W.G. Le Roux

Detecting Rotor Faults in Low Power Permanent Magnet Synchronous Machines

This paper investigates the experimental implementation and detection of rotor faults in permanent magnet synchronous machines. Methods are shown how to experimentally introduce static and dynamic eccentricities and broken magnet cases. A new magnet flux estimation that does not require the measurement of the rotor position or speed is developed. The detection of these and other rotor faults by measuring only the stator currents and voltages are shown experimentally. The paper concludes by contributing a description of a condition-monitoring scheme for detection rotor faults

Detecting rotor faults in permanent magnet synchronous machines

This paper investigates the experimental implementation and detection of rotor faults in permanent magnet synchronous machines. Methods are shown of how to experimentally introduce static and dynamic eccentricities and broken magnet cases. A magnet strength estimation that does not require the measurement of the rotor position or speed is developed. The detection of these and other rotor faults by measuring only the stator currents and voltages are shown experimentally. The paper concludes with a description of a condition-monitoring scheme for detection of rotor faults.

Optimum Small-Scale Open and Direct Solar Thermal Brayton Cycle for Pretoria, South Africa

The open and direct solar thermal Brayton cycle is exposed to various weather conditions like changing solar irradiation, wind and surrounding temperature. The geometries of the receiver and recuperator and the turbine operating point as parameter can be optimised in such a way that they accommodate these weather changes and allow for high net power output throughout a typical year. In this paper, a method of obtaining these parameters based on total entropy generation minimisation is presented. A parabolic dish concentrator with a diameter of 4.8 m is used as well as an off-the-shelf turbo-machine. Results show that the net absorbed power at the receiver and maximum allowed receiver surface temperature play important roles in determining the optimum operating point and maximum net power output.Copyright

Maximum Net Power Output of the Recuperative Open and Direct Solar Thermal Brayton Cycle

The small-scale open and direct solar thermal Brayton cycle with recuperator has several advantages. These include low operation and maintenance costs and high recommendation. The main disadvantages of this cycle are the pressure losses in the recuperator and receiver, turbo-machine efficiencies and recuperator effectiveness, which limit the net power output of such a system. Thermodynamic optimization can be applied to address these disadvantages in order optimize the receiver and recuperator and to maximize the net power output of the system at any steady-state condition. The dynamic trajectory optimization method is applied to maximize the net power output of the system by optimizing the geometries of the receiver and recuperator, limited to various constraints. Standard micro-turbines and parabolic dish concentrator diameters of six to eighteen meters are considered. An optimum system geometry and maximum net power output can be generated for each operating condition of each micro-turbine and concentrator combination. The results show how the irreversibilities are spread throughout the system optimally, in order for the system to produce its maximum net power output. It indicates that the optimum operating point of a micro-turbine is at the point where the internal irreversibilities are approximately three times larger than the external irreversibilities.Copyright

Small-Scale Dish-Mounted Solar Thermal Brayton Cycle

Abstract The small-scale dish-mounted solar thermal Brayton cycle in the 1- to 20-kW range has several advantages such as mobility, bulk manufacturing, cogeneration, and hybridization. Another advantage is that an off-the-shelf turbocharger from the motor industry can be applied as the microturbine in the cycle. The main disadvantages are low turbine and compressor efficiencies as well as heat and pressure losses. The chapter shows that the method of total entropy generation minimization can be used to maximize the net power output of the cycle by optimizing an open-cavity tubular solar receiver and counterflow plate-type recuperator. Results show that, with the use of an off-the-shelf turbocharger and low-cost optics, the cycle could generate solar-to-mechanical efficiencies of up to 12% with much room for improvement. Remaining challenges and future possibilities are discussed. It is recommended that the cycle should be further developed and investigated as a clean energy technology.