The Problem: Rotatable Sensor Disc in the 1FT5072
The Siemens 1FT5072-1AC71-1AB0 servomotor contains a disc (part no. 165 417 4201c) carrying three HKZ101E sensors mounted in the NDE (non-drive end) motor shield. Because the disc can be rotated within the shield, removing it during a bearing replacement destroys the commutation reference. If the disc is refitted at an arbitrary angle, the drive receives incorrect rotor-position information, producing poor torque, rough running, or failure to start. The disc angle must be restored to the factory position before the motor is recommissioned.
First Check: Look for Factory Alignment Marks
Before rotating the disc, inspect the disc itself, the NDE shield, and the sensor carriers for factory scribe marks, paint dots, or index notches. If a mark exists, reassemble the disc to that mark and verify with a no-load test run. If no marking is present — or if the disc was already moved before the marks were recorded — the position must be re-established by alignment rather than by guesswork, because a trial-and-error fit can leave the motor running with wrong commutation timing.
Official Procedure: Siemens 1FT5 Maintenance Manual
Siemens documents the service procedure for this motor family in the manual Three-phase servomotor 1FT5 06.-13 — Maintenance, Edition 04.93, Order No. 610.43098.02. Obtain this document through Siemens Industry Online Support before attempting alignment; it is the authoritative source for the sensor-disc positioning method on the 1FT5 series. Do not rely on generic servo practice, since the correct disc angle is defined relative to this motor's winding and feedback arrangement.
Drive-Based Alignment and Service Options
Many servo inverters include a commissioning function that measures the alignment (resting) angle of the position feedback. Whether the specific inverter driving your 1FT5072 offers this function is not confirmed by the available evidence — check the drive's commissioning documentation for a commutation/angle measurement routine before assuming it exists. If neither a drive function nor the manual procedure is practical in-house, the remaining options are a specialist repair shop equipped for hall sensor and encoder alignment, or your regional Siemens Service organization, both of which can set the disc angle with dedicated equipment.
FAQ
What position feedback does the Siemens 1FT5072-1AC71-1AB0 use?
The motor uses a rotatable disc (part no. 165 417 4201c) fitted with three HKZ101E sensors, mounted in the NDE motor shield. Disc angle defines the commutation reference, so it must be restored after any disassembly.
Is there an official alignment procedure for the 1FT5 servomotor hall sensors?
Yes. Siemens covers it in the manual "Three-phase servomotor 1FT5 06.-13 — Maintenance, Edition 04.93, Order No. 610.43098.02," available via Siemens Industry Online Support.
Can the servo drive measure the hall sensor alignment angle automatically?
Many servo inverters provide a resting-angle/alignment measurement function, but support in your specific drive is unconfirmed — verify in the drive's commissioning documentation. Otherwise use the manual procedure or Siemens Service.