Modelling of a DC excitation of a synchronous generator

This paper describes the modelling of a DC excitation system of a synchronous generator. DC excitation system is one of the various methods of excitation that are applied in power systems. Even though the AC excitation methods are commonly used nowadays, this method still has wide usage in many power system industries. A mathematical model is developed using differential equations from the first principles. Transfer functions of the developed equations are presented and implemented in Matlab Simulink. The performance of the DC excitation is analysed under steady state and transient operations

Evaluation of rotor design parameters for minimising torque ripple on a synchronous reluctance machine using multifactor ANOVA

Abstract: This paper presents a method for evaluating, both qualitatively and quantitatively, the effects of specific rotor design parameters on the performance of a synchronous reluctance machine. The method uses multi-factor experimental design, with Analysis of Variance (ANOVA), and Finite Element Analysis (FEA) to determine the optimal rotor design parameter according to a specific objective. Using this method, two factors - rotor flux barrier pitch angle and barrier width - are selected at simultaneously varied levels for assessment with the aim of minimising the response variable, which is, the torque ripple. Results from the investigation show that the influence of the rotor flux barrier pitch angle on the torque ripple is more statistically significant than the influence of the barrier width. However, the effect of the barrier width on the actual torque is more significant

Performance evaluation of a nine-phase self-excited induction generator

This paper evaluates the performance of a self-excited nine-phase induction generator. The advantage of using Multi-phases(more than three-phases)are well known such as High power handling capability by dividing the required power between multiple phases, higher reliability, reduced harmonics and Fault tolerant. For a nine-phase machine, if failure occurs the machine can still operate since each three phase group can be made independent from each other. In this study, mathematical model is developed directly from the equivalent circuit of nine-phase self-excited induction generator by means of nodal admittance method. The stator of a conventional 1.5 kW, 4-pole, 50 Hz three-phase squirrel cage induction machine has been modified to nine-phase induction machine. The excitation is provided by 9 capacitors each rated 40 uF and 450 V

Fault-tolerance of five-phase induction machines with mixed stator winding layouts : torque ripple analysis

Abstract The mixed winding layouts proposed in this paper are obtained by combining double and triple layer (DTL) windings in stator slots. Previous work has touched upon on the ability of three-and five-phase induction machines (IMs) with mixed winding layouts to produce torque with less ripple contents. However, their advantage when operating under open-circuited faults is yet to be comprehensively reported. This paper presents the fault-tolerant ability of Fivephase Induction Machines (FPIMs) with mixed winding layouts to produce torque with less ripple contents. The windings are designed as 2-pole and chorded with one slot, thereafter referred to as “DTL-14/15” and when chorded with two slots, thereafter referred to as “DTL-13/15. The magnetic conditions in the FPIMs are analyzed using Finite Element Method (FEM). The results evidenced that the FPIMs with the proposed DTL-14/15 and DTL-13/15 chorded coils reduced the torque ripple by a margin of about 60 % while operating with open-circuited faults respect to FPIMs with conventional double layer (DL) winding of the same coil span and operating under the same conditions. The results also prove that there is a great correlation between FEM (simulation) and experimental results

Novel synchronous reluctance motor with sinusoidal rotor lamination shape for less torque ripple contents

Abstract: This paper presents the analysis of a novel Synchronous Reluctance Motor (SynRM), which has an axially sinusoidal rotor lamination shape. The sinusoidal lamination shape is used to vary magnetic flux in the q-axis direction. Therefore, cancelling some torque harmonics produced by stator slotting effects and rotor anisotropy, while maintaining the average torque. The stator of a 5.5 kW, 4-pole, 50 Hz conventional three-phase squirrel cage induction motor, with distributed and chorded by one slot, double layer winding, is used for both standard and novel motors. The Finite Element Analysis (FEM) is used to study the electromagnetic parameters of interests. The FEA results are validated by means of practical measurements. The results obtained from both FEA and practical measurements evidenced that the novel SynRM dropped tremendously the torque ripple contents while still maintained the average torque. The drop in torque ripple contents is mainly due to mitigation of the most dominant torque harmonics caused by stator slotting and rotor anisotropy

Performance indexes’ evaluation of a novel synchronous reluctance motor with sinusoidal rotor shape

Abstract: This paper presents the evaluation of performance indexes of a novel Synchronous Reluctance Motor (SynRM), which has an axially sinusoidal rotor lamination shape. The stator of a 5.5 kW, 4-pole, 50 Hz conventional three-phase squirrel cage induction motor, with distributed and chorded by one slot, double layer winding, is used for both standard and novel synchronous reluctance motors. Due to the nature of the sinusoidal rotor structure, the 3D Finite Element Analysis (FEA) is utilized to study the electromagnetic parameters of interests. The SynRM with sinusoidal rotor shape results are compared with the standard SynRM without cut-off on the q-axis. The FEA results are validated by means of practical measurements. From both FEA and measured results, it is evident that the novel SynRM enhances the performance indexes of interests such as torque density, torque ripple factor and efficiency

Investigation into effects of a novel rotor cut-off design for synchronous reluctance machines

Abstract: This paper presents an investigation into the effects of a novel rotor cut-off design on the performance of a synchronous reluctance machine. The rotor design consists of a sinusoidal lamination shape in the axial direction thereby varying the magnetic flux in the q-axis direction and reducing torque harmonics due to slotting effects. The presented study uses single-factor experimental design, with Analysis of Variance (ANOVA), and Finite Element Analysis (FEA) to quantitatively and qualitatively assess the effects of the rotor cut-off on the torque, torque ripple, saliency, power factor and efficiency of the machine. Results of the investigation indicate that although variation in the rotor cut-off design significantly reduces the torque ripple, the effects on the average output torque, saliency, power factor of the machine are relatively insignificant. Index Terms—Synchronous Reluctance Machine; Rotor Design; ANOVA; FEA

Performance evaluation of a three-phase induction machine with auxilliary winding fed by a leading reactive current

Abstract In this paper the performance of three-phase induction machine equipped with a three-phase auxiliary winding which is only magnetically coupled to the stator main winding is evaluated. A capacitive load is connected in parallel to each phase of the auxiliary winding and serves to inject a leading reactive current into the machine. Steady state and dynamic performance of the machine are evaluated under various loading and compensative conditions. The experimental results show that it possible to obtain a comparatively good power factor with a fixed capacitive load for various loadings of the asynchronous machine

Torque ripple minimization in synchronous reluctance motor using a sinusoidal rotor lamination shape

Abstract: A Synchronous Reluctance Motor (SynRM), which has sinusoidal rotor lamination shape in the axial direction, is proposed. The sinusoidal lamination shape is utilized to vary the magnetic flux in the q-axis direction. Therefore, cancelling some torque harmonics produced by slotting effects. The stator geometry of a 1.5 kW, conventional three-phase squirrel cage induction motor, with distributed double layer winding, chorded by one slot, is used for both basic and proposed models. Due to the axial geometry design of sinusoidal lamination shape for the proposed model, 3-D Finite Element Method (FEM) is used for dynamic analysis. From the FEM results, it evidenced that with current vector angle of 45oelectric, the proposed model reduced the torque ripple content by more than 60 % and still maintained the average torque