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The nine-phase six-terminal induction machine has recently been proposed as a promising contender to the conventional six-phase asymmetrical winding machine in terms of torque density, phase current quality, stator winding simplicity, and fault-tolerant capability. However, the relatively lower dc-link voltage utilization of a single neutral arrangement in multiphase machines with multiple three-phase windings represents, in general, a technical challenge when compared to windings with isolated star points. Therefore, this paper proposes a new pseudo six-phase winding layout suitable for medium-voltage high-power induction machines, which employs quadruple three-phase stator winding sets, while providing the same terminal behavior of a nine-phase six-terminal winding. Additionally, like the traditional six-phase winding, two possible neutral arrangements can be configured. The proposed winding configuration provides the same dc-link voltage utilization as in conventional dual three-phase winding machines with isolated neutrals. The effect of the circulating zero-sequence current component experienced with a single neutral arrangement can also be avoided. A 1.5 Hp prototype induction machine is used to experimentally validate the proposed six-phase winding layout under both healthy and fault conditions. [ABSTRACT FROM AUTHOR]

The nine-phase six-terminal induction machine (IM) has been recently proposed as a promising contender to the conventional asymmetrical six-phase type in terms of torque density, stator winding simplicity, and fault-tolerant capability. The stator is composed of nine phases, which are connected in a fashion to only provide six stator terminals. Therefore, this connection combines the high performance of a nine-phase winding with the terminal behavior of a six-phase machine. This paper introduces the machine mathematical model based on the vector space decomposition (VSD) modeling approach. The required current and voltage sequence transformation matrices are derived such that the machine is mathematically regarded as an equivalent six-phase IM with only three decoupled subspaces. This way, the same VSD-based controller structures conventionally applied to six-phase-based systems can be preserved. A 1.5-hp prototype IM is used to experimentally validate the machine model under both healthy and open-phase conditions. [ABSTRACT FROM AUTHOR]

This paper proposes a new winding layout for high-power medium-voltage nine-phase induction machines (IMs) based on a single-layer concentrated winding layout having a unity winding factor. The machine is fundamentally an asymmetrical nine-phase IM, where phases are connected in such a way as to provide six terminals that are fed from two three-phase inverters. Compared to a conventional asymmetrical six-phase IM with the same stator and copper volumes, it provides improved torque density, a higher torque/current ratio, and a simpler winding layout. Finite-element simulation is used to compare the proposed winding layout with a conventional split-phase six-phase IM to assess the claimed merits. A 1.5-hp prototype IM is also used for experimental verification. The experimental results are given under both healthy and fault conditions, where the faulty converter is completely disabled. The achievable derating factors under this case are then given and compared with those of conventional six-phase IMs. [ABSTRACT FROM PUBLISHER]

This paper presents the steady-state mathematical model of a five-phase induction machine with a combined star/pentagon connection. The connection splits the stator winding into two five-phase windings displaced in space by $\pi$/10 and connected in a combined star/pentagon configuration. Recent work limited to an experimental investigation demonstrated that the connection possesses improved fault tolerance when compared to a conventional star-connected stator, as well as avoids the pentagon connection problems. Although the machine has five-phase terminals, it is intrinsically an asymmetrical ten-phase machine, which introduces additional subspaces in the machine's mathematical model. In order to theoretically investigate and thoroughly assess this connection against conventional connections, this paper introduces the steady-state mathematical model based on vector space decomposition and symmetrical component theory. Finite-element analysis is first used to investigate the different harmonic current components induced in the cage rotor circuit, upon which the effect of different subspaces can be clarified and the required transformation matrix from phase variables to their sequence components can be derived. The model is verified using a 1-kW prototype five-phase induction machine. [ABSTRACT FROM PUBLISHER]

The most recent literature on multiphase machine drives is based on voltage-source converter (VSC) systems utilizing different modulation techniques. Very little attention is given to the multiphase current-source converters (CSCs). Applying CSCs in high-power multiphase drive systems is promising and can effectively solve many technical problems associated with conventional VSC-based systems. This paper proposes a space vector pulsewidth-modulation (SVPWM) scheme suitable for a five-phase CSC. Generally, in SVPWM-CSCs, a current path should be provided for the dc-link current by ensuring that one pair of upper and lower switches is always on. Applying this constraint yields 25 different space vectors, which are mapped into two concentric decagons with ten equal sectors in the $\alpha\beta$ and $xy$ sequence planes. Each sector has two active-large vectors, two active-small vectors, and a null vector. Moreover, the active-large vectors in the $\alpha\beta$ plane are active-small vectors in the $xy$ plane, and vice versa. In the proposed scheme, the ampere-second concept is utilized to determine the ratio between the dwelling times of the large and small vectors such that the $xy$ current components are nullified, the utilization of the input dc-current is maximized, and the switching transitions are minimized, which, in turn, minimizes the CSC switching losses. The proposed scheme can effectively provide sinusoidal converter currents, which is suitable for motor drives and energy conversion applications. The proposed scheme is verified using a 1-kW prototype five-phase induction motor fed by a five-phase CSC. [ABSTRACT FROM PUBLISHER]

One of the main merits offered by multiphase machines is their high fault-tolerant capability. Literature has demonstrated that the performance of multiphase induction machines under fault conditions is affected by the employed stator winding connection. In open-loop controlled five-phase machines, the star connection is favorable under healthy conditions while the pentagon connection is favorable and yields a lower derating factor under the open phase condition. In this paper, a new combined star/pentagon single layer winding layout that combines the advantages of both star and pentagon connections is proposed for a five-phase induction machine. Although the proposed winding is intrinsically an asymmetrical ten-phase machine, the proposed connection allows for only five-phase terminals. Moreover, the proposed winding not only yields better flux distribution compared to a conventional single layer winding, but also provides a complete cancellation of the third-order harmonic flux component caused by the induced third sequence currents due to the saturation effect and/or under unbalanced operation. Hence, the machine losses are decreased, which improves the overall machine efficiency. For the healthy case, the machine is similar to a conventional star connected five-phase machine. However, with one phase open, the proposed connection results in a lower derating factor compared to conventional connections for both open-loop and optimal current control techniques. A 1-kW prototype machine is used for experimental verification. [ABSTRACT FROM AUTHOR]

Fractional slot concentrated windings (FSCWs), or modular windings, have shown promise with permanent magnet machines. However, their inability to produce high quality travelling fields has limited their application from spreading to induction machines. This paper presents the design considerations and tradeoffs involved in applying FSCWs to five-phase induction machines using the conventional three-phase lap wound machine as a reference. Previous work has touched upon the application of modular windings to three-phase induction machines, concluding that a conventional distributed winding is superior in terms of torque production and rotor bar losses. In applications such as high frequency induction machines and manually wound electrical submersible pump motors, the proposed machine topology provides advantages that may warrant its application despite an apparent power density penalty. In this paper, a prototype five-phase modular winding induction machine designed to significantly reduce the effect of space harmonics is investigated through simulations and experimentally. [ABSTRACT FROM PUBLISHER]