Volt-ampere constrains and its influence on inductance limits in high speed PM machine design

Permanent magnet machines are widely researched for application in electric traction, aero-engine starter generators and many other industrial systems that require high performance. This paper presents the procedure for the design a surface PM machine with consideration on the volt-ampere limitations of the inverter / active rectifier. The relationship between the stack length and number of turns of the machine and its influence on the operating range is analytically derived and represented in an inductance-limit plot. Regions of this inductance-limit plot indicate the machine operating limits under volt-ampere limitations and maximum current limitations. A procedure for the determination of the number of turns and stack length to satisfy given volt-ampere requirement is outlined and is applied to the design of an aircraft starter alternator. Machine solutions over different number of slot/pole values are evaluated. A suitable machine solution is selected and prototyped. Simulation results are presented for the final selection of machine designs.