F07900 — Drive: Motor blocked

F07900 means the drive has detected the motor as blocked: the motor ran at its torque limit for longer than the delay time in p2177 while its speed stayed below the threshold in p2175. In servo operation the same code is additionally titled "Drive: Motor blocked/speed controller at its limit", because a speed controller repeatedly driving into its limit produces the same detection. Depending on the drive configuration, the condition can also be signalled as an alarm or without any automatic response instead of as a fault.

• The motor has been at its torque limit for longer than the delay in p2177 while the speed remained under the value in p2175.
• The speed actual value oscillates and the speed controller output repeatedly reaches its limit.
• For the vector drive objects: with simulation mode on (p1272 = 1) and speed-encoder closed-loop control selected (p1300 = 21), the detection responds when no encoder signal comes back from the motor that the closed-loop control drives with its torque setpoint.
• On the G120, thermal monitoring of the power unit can lower the current limit (see p0290), so the motor decelerates into the blocked condition.

1. Make sure the motor can actually turn freely — release any mechanical blockage at the driven machine.
2. Check the effective torque limits: r1538 for the upper direction and r1539 for the lower direction of rotation.
3. Review the Motor blocked monitoring values and correct them if they do not suit the application (p2175, p2177).
4. Check the inversion of the actual value (p0410).
5. Check the motor encoder connection and the set encoder pulse number (p0408).
6. If the Basic positioner (EPOS) function mode was active, deselect it first, then recheck and re-enter the motoring (p1528) and regenerative (p1529) torque limits.
7. In simulation mode with speed encoder, the power unit carrying the motor must be switched on and fed with the torque setpoint of the simulated closed-loop control; if that is not possible, change over to encoderless control (see p1300).
8. Check the direction of rotation enable signals that act on a flying restart (p1110, p1111).
9. Under U/f control, check the current limit (p0640) and the ramp-up time (p1120).
10. On the G120, check the power unit overload response (p0290), because thermal derating of the current limit can bring the drive into this condition.
11. On SERVO in encoderless operation with motors rated below 300 W, increase the pulse frequency (p1800).
12. On blocksize devices in encoderless operation with a current controller sampling time p0115[0] under 80 µs, either set the pulse frequency to p1800 = 1 / p0115[0] or raise the changeover speed of the model (p1755).

• p2175 — speed threshold below which the blocked detection engages; check whether the set value matches the application.
• p2177 — delay time that torque-limit operation is tolerated before the message comes.
• r1538 (CO) — upper effective torque limit to compare against the torque actually demanded.
• r1539 (CO) — lower effective torque limit, relevant for the negative direction of rotation.
• p1272 — switches the simulation mode on (= 1); one trigger of this code exists only in that mode.
• p1300 — control operating mode; value 21 selects the speed-encoder closed-loop control involved in the simulation-mode trigger.
• p0410 — inversion of the encoder actual value; verify it when a motor encoder is used.
• p0408 — pulse number of the rotary encoder; confirm it matches the encoder fitted.
• p1528 / p1529 (CI) — scaling of the upper and lower torque limit; recheck after the EPOS function mode has been deselected.
• p1110 / p1111 — inhibit the negative and positive direction; check both when a flying restart is used.
• p0640 — current limit to review when the drive runs U/f control.
• p1120 — ramp-up time of the ramp-function generator, also part of the U/f check.
• p0290 — sets the power unit overload response; its thermal derating of the current limit is a trigger on the G120.
• p1800 — pulse frequency; raise it for encoderless SERVO operation with small motors.
• p0115 — sampling time of the supplementary functions; on blocksize devices with p0115[0] under 80 µs, adapt p1800 or p1755.
• p1755 — changeover speed of the encoderless motor model; raising it is the alternative to the p1800 setting on blocksize devices.

Eliminate the mechanical blockage or the parameter mismatch first, then acknowledge the fault without delay. The drive stays tripped until the acknowledgement is carried out and can only be restarted afterwards.