F52970 — OA: Power unit not permissible

F52970 is raised when the power unit connected to this Control Unit is not permissible — the manual carries the message under the title OA: Power unit not permissible, i.e. the power unit and the Control Unit that are currently combined do not form an allowed pairing. The drive coasts down, and a plain acknowledgment does not remove the fault: the power supply has to be switched off and on again before the drive will restart. The remedy is a hardware one — replace the power unit with a permissible one; the manual handles this in its converter replacement procedure, which is summarized in the checks below.

• The power unit connected to this Control Unit is not permissible.

1. Confirm that the replacement is permissible. A converter may only be replaced by another converter under certain preconditions: the new converter must have the same or a more recent firmware version, and either the same power rating, or a different power rating at the same frame size — in that case the quotient (rated motor power)/(rated converter power) must lie between 0.25 and 1.5. Where the preconditions are not met, the drive must be recommissioned after the replacement.
2. Back up the settings. Upload the settings of the converter being replaced to an external storage medium, e.g. a memory card. If no backup exists, the new converter must be commissioned as a completely new converter.
3. Disconnect the line voltage and observe the discharge time. After the supply is switched off, it can take up to 5 min. until the capacitors have discharged to a non-hazardous level; check the voltage at the converter connections before removing any connection cables. Note also that components such as the heat sink or line reactor can remain hot for some time after operation — do not touch them during or immediately following operation.
4. Swap the hardware. Remove the connecting cables, remove the defective converter, install the new converter and reconnect all cables. Connect the 3 phases of the motor lines in the correct sequence — interchanging two phases reverses the direction of rotation and can damage the machine or system. Repairs may only be carried out by Siemens customer service, a repair center authorized by Siemens, or specialist personnel thoroughly acquainted with the warnings in the manual; only original spare parts may be used.
5. Restore or create the settings. Switch the line voltage on. If a backup exists, download it to the new converter — automatically from the memory card at power-up, manually from the memory card via the BOP-2, or from the IOP-2 operator panel (a memory card can store up to 99 different backups). Otherwise commission the converter as a new converter.
6. Check the download result and the drive. If the converter outputs Alarm A01028, the loaded settings are not compatible: delete the alarm with p0971 = 1 and recommission the drive. If no A01028 appears, the converter accepts the loaded settings; back the settings up so they are protected against power failure, and check that the new converter works properly.

• p0971 (Save parameters / Save par) — enter p0971 = 1 if Alarm A01028 appears after a settings download: the save deletes the alarm, and the drive must then be recommissioned.

A normal acknowledgment does not clear this fault: it is acknowledged only by switching the converter power supply off and on again. Because the cause is the hardware pairing, the power unit must be replaced with a permissible one first; once the replacement is installed and its settings loaded or newly commissioned, the next power-up acknowledgment clears F52970 and the drive can restart.