Abstract
In electrical machines, iron losses are essential for electromagnetic and thermal designs and analyses. Although many models have been proposed to predict iron losses in magnetic materials, the calculation of iron losses under non-sinusoidal excitations is still an open field. Most works concern the influences of the value, the change rate or the frequency of flux density in the frequency domain. In this paper, we propose an engineering model for predicting loss characteristics with given waveforms of flux density in the time domain. The characteristics are collected from the knowledge of the iron loss in a laminated ring-shaped transformer. In the proposed model, we derive mathematical formulas for exciting currents in terms of flux density by describing the function methods through multi-frequency tests with sinusoidal excitations. The non-linearity of the material is interpreted by branches of conductances accounting for hysteresis and eddy-current losses. Then, iron losses are calculated based on the law of conservation of energy. An experimental system was built to evaluate the magnetic properties and iron losses under sinusoidal and non-sinusoidal excitations. Actual measurement results verify the effectiveness of the proposed model.
Highlights
Various types of excitation conditions were applied to electrical machines with power electronics technology
The use of pulse width modulation (PWM) and non-linear loads results in a difficulty in iron loss prediction in magnetic materials
Following the modern research on iron losses in magnetic materials, iron losses can be decomposed into three main components, referred to as hysteresis, eddy-current and excess losses
Summary
Various types of excitation conditions were applied to electrical machines with power electronics technology. Many models, which are based on physical or numerical methods [1,2,3,4,5,6,7,8,9], have been proposed by different researchers, predicting iron losses in magnetic materials, when a non-sinusoidal voltage excitation is applied, has not yet been entirely solved and is still an open research field. The most frequently-used materials for electrical machines are non-oriented silicon steel, in which losses with the same magnitude, but different directions can be assumed to be the same according to its isotropy In this way, iron losses can be predicted by analyzing the relationship between flux density and iron losses in the time domain. Based on the above contents, we established an engineering model for predicting iron losses under non-sinusoidal excitations by using multi-frequency sinusoidal data together with given waveforms of flux density.
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