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The application of multiphase machines in high-power applications is now a recognized alternative, thanks to their higher fault-tolerance when compared with standard three-phase systems. Although multiphase machines with multiples of three-phase winding sets have been favored in many applications, literature has shown that machines with a prime number of phases, such as five-phase machines, generally outperform other phase orders, especially in terms of machine torque density. One of the major problems when dealing with a prime number of phases either in academic research or industrial applications is the special stator design. This paper provides a general technique to rewind standard off-the-shelf three-phase stator frames with any general prime phase order while preserving the same copper volume. The proposed winding layout is derived using the star of slots theory and the concept of stator winding shifting. Finite-element simulations are used to investigate examples with different phase orders, while experimental investigation is carried out to corroborate the proposed concept by rewinding a standard three-phase stator as a five-phase machine. [ABSTRACT FROM AUTHOR]

The steady-state modeling of multiphase induction machines (IMs) with m phases under open-line fault conditions is usually carried out based on symmetrical component theory. Hence, the estimation of the machine characteristic curves usually involves complex mathematical calculations and inversion of high-order matrices, which complicates the analysis. Moreover, the effect of the different subspaces’ impedances on the machine performance cannot be easily recognized using this modeling technique. Instead, this paper presents the first attempt to derive a simple equivalent circuit for a five-phase IM under open-line conditions that includes the effect of all subspaces in a single circuit. The derivation is carried out for both star and pentagon connections. The equivalent circuit can be a simple technique to explain the advantages obtained from a pentagon connection compared to the star connection under open-circuit faults. It can also be used to derive a simple expression for torque gain and torque ripple magnitude for different stator connections based on the circuit parameters. The derived equivalent circuits are verified using a 1-kW five-phase prototype machine. [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]

Despite the increased interest in multiphase induction machines for safety-critical applications, machine parameter identification for the different sequence planes is still a challenging research point. In most available literature, the effect of nonfundamental sequence planes is overlooked due to the assumption of sinusoidal winding distribution and healthy operation. However, in a single layer or concentric winding layout with an odd number of phases, the effect of flux produced by nonfundamental sequence planes cannot be ignored for the open-phase case. This paper proposes a simple offline method to estimate the parameters of a five-phase induction machine corresponding to different sequence planes. The proposed technique can estimate the stator leakage inductance as well as the magnetizing inductance of both fundamental and third sequences by applying a quasi-square voltage to the stator winding while the machine is running at no-load. Consequently, the rotor circuit parameters of the fundamental sequence plane can be simply obtained by deducting the stator impedance from the blocked rotor machine impedance. For the third sequence plane, an approximate relation to estimate these parameters based on the measured fundamental sequence rotor parameters is also given. An experimental 1.5 Hp prototype machine is used to verify the proposed technique. [ABSTRACT FROM PUBLISHER]

This paper studies the effect of stator winding configuration on the performance of five-phase induction machines under healthy as well as faulty conditions. The study compares two connections, namely, star and pentagon connections. The comparison is conducted using both simulation and experimental results. The steady-state model based on symmetrical components theory is introduced for both connections with one-line open due to a converter fault, and the corresponding machine characteristic curves are estimated. During faults, two alternatives for machine operation are possible, namely, open-loop control and optimal current control. While the first alternative corresponds to higher torque ripple and unbalanced winding currents, the second option necessitates unbalanced phase voltages and typically an increased dc-link voltage to source the required optimal currents. Consequently, an increase in the employed semiconductor device rating is required, which is a critical design factor particularly in medium-voltage applications. A new V/f control technique is proposed to ensure disturbance-free operation with one-line open for both winding connections. Based on the unbalanced machine model and experimental verification, the derating factors that ensure safe machine operation for both winding connection alternatives are calculated. The comparison between the two connections shows the superiority of the pentagon connection under fault conditions in terms of efficiency, average torque, torque ripples, and derating factor. [ABSTRACT FROM PUBLISHER]