F31117 — Encoder 1: Inversion error signals A/B/R

F31117 reports that on Encoder 1 the evaluation of a square-wave encoder (bipolar, double ended) no longer sees the complementary signals A*, B* and R* as inverted images of A, B and R. The manuals for the G130, G150, S120 and S150 describe this fault alike. Depending on how the drive is configured, the same condition can also be output as an alarm or with no reaction instead of a fault.

For the SMC30 with article number 6SL3055-0AA00-5CA0 or 6SL3055-0AA00-5CA1, for the CUA32 and for the CU310-2 (CU310 in the second manual), the note adds a second situation that raises this fault: a square-wave encoder without track R is in use while track monitoring (p0405.2 = 1) is activated.

• For a square-wave encoder (bipolar, double ended), the signals A*, B* and R* are not applied inverted with respect to the signals A, B and R.
• On the SMC30 with article number 6SL3055-0AA00-5CA0 or 6SL3055-0AA00-5CA1, on the CUA32 and on the CU310-2/CU310: a square-wave encoder without track R is used while track monitoring (p0405.2 = 1) is activated.

1. Check the encoder and its cable.
2. Confirm that the encoder actually outputs the signals together with the associated inverted signals (A* against A, B* against B, R* against R).
3. If the encoder is connected through one of the SMC30 article numbers listed above, check the setting of p0405: p0405.2 = 1 is only possible when the encoder is connected at X520.
4. If the square-wave encoder has no track R, set the jumpers at the encoder terminal: pin 10 (reference signal R) with pin 7 (encoder power supply, ground), and pin 11 (reference signal R inverted) with pin 4 (encoder power supply). The terminal is X520 on the SMC30, X220 on the CUA32 and X23 on the CU310-2; the second manual additionally places the CUA32 jumpers at X23.

The drive puts the fault cause into the message value in binary and also holds it in r0949. The manual decodes it bit by bit:

• Bits 0 ... 15: only for internal Siemens troubleshooting.
• Bit 16: error track A.
• Bit 17: error track B.
• Bit 18: error track R.

• r0949 — fault value: read it in binary for this fault; bit 16, bit 17 or bit 18 names the failed track A, B or R.
• p0405 — square-wave encoder track A/B: its bit .2 is the track monitoring that raises this fault when no track R is wired; with the listed SMC30 versions, p0405.2 = 1 is only permissible at X520.
• p0491 — motor encoder fault response ENCODER: sets how the drive reacts when this encoder fault occurs; the manual cross-refers to it directly under this fault.

Once the cause has been removed, the fault is cleared by an immediate acknowledgement. Where the drive is configured to output the same condition only as an alarm or with no reaction, the manual specifies no acknowledgement for it.