Siemens · SINAMICS G120
The motor temperature sensor has an open or short circuit, causing a loss of its signal. This results in the drive's temperature monitoring switching to a thermal model instead of direct sensor input, which can lead to inaccurate temperature protection if the underlying issue is not resolved. Continuous operation with a faulty sensor could lead to motor overheating and damage.
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Verify the motor temperature sensor type (e.g., PTC, KTY, PT1000) and measure its resistance at the motor side according to manufacturer specifications (e.g., 25°C resistance).
Measure resistance across the motor temperature sensor input terminals (e.g., X12:1 and X12:2) at the drive with power off; compare to the expected sensor resistance.
Inspect continuity and insulation of the motor temperature sensor cable from the motor to the drive terminals (e.g., using a multimeter for open/short circuits).
Check drive parameters related to temperature monitoring (e.g., P600, P601) to ensure they match the installed sensor type.
Clean and re-terminate the temperature sensor wires at the drive's input terminals (e.g., X12) to ensure solid electrical contact.