Functional Software description56 DCS 500 Software DescriptionThe field current must change direction during a period of 2 sec,otherwise signal ACK_FEXC1_ON goes to 0 and RDYRUN andRDYREF are set to 0.Following parameters are needed to supervise the function:F1 CURR GT MIN L (1305) Defines the minimum level for the fieldcurrentREV.REV HYST (1318) The sign of the torque reference definesthe field direction. Actual field direction is based on comparison offield current reference and actual. The hysteresis is used in actualcurrent measurement when field reversal acknowledge signal isproduced.REV.FLUX TD (1320) If real FLUX of the motor does not followrapidly the field current, e.g. in very old DC-motors, it can be nec-essary to make an extra delay for defining the field direction. Nor-mally this time can be 0.Following signals are needed for the controllers and for somemeasurements:Bit 5 of TC_STATUS (11204) is the TC_FIELD_CHANGE indicationand during field reversal this signal blocks the armature currentcontroller, the I-part of the speed controller and updates the speedramp output with a measured speed value.Opti-Torque The time that is normally needed for changing the field direction isquite long because of the big inductance of the field winding. Thistime can be reduced in certain cases by using the OPTI-TORQUE-function.
