A07400 — Drive: DC link voltage maximum controller active

A07400 signals that the DC link voltage maximum controller (Vdc_max controller) has switched in. The DC link voltage has passed the upper switch-in threshold — the level is shown in r1242 (vector control) or r1282 (U/f control), while the SERVO description names p1244 as the threshold. While it is active, the controller lengthens the ramp-down times on its own so that the DC link voltage (r0070) stays within the permissible limits. The drive does not trip, but the manual warns that the actual speed can deviate from the setpoint (a system deviation) for as long as the controller intervenes. The manual also notes a side effect: with the Vdc_max controller switched out (disabled), this message is the reason the ramp-function generator output tracks the speed actual value. Depending on how the drive is configured, the same condition can also be signalled with no reaction (N) instead of as this alarm.

• The DC link voltage has risen above the upper switch-in threshold of the Vdc_max controller; for vector control this level is shown in r1242, for U/f control in r1282.
• The SERVO description names the upper switch-in threshold p1244 as the trigger instead, and otherwise reports the same behaviour.

1. If the controller should not intervene at all, give the drive more time to ramp down: increase p1121 (ramp-function generator ramp-down time) and p1135 (OFF3 ramp-down time).
2. Alternatively, switch the Vdc_max controller off: p1240 = 0 for vector control, p1280 = 0 for U/f control (the SERVO remedy names only p1240 = 0).
3. If the ramp-down times must stay as they are, use a chopper or regenerative feedback unit — the SERVO wording of the same measure says Braking Module or regenerative feedback unit.

• r1242 — switch-in level of the Vdc_max controller (vector control); the alarm reports that this level was exceeded.
• r1282 — the same switch-in level for U/f control.
• r0070 — the DC link quantity the controller holds within the permissible limits while it is active.
• p1240 — Vdc controller configuration; set it to 0 to switch the controller off under vector control.
• p1280 — the same configuration for U/f control; 0 switches the controller off.
• p1244 — upper DC link voltage threshold, named as the activation threshold in the SERVO description.
• p1121 — ramp-function generator ramp-down time; increase it so the controller need not intervene.
• p1135 — OFF3 ramp-down time; the second ramp-down time the remedy offers to increase.

No acknowledgement is required. This alarm is automatically withdrawn after the upper threshold has been distinctly exceeded. The SERVO text even states a remedy is «Not necessary» for the alarm itself; the measures above are only for keeping the controller out of the ramp-down permanently.