| Motor Switch at Running | Conduct motor switch in the running process of the frequency invert |
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ERR35 – Motor Switching While Running
What this means
ERR35 occurs when the VFD detects that the motor was connected, disconnected, or switched while the VFD was actively running.
In simple terms:
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The spindle or motor connection changed while powered
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The VFD detected an unsafe electrical condition
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The VFD shut down to protect itself and the motor
This is a safety protection fault, not a performance issue.
Why This Is a Problem
VFDs are designed to drive a motor through a continuous, stable connection.
Switching the motor while running can:
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Create large voltage spikes
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Damage output transistors
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Destroy internal current sensing components
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Permanently damage the VFD
ERR35 exists to prevent catastrophic hardware failure.
Common Causes
1. Plugging or unplugging the spindle while powered
Examples:
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Connecting or disconnecting the spindle cable
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Reseating aviation connectors
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Moving motor cables between machines
Even if the spindle is not spinning, this can still trigger ERR35 if the VFD is enabled.
2. Using a switch or relay between VFD and motor
Any device placed between the VFD and spindle is unsafe, including:
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Manual switches
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Relays
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Contactors
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Tool-changing systems not designed for live switching
The motor must be directly wired to the VFD at all times.
3. Automatic tool changers wired incorrectly
If an ATC system:
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Interrupts motor phase lines
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Switches motor connections during operation
ERR35 will occur and damage may follow.
4. Power cycling only part of the system
For example:
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VFD powered
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Motor power disconnected
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Control logic still active
This can confuse the VFD into thinking the motor was switched live.
What to Do If ERR35 Appears
Step 1: Shut everything down
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Stop the spindle
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Power off the VFD
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Disconnect input power completely
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Wait 2–3 minutes
Step 2: Inspect motor wiring
Check for:
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Loose connectors
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Damaged aviation connectors
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Improper switches or relays in motor wiring
Step 3: Remove any switching devices
The motor must be:
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Permanently connected
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Directly wired
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Never switched while powered
What Will Not Fix ERR35
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Changing feeds or speeds
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Adjusting acceleration
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Re-running motor identification
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Clearing the alarm without correcting wiring
ERR35 will return until the wiring issue is resolved.
Important Warning
Repeated ERR35 events can permanently damage:
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Output transistors
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Driver boards
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Current sensing circuits
If ERR35 has occurred multiple times, further operation may not be safe.
Summary
ERR35 means the motor connection changed while the VFD was running.
Most common causes:
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Plugging or unplugging the spindle while powered
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Using switches or relays between VFD and motor
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Incorrect ATC wiring
This is a wiring and usage issue, not a spindle defect.
