Evaluation of experimental methods for determining the magnetically nonlinear characteristics of electromagnetic devices

Štumberger, Gorazd; Polajžer, Boštjan; Štumberger, B.; Toman, M.; Dolinar, Drago

doi:10.1109/tmag.2005.854992

Cited by 44 publications

(25 citation statements)

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“…A "time-stepping" solution proceeds by integrating (1) step-by-step, and from the new flux-linkages at the end of each time-step the currents must be obtained by inverting (2), ready for the next time-step. Sometimes (2) is expressed in the form (3) so that the necessary inversion is a simple matrix operation.…”

Section: A the Problem To Be Solvedmentioning

confidence: 99%

“…The finite-element method is fundamentally a method of evaluating (2). Known phase currents are expressed as current-density in slot regions, and the unknown flux-linkages are computed from line integrals of vector potential along the winding conductors.…”

Section: A the Problem To Be Solvedmentioning

confidence: 99%

“…The magnetization curves then have the general form (8) The magnetization curves in this form can be obtained by transformation from finite-element evaluations of (2). In general is a function not only of but also of (cross coupling) and even of , and likewise is a function of and as well as .…”

Section: Mathematical Form Of the Magnetization Curvesmentioning

confidence: 99%

“…In general is a function not only of but also of (cross coupling) and even of , and likewise is a function of and as well as . The functional relationships (8) require a vast number of finite-element calculations to define them [2], as well as an appropriate interpolating function. They are much more complex than (7), which have the form (9) in which there is no cross coupling and no variation with rotor position, and which are easily inverted even when they are nonlinear.…”

Section: Mathematical Form Of the Magnetization Curvesmentioning

confidence: 99%

“…But it requires good calculations to achieve this. With no variation, the magnetization curves have the form (10) This is the form presented in [2], but only in the form of graphical data with no attempt to provide the interpolating function that is necessary in connection with the time-stepped solution of the voltage equations.…”

Section: Mathematical Form Of the Magnetization Curvesmentioning

confidence: 99%

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Performance estimation of interior permanent-magnet brushless motors using the voltage-driven flux-MMF diagram

et al. 2006

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The flux-magnetomotive force (flux-MMF) diagram, or "energy conversion loop," is a powerful tool for computing the parameters of saturated interior permanent-magnet brushless motors, especially when the assumptions underlying classical dq theory are not valid, as is often the case in modern practice. Efficient finite-element computation of the flux-MMF diagram is possible when the motor current is known a priori, but in high-speed operation the current regulator can lose control of the current waveform and the computation becomes "voltage-driven" rather than "current-driven." This paper describes an efficient method for estimating the motor performance-average torque, inductances-by solving the voltage-driven problem. It presents experimental validation for a two-pole brushless interior permanent-magnet motor. The paper also discusses the general conditions under which this method is appropriate, and compares the method with alternative approaches. . It is well known that when the magnets are embedded inside the rotor iron, as in the "interior permanent-magnet motor" (IPM), calculations based on classical theory can be unreliable, mainly because of the variation of parameters due to saturation. IndexFor example in such machines can vary by at least 700% between no-load and full-load, while cross saturation influences the -axis parameters in a complex manner [1]- [7], [9]. The difficulties are increased by the use of fractional-slot windings with small numbers of slots/pole (even less than 1), non-circular laminations, and other departures from the ideal machine, so that neither the EMF waveform nor the variation of inductance with rotor position is sinusoidal. , and although they allow for cross-saturation effects they restrict themselves to steady-state operation and ignore the effect of rotor position on the -axis parameters.As long as the current waveform is known a priori, these problems can be overcome in an efficient computation in which the finite-element method is used to determine one cycle of the flux-linkage waveform, which is then plotted against the current waveform to establish a "loop" whose area gives the average electromagnetic torque. This loop diagram is known as the "flux-MMF diagram" or "i-psi loop" or "energy conversion loop" [9]. Bearing in mind that finite-element formulations are fundamentally always "current-driven," the computation is efficient because of the foreknowledge of the current waveform, so that a series of current values can be used as inputs to the finite-element process. This method does not necessarily rely on theory. At higher speeds it is normal for the current-regulator to lose control of the current waveform, and ultimately at the highest speeds the drive may operate in six-step mode. In this case, the applied voltage waveform is known but the current waveform is not. Similarly, if the machine is generating into a rectifier, the applied voltage at the machine terminals is known or calculable, whereas the current waveform is unknown.The accuracy of the finite-element m...

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Section: A the Problem To Be Solvedmentioning

confidence: 99%

Section: A the Problem To Be Solvedmentioning

confidence: 99%

Section: Mathematical Form Of the Magnetization Curvesmentioning

confidence: 99%

Section: Mathematical Form Of the Magnetization Curvesmentioning

confidence: 99%

Section: Mathematical Form Of the Magnetization Curvesmentioning

confidence: 99%

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