| Fast Current-limiting Timeout | The running current of the frequency inverter continues to be larger, which exceeds allowable current-limit time |
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ERR34 – Fast Current-Limiting Timeout
What this means
ERR34 indicates that the VFD entered current-limiting mode to protect itself, but the excessive current condition lasted longer than the VFD allows, so it shut down.
In simple terms:
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The spindle was drawing too much current
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The VFD tried to limit it automatically
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The overload condition did not clear in time
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The VFD stopped to prevent damage
This is a load-related fault, not an internal electronics failure.
What Causes ERR34
1. Cutting load is too high
The most common cause.
Examples:
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Too deep of a cut
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Feed rate too aggressive
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Large diameter tooling on a smaller spindle
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Dull or damaged tool
The spindle demands more torque than the motor or VFD can supply continuously.
2. Mechanical stall or binding
If the spindle is suddenly slowed or stopped:
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Tool collision
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Material shifting
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Chips packing in a pocket
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Bearing or collet issue
The VFD will see sustained high current and trigger ERR34.
3. Undersized spindle or VFD for the job
If the job consistently pushes the limits:
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Motor power may be insufficient
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VFD current rating may be too low
For example, heavy cuts in aluminum or steel with a smaller spindle.
4. Acceleration into load
If the spindle is:
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Still ramping up to speed
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Already near current limit
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Then immediately engages material
The combined load can exceed allowable current-limit time.
What to Check First
Step 1: Reduce cutting load
Start with the easiest fixes:
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Reduce depth of cut
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Reduce feed rate
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Increase RPM if tooling allows
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Use smaller tooling where possible
If ERR34 disappears, the issue was purely load-related.
Step 2: Inspect tooling and material
Check for:
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Dull bits
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Improper tool length
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Chip evacuation issues
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Workpiece movement or vibration
Step 3: Verify spindle size is appropriate
If ERR34 happens frequently during normal work:
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The spindle may be undersized for the operation
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The VFD may be at its continuous current limit
This is especially common when pushing hobby-class spindles into production-level work.
Step 4: Check acceleration settings
A very aggressive acceleration can contribute to this fault:
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Ensure acceleration time is reasonable
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Avoid engaging material before reaching full RPM
What Will Not Fix ERR34
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Power cycling alone
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Re-running motor identification
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Changing voltage settings
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Replacing cables
ERR34 is not caused by wiring or configuration errors.
When to Contact Support
If ERR34:
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Occurs during light cutting
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Happens immediately at startup
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Appears even when the spindle is unloaded
Please contact support, as that may indicate:
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Incorrect motor parameters
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Incorrect VFD sizing
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A mechanical issue within the spindle
Summary
ERR34 means the VFD was protecting itself from sustained over-current.
Most common causes:
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Cutting too aggressively
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Mechanical stall
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Spindle or VFD undersized for the task
This is a use-case and load issue, not a hardware failure.
