Published in IET Electric Power Applications Received on 16th December 2007 doi: 10.1049/iet-epa:20070507 ISSN 1751-8660 Dynamic performance of a vector-controlled five-phase synchronous reluctance motor drive: an experimental investigation A. Iqbal * School of Engineering, Liverpool John Moores University, Byrom Street Campus, Liverpool L3 3AF, UK * Present address: Department of Electrical Engineering, Aligarh Muslim University, Aligarh 202002, India E-mail: atif_iqbal1@rediffmail.com Abstract: Multi-phase ac motor drives are nowadays considered for various applications due to numerous advantages that they offer when compared with their three-phase counterparts. In principle, control methods for multi-phase machines are the same as for three-phase machines. The operation of an indirect vector- controlled five-phase synchronous reluctance machine with current control in the stationary reference frame is analysed. Performance, obtainable with ramp-comparison current control, is illustrated for a number of operating conditions on the basis of experimental results. Full decoupling of rotor flux control and torque control is realised. Excellent dynamic response is achieved during acceleration, deceleration and reversing transients of machine. 1 Introduction Variable speed electric drives predominately utilise the three- phase machines. However, since the variable speed ac drives require a power electronic converter for their supply (in vast majority of cases, an inverter with a dc link), the number of machine phases is essentially unlimited. This has led to an increase in the interest in multi-phase ac drive applications, since multiphase machines offer some inherent advantages over their three-phase counterparts. A number of interesting research results have been published over the years and detailed reviews are available in [1, 2]. Major advantages of using a multi-phase machine instead of a three-phase machine are detailed in [1–3] and are higher torque density, greater efficiency, reduced torque pulsations, greater fault tolerance and reduction in the required rating per inverter leg (and therefore simpler and more reliable power-conditioning equipment). Additionally, noise characteristics of the drive improve as well [4]. Higher torque density in a multi-phase machine is possible since, apart from the fundamental spatial field harmonic, space harmonic fields can be used to contribute to the total torque production [3, 5, 6]. This advantage stems from the fact that vector control of the machine’s flux and torque, produced by the interaction of the fundamental field component and the fundamental stator current component, requires only two stator currents (d-q current components). In a multi-phase machine, with at least five phases or more, there are therefore additional degrees of freedom, which can be utilised to enhance the torque production through injection of higher-order current harmonics. In a five-phase induction machine third harmonic current injection can be used [5, 6] to enhance the overall torque production. Multi-phase synchronous reluctance (Syn-Rel) motor has the same stator structure as that of a multi-phase induction motor, however, the rotor can have a simple structure obtained by removing cut out from a round rotor. Syn-Rel offers the inherent ruggedness, simplicity and ease of maintenance of squirrel cage motors. It has gained popularity as an alternative solution to induction motor drive due to low cost and simpler structure. The vector control approach to a five-phase Syn-rel motor with concentrated winding on the stator is reported in [7, 8] with current control in rotating reference frame. The space vector pulse width modulation (SVPWM) is used to 298 IET Electr. Power Appl., 2008, Vol. 2, No. 5, pp. 298–305 & The Institution of Engineering and Technology 2008 doi: 10.1049/iet-epa:20070507 www.ietdl.org