F33120 — Encoder 3: Encoder power supply fault

F33120 reports that the drive has detected a power supply fault on encoder 3, the third encoder connected to the drive object. The manuals title the message Encoder 3: Encoder power supply fault and Encoder 3: Power supply voltage fault — the meaning is the same. Which condition actually raised the code is told by the fault value in r0949, which must be read as a binary number. Depending on how the drive is configured, the same condition can also be output as an alarm or without any reaction instead of a fault.

• The sense line of the encoder reports an undervoltage (bit 0 of the fault value).
• The encoder power supply is drawing an overcurrent (bit 1).
• An overcurrent flows in the encoder power supply on the cable for the resolver excitation, on the negative line (bit 2) or on the positive line (bit 3).
• The 24 V power supply through the Power Module (PM) is overloaded (bit 4).
• At the EnDat connection of the converter the manual names an overcurrent (bit 5), an overvoltage (bit 6) or a hardware fault (bit 7).
• The manual warns that interchanging certain encoder cables it names reverses the pins of the operating voltage, which can destroy the encoder.

1. Read the fault value in r0949 as a binary number and note which bits are set.
2. Bit 0: check that the correct encoder cable is connected, check the plug connections of the encoder cable, and on an SMC30 check the parameterization in p0404.22.
3. Bits 1, 2 or 3: check that the correct encoder cable is connected; if it is, replace the encoder or the encoder cable.
4. Bit 5: check that the measuring unit is correctly connected at the converter; otherwise replace the measuring unit or the cable to the measuring unit.
5. Bits 6 or 7: replace the defective EnDat 2.2 converter.

The drive stores the fault cause in r0949; interpret it in binary, one condition per bit:

• 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

• r0949 — read the stored fault value here in binary; the set bits tell you which power supply condition triggered F33120 and therefore which check to run.
• p0404 — the encoder configuration effective in the drive; when bit 0 is set on an SMC30, verify its parameterization in p0404.22.

The fault stops the drive with an OFF1. After the cause found via the fault value has been corrected, acknowledge the fault while the pulses are inhibited; the drive can then be restarted.