M. V. Ferreira da Luz

Small Linear PM Oscillatory Motor: Magnetic Circuit Modeling Corrected by Axisymmetric 2-D FEM and Experimental Characterization

Linear permanent-magnet (PM) actuators with short strokes represent an excellent alternative to pneumatic or hydraulic actuators in different fields of application, whenever fast response, flexibility, high reliability, and safety are required. The purpose of this paper is to present a new hybrid model and a testing sequence to rather completely characterize a small PM oscillatory motor for compressor-like applications. The hybrid model is composed of an iterative nonlinear magnetic circuit method which is corrected by an axisymmetric (2-D) finite-element method (FEM) model. The benefit that this hybrid model has is its low computation time when compared with similar analysis using 3-D FEM. This characteristic is very significant for industrial usage.

Analysis of a permanent magnet generator with dual formulations using periodicity conditions and moving band

In this paper, a three-dimensional permanent magnet generator is modeled using both a- and h-formulations. The rotor movement is modeled by means of the moving band technique in which a dynamic allocation of periodic or antiperiodic boundary conditions is performed. The results obtained with dual formulations are compared with experimental ones and allow evaluation of the effects of the element distortion in the moving band on global quantities such as the electromotive forces.

Magnet flux optimization method for Line-Start Permanent Magnet motors

The use of induction motors is the right choice for a great number of household appliances which look for cost-competitive solutions. Therefore, in the past few years, the energy consumption became also an important issue which drives the design of electrical motors, although, permanent magnet motors came to stay. Most of the solutions which are significantly efficient to worth using have also a high cost due to electronics, and among the few options that can be used on this kind of application is the Line-Start Permanent Magnet (LSPM) motor. This paper shows a simple design procedure to increase the net flux generated by the magnets maximizing the magnet short-circuit reluctance and reducing the flux loss in the rotor slot bridges. This method can be used to reduce the magnet volume, also reducing the total cost of the motor, which can contribute to make the LSPM motor a real option to substitute the induction motors in the future. The LSPM motor is analyzed using a 2D finite element method and the rotor movement is modeled by means of the moving band. This approach allows to investigate the influence of design variations on the dynamic behaviour of the LSPM motor.

Connection boundary conditions with different types of finite elements applied to periodicity conditions and to the moving band

Connection boundary conditions are studied with the finite element method using different types of mixed finite elements, i.e. nodal, edge and facet elements of different shapes and degrees, used in both b‐ and h‐conform formulations. The developed associated tools are first applied to periodicity boundary conditions before being applied to the treatment of the moving band in 2D and 3D. This step by step approach enables their validation before pointing out the effect of the considered elements on the accuracy of the moving band method. A special attention is given to the consistency of these boundary conditions with gauge conditions and source magnetic fields.

Generalization of coupled circuit-field calculation for polyphase structures

A method allowing generalization of coupled circuit-field calculation for polyphase electromagnetic devices is presented. Finite element method is used to model electromagnetic devices in 2D and the static converter circuit is studied in the state space. State-variable and field equations are then coupled together and solved simultaneously, step by step in time. An application with a three-phase half-wave rectifier fed by a three-phase transformer is presented. An iron losses calculation based on the separation model, in which the iron loss is composed by hysteresis, eddy current and excess loss components is also presented.

Analytical and 3D FEM modeling of a tubular linear motor taking into account radial forces due to eccentricity

Electrical linear motors are electromechanical devices that produce short unidirectional or bidirectional strokes. The purpose of this work is to model a tubular linear motor (TLM) using 2D and 3D finite element (FE) method and analytical equations. The 2D and 3D FE magnetodynamic analyses are performed using a magnetic vector potential formulation. The linear displacement is modeled by means of a layer of finite elements placed in the air gap. The analytical model is obtained from a magnetic circuit formed by reluctances and magnetomotive forces. The topologies of these circuits change for each position of the mover. In this paper, the modeling of TLM is carried out focusing the optimization of analytical model and the calculation of radial forces in the presence of eccentricity. In addition, a comparison between simulated and measured performance on a motor prototype is reported.

Stray load losses calculation routine based on the eh-star method

The eh-star method is a procedure proposed in the IEC 60034-2-1 standard to determine the stray load losses in three-phase induction motors. In this test, the motor is fed by an unbalanced supply, which is obtained using an electrical resistance (Reh) in parallel with two phases of the star-connected motor and a single-phase source. The purpose of this paper is to present a new calculation routine that determines the stray load losses from eh-star test data. This routine is obtained from an electrical circuit, in which the unbalanced supply results from two phases and the neutral of the generator, eliminating Reh. The results show that the proposed method presents good agreement with the conventional eh-star method.

Performance evaluation of brushless DC permanent magnet motor using Finite Element Method

This paper presents the performance evaluation of two different size 6 slots and 4 poles brushless DC permanent magnet motor. These devices were simulated and tested in order to obtain efficiency, iron losses, copper losses, and shaft power. The simulation was done using a program called Finite Element Method Magnetics (FEMM) and a script based on the programming language Lua. The electrical steel sheet was characterized through an Epstein experiment, and the results were applied to improve the simulation. Furthermore a dynamometer was used to check the method applied. It was observed that the calculation method allows predicting the motor performance with reasonable precision.

Development of analytical equations to calculate the cogging torque in transverse flux machines

Cogging torque is produced in a permanent magnet machine by magnetic attraction between the rotor permanent magnets and the stator teeth. It is an undesirable effect that contributes to torque ripple, vibration and noise of the machine. In this paper, the resultant cogging torque values are computed using a three-dimensional (3D) finite element analysis. For this, the rotor movement is modeled by means of the moving band technique in which a dynamic allocation of periodic or anti-periodic boundary conditions is performed. The 3D finite element method is the most accurate tool to carry out cogging torque. However, it does not easily allow a parametric study. For this reason, an analytical model was developed in order to predict the cogging torque. The tools are intended to be used for the study of transverse flux machines.

Iron losses modeling under rotational magnetic flux

Rotational magnetic flux is found in electromagnetic devices such as three-phase transformers and rotational electric machines. For the same flux magnitude, under rotational flux the iron losses are, usually, greater than the alternating ones. In this work the iron losses behavior is investigated under rotational flux. Experimental curves are obtained from a rotational single sheet tester and the losses components analyzed.