SLLSFU1A December 2023 – July 2024 MCF8315C
PRODMIX
Upon completing the motor position initialization with either align, double align, IPD or slow first cycle, the MCF8315C begins to accelerate the motor in open loop. In MCF8315C, the current limit in open loop is set by ILIMIT or OL_ILIMIT based on the configuration of OL_ILIMIT_CONFIG and the speed is increased using this current limit. In open loop, the control PI loops for Iq and Id actively control the currents. The angle during open loop is provided from the ramp generator as shown in Figure 6-30.
The function of the open-loop operation is to drive the motor to a speed at which the motor generates sufficient BEMF to allow the back-EMF observer to accurately detect the position of the rotor. The motor is accelerated in open loop and speed at any given time is determined by Equation 7. In MCF8315C, open loop acceleration coefficients, A1 and A2 are configured through OL_ACC_A1 and OL_ACC_A2 respectively.