OH3 External Overheat fault in Toshiba drive
OH3 External Overheat (Analog Input) fault in Toshiba drive
Description This is a user-configured fault. Toshiba drives allow you to use an Analog Input (like VI or II) as a thermal protection input for a PTC thermistor. OH3 trips when the voltage on this input drops below or exceeds a set threshold, indicating the motor is hot. Causes
1. Motor Overheating: The thermistor embedded in the motor is hot.
2. Wiring Break: The PTC circuit is open. Since the drive injects current and reads voltage, an open wire looks like infinite resistance (or high voltage), triggering the trip.
3. Parameter Mismatch: The input terminal (e.g., VI) was accidentally assigned to "PTC" function when it is actually being used for a speed pot. Solution Check Parameter F109 (VI Input Function) or similar. If it is set to "PTC Thermal," the drive expects a temperature sensor. If you are using a potentiometer for speed control, change this parameter back to "0" (Frequency Reference).
If you are using a PTC, measure the resistance of the sensor loop. It should be low (e.g., 50-200 ohms) when cold. If it is infinite, the wire is broken.
Description This is a user-configured fault. Toshiba drives allow you to use an Analog Input (like VI or II) as a thermal protection input for a PTC thermistor. OH3 trips when the voltage on this input drops below or exceeds a set threshold, indicating the motor is hot. Causes
1. Motor Overheating: The thermistor embedded in the motor is hot.
2. Wiring Break: The PTC circuit is open. Since the drive injects current and reads voltage, an open wire looks like infinite resistance (or high voltage), triggering the trip.
3. Parameter Mismatch: The input terminal (e.g., VI) was accidentally assigned to "PTC" function when it is actually being used for a speed pot. Solution Check Parameter F109 (VI Input Function) or similar. If it is set to "PTC Thermal," the drive expects a temperature sensor. If you are using a potentiometer for speed control, change this parameter back to "0" (Frequency Reference).
If you are using a PTC, measure the resistance of the sensor loop. It should be low (e.g., 50-200 ohms) when cold. If it is infinite, the wire is broken.
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