F30074 — Communication error between the Control Unit and Power Module

F30074 means that communication between the Control Unit (CU) and the Power Module (PM) over their internal DRIVE-CLiQ interface is no longer possible. The manuals' most common explanation is a CU that was withdrawn from the Power Module during operation or is incorrectly inserted. Depending on the drive's configuration, the same condition can also be issued as an alarm (A) instead of a fault. The fault value in r0949, interpreted hexadecimal, tells you which specific situation the drive recorded.

• The CU has been withdrawn from the Power Module or is incorrectly inserted, so the interface link between CU and PM is down.
• On the G120C the manual names one further possible cause: the external 24 V Control Unit power supply has dipped to ≤95% of the rated voltage for ≤3 ms.
• Everything else depends on the fault value: withdrawal during operation although encoderless safe motion monitoring is enabled, or a CU mounted on a Power Module with a different code number, with a different serial number despite the same code number, or of a power/performance class (chassis unit) that is not supported — see the decoding below.

1. Read the fault value in r0949 and interpret it hexadecimal; match it against the decoding below to see which situation the drive recorded.
2. If the CU was withdrawn or is not properly seated, reinsert the Control Unit — or the Control Unit Adapter (CUAxx) on the chassis units — onto the original Power Module and continue operation.
3. Check the external 24 V supply of the Control Unit, in particular on the G120C, where a dip to ≤95% of the rated voltage for ≤3 ms is named as a possible cause.
4. If required, carry out a POWER ON of the CU and/or the CUA. For fault value 1 hex, the G120/G120XA manuals prescribe a POWER ON of the Control Unit; for fault values 0 hex and 20A hex they call for inserting the Control Unit on an appropriate Power Module, with a POWER ON if required.

The manuals print the message value as %1: it is the fault value, stored in r0949 and to be interpreted hexadecimal. Decoding as the manuals give it:

• 0 hex — a Control Unit with external 24 V supply was withdrawn from the Power Module during operation, or with the Power Module switched off the external 24 V supply for the Control Unit was interrupted for some time.
• 1 hex — the Control Unit was withdrawn during operation although the encoderless safe motion monitoring functions are enabled; this is not supported. After re-inserting the Control Unit, communication to the Power Module is no longer possible.
• 20A hex — the Control Unit was inserted on a Power Module which has another code number.
• 20B hex — the Control Unit was inserted on a Power Module which, although it has the same code number, has a different serial number. The G120 and G120XA manuals add that the Control Unit then executes an automatic warm restart to accept the new calibration data.
• 601 hex — the Control Unit was inserted on a Power Module whose power/performance class (chassis unit) is not supported.

• r0949 — displays the fault value for this code; read it here and interpret it hexadecimal to identify which of the CU/PM situations listed above occurred.

First remove the cause — reinsert the CU (or CUAxx), restore the external 24 V supply, or mount the CU on the matching Power Module. The fault is then acknowledged immediately, without waiting time, and the reaction is none: the code itself does not switch the drive off. For fault value 1 hex a POWER ON of the Control Unit is required before returning to service; on the chassis units a POWER ON of the CU and/or the CUA is carried out where required. When the drive raises the same condition as an alarm (A), it requires neither reaction nor acknowledgment.