F07984 — Drive: Speed controller optimization, moment of inertia

F07984 aborts the moment of inertia identification of the rotating speed controller optimization: the drive applies a speed setpoint step, evaluates the response, and could not identify the moment of inertia reliably, so the measurement is aborted. The reason is stored as a decimal fault value in r0949; values 1 to 11 are defined, and each has its own remedy below. If the identification is not required on the drive, the routine can be disabled with p1959.2.

• A fault occurred while the drive was identifying the moment of inertia.
• In most cases a speed limit or the suppression (skip) bandwidth prevented the test setpoint from being reached (fault values 2 to 7).
• In other cases the measured response was unusable: no steady-state speed, too little torque difference after the setpoint step, too few data, or the speed changed too little or in the incorrect direction (fault values 1 and 8 to 10).
• The identified moment of inertia can also be implausible compared with the preset motor moment of inertia p0341 (fault value 11).

1. Fault value 1 — speed does not reach a steady state: check the motor parameters (rating plate data) and the moment of inertia entries p0341 and p0342; after each change recalculate with p0340 = 3. Carry out a motor data identification routine (p1910). If required, reduce the dynamic factor p1967 below 25 %.
2. Fault values 2 and 5 — minimum limiting active: adapt the speed setpoint (p1965) or the minimum speed (p1080).
3. Fault values 3 and 6 — suppression (skip) bandwidth active: adapt the speed setpoint (p1965) or the suppression (skip) bandwidths (p1091 ... p1094, p1101).
4. Fault values 4 and 7 — maximum limiting active: adapt the speed setpoint (p1965) or the maximum limits (p1082, p1083 and p1086).
5. Fault value 8 — torque difference after the setpoint step too low: the total drive moment of inertia is far higher than that of the motor (refer to p0341, p0342). Deselect the rotating measurement (p1960), enter the moment of inertia in p0342, recalculate the speed controller with p0340 = 4 and repeat the measurement.
6. Fault value 9 — too few data: check the moment of inertia (p0341, p0342); afterwards recalculate with p0340 = 3 or 4.
7. Fault value 10 — speed changed too little or in the incorrect direction: check the moment of inertia (p0341, p0342); afterwards calculate with p0340 = 3.
8. Fault value 11 — identified moment of inertia not plausible: reduce the motor moment of inertia p0341 (e.g. by a factor of 0.2) or increase it (e.g. by a factor of 5) and repeat the measurement.

• The drive stores the cause as a decimal value in r0949 (the manual says: interpret decimal). The values mean:
• 1: The speed did not reach a steady-state condition.
• 2: The speed setpoint was not able to be approached because the minimum limiting is active.
• 3: The speed setpoint was not able to be approached because the suppression (skip) bandwidth is active.
• 4: The speed setpoint was not able to be approached because the maximum limiting is active.
• 5: The speed could not be increased by 10 % because the minimum limiting is active.
• 6: The speed could not be increased by 10 % because the suppression (skip) bandwidth is active.
• 7: The speed could not be increased by 10 % because the maximum limiting is active.
• 8: The torque difference after the speed setpoint step is too low to reliably identify the moment of inertia.
• 9: Too few data to reliably identify the moment of inertia.
• 10: After the setpoint step, the speed changed too little or in the incorrect direction.
• 11: The identified moment of inertia is not plausible compared with the preset motor moment of inertia p0341.

• r0949 — read it as a decimal fault value; it names which of the eleven identification checks failed.
• p0341 — the preset motor moment of inertia; check it before repeating, and for fault value 11 deliberately change it (e.g. factor of 0.2 lower or factor of 5 higher).
• p0342 — ratio between total and motor moment of inertia; check it together with p0341, and for fault value 8 enter the known total moment of inertia here.
• p0340 — set it to 3 to recalculate after motor data or inertia corrections; set it to 4 for fault value 8 to recalculate the speed controller after entering p0342.
• p1910 — starts the motor data identification routine for fault value 1.
• p1965 — the test speed setpoint of the optimization; adapt it when a limit or skip bandwidth blocks the measurement.
• p1967 — dynamic factor of the optimization; reduce it below 25 % if the speed does not settle.
• p1080 — minimum speed; adapt it for fault values 2 or 5.
• p1091 ... p1094, p1101 — skip speeds and skip bandwidth; adapt them for fault values 3 or 6.
• p1082, p1083, p1086 — maximum speed and the directional speed limits; adapt them for fault values 4 or 7.
• p1960 — deselect the rotating measurement here for fault value 8.
• p1959 — rotating measurement configuration; p1959.2 disables the moment of inertia identification routine.

F07984 occurs during a commissioning measurement, so there is no production sequence to recover: correct the parameter named by the fault value, acknowledge the fault and restart the speed controller optimization so the measurement runs again. The drive stops when the fault trips; the stop behaviour per family is shown in the table for each drive. The manual describes no further reset procedure, and if the measurement is not needed, p1959.2 disables it.