Scope of this technical record
Workflow for speed feedback / tachometer instability before speed-controller tuning or CUD1 replacement.
Qualified personnel only. Keep checks controlled and low speed until feedback is proven.
6RA70 feedback workflow
The workflow separates tachometer, encoder and CUD1 input evidence.
6RA70 speed feedback workflow
Workflow purpose
The workflow proves the selected feedback source, wiring, polarity, scaling, mechanical coupling and actual-speed parameter behavior before internal input or controller tuning decisions.
When to stop
Stop if feedback source is unknown, tach polarity is unknown, encoder channel condition is unknown, or actual speed does not match the machine at low speed. Do not tune around an unproven signal.
Field record checklist
- Feedback source
- Polarity
- Scaling
- Cable / shield
- Coupling
- Actual speed
- CUD1 input
Technical basis and reference documents
This is an independent editorial technical reference. Original manufacturer documentation remains controlling for installation, repair and commissioning decisions.
OEM troubleshooting reference for 6RA70 fault values, tachometer checks, CUD1 / power-interface context and optimization-run faults.
Base operating and commissioning context for SIMOREG DC-MASTER converters, parameterization and speed-sensing setup.
Linked records
Speed-feedback cases should separate the selected feedback source, feedback polarity, scaling, tachometer voltage, encoder pulses, wiring shield, mechanical coupling, analog input or encoder interface, and parameter set. A drive can appear to have a controller problem when the actual feedback signal is inverted, scaled incorrectly, intermittent or mechanically uncoupled.
F050 belongs on an optimization-run evidence route. The fault can be caused by the selected P051 / P052 run, motor data, current-loop preparation, insufficient or excessive armature current, field condition, load torque, blocked machine movement, feedback scaling or fault-value-specific conditions. It should not be reduced to a generic controller failure.
Separates speed-feedback instability into selected feedback source, analog tachometer polarity and voltage, encoder pulse evidence, wiring, shielding, mechanical coupling and CUD1 feedback input boundaries.
Maps F050-style optimization failures through selected run type, commissioning order, motor data, armature current build-up, field proof, load isolation and feedback credibility before a control-board decision.
Turn this record into a qualified service request
A repair decision is much more reliable when the request includes the exact identity of the drive, the first fault evidence and the machine condition when the symptom appeared.
- Complete drive type code / MLFB or nameplate model
- Fault code, fault value and first event before reset
- When the event appears: power-up, enable, ramp, run, decel or stop
- Motor/cable connected or isolated during the symptom
- Visible board, option-card, module and connector identifiers
- Previous repair history, replacement parts and repeat-failure pattern