This example demonstrates idealized field weakening of a quasistatic permanent magnet synchronous machine.
At standstill, the q-axis current is prescribed by a short ramp up to the nominal current.
The d-axis current is controlled to keep voltage ≤ nominal voltage, while speed is varied up to four times nominal speed like in an automotive application.
Total stator current is kept ≤ nominal total current. Simulate and plot versus smpm.wMechanical:
fieldWeakeningController.vs: stator voltagefieldWeakeningController.is: stator currentfieldWeakeningController.id: d-axis currentfieldWeakeningController.iq: q-axis currentIt can be seen that when field weakening begins negative d-axis current is increased from zero while the q-axis current current has to be reduced (current limit) to enable increase of the d-axis current (voltage limit).
INominal denotes total nominal current, which can be applied without exceeding maximum temperature.