System (ANFIS) is utilized, coupled with a multi-objective optimization algorithm, as a surrogate model of the electric motor. This allows for the cons...

Two original numerical techniques are presented for the finite–element (FE) unsteady analysis of permanent magnet synchronous motors (PMSM) and induction motors (IM) operating in demanding aerospace applications. The first technique is the electromagnetic and thermal analysis weak coupling using a multi–slice FE model. The advantage of this techniq...

In this paper a unified approach for several synchronous machine current waveform optimization problems is presented. It is shown that the problems of ohmic losses minimization with and without the constraint of constant torque waveform admit solutions which can be described by the same equation in different vector spaces. The constraint of open-ci...

This paper proposes a multi-objective optimization methodology for speed and torque trajectories of a light electric vehicle (LEV) traveling on a predefined route. The procedure introduced accounts for speed constraints and various elevation profiles and involves determination of the overload operation tolerances. The proposed technique facilitates...

This paper proposes a hybrid, multi-objective optimization algorithm enabling global optimum tracking in permanent magnet traction motor design. The methodology developed is based on Artificial Bee Colony (ABC) technique, Strength Pareto Evolutionary Algorithm (SPEA2) and Differential Evolution (DE) strategy ensuring fast and reliable convergence t...

This paper proposes a robust optimization algorithm, enabling global optimum tracking and manufacturing uncertainty factors handling, for high speed permanent magnet motor design. A new robustness criterion is introduced considering effectively the impact of the construction tooling uncertainties on the design variables in all objectives. An Adapti...

This paper introduces an evolutionary optimization procedure for the design of Permanent Magnet Motors (PMM) for Electric Vehicle (EV) applications, considering a specific drive cycle with multiple operating points. For the purposes of the analysis, the New European Drive Cycle (NEDC) has been employed with two alternative PMM configurations. Energ...

The paper develops a special element of tubular geometry based on the analytical solution of diffusion equation combined with standard finite elements, for analysis of electromagnetic shielding effectiveness in power cables due to power static converter operation. Particular simulations analyze the exposure levels due to variable frequency magnetic...

In this paper the optimization procedure of a Salient Pole Synchronous Motor (SPSM) for Low Rotational Speed (LRS) Marine Electric Propulsion Systems (MEPS) is presented involving preliminary and critical design stages. The objective function introduced for motor critical design includes the construction, operating and maintenance costs of the moto...

The paper proposes a hybrid analytical — Finite Element Method (FEM) methodology for loss evaluation in Electric Vehicle (EV) traction motor applications. In this class of problems eddy current losses in Permanent Magnets (PMs) and iron laminations constitute an important part of overall drive efficiency, representing a key design target. Both Surf...

This paper proposes an innovative hybrid multi-objective (MO), fast converging optimization algorithm, enabling global optimum tracking in permanent magnet traction motor design. The methodology developed is based on Artificial Bee Colony (ABC) technique, strength pareto evolutionary algorithm (SPEA2) and Differential Evolution (DE) strategy ensuri...

This paper investigates the design and application of an improved SHaft Generator (SHG) system for an actual Ro- Ro ship, comprising a Permanent Magnet Synchronous Generator (PMSG) and a back-to-back converter. The system can operate both in generator and motoring mode, providing active power and ancillary services to the ship’s grid, and driving t...

This paper investigates the electromagnetic and thermal behavior of a Double Layer Interior Permanent Magnet Motor (DLIPMM) over a wide load and speed range for an Electric Vehicle (EV) application. The DLIPMM is simulated via a transient 2D Finite Element (FE) model, allowing for the accurate mapping of the motor’s main performance indexes. Simula...

In this paper, a comparative optimal design of Permanent Magnet Motors (PMMs) for aerospace actuation applications based on single and double layer Fractional Slot Concentrated Winding (FSCW) topologies with different motor segmentation strategies is undertaken, by means of a combined electromagnetic, fault tolerance and thermal evaluation. Initial...

A pod is a propeller propulsion device installed externally to the ship's hull. The pod system comprises a short propulsion shaft, on which the propulsion electric motor is mounted. In most cases, propulsion is achieved by means of fixed pitch propellers powered by an AC synchronous motor (conventional, permanent magnet) or asynchronous electric mo...

This paper proposes a multi-objective optimization methodology for speed and torque trajectories of a light electric vehicle (LEV) traveling on a specific open route. The procedure introduced accounts for speed constraints and various elevation profiles and involves determination of the overload operation tolerances. The LEV under consideration com...

This paper proposes finite element (FE) numerical methodologies for the transient heat transfer analysis of highly integrated actuators for demanding aerospace applications. A FE surface heat source is developed which permits to independently simulate the thermal performance of the housing of the actuator. As a result, the complexity of the FE mode...

This paper develops an appropriate predictive current controller (PCC) for fast torque monitoring and high-performance operation of a permanent-magnet synchronous motor (PMSM) drive involving constant switching frequency. The proposed controller is based on a convenient combination of deadbeat and direct predictive control (DPC) techniques. Its res...

This paper introduces a particular Permanent Magnet Motor (PMM) design methodology, considering advanced magnetic materials characteristics, for aerospace actuator applications. In this class of problems, increased electromagnetic power density, fault tolerance and high temperature withstand properties are of major importance and favored single and...

The paper introduces a magnetic flux control algorithm for the minimization of losses in Induction Motor (IM) drives. The proposed methodology accounts for search time delays and IM model deficiencies and has been applied to minimize power losses. The controller is validated on an IM prototype and offers improved transient response.

Three dimensional (3–D), finite–element (FE) models and original lumped–parameter networks are developed for the transient thermal analysis of a permanent magnet motor (PMM) and an induction motor (IM) specifically designed and optimized for a demanding aerospace actuation application. A systematic comparison between the two different thermal model...

In this work, a split transformer topology is proposed for use in a wireless electric vehicle charger. The topology presents desirable characteristics concerning minimization of the air gap, easiness of alignment, weight and cost. Comparison is performed with spiral topologies presented in relevant literature. The coupling coefficient of the system...

In this paper the strategy of the extraction of an advanced simulation model of interior permanent magnet synchronous machine is suggested in order to be employed by Model Predictive Control schemes. The conventional dq-axis mathematical model is modified in order to include data derived from finite element analysis (FEA). Indirect interaction betw...

In this paper the important impact of high temperature withstand on performance of electromagnetic actuators for aerospace applications is illustrated. Particular materials enabling high performance and increased reliability in such applications are analysed both through numerical simulations and experimental validation. Specific examples outline a...

Design optimization of traction motors for light electric vehicles over an operating point is an adequate way of achieving higher overall efficiency under a standard driving scheme of the vehicle. However, this work proves that a direct comparison of similar candidates regarding efficiency values under a predetermined operating point does not yield...

This paper presents the design of geometrically similar switched reluctance machines based on similarity theory and scale factors techniques. The fundamental theory for the development of the proposed methodology is described. The proposed methodology is used for the design of a particular 21.6 W three phase 6/4 pole switched reluctance motor, whic...

In this paper, a detailed analysis over a reference electric vehicle’s drive cycle of an interior Permanent Magnet Synchronous Motor (IPMSM) is implemented, in terms of motor performance, efficiency and field weakening capability. Initially, the electromagnetic field characteristics of a geometrically optimized IPMSM are investigated for various mo...

In the present work, the issue of integrating numerous EVs into the Greek interconnected electricity system is studied, through the implementation of a novel smart EV charging strategy, regarding a daily scheduling process with the view of maximizing the penetration of energy produced by wind farms, considering the stochastic behaviour of Wind and...

This paper deals with the implementation of a fast, fully integrated Maximum Power Point Tracking (MPPT) algorithm, in order to efficiently control a Photovoltaic (PV) system incorporated into a battery-Electric Vehicle (EV) roof. Major challenges for such PV systems are the rapidly changing irradiance conditions and partial shading of the PV cells...

In this paper, a simple algorithmic enhancement for MPPT methods is introduced, which mathematically determines if the PV system is shaded, thus avoiding unnecessary curve scanning to locate the global maximum if it is unshaded. The proposed technique improves the overall efficiency and applies to any PV system at any irradiance distribution, using...

In this work, a split transformer topology is proposed for use in a wireless electric vehicle charger. The topology presents desirable characteristics concerning minimization of the air gap, easiness of alignment, weight and cost. The coupling coefficient of the system for various air gaps and misalignment conditions is extracted by 3D simulations...

The paper introduces a magnetic flux control algorithm for the minimization of losses in Induction Motor (IM) drives. The proposed methodology accounts for search time delays and IM model deficiencies and has been applied to minimize power losses. The controller is validated on an IM prototype and offers improved transient response..

Two original numerical techniques are developed for the finite element (FE) transient analysis of induction and permanent magnet motors operating in demanding aerospace applications. The first technique is the electromagnetic and thermal analysis weak coupling using a multiple slices 2D FE model. The advantage of the specific technique is the repre...

This paper deals with analyzing and resolving Power Quality (PQ) issues in electric energy systems of ships with extensive electrification. Within this framework, optimized configurations of critical subsystems are studied in depth: shaft generators, thrusters, pods and protection against lightning. The anticipated results obtained from a large sca...

This paper introduces a particular direct driven Shaft Generator (SG) system for implementation in an existing Ro-Ro (Roll on board-Roll off board) trailer-passenger ship. In a first step, both a high speed (1200rpm) Salient-Pole Synchronous Generator (SPSG) and a low speed (400rpm) direct driven Permanent Magnet Synchronous Generator (PMSG) of the...

Design optimization, favoring efficiency maximization, is the subject of extended current research in small electric traction motor applications, aiming the increase in efficiency to be achieved without compromising power density. This paper proposes a mixed technique based on a particular multi-objective, population-based optimization methodology,...

This paper investigates the harmonic losses and torque ripple of a surface permanent magnet (SPM) motor driven by pulsewidth-modulated inverter for a wide range of switching frequencies (SFs), using a 2-D nonlinear time stepping finite-element model, including strand conductors proximity effect, coupled with an appropriate external electric circuit...

This paper presents an overview of high performance electrical machines for aerospace applications. The drive towards aircraft electrification is highly dependent on the performance and reliability of electrical machine drive systems. A review of the advancements of electrical machine constituent materials which are being applied in the aerospace s...