1
Motor winding or cable insulation failure
criticalCheckDisconnect motor leads from the drive, then megger winding-to-ground at 500V. Expect ≥1 MΩ cold. Never megger with the drive connected.
FixRepair or replace the motor / cable. Wet or oil-soaked motors sometimes recover after baking out.
ToolsInsulation tester (megger)
SafetyDisconnect the drive completely before meggering — IGBTs will be destroyed otherwise. Discharge windings to ground afterwards.
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2
Accel ramp too short for the airend load
medRotary screw
CheckCompare accel time with OEM value; note whether trips occur only at start.
FixIncrease accel time in small steps; verify the inlet valve is closed during start.
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3
Loading against pressure (inlet valve not closing)
highRotary screw
CheckVerify the load solenoid is de-energised at start and the inlet valve is shut.
FixRepair or replace the load solenoid / inlet valve so the machine always starts unloaded.
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4
Failed output IGBT module
criticalCheckWith power off and bus discharged, diode-check the drive output terminals U, V, W to DC+ and DC−; readings should be symmetrical.
FixReplace the drive or power module.
ToolsMultimeter (diode mode)
SafetyWait for the full DC bus discharge time on the drive label and verify 0 VDC at the bus terminals before touching anything.
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Safety
Lockout/tagout before opening enclosures. Verify zero energy. Bleed system pressure before opening any pneumatic connection.