Regenerative Testing of Multiphase Machines with Multiple Three-phase Windings

Testing of high power machines requires a significant investment into sophisticated equipment and floor space. Over the years, various methods aimed at reducing the cost have been developed, including, for example, mixed frequency testing (also known as synthetic loading) and back-to-back testing. While most of these techniques can be directly applied to multiphase machines as well, a particular stator winding topology - namely, the use of multiple three-phase windings, leads to a possibility to realise regenerative testing of the machine by operating some three-phase windings in motoring and some in generation. As a consequence, testing can be conducted without the need to have a loading machine and with very small energy consumption, governed by the combined machine and inverter losses. The paper describes application of regenerative testing in conjunction with machines with an even number of three-phase windings and details the control scheme used for a permanent magnet six-phase synchronous machine. Full power testing is enabled without the requirement for a mechanical load. Simulation and experimental results, illustrating the operation of one three-phase winding in motoring and the other in generation and collected from a 150 kW rig with a permanent magnet synchronous machine, are included.