The Minor Hysteresis Loop Under Rotating Magnetic Fields in Machine Laminations

Abstract

In rotating ac machines, the saturated flux density waveforms contain harmonics, which create minor hysteresis loops. The minor hysteresis loops in machine laminations constitute an additional loss which requires modifications in traditional core loss formulas. This causes a serious challenge in core loss estimation. The task becomes more competitive under rotating magnetic fields, where the minor loop behavior has not been investigated yet. This paper highlights the problem of harmonics in rotating fields and its effect on the core loss estimation. In addition, the behavior of minor loops under rotating fields is compared with the minor loops under pulsating fields. Measurements were carried out on a nonoriented silicon steel sample of M36G29 with different fundamental frequencies of interest to the industry, 60 Hz and 400 Hz, with consideration of the third harmonic at each frequency. A design of magnetizing test fixture based on an electromagnetic Halbach array is used to perform these measurements. Results are presented and discussed.Index Terms-Electrical steel, Halbach array, Madelung's rules, magnetic minor hysteresis loop, rotational core loss. Natheer Alatawneh (M'13) was born in Amman, Jordan. He received the M.S.

Iron Loss Analysis of a Concentrated Winding Type Interior Permanent Magnet Synchronous Motor with Single and Dual Layer Magnet Shape

“…The first method, i.e., the FFT frequency separation method, is simple; however, the minor loop effect caused by harmonics is not considered. Hence, by considering the dynamic hysteresis model, the minor loop effect and excess losses can be considered [5][6][7]. Therefore, the second iron loss calculation method is used to calculate the additional P hys separately, as shown in Equation ( 6) [8]:…”

“…In the conventional loss separation concept [1][2][3], the total power loss can be expressed as the sum of three independent terms, considering the harmonic and rotational fluxes. However, in many cases, the magnetic flux waveform in the laminated core of an electrical machine is not sinusoidal, and the hysteresis loop contains many minor loops [4][5][6][7]. Therefore, iron loss separation concepts [1][2][3] are insufficient for electric machines with high flux saturation.…”

Analytical Evaluation of Core Losses, Thermal Modelling and Insulation Lifespan Prediction for Induction Motor in Presence of Harmonic and Voltage Unbalance

“…A fast core loss on induction motor has been estimated based on the piecewise variable parameter model by Zhao et al [20] which considers the voltage harmonic components of the inverter. The rotational losses have been reported by Alatawneh N., and Pillay, [21] in which the effect of minor loops on the core losses have been taken into account. Moreover, an improved generalized Steinmetz equation has been proposed by Venkatachalam et al [22].…”

Accuracy of time domain extension formulae of core losses in non‐oriented electrical steel laminations under non‐sinusoidal excitation

“…Vectorial flux pattern may or may not be associated with minor loops, i.e. if one or both of the radial and tangential components have minor loops then the associated major hysteresis loops contain minor loops [17].…”