| Encoder Fault | The frequency inverter is unable to identify the data of the encoder |
|
ERR25 – Encoder Fault
What this means
ERR25 indicates that the VFD is unable to read or interpret encoder data.
In simple terms, the VFD is expecting feedback from an encoder, but the data it is receiving is missing, invalid, or inconsistent.
Important Note for Most CNC Users
Most CNC spindle systems do NOT use encoders.
If your spindle setup does not include an encoder or PG (pulse generator) card:
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ERR25 typically means encoder mode was enabled unintentionally
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The fault does not indicate a spindle or VFD hardware failure
This is very often a configuration issue.
Why This Happens
ERR25 occurs when the VFD is configured for encoder-based feedback control, but:
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No encoder is present
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The encoder type does not match configuration
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Encoder wiring is incorrect
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The encoder signal is unstable or missing
Most Common Causes We See
1. Encoder mode enabled without an encoder (most common)
This is by far the most frequent cause.
If the VFD expects encoder feedback but none exists, ERR25 will trigger immediately.
2. Incorrect encoder type configured
Encoders vary by:
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Resolution
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Signal type
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Output format
If the configured encoder type does not match the installed encoder, the VFD cannot decode the signal.
3. Encoder wiring issues
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Incorrect terminal connections
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Reversed signal polarity
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Broken or loose wires
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Missing encoder power supply
Encoder wiring must be exact.
4. Faulty encoder or PG card (less common)
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Encoder hardware failure
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PG card failure or improper installation
This is rare and usually only considered after wiring and configuration are verified.
What to Check First
Step 1: Confirm whether your system actually uses an encoder
Ask:
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Does your spindle include an encoder?
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Is there a PG card installed in the VFD?
If not, encoder mode should be disabled.
Step 2: Disable encoder feedback if not required
For most CNC spindle setups:
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Disable encoder or closed-loop feedback modes
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Use standard open-loop RPM control instead
This typically resolves ERR25 immediately.
Step 3: If an encoder is used, verify configuration
Confirm:
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Encoder type matches the hardware
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Encoder resolution is set correctly
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Feedback mode is appropriate for the application
Step 4: Inspect encoder wiring
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Power down the VFD
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Check all encoder connections
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Verify correct terminals and polarity
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Inspect for damaged or loose wires
Step 5: Inspect encoder hardware (if applicable)
If wiring and configuration are correct:
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Inspect the encoder itself
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Verify PG card installation
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Check for visible damage
What ERR25 Is Not
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Not a spindle motor fault
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Not a cutting load issue
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Not a voltage or current problem
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Not EMI related
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Not a controller software issue
ERR25 is strictly related to encoder feedback configuration or hardware.
Recommended Action for CNC Spindle Systems
For the vast majority of CNC spindle applications:
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Encoder feedback is not required
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Encoder modes should remain disabled
This avoids unnecessary complexity and nuisance faults.
Summary
ERR25 means the VFD cannot identify valid encoder data.
Most common causes:
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Encoder mode enabled without an encoder
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Incorrect encoder configuration
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Encoder wiring issues
If your spindle does not use an encoder, disabling encoder feedback is usually the correct solution.
