9 research outputs found
Efeito do peso do ovo e do seu tempo de armazenamento sobre a viabilidade dos pintos do dia
Este trabalho foi desenvolvido com o intuito de estudar o efeito do peso do ovo e do seu tempo de armazenamento sobre a viabilidade dos pintos do dia, resultantes de um bando de galinhas Shaver Redbro cruzadas com galos Starcross x Shaver carecos. Neste sentido, na cidade de Bragança (latitude 410 49'N, longitude 60 40'W e altitude 720 metros), mais precisamente na Quinta de Santa Apolónia, pertencente à Escola Superior Agrária de Bragança, foram efectuadas quatro séries de incubação utilizando no seu conjunto, 333 ovos sujeitos a um período de armazenamento que variou entre 2 e 34 dias (15,6+9,1 dias)
Magnetization dependent demagnetization characteristic of rare-earth permanent magnets
Accurate demagnetization modelling is mandatory for a reliable design of rare-
earth permanent magnet applications, such as e.g. synchronous machines. The magnetization of rare-earth permanent magnets requires high magnetizing fields. For technical reasons, it is not always possible to completely and homogeneously achieve the required field strength during a pulse magnetization, due to stray fields or eddy currents.
Not sufficiently magnetized magnets lose remanence as well as coercivity and the demagnetization characteristic becomes strongly nonlinear. It is state of the art to treat
demagnetization curves as linear. This paper presents an approach to model the nonlinear demagnetization in dependence on the magnetization field strength. Measurements of
magnetization dependent demagnetization characteristics of rare-earth permanent magnets
are compared to an analytical model description. The physical meaning of the model
parameters and the influence on them by incomplete magnetization are discussed for
different rare-earth permanent magnet materials. Basically, the analytic function is able
to map the occurring magnetization dependent demagnetization behavior. However, if
the magnetization is incomplete, the model parameters have a strong nonlinear behavior and can only be partially attributed to physical effects. As a benefit the model can
represent nonlinear demagnetization using a few parameters only. The original analytical model is from literature but has been adapted for the incomplete magnetization.
The discussed effect is not sufficiently accurate modelled in literature. The sparse data
in literature has been supplemented with additional pulsed-field magnetometer measurements
Measurement and simulation of a rotational single sheet tester
The accurate prediction of iron losses has become a prominent problem in
electromagnetic machine design. The basis of all iron loss models is found in the spatial
field-locus of the magnetic flux density (B) and magnetic field (H). In this paper the behavior
of the measured BH-field-loci is considered in FEM simulation. For this purpose, a vector
hysteresis model is parameterized based on the global measurements, which then can be used
to reproduce the measurement system and obtain more detailed insights on the device and its
local field distribution. The IEM has designed a rotary loss tester for electrical steel, which
can apply arbitrary BH-field-loci occurring during electrical machine operation. Despite
its simplicity, the proposed pragmatic analytical model for vector hysteresis provides very
promising results
Advanced Soft- and Hard-Magnetic Material Models for the Numerical Simulation of Electrical Machines
Magnetic anisotropy under arbitrary excitation in finite element models
Magnetic properties of silicon iron electrical steel are determined by using
standardized measurement setups and distinct excitation parameters. Characteristic values
for magnetic loss and magnetization are used to select the most appropriate material for
its application. This approach is not sufficient, because of the complex material behavior
inside electrical machines, which can result in possible discrepancies between estimated
and actual machine behavior. The materials’ anisotropy can be one of the problems why
simulation and measurement are not in good accordance.With the help of a rotational single
sheet tester, the magnetic material can be tested under application relevant field distribution.
Thereby, additional effects of hysteresis and anisotropy can be characterized for detailed
modelling and simulation