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Modular motor drives can be considered as multi‐agent systems, in which the agents can work together to reach a common goal. One agent in such a modular motor drive consists of only a subset of the machine phases and power electronic converter modules, and is equipped with a dedicated controller. When the dc‐links of the different agents are connected in series to a single voltage source, giving rise to a so‐called stacked polyphase bridges converter, the power electronic converter components can have low voltage ratings. However, a voltage balancing controller must ensure that the total dc‐link voltage is distributed evenly among the agents when working in motoring mode. The goal of this research is to propose a multi‐agent voltage balancing algorithm based on dynamic average consensus, which depends solely on local computations, local measurements, and neighbour‐to‐neighbour communication. The scalability and reliability of the modular hardware are hence extended towards the control. Simulations and experimental results on a 4 kW modular axial‐flux PMSM demonstrate the feasibility of the concept. [ABSTRACT FROM AUTHOR]

A stacked polyphase bridge converter consists of multiple standard, three‐phase two‐level voltage source inverters connected in series to the same dc voltage source. The authors present a decentralised and dynamic dc‐bus reconfiguration strategy for this type of converter. The innovation of the proposed strategy lies in its ability to isolate or reactivate one of the inverters in the series connection online, even in motoring mode, enabling increased fault tolerance and an extended speed range. Both the required hardware alterations and the multi‐agent control strategy are addressed. Its major benefits compared to the state‐of‐the‐art are that only two additional active, unidirectional semiconductor switches are required per inverter, and that the control is based on local computations, local measurements and neighbour‐to‐neighbour communication only. Hence, the scalability and reliability of the hardware are extended towards the control. Simulations and experimental results on a 4 kW modular axial‐flux PMSM prove the feasibility of the concept, and validate that the dc‐bus can be reconfigured in 100 ms, without torque interruption. [ABSTRACT FROM AUTHOR]

A modular motor drive (MMD) can be considered as a multi‐agent system, in which the agents work together to reach a common goal. One agent in such an MMD comprises only a subset of the concentrated windings and power electronic converter modules and is equipped with an independent controller. The goal of this research is to let the agents cooperate to distribute a torque demand among them in a completely decentralised way, in order to comply with the flexibility and reliability of modular motor drives. However, the current condition of each agent must still be taken into account during this torque allocation. To limit the communication load, only communication between neighbouring agents is allowed. The combination of a gossip consensus algorithm and multiple decentralised PI current controllers is used for this purpose. Simulations and experimental results on a modular axial‐flux permanent magnet synchronous machine consisting of five agents confirm that the total torque demand is delivered under the proposed control strategy, even during agent malfunctions, under random communication link failures and with non‐identical agents. [ABSTRACT FROM AUTHOR]

When optimizing the design of electrical machines, it is recommended to take into account the effect of the manufacturing processes on the core losses and magnetic properties of the electrical steel. This paper demonstrates a methodology for incorporating the effects of interlocking, a process frequently applied to fix a stack of laminations, on the magnetic properties of the machine core. The methodology requires magnetic measurements on several sets of Epstein strips. The proposed methodology is demonstrated on NO27, a low loss grade of electrical steel. A validation is done to show the transferability from Epstein strips to a realistic stator core geometry. The results show that the proposed methodology succeeds accurately in predicting the degrading impact of interlocking on the magnetic properties of electrical steel laminations. Additionally, the effect of magnetic anisotropy on the degrading impact of interlocking is investigated. © 2020 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Yokeless and segmented armature (YASA) axial flux permanent magnet synchronous machines may have asymmetrical demagnetisation defects in their two rotors. Condition monitoring, therefore, becomes more complicated than in conventional single rotor machines. To develop a real‐time condition monitoring algorithm for demagnetisation faults in YASA machines – which requires solving an inverse problem – a fast forward model is necessary. A frequency‐based analytical model is used to calculate the three‐phase terminal voltages based on the three‐phase current waveforms and the demagnetisation defects including asymmetrical defects in the two rotors. To reduce the computational time of the forward model, this study focuses on the sensitivity of different voltage harmonics on several demagnetisation faults. To this end, the Cramér–Rao lower bound technique is used to analyse the harmonics sensitivity to the demagnetisation faults. The goal of the sensitivity analysis is to select an appropriate set of harmonics that gives maximal information about the defects. It becomes much faster and useful for real‐time condition monitoring. The results of the analysis show that the subharmonics around and including the fundamental are the most sensitive harmonics to the demagnetisation defects. The analytical model is validated with experimental data and finite element simulations. [ABSTRACT FROM AUTHOR]

SUMMARY The stray field outside outer rotor permanent magnet synchronous motors can be used for rotor position detection. The focus of the research is on the optimal position of the sensors in order to provide accurate rotor position information. By using 2D and 3D models, the effect of the radial, circumferential and axial position of the sensors on the output signal is shown. Furthermore, the effects of the rotor yoke thickness and the stator current are studied: a thick rotor yoke obviously reduces the stray field amplitude, and high stator currents slightly shift the switching points of the Hall sensors, making the position information less accurate. Also, the rotor temperature and the orientation of the sensors towards the direction normal to the rotor surface are important: modifying the orientation causes a phase shift and is a way to tune the sensors without changing the position. Experiments show that an accurate brushless DC control is possible based on Hall sensors in the stray field. The motor and brushless DC control are used for a wheel drive of an ultra-light electric vehicle. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]