| Motor-to-ground short circuit | Motor-to-ground short circuit |
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ERR17 – Motor-to-Ground Short Circuit
What this means
ERR17 indicates that the VFD has detected a short circuit between one of the motor phases (U, V, or W) and ground.
In simple terms, one of the spindle’s power conductors is making unintended contact with ground somewhere along the motor cable or inside the spindle.
This is a serious electrical fault, and the VFD is behaving correctly by shutting down immediately to prevent damage or injury.
Why This Happens
Three-phase spindle motors require full electrical isolation between:
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U, V, and W motor phases
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Ground (earth)
If any phase contacts ground, current flows where it should not, creating a potentially dangerous condition.
The VFD continuously monitors for this and faults instantly when detected.
Most Common Causes We See
1. Damaged spindle cable (most common)
Examples:
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Insulation worn through in a drag chain
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Cable pinched by machine motion
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Sharp bends causing internal conductor damage
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Abrasion near strain reliefs or connectors
This is the most frequent cause of ERR17.
2. Connector damage or contamination
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Coolant intrusion into motor connector
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Metal chips or conductive dust inside connector
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Bent or damaged pins contacting the connector shell
Even small contamination can cause a ground fault.
3. Improper wiring or repair
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Exposed conductor touching grounded enclosure
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Incorrect connector re-termination
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Stray wire strands contacting ground
This can occur after maintenance or modifications.
4. Internal spindle motor fault (less common)
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Insulation breakdown inside the motor
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Manufacturing defect or internal damage
This is rare, especially if the spindle was previously operating normally.
What to Do Immediately
Step 1: Stop and power down
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Turn off the VFD immediately
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Unplug the VFD from mains power
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Allow internal capacitors to discharge fully
Do not reset and retry repeatedly.
Step 2: Do not continue operating
Continuing to power the system can:
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Damage the spindle motor
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Damage the VFD output stage
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Create a safety hazard
ERR17 should never be ignored.
What to Check (Visual Only)
Without powering the system:
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Inspect the full length of the spindle cable
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Check drag chain entry and exit points
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Inspect connectors for moisture, debris, or damage
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Look for crushed, cut, or abraded insulation
Do not attempt electrical testing unless you are qualified.
When to Contact Support
If you encounter ERR17:
📩 Immediately contact [email protected]
We will:
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Help identify whether the fault is cable-related or motor-related
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Provide guidance on safe next steps
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Advise on repair or replacement options if needed
Photos of the cable, connectors, and routing are very helpful.
What ERR17 Is Not
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Not a controller or software issue
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Not caused by feed rates or cutting load
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Not a configuration or parameter problem
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Not EMI related
ERR17 is a real electrical fault that must be addressed physically.
Summary
ERR17 means the VFD has detected a motor phase shorted to ground.
Most common causes:
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Damaged spindle cable
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Connector contamination or damage
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Insulation failure
The VFD is protecting you and the equipment.
Power down immediately and contact support before proceeding.
