F07551 fault in siemens 6RA80 DC Drive indicate that the No commutation angle information. This means the commutation angle information is missing. This means that synchronous motors cannot be controlled (closed- loop control).

1. check the encoder parameterization (p0404).
2. use an encoder with track C/D, EnDat interface of Hall sensors.
3. use an encoder with sinusoidal A/B track for which the motor pole pair number (r0313) is an integer multiple of the encoder pulse number (p0408).
4. activate the pole position identification routine (p1982 = 1).