Siemens · SINAMICS G120
One of the inverter's output phases to the motor is disconnected or open-circuited. This causes unbalanced current flow to the motor, leading to excessive motor heating, reduced torque, and potential damage to both the motor and the inverter if operation continues.
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De-energize the drive and disconnect the motor cables (U, V, W) from the drive's output terminals.
Measure the resistance between each pair of motor phase terminals (e.g., U-V, V-W, W-U) directly at the motor, ensuring readings are balanced and within specification.
Check continuity of each motor cable conductor (e.g., U, V, W) from the drive end to the motor terminal box using a multimeter.
Inspect and tighten all connections at the drive output terminals (e.g., U, V, W) and the motor terminal box.
If an output contactor or reactor is used, bypass it temporarily for testing or measure its phase resistances/continuity.