Phase angle advance assumes that there is a linear relationship between angular velocity and direct-axis current. This is not the case. Optimum torque production can be obtained by following the Maximum Torque Per Ampere or “MTPA” curve.
PCD’s Software control strategy uses proprietary algorithms to identify motor characteristics and
exploit all of these characteristics to deliver optimum control of torque across the entire speed range.
The graphic to the right shows the MTPA curve of a motor followed by the controller for a salient pole permanent magnet synchronous machine in the constant torque regime. It also shows the current limiting circle for constant power operation and the Maximum Torque Per Volt “MTPV” to go beyond this region into a decreasing power regime as the voltage ellipse collapses at higher speeds.