A high-fidelity two-axis model of an interior permanent-magnet synchronous machine (IPM) presents a convenient way for the characterization and validation of motor dynamic performance during the design stage. In order to consider a nonlinear IPM nature, the model is parameterized with a standard dataset calculated beforehand by finite-element analysis. From two possible model implementations, the current model (CM) seems to be preferable to the flux-linkage model (FLM). A particular reason for this state of affairs is the rather complex and time-demanding parameterization of FLM in comparison with CM. For this reason, a procedure for the fast and reliable parameterization of FLM is presented. The proposed procedure is significantly faster than comparable methods, hence providing considerable improvement in terms of computational time. Additionally, the execution time of FLM was demonstrated to be up to 20% shorter in comparison to CM. Therefore, the FLM should be used in computationally intensive simulation scenarios that have a significant number of iterations, or excessive real-time time span.

This paper presents a method for the detection of broken rotor bars in an induction motor. After introducing a simplified dynamic model of an induction motor with broken cage bars in a rotor field reference frame which allows for observation of its internal states, a fault detection algorithm is proposed. Two different motor estimation models are used, and the difference between their rotor flux angles is extracted. A particular frequency component in this signal appears only in the case of broken rotor bars. Consequently, the proposed algorithm is robust enough to load oscillations and/or machine temperature change, and also indicates the fault severity. The method has been verified at different operating points by simulations as well as experimentally. The fault detection is reliable even in cases where traditional methods give ambiguous verdicts.

This study presents the dependence of the level and harmonic structure of the cogging torque in permanent magnet synchronous motors (PMSM) to imperfections of permanent magnet (PM) dimensions and positions, which can not be avoided in massproduction. Slightly diverse dimensions and misplacements of PMs are introducing asymmetries in magnetic field distribution which cause additional harmonic components. A finite element method (FEM) and Fast Fourier transform (FFT) were used to calculate cogging torque harmonic components with regard to several combinations of PM assembly imperfections. It has been established and proved that unequal PMs cause magnetic asymmetries which give rise to additional cogging torque harmonic components and consequently increase the total cogging torque. It is also shown that in some particular combinations the influence of an individual PM imprecision could compensate with others due to different phase shifts which can result even in the decrease of cogging torque. Considering presented results it is possible to foresee which additional harmonic components will comprise the cogging torque of mass-produced PMSMs due to PM imperfections. In this way the designers are able to predetermine required manufacturing tolerances to keep the level of cogging torque in a admissible level. Simulation results were verified and confirmed by laboratory tests.

High performance motor drive applications require permanent—magnet synchronous motors that produce smooth torque with very low components of cogging torque. To fulfil such demands a variety of design techniques can be used to reduce or even eliminate cogging torque components. Rotor design techniques are in comparison to the stator ones much more effective, but their effectiveness depend considerably on the motor design parameters. Calculations have shown that the cogging torque can be significantly reduced while maintaining the output torque at the same level by the appropriate use of two or more presented techniques. However, the detailed analysis of cogging torque components has revealed that besides well-know native cogging torque components also additional cogging torque components exist which are provoked by assembly tolerances in mass—production. Since these two groups of cogging torque components are concerning design techniques mostly in contradiction, a minimization of the total cogging torque becomes a challenging task. A finite element method and Fast Fourier transformation were used to study the sensitivity of several motor simulation models with regard to manufacturing tolerances and assembly imperfections. On the bases of numerous simulations and analyses, it follows that manufacturing assembly tolerances and material imperfections cause the phenomena of additional cogging torque harmonic components, which are not present in the case of a perfect motor. The ascertainment that some permanent—magnet motor designs are more sensitive to the phenomenon of additional harmonic components in cogging torque than the others is an important fact for the producers of such motors, which must be seriously considered in the process of motor design optimization.

Outdated, oversized variable speed pump drives (VSDPs) in industry lead to sub-optimal energy efficiency and considerable energy losses. This paper proposes methods to develop 2D efficiency maps for motors, converters, and pumps using polynomial surface fitting, which enables efficiency evaluation in a wide operating range. The method was applied to an oversized VSDP in an industrial chilled water supply system, comparing the original system with five alternative VSDP combinations with high-efficiency motors and pumps. The five VSDP variants demonstrated average energy savings of around 30%, with the synchronous reluctance motor (SRM) configurations outperforming the induction motor (IM) configurations by up to 7 percentage points, particularly at low loads. The high-efficiency SRM-based 252-IE5 variant delivered the best overall energy performance, highlighting the benefits of optimised system sizing and motor selection for energy savings. The proposed method can be used in both industrial and residential applications and offers great advantages in process systems that require variable flow and pressure of water or other fluids during operation, such as HVAC, water supply and wastewater treatment, district heating, etc. The development of a VSDP drive with efficient energy optimisation is an interdisciplinary problem of mechanical and electrical engineering, and without the interaction of engineers from both fields the result will not be optimal. We try to present our method so that it can be a reliable tool for mechanical, electrical, and other engineers or researchers to assist them in finding possible energy savings, performing energy audits, and selecting the most suitable components when modernising existing or developing new systems.

The equivalent inductance of three-phase induction motors is experimentally investigated in this paper, with particular reference to the frequency range from 1 kHz to 20 kHz, typical for the switching frequency in inverter-fed electrical drives. The equivalent inductance is a basic parameter when determining the inverter-motor current distortion introduced by switching modulation, such as rms of current ripple, peak-to-peak current ripple amplitude, total harmonic distortion (THD), and synthesis of the optimal PWM strategy to minimize the THD itself. In case of squirrel-cage rotors, the experimental evidence shows that the equivalent inductance cannot be considered constant in the frequency range up to 20 kHz, and it considerably differs from the value measured at 50 Hz. This frequency-dependent behaviour can be justified mainly by the skin effect in rotor bars affecting the rotor leakage inductance in the considered frequency range. Experimental results are presented for a set of squirrel-cage induction motors with different rated power and one wound-rotor motor in order to emphasize the aforesaid phenomenon. The measurements were carried out by a three-phase sinusoidal generator with the maximum operating frequency of 5 kHz and a voltage source inverter operating in the six-step mode with the frequency up to 20 kHz.