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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 proposes a six-phase surface-mounted permanent-magnet machine with a 24-slot/10-pole fractional slot winding, which not only eliminates the air-gap flux subharmonics, but also minimizes the effect of slot harmonics, which highly affect both the core and magnet losses. The six-phase winding design also offers an improved drive train availability for electric vehicle applications due to its inherent high fault-tolerant capability. When compared with a three-phase design, the proposed winding offers approximately 3.5% improvement in torque density, a significant reduction in both the core and magnet losses, and an improved overall efficiency. The proposed winding is deduced based on the stator shifting concept of two 12-slot/10-pole stators with single tooth windings. The coil span of the resulting machine will be two slots, which stands as a compromise between single tooth and distributed windings. The concept of stator shifting is first presented, and then, a prototype machine is designed and simulated using the 2-D finite-element analysis to validate the proposed concept. A comparative study is also carried out to compare six-phase and three-phase designs with the same slot/pole combination and also with the 18-slot/10-pole combination, which was recently shown to be a competitive alternative. [ABSTRACT FROM AUTHOR]

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 interior permanent magnet (IPM) machine equipped with a fractional-slot concentrated winding (FSCW) has met an increasing interest in electric vehicle applications due to its higher power density and efficiency. Torque production is due to both PM and reluctance torques. However, one of the main challenges of FSCWs is their inability to produce a high-quality magnetomotive force (MMF) distribution, yielding undesirable rotor core and magnet eddy-current losses. Literature shows that the reduction of low-order space harmonics significantly reduces these loss components. Moreover, it has been previously shown that by employing a higher number of layers, although causing some reduction in the winding factor of the torque-producing MMF component, both machine saliency and reluctance torque components are improved. Recently, a dual three-phase winding connected in a star/delta connection has also shown promise to concurrently enhance machine torque of a surface-mounted PM machine while significantly reducing both rotor core and magnet losses. In this paper, a multilayer winding configuration and a dual three-phase winding connection are combined and applied to the well-known 12-slot/10-pole IPM machine with v-shaped magnets. The proposed winding layout is compared with a conventional double-layer winding, a dual three-phase double-layer winding, and a four-layer winding. The comparison is carried out using 2-D finite-element analysis. The comparison shows that the proposed winding layout, while providing similar output torque to a conventional double-layer three-phase winding, offers a significant reduction in core and magnet losses, correspondingly a higher efficiency, improves the machine saliency ratio, and maximizes the reluctance toque component. [ABSTRACT FROM AUTHOR]

One of the main drawbacks of nonoverlapped coils in fractional slot concentrated winding permanent magnet (PM) machines are the high eddy current losses in both rotor core and permanent magnets induced by the asynchronous harmonics of the armature reaction field. It has been shown in the literature that the reduction of low space harmonics can effectively reduce the rotor eddy current losses. This paper shows that employing a combined star-delta winding to a three-phase PM machine with fractional slot windings and with a number of slots equal to 12, or its multiples, yields a complete cancellation to the fundamental magneto-motive force (MMF) component, which significantly reduces the induced rotor eddy current. Besides, it offers a slight increase in machine torque density. A case study on the well-known 12-slot/10-pole PM machine is conducted to explore the proposed approach. With the same concept, the general $n$ -phase PM machine occupying $4n$ slots and with a dual $n$ -phase winding is then proposed. This configuration offers a complete cancelation of all harmonics below the torque producing MMF component. Hence, the induced eddy currents in both rotor core and magnets are significantly reduced. The winding connection and the required number of turns for both winding groups are also given. The concept is applied to a 20-slot/18-pole stator with a dual five-phase winding, where the stator winding is connected as a combined star/pentagon connection. The proposed concept is assessed through a simulation study based on 2-D finite element analysis. [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]

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]

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]