F07937 — Drive: Speed deviation between motor model and external speed

F07937 is raised by the drive's speed monitoring. The monitoring continuously compares two speed actual values: the smoothed speed of the motor model (r2169) and the external speed actual value at the actual-value input of the speed controller (r1443). If the absolute value of the difference between the two exceeds the tolerance threshold p3236 for longer than permitted by p3238, the fault is raised. No message value is output with this fault. Depending on how the drive is configured, the same condition can also be output with no reaction (N).

• The interconnection or the scaling of the external encoder signal is incorrect (p1440, p2000).
• The speed encoder for the external encoder signal is faulty.
• The polarity or the gain of the encoder signal is incorrect.
• The smoothing time constant for the model speed used by the monitoring is set too high (p2157).
• The smoothing time constant or the threshold values used by the monitoring are set too low (p3236, p3238).

1. Check that the external speed matches the motor speed (compare p1440 and r1443).
2. Check the polarity of the external speed (r1443).
3. Check the interconnection of the connector input and the scaling of the signal (p1440, p2000).
4. If no external encoder signal is being used: check the speed signal r0061. If it shows significant ripple, check the speed encoder and, if required, increase p0492.
5. The monitoring itself is set up in p2149 (monitoring configuration).

• r2169 — the smoothed actual speed of the motor model; one of the two signals this monitoring compares.
• r1443 — the speed actual value at the actual-value input of the speed controller (the external speed); the second compared signal, to be checked alongside r2169.
• p3236 — speed threshold value 7: the tolerance threshold the speed difference may not exceed.
• p3238 — how long the deviation between motor-model speed and external speed is tolerated before the fault is raised.
• p1440 — interconnects the external speed signal to the actual-value input; check this interconnection.
• p2000 — reference speed / reference frequency; the scaling against which the external signal is evaluated.
• r0061 — the unsmoothed actual speed; check it when no external encoder signal is used.
• p0492 — maximum speed difference per sampling cycle; increase it if r0061 shows significant ripple.
• p2149 — monitoring configuration, where this comparison is configured.

When the fault trips, the drive switches off and the motor coasts to a standstill; the reaction can be configured differently. Acknowledgement is immediate: once the cause has been corrected, the fault can be acknowledged straight away, without any special sequence, and the drive restarted. Where the condition is configured to be output with no reaction (N), the drive neither trips nor expects an acknowledgement — reaction and acknowledgement are then both NONE.