SLLSFQ7 November 2023 MCF8329A
PRODUCTION DATA
PMSM motors can be operated not only in the constant torque region below the base speed (normally rated speed) but also in the constant power region above the base speed, but the base speed can be varied according to current and voltage limitation. MCF8329A provides a flux weakening control, to increase the speed beyond the motor rated speed. The flux weakening can be enabled by setting 1b to FLUX_WEAKENING_EN. The flux weakening control uses a PI control loop as shown in Figure 7-34, to create the Idref. Kp and Ki coefficients for flux weakening loop are configured through FLUX_WEAKENING_KP and FLUX_WEAKENING_KI.
The absolute maximum value of flux weakening current reference (Id_FW) can be limited as a percentage of ILIMIT by configuring FLUX_WEAKENING_CURRENT_RATIO. If FLUX_WEAKENING_CURRENT_RATIO = 0b, then only circular limit is in place, in that case iq2 + id2 is limited to ILIMIT. If Id_FW absolute value increases then iq is reduced to meet circular limit.
User can configure the modulation index reference, Vs_ref (shown in Equation 11) below that the flux weakening is not active and Id_FW is made to zero. The configuration is available in the bits FLUX_WEAKENING_REF ERENCE.
The Idref can be zero or minimum of id reference from flux weakening or MTPA. The variable FLUX_MODE_REFERENCE is available in the volatile memory (RAM) and a non-zero value can overwrite Id_FW and Id_MTPA.