Induction Motor Core Research Articles

A New Hysteresis Loss Estimation in the Induction Motor Core Considering Rotating Magnetic Fields

A rotating machine such as inductor motor has highly distorted elliptical magnetic flux densities in its stator core. The iron loss estimation taking into account the rotating magnetic field is significant not only for the design but also for the performance analysis of electrical machines. A rotational hysteresis loss formula is also proposed to improve the computation accuracy especially when the magnetic flux density is high or the axis ration of a rotational magnetic flux density is big. For an induction motor core model, iron losses are experimentally measured on the top sheet of the core by using a self-developed B–H vector sensor. The proposed iron loss model is validated through comparisons of the calculated iron losses with experimentally measured ones.

A Complex-Valued Rotating Magnetic Property Model and Its Application to Iron Core Loss Calculation

This paper presents a complex-valued model when considering rotational magnetic properties of an electrical steel sheet from the viewpoint of improving the computation efficiency. The effective magnetic reluctivity and magnetic hysteresis coefficients in this model were interpolated from measured data based on a 2-D rotational magnetic property measurement system, in which the effect of higher harmonic terms of magnetic field intensity after saturation was considered. To reduce the computation error to some extent resulted from complex approximation of magnetic field quantities, the effective magnetic coefficients were expressed as the function of magnitude and direction of magnetic flux density. Considering transformer and three-phase induction motor core models as examples, the magnetic field distribution and core loss were calculated and the effectiveness of the proposed model was verified with the experimental results.

Effect of Magnetostriction Anisotropy in Nonoriented Electrical Steels on Deformation of Induction Motor Stator Cores

Magnetostriction in nonoriented (NO) electrical steels is a harmful source of vibration and acoustic noise in electrical machines. It is far more anisotropic than specific power loss, which results in more complexity in prediction of the vibration and acoustic noise. An investigation of the anisotropy in magnetostriction and mechanical elastic properties of a NO steel is presented in this paper. Measurements of deformation in the stator teeth of an induction motor model core were conducted in order to study the effect of the magnetostriction anisotropy. Strain due to Maxwell forces in the air gap was calculated and compared with the measured deformation. Measurement results indicate that anisotropic magnetostriction has a great impact on unsymmetrical deformation of the stator teeth of induction motor cores.

Distribution on localized two‐dimensional magnetic properties of three‐phase induction motor core

Improving material characteristics and optimizing technical designs have been studied from the standpoint of efficiency improvement of electrical machinery and apparatus. Unfortunately, the local magnetic properties in actual cores are still not understood fully. On the other hand, there is understanding of the two-dimensional magnetic property, that is, the relationship between the magnetic field strength vector H and the magnetic flux density vector B, which are not usually parallel but have a phase angle. Therefore, local magnetic properties in an actual constructed core should be measured as a vector relation. This paper presents the local magnetic properties in a three-phase induction motor model core, which are measured with a two-dimensional measurement sensor. © 2000 Scripta Technica, Electr Eng Jpn, 133(4): 34–40, 2000

Localized distribution of two-dimensional magnetic properties in three-phase induction motor core model

Improving material characteristics and optimizing technical designs have been studied from the standpoint of efficiency improvement of electrical machinery and apparatus. Unfortunately, the local magnetic properties in the actual core are still not fully understood. On the other hand, the concept of the two-dimensional (vector) description of the magnetic properties was developed. It means that the description of the relationship between the magnetic field strength vector H and the magnetic flux density vector B which are usually not parallel but have the phase angle, by means of a permeability tensor. In general, the magnetic quantities show not only the non-linearity of amplitude but also a spatially different angular position (we call it spatial-phase angle). Therefore, the local magnetic quantities in an actual constructed core should be measured as vector quantities. This paper presents the local magnetic quantities in a three-phase induction motor model core, which were measured with the two-dimensional measurement sensor.

Methods for predicting rotational iron losses in three phase induction motor stators

Iron losses in electrical machines are difficult to predict. Discrepancies between tested and calculated no-load core losses are sometimes large. In induction motors, a large portion of the stator core is subjected to flux that rotates in the plane of the laminations. Losses due to rotating flux differ from those observed under alternating flux conditions. This paper describes direct approaches for coupling rotational iron loss measurements with finite element analysis (FEA) results that yield the distribution of rotational flux in induction motor cores. Using these methods, the prediction of no-load core loss can be made to include the effects of rotational iron losses.

Distribution on localized two-dimensional magnetic properties of three-phase induction motor core

Improving material characteristics and optimizing technical designs have been studied from the standpoint of efficiency improvement of electrical machinery and apparatus. Unfortunately, the local magnetic properties in actual cores are still not understood fully. On the other hand, there is understanding of the two-dimensional magnetic property, that is, the relationship between the magnetic field strength vector H and the magnetic flux density vector B, which are not usually parallel but have a phase angle. Therefore, local magnetic properties in an actual constructed core should be measured as a vector relation. This paper presents the local magnetic properties in a three-phase induction motor model core, which are measured with a two-dimensional measurement sensor. © 2000 Scripta Technica, Electr Eng Jpn, 133(4): 34–40, 2000

The influence of compressive stress on the magnetic flux density in the three-phase induction motor core model

The magnetic properties are very sensitive to stress acting on practical constructed cores. However the influence has been not yet fully investigated for real cores, because the estimation of the distribution of stress is very difficult. In this paper, the local properties in the three-phase induction motor model core under compressive stress have been measured to investigate its influence in detail. The result shows that the compressive stress will cause slight enlargement of the rotational iron losses.

Iron loss under PWM voltage supply on Epstein frame and in induction motor core

A systematic PWM iron loss study has been carried out. All the loss components can be given as functions of the sum of pulses width in half a period. PWM loss surplus when compared with the sinusoidal supply is more pronounced in the laminations with more important part of dynamic loss in the whole loss outcome. Along the constant flux trajectories in variable speed regimes of the induction machines the iron losses are also constant. The underlying analysis has been developed for an alternative magnetic field and tested on an Epstein frame. However, the iron loss invariability (per cycle) on the constant flux trajectories has been confirmed in motor measurements, where the actual field is far more complicated.

No-load induction motor core losses using a combined finite-element/state-space model

A combined finite-element/state-space (CFE-SS) modeling is used to compute the no-load core losses in three-phase induction motors. The CFE-SS is totally within the embrace of the ABC frame of reference. Consequently, the current, flux linkages, winding magnetomotive forces, and flux density waveforms include as many space harmonic terms, caused by motor magnetic circuit geometries and winding layouts, as necessary. The resulting harmonically rich flux density waveforms are used to calculate the no-load core losses (hysteresis and eddy current losses) of a case-study three-phase, 1.2-hp, squirrel-cage induction motor. In addition, those results are compared with conventionally computed core losses obtained using only the fundamental components of the flux density waveforms. A substantial increase in the core losses due to the significant harmonic contents of the flux density waveforms is reported.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

No-Load Induction Motor Core Losses

A detailed method of calculating the no-load core losses of induction motors is presented whereby each loss component is estimated separately. There is included a discussion of extra losses due to imperfection in workmanship. Calculated and test results on a few commercial machines are given as an indication of the reliability of this method.

Induction motor core losses

An analysis of the core losses in induction motors is the object of the research described in this paper. The authors subdivide the core losses into six elements and point out that only one of the six is ordinarily calculated by designing engineers, with resulting large discrepancies between expectation and fact. The belief is expressed that to calculate other elements approximately is entirely feasible and that such calculations would explain most of the variations in core loss now attributed to imperfections in manufacture. Rational formulas are developed for the losses in the core back of the teeth, which are found to give larger values than the more approximate formulas now in use, and the conclusions are presented in the form of charts giving the correction factors to apply to the usual formulas for all ordinary conditions. A Webb floating dynamometer, which was constructed for the measurement of the extremely small torques due to these core losses, is described: and results on the losses in a smooth-core rotor obtained with it are presented. These results and those obtained by an independent electrical method of testing are compared with the expected values based on the theoretical conclusions previously derived, reasonable agreement being found.