I. Overload Protection (OL)

1.  When "FO OL" is displayed on the AC drive keypad with "OL" blinking, press the "∧" key to enter the fault inquiry mode. You can view parameters such as the operating frequency, output current, and operating status at the time of the fault. Based on the operating status and the magnitude of the output current: If the output current is excessively high, it may be caused by an excessive load. In this case, adjust acceleration/deceleration times, the V/F curve, torque boost, etc. If the overload persists, consider reducing the load or replacing the AC drive with one of higher capacity.

2.  If the output current during the fault inquiry is not high, check whether the parameters of the electronic thermal overload relay are set appropriately.

3.  Check the Hall sensor and its wiring for any issues.

II. Overheating Protection (OH)

1.  Check if the temperature switch wire connector is properly inserted. Use a multimeter to test whether the temperature switch wire is open-circuit. If it is, it can be concluded that the temperature switch wire is broken or the temperature switch itself is faulty.

2.  Overheating protection caused by a faulty cooling fan.

3.  High ambient temperature leading to poor heat dissipation, causing high internal temperature of the AC drive and triggering overheating protection.

4.  For AC drives with a seven-unit IGBT module including the rectifier bridge, temperature detection is performed by utilizing the resistance change of the thermistor inside the IGBT. If an "OH" overheating protection occurs, possible causes are:

    ① The comparator is faulty, outputting a high level.

    ② The comparator's reference resistor has changed value, resulting in a lower comparison voltage.

    ③ Abnormal resistance of the thermistor inside the IGBT.