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Open-phase faults in multiphase PMSMs could occur either through an electrical failure or by selective isolation of one or a higher number of phase windings. In such cases, post-fault currents are injected into the remaining healthy windings to maintain an average torque. However, considerable torque ripple may be present if the post-fault currents are not properly designed. Accordingly, a generic approach is proposed in this paper for designing post-fault currents including non-fundamental harmonics that lead to maximum post-fault average torque with suppressed torque ripple in open-end multiphase PMSMs. The proposed scheme is not restricted by the number of open-phase faults. In the proposed algorithm, the post-fault currents are parameterized, based on which the instantaneous post-fault torque is exhaustively formulated. An optimization algorithm is then used to obtain the optimal parameters of the post-fault currents. Experimental tests on a prototype open-end five-phase PMSM under different fault scenarios are used validate the torque ripple suppression capability of the proposed approach.

A sliding-mode-based control scheme with integral action for combined speed and direct thrust force control of a linear permanent-magnet synchronous motor is proposed. A nonlinear state-space model for the combined dynamics of speed and thrust force as system states is utilized for the synthesis of the sliding-mode control law. Direct integral action is also included in the control lawto eliminate the steady-state error in the speed tracking. The sensorless speed estimation is performed by using an adaptive flux observer with a modified dual boundary layer sliding-mode component. Lyapunov stability analysis to prove the global asymptotic stabilities of both the controller and observer is provided. The effectiveness of the proposed method is validated experimentally and demonstrates excellent transient and steady-state speed control performance.

An optimal control scheme synthesized using a linear quadratic regulator-based approach for combined speed and direct thrust force control of permanent magnet synchronous motor (PMSM) is proposed. A novel multiple-input-multiple-output state space model, having stator flux, thrust force, and mover's speed as states, is formulated for the linear PMSM where the state transition matrix is independent of mover's speed. An optimal linear state feedback control scheme is designed using the optimal linear quadratic regulator technique. Integral action is added to the designed control scheme by state augmentation to minimize the steady-state error. Experimental results clearly prove that the proposed optimal control scheme results in a faster transient response of speed and force with improved steady-state regulation of force and flux when compared with the state of the art.

© 2016, Institution of Engineering and Technology. All rights reserved.In the conventional dq model of permanent magnet machines, machine parameters are assumed sinusoidal, leading to a smooth calculated output torque. This is justifiable in distributed-wound stators. However, in permanent magnet machines with concentrated-wound stators, the assumption of sinusoidal machine parameters is no longer valid. Therefore, an extended dq model is proposed in this paper for machines with non-sinusoidal parameters. A detailed torque equation is also derived that explains different sources of torque ripple. Tests are introduced for determination of the parameters in the proposed model. Experimental results from a prototype concentrated-wound interior permanent magnet machine are used for validation of the proposed extended dq model.

A novel approach based on the finite element method is proposed to calculate accurately the winding losses and short circuit forces caused by harmonic currents in a furnace transformer. The technique derives the appropriate partial differential equation required to determine the harmonic currents. The technique is validated by its application to a benchmark furnace transformer where experimental results demonstrate the accuracy of the developed technique. The contribution of harmonic currents to winding losses is shown to be significant in the benchmark furnace transformer, whereas the contribution of harmonic currents to short-circuit forces is limited. © 1965-2012 IEEE.

A novel approach based on the finite element method is proposed to calculate accurately the winding losses and short circuit forces caused by harmonic currents in a furnace transformer. The technique derives the appropriate partial differential equation required to determine the harmonic currents. The technique is validated by its application to a benchmark furnace transformer where experimental results demonstrate the accuracy of the developed technique. The contribution of harmonic currents to winding losses is shown to be significant in the benchmark furnace transformer, whereas the contribution of harmonic currents to short-circuit forces is limited. © 1965-2012 IEEE.

A new approach which integrates multiple nonlinear constrained optimization algorithms in conjunction with an improved heuristic algorithm is presented. The approach includes capitalization of losses in the global design optimization process of three-phase oil-immersed distribution transformers. In addition, the proposed technique incorporates finite element-based electromagnetic analysis for losses, short circuit impedance and forces, in order to assess the globally optimum design produced by the approach against design specifications. We present practical results from a range of distribution transformers designed using existing techniques and the new approach. The practical results demonstrate the significant improvements in design when compared with existing techniques. © 1965-2012 IEEE.

A new approach which integrates multiple nonlinear constrained optimization algorithms in conjunction with an improved heuristic algorithm is presented. The approach includes capitalization of losses in the global design optimization process of three-phase oil-immersed distribution transformers. In addition, the proposed technique incorporates finite element-based electromagnetic analysis for losses, short circuit impedance and forces, in order to assess the globally optimum design produced by the approach against design specifications. We present practical results from a range of distribution transformers designed using existing techniques and the new approach. The practical results demonstrate the significant improvements in design when compared with existing techniques. © 1965-2012 IEEE.