F07551 — Drive encoder: No commutation angle information

F07551 is raised when the drive encoder (component Encoder 1) is not supplying any commutation angle information. Without this angle the drive cannot control a synchronous motor in closed loop, so it trips the drive. The manual names two distinct situations behind the fault, and the fault value in r0949 tells you which one applies and which drive data set is affected.

The manual names two situations that leave the drive without a commutation angle:

• Fault cause 1 — the motor encoder used does not supply an absolute commutation angle.
• Fault cause 2 — the selected ratio of the measuring gear does not match the motor pole pair number.

1. Read the fault cause and the affected drive data set from r0949 (decimal yyyyxxxx) so you know whether you are dealing with cause 1 or cause 2.
2. Fault cause 1: check the encoder parameterization (p0404).
3. Fault cause 1: use an encoder with track C/D, an EnDat interface or Hall sensors.
4. Fault cause 1: with a sinusoidal A/B track encoder, the motor pole pair number (r0313) multiplied by the gear ratio (p0432/p0433) must be less than the encoder pulse number (p0408) — or an integer multiple of it.
5. Fault cause 1: for motor encoders without absolute position information, activate the pole position identification routine (p1982 = 1).
6. For the VECTOR drive objects, the manual additionally states that after the pole position identification the angular commutation offset should be determined using the encoder adjustment (p1990).
7. Fault cause 2: make sure the quotient of the pole pair number divided by the ratio of the measuring gear is an integer number: (p0314 * p0433) / p0432.
8. Note for operation with track C/D: this quotient must be less than 8.

The message text carries two placeholders: %1 is the fault cause, %2 the drive data set. The drive writes the value into r0949 — interpret it as a decimal number yyyyxxxx:

• yyyy = fault cause: 1 dec — the motor encoder used does not supply an absolute commutation angle; 2 dec — the selected ratio of the measuring gear does not match the motor pole pair number.
• xxxx = the affected drive data set.

• r0949 — fault value: holds this fault's fault cause (yyyy) and affected drive data set (xxxx) as the decimal number yyyyxxxx.
• p0404 — effective encoder configuration: the first thing to check for fault cause 1.
• r0313 — actual (or calculated) motor pole pair number: enters the sinusoidal A/B track condition (r0313 multiplied by the gear ratio versus p0408).
• p0432 / p0433 — gearbox factors for encoder revolutions and motor/load revolutions: together they form the gear ratio used in the sinusoidal A/B condition and in the integer quotient.
• p0408 — rotary encoder pulse number: the sinusoidal A/B condition compares against this pulse number.
• p1982 — pole position identification selection: set it to 1 to activate the routine for motor encoders without absolute position information.
• p1990 — encoder adjustment to determine the angular commutation offset: per the manual for the VECTOR drive objects, use it after p1982 = 1.
• p0314 — enters the quotient (p0314 * p0433) / p0432 that must be an integer for fault cause 2.

F07551 trips the drive and the motor coasts down. The fault is acknowledged immediately, but only after POWER ON: switch the drive supply off and on again before the drive can be restarted.