Efficiency evaluation of permanent magnet synchronous machines using the synthetic loading technique

• Main Author: Abbas, Abdelaziz Yousif Mohamed
• Published: University of Strathclyde 2009
• Subjects: 502.85
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.510723

This thesis investigates the application of the synthetic loading technique for efficiency evaluation, of permanent magnet (PM) synchronous machines. The standard tests require specialist test facilities, additional machines, and for large machines, linear machines, or vertical mounted machine and floor space. Therefore, an efficiency test method that avoids the need for an external mechanical load is desirable. Synthetic loading can determine machine losses and eliminates the need for a mechanical load connected to the test machine. The synthetic loading technique forces the machine under test to accelerate and decelerate thereby alternating between motor-generator action. If configured correctly the machine, on average over each synthetic loading cycle, operates at rated rms current, rated rms voltage and rated speed, thus producing rated copper loss, iron loss and friction and windage loss. The thesis considers how to properly configure synthetic loading for PM synchronous machines. A derivation of the mathematical models of the synthetic loading technique applied to the permanent magnet synchronous machines is provided in the thesis. The model is based on the direct and quadrature axis equivalent circuits. From the mathematical model, a quadrature axis current algorithm is proposed which is used to develop the speed equation and the stator direct and quadrature axis voltage and current equations. The thesis also establishes a generalised mathematical model of the synthetic loading technique for permanent magnet synchronous machines. Using the derived equations, the effects of synthetic loading frequency on the dc link voltage and the inverter phase-leg volt-ampere rating are analysed. This shows that the synthetic loading technique requires an increased dc link voltage and inverter volt-ampere rating compared to the standard efficiency test technique. A test rig is constructed and used to assess synthetic loading for fractional hp machines. The research verifies the synthetic loading technique experimentally for three permanent magnet synchronous machine types: the surface-mount PM synchronous machine, the interior PM synchronous machine and the linear PM synchronous machine. Simulation and experimental results from synthetic loading are compared with the standard efficiency test. The simulation and the experimental results show that the synthetic loading technique is capable of evaluating the efficiency of the permanent magnet synchronous machines. The key contributions of this work concerns the mathematical model of PM synchronous machines under synthetic loading, the hardware and software implementation and validation of synthetic loading as a technique for efficiency evaluation of PM synchronous machines.