Danfoss · VLT Micro Drive FC 51
The motor's thermistor input indicates an over-temperature condition, or the thermistor or its connection is disconnected. This provides direct thermal protection for the motor, signaling a critical overheating risk if not addressed.
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Measure the resistance of the motor thermistor directly at the motor terminals using an ohmmeter (e.g., 250 Ohms to 1.5 kOhms for PTC at room temp).
Verify continuity of the thermistor wiring from the motor to the drive's dedicated thermistor input terminals (e.g., X3:1, X3:2).
Check the motor's operating current (P0-03) and motor surface temperature with an infrared thermometer to confirm actual thermal state.
Ensure the thermistor input parameter (P3-05) is correctly configured for the connected sensor type (e.g., PTC, KTY, NTC).
Inspect the motor cooling fan for proper operation and clean any debris from motor cooling fins.