F07902 — Drive: Motor stalled

F07902 tells you the drive has identified the motor as stalled: while energized it did not turn as expected, and the condition lasted longer than the delay time p2178 permits. Which stall monitor triggered is stored as a decimal number in the fault value r0949. Depending on the drive configuration, the very same stall condition can also be output only as an alarm or without any reaction.

• The motor stayed at standstill under power for longer than the stall delay p2178.
• Recognition comes from one of the motor-model monitors — a speed threshold, a model error threshold, or the deviation between flux setpoint and flux actual value; a further detection path exists only for separately excited synchronous motors.
• Situations the manual names as triggering it: a stall caused purely by the load, running the drive immediately after switch-on when the excitation time was strongly shortened, and — with fault value 2 — very fast acceleration into the field-weakening range.

1. First confirm that motor data identification (p1910) and the rotating measurement (p1960) were actually carried out; r3925 shows the result (G120: p1900, r3925). For a synchronous motor with encoder, the encoder must have been adjusted (p1990).
2. With speed encoder: check the speed signal for an interrupted cable, wrong polarity, wrong pulse number or a broken encoder shaft. If the data set changeover selects a second speed encoder, make sure it is mounted on the same motor that is being controlled. If nothing is wrong, the fault tolerance p1744 or p0492 may be raised; for resolvers with high signal ripple raise p0492 and smooth the speed signal (p1441, p1442).
3. Without speed encoder: check whether the drive stalls only under load in the controlled mode, or already with the speed setpoint at zero. If so, raise the current setpoint via p1610 (G120 additionally p1611) or, for passive loads, set p1750.2 = 1 — sensorless vector control to standstill. On G120 also extend ramp-up time p1120 and ramp-down time p1121, and check via p1755 whether the drive was in the open-loop speed-control range.
4. If the excitation time p0346 was significantly reduced and the drive stalls right after switch-on, raise p0346 again (G120: alternatively select quick magnetizing via p1401).
5. Check the current controller (p1715, p1717) and the speed adaptation controller (p1764, p1767); if their dynamic response was strongly reduced, restore it.
6. Check that the motor cables are not disconnected (G120 cross-refers to A07929) and check the current limits (p0640, r0067, r0289): if they are too low, the drive cannot magnetize. The G115D and G120C tables condense the whole remedy to these two checks after motor identification.
7. If fault value 2 occurs while the motor accelerates very quickly into the field-weakening range, reduce p1596 or p1553 so the deviation between flux setpoint and flux actual value becomes smaller.
8. Separately excited synchronous motors (with speed encoder): check the speed signal (cable, polarity, pulse number), verify the motor parameterization from rating plate and equivalent circuit diagram, check the excitation equipment and its interface to the closed-loop control, set the highest possible dynamic response of the excitation current control, look for oscillation in the speed control and use a bandstop filter against resonance, and do not exceed the maximum speed (p2162).
9. Only when all these checks find no genuine fault may the fault tolerance (p1745) or the stall delay (p2178) be increased.

The message value is r0949, interpreted as a decimal number. The entries for G130, G150, S120 and S150 decode it as:

• 1 — stall detection via r1408.11, using the thresholds p1744 and p0492.
• 2 — stall detection via r1408.12 (p1745) or via the flux difference r0083 ... r0084.
• 3 — stall detection via r0056.11, only for separately excited synchronous motors.
• On G120 the numbering differs: value 1 is reserved, and value 2 means detection via r1408.12 (p1745) or via r0084 ... r0083. The G115D and G120C tables print no fault value.

• p2178 — motor stalled delay time; the fault trips once the stall outlasts it, and it may be raised last.
• r0949 — fault value; read it as a decimal to identify the triggering monitor.
• p1744 — speed threshold for stall detection; with-encoder fault tolerance that can be raised.
• p0492 — second with-encoder fault tolerance; raised for resolvers with high signal ripple.
• p1745 — error threshold for stall detection; encoderless fault tolerance that can be raised.
• r0083 — flux setpoint; its deviation from r0084 defines detection 2.
• r0084 — flux actual value in that comparison.
• p1910 — motor data identification; confirm it was carried out.
• p1960 — rotating measurement; confirm it was carried out.
• r3925 — displays the result of identification and rotating measurement.
• p1900 — motor data identification and rotating measurement on G120.
• p1990 — encoder adjustment; must have been done for synchronous motors with encoder.
• p1441 — actual-velocity smoothing; raised for resolver signal ripple.
• p1442 — speed-controller smoothing of the actual speed; same purpose.
• p1610 — raises the current setpoint when the load alone stalls the drive.
• p1611 — additional acceleration torque, raised with p1610 on G120.
• p1120 — ramp-up time, extended on G120 when the load causes the stall.
• p1121 — ramp-down time, extended likewise.
• p1755 — shows the open-loop speed-control range on G120.
• p0346 — motor excitation time; restore it if it was strongly shortened.
• p1401 — flux control configuration; quick magnetizing on G120 as an alternative.
• p1715 — current controller gain; restore the dynamic response if it was reduced.
• p1717 — current controller integral time; same action.
• p1764 — speed adaptation gain of the encoderless motor model; restore if reduced.
• p1767 — speed adaptation time of that model; same action.
• p0640 — current limit; if too low, the drive cannot magnetize.
• r0067 — checked together with p0640 during the current-limit verification.
• r0289 — maximum power unit output current, part of the same check.
• p1596 — field-weakening controller time; reduce it against fault value 2.
• p1553 — stall limit scaling; the alternative to p1596.
• p2162 — maximum-speed hysteresis; separately excited synchronous motors must stay below it.

Acknowledge the fault immediately — no waiting time applies — and restart the drive only after the cause has been removed. Where the configuration outputs the stall only as an alarm or without any reaction, there is nothing to acknowledge.