F31120 — Encoder 1: Encoder power supply fault

F31120 reports that the drive has detected a fault in the power supply it provides for encoder 1. The S120/S150 list manual titles the code Encoder 1: Encoder power supply fault, the G130/G150 list manual Encoder 1: Power supply voltage fault; both describe the same monitoring with the same bit assignments and the same remedies, so this page treats them as one. The drive writes the fault cause into r0949, and interpreted as a binary number every set bit names the supply condition that tripped. Depending on how the drive is configured, the same condition can also be output with no reaction (N) or as an alarm (A) instead of a fault.

• The encoder 1 power supply monitoring has tripped; which of the monitored supply conditions fired is readable from the binary fault value in r0949.
• The manual warns specifically about cabling: If the encoder cables 6FX2002-2EQ00-.... and 6FX2002-2CH00-.... are interchanged, this can result in the encoder being destroyed because the pins of the operating voltage are reversed.

1. Read the fault value in r0949 as a binary number; which bit or bits are set decides the steps that follow.
2. Bit 0 (undervoltage on the sense line): check that the correct encoder cable is connected, check the plug connections of the encoder cable, and with an SMC30 check the parameterization in p0404.22.
3. Bits 1, 2 or 3 (overcurrent in the encoder power supply or on the resolver excitation cables): check that the correct encoder cable is connected; if the condition persists, replace the encoder or the encoder cable.
4. Bit 5 (overcurrent at the EnDat connection of the converter): check that the measuring unit is correctly connected at the converter; replace the measuring unit or the cable to the measuring unit.
5. Bits 6 or 7 (overvoltage or hardware fault at the EnDat connection of the converter): replace the defective EnDat 2.2 converter.

The drive enters the fault cause into r0949; interpret the value as binary. Each bit names one condition:

• Bit 0: undervoltage condition on the sense line.
• Bit 1: overcurrent condition for the encoder power supply.
• Bit 2: overcurrent condition for encoder power supply on cable resolver excitation negative.
• Bit 3: overcurrent condition for encoder power supply on cable resolver excitation positive.
• Bit 4: the 24 V power supply through the Power Module (PM) is overloaded.
• Bit 5: overcurrent at the EnDat connection of the converter.
• Bit 6: overvoltage at the EnDat connection of the converter.
• Bit 7: hardware fault at the EnDat connection of the converter.

For bit 4 the manual names no separate remedy.

• r0949 — fault value: read it as binary here; each set bit identifies the encoder power supply condition behind F31120.
• p0404 — effective encoder configuration: with an SMC30 and bit 0 set, check the parameterization in p0404.22.
• p0491 — motor encoder fault response ENCODER: the manual cross-references it for this code; it sets how the drive responds when this encoder fault occurs.

As a fault, F31120 requires a PULSE INHIBIT acknowledgment: the drive pulses must be inhibited before the fault can be cleared, after which the drive can be restarted. Where the drive outputs the same condition with no reaction (N) or as an alarm (A), the manual specifies no reaction and no acknowledgment.