Optimal torque control of interior permanent magnet synchronous machines in the full speed range

Optimally designed interior permanent magnet synchronous machines using finite element software, and control of such machines using powerful digital signal processing controllers, is common-place today. With field orientated control, the maximum torque per ampere control strategy for unsaturated voltage conditions (below base speed) is well known; the field weakening strategy however, can be rather daunting. In this paper a straightforward torque control strategy for the entire speed range is demonstrated. Practical implementation is very simple, since the calculations are removed from the load of the digital signal processor and are done off-line in an automated process. The process relies on machine specific data from finite element analysis and therefore includes non-linear effects such as saturation and cross-coupling. Simulated and practical results for the steady state show that the torque is controlled effectively in the entire speed range.