Steady-state analysis and stability of synchronous reluctance motors considering saturation effects

This paper investigates the influence of the magnetic saturation on the performance of a Synchronous Reluctance Motor (SynRM) at steady-state. In addition, the stability limits for the SynRM are studied using a suggested more accurate method. The saturation and cross-saturation effects on both direct (d) and quadrature (q) axis flux linkages are considered. A Finite Element Method (FEM) is used to obtain an accurate representation for the dq-axis flux linkages relations. In order to reduce the calculation time of the finite element analysis, a look-up table (LUT) for the dq-axis flux linkages is generated based on the FEM to be used for simulating the SynRM characteristics. It is found that the magnetic saturation in the adopted motor results in an enlarged region of stable operation of the SynRM by about 200 % compared with the unsaturated case. The results show the importance of including the saturation factors on the performance of the SynRM and its stability limits. Hence, the magnetic saturation effect will not only reflect on the stability of the motor but also on the whole drive system

Performance evaluation of synchronous reluctance motors with and without permanent magnets

Nowadays, a growing interest in the efficiency and the cost of electrical machines has been noticed. Therefore, Synchronous Reluctance Motors (SynRMs) have become more attractive, thanks to their higher efficiency and nevertheless acceptable cost compared to induction machines. The rotor design of SynRMs with or without permanent magnets (PMs) has a huge effect on the motor efficiency, torque density and power factor. This paper introduces an evaluation for the performance of SynRMs with and without PMs in terms of efficiency, torque and power factor maps. Three different rotor designs for the same machine have been compared. For one machine, the experimental measurements have been obtained and the validation of the simulation results have been confirme

Performance comparison of conventional synchronous reluctance machines and PM-assisted types with combined star-delta winding

This paper compares four prototype Synchronous Reluctance Motors (SynRMs) having an identical geometry of iron lamination stacks in the stator and rotor. Two different stator winding layouts are employed: a conventional three-phase star connection and a combined star-delta winding. In addition, two rotors are considered: a conventional rotor without magnets and a rotor with ferrite magnets. The performance of the four SynRMs is evaluated using a two-dimensional (2D) Finite Element Model (FEM). For the same copper volume and current, the combined star-delta-connected stator with Permanent Magnets (PMs) in the rotor corresponds to an approximately 22% increase in the output torque at rated current and speed compared to the conventional machine. This improvement is mainly thanks to adding ferrite PMs in the rotor as well as to the improved winding factor of the combined star-delta winding. The torque gain increases up to 150% for low current. Moreover, the rated efficiency is 93.60% compared to 92.10% for the conventional machine. On the other hand, the impact on the power factor and losses of SynRM when using the star-delta windings instead of the star windings is merely negligible. The theoretical results are experimentally validated using four identical prototype machines with identical lamination stacks but different rotors and winding layouts

Hybrid photovoltaic-thermoelectric generator powered synchronous reluctance motor for pumping applications

The interest in photovoltaic (PV) pumping systems has increased, particularly in rural areas where there is no grid supply available. However, both the performance and the cost of the whole system are still an obstacle for a wide spread of this technology. In this article, a hybrid photovoltaic (PV)-thermoelectric generator (TEG) is investigated for pumping applications. The electric drivetrain comprises a synchronous reluctance motor and an inverter. A control strategy for the drivetrain is employed to execute two main tasks: 1) driving the motor properly to achieve a maximum torque per Ampere condition and 2) maximizing the output power of the PV system at different weather conditions. This means that the conventional DC-DC converter is not used in the proposed system. Moreover, batteries, which are characterized by short life expectancy and high replacement cost, are also not used. It is found that the motor output power and the pump flow rate are increased by about 9.5% and 12% respectively when the hybrid PV-TEG array is used compared to only using PV array. Accordingly, the performance, cost and complexity of the system are improved. Measurements on an experimental laboratory setup are constructed to validate the theoretical results of this work

Solar array fed synchronous reluctance motor driven water pump : an improved performance under partial shading conditions

An improved performance of a photovoltaic (PV) pumping system employing a synchronous reluctance motor (SynRM) under partial shading conditions is proposed. The system does not include the dc-dc converter that is predominantly being utilized for maximizing the output power of the PV array. In addition, storage batteries are also not contained. A conventional inverter connected directly to the PV array is used to drive the SynRM. Further, a control strategy is proposed to drive the inverter so that the maximum output power of the PV array is achieved while the SynRM is working at the maximum torque per Ampere condition. Consequently, this results in an improved system efficiency and cost. Moreover, two maximum power point tracking (MPPT) techniques are compared under uniform and partial shadow irradiation conditions. The first MPPT algorithm is based on the conventional perturbation and observation (P&O) method and the second one uses a differential evolution (DE) optimization technique. It is found that the DE optimization method leads to a higher PV output power than using the P&O method under the partial shadow condition. Hence, the pump flow rate is much higher. However, under a uniform irradiation level, the PV system provides the available maximum power using both MPPT techniques. The experimental measurements are obtained to validate the theoretical work

EVALUATION OF THE IMPLEMENTATION OF NOMADIC EDUCATION CURRICULUM AND ITS IMPACT ON SOCIO-ECONOMIC AND EDUCATIONAL DEVELOPMENT OF NOMADS IN NASARAWA AND PLATEAU STATES, NIGERIA

ABSTRACT This study evaluated the implementation of nomadic education curriculum and its impact on the socio-economic and educational development of nomads in Nasarawa and Plateau States. The study was guided by eight research questions while eight hypotheses were formulated and tested at 0.05 level of significance. The survey design was adopted for the study. The total sample of the study was 1000 comprising 400 nomadic primary school teachers, 400 nomadic pupils and 200 nomadic parents. Simple random and purposive sampling techniques were used. Data were collected using three instruments; Nomadic Education Teachers Questionnaire (NETQ), Nomadic Education Pupils Questionnaire (NEPQ) and Nomads Interview on Nomadic Education (NINE). Crobach Alpha coefficient was used to estimate the reliability of the instruments. The reliability coefficient of NETQ was 0.89 while NEPQ was found to be 0.78. Data collected were analysed using simple percentage to analyse demographic item means and cut-off means were used to answer the research questions. One-sample t-test was used to test the hypotheses at 0.05 level of significance. Results of the findings showed that there was significant difference between the mean ratings of extent of availability of manpower for the implementation of Nomadic Education curriculum (P = 0.00 < 0.05). There was also a significant difference between the mean ratings of the items on adequacy of educational resources for the implementation of the nomadic education curriculum (P = 0.00 < 0.05). Further findings shows that there was again a significant difference between the means rating on the extent of supervisory practices in nomadic schools (P = 0.00 < 0.05). There was also a significant difference between the means rating of items on accessibility of pupils to nomadic schools (P = 0.00 < 0.05). Result again indicated that there was a significant difference between the mean ratings on extent of willingness of pupils to attend nomadic schools (P = 0.00 < 0.05). In the vein, result shows a significant difference between the mean ratings of a communal crises on the implement of nomadic education curriculum (P = 0.00 < 0.05). The result further indicated a significant difference between the mean ratings of nomadic education curriculum on socio-economic life of nomads. There was again a significant difference between the mean ratings of nomadic education curriculum on educational development of nomads (P = 0.00 < 0.05). Based on the findings, it was therefore recommended among others that both Nasarawa and Plateau State governments should adopt a strong policy towards the implementation of nomadic education. It also recommended that government should employ qualified teachers and personnels to teach nomads