Handling Measures For High Temperature Alarm Of Frequency Converter

A high-temperature alarm from the frequency converter (codes such as OH, OH1, OH2, etc.) is a common fault, usually indicating that the radiator temperature or internal ambient temperature has exceeded the protection threshold. The core approach to troubleshooting is: first, derate the inverter or shut it down for cooling, then check for the heat source. The following are systematic handling measures:

I. Safe Shutdown and Preliminary Inspection
1. Shutdown and Power Disconnection: Stop the inverter's output and disconnect the main circuit power supply.

2. Cooling Wait: Wait at least 10-15 minutes to allow the inverter to cool naturally.

3. Touch Test: After power disconnection, touch the radiator base plate with an infrared thermometer or the back of your hand. If it is hot to the touch (>80℃), it is confirmed to be truly overheated; if it is only warm but reports a high temperature, it may be a sensor or circuit problem.

II. System Troubleshooting

(I) Environment and Ventilation
1. Ambient Temperature: Measure the ambient temperature around the inverter. If it exceeds 40℃ (50℃ for some models), ventilation needs to be improved or air conditioning installed. 2. Ventilation Space: At least 10 cm of ventilation space should be reserved above and below the frequency converter, ensuring unobstructed airflow at the inlet and outlet.

3. Heat Accumulation Inside the Cabinet: Are there other heat-generating components around the control cabinet? It is recommended to remove these heat-generating components or install a forced exhaust fan.

(II) Cooling System

1. Fan Inspection: After powering on, observe whether the cooling fan rotates normally. If the speed is significantly slower, noisier, or not rotating at all, the fan needs to be replaced.

2. Airflow Blockage: Disconnect the power supply and use dry, low-pressure compressed air to blow air from bottom to top or from inside to outside the heat sink and airflow duct.

Common blockage points: Inlet filter, dust accumulation at the base of the heat sink, lint on the fan blades.

3. Filter Cleaning: If the cabinet door has a dust filter, remove it, rinse with clean water, and let it dry.

(III) Load and Operating Parameters

1. Output Current: Check whether the output current of the inverter is close to or exceeds the rated value during operation. Long-term overload operation will generate a lot of heat. Reduce the load, extend the acceleration and deceleration time, or replace with a higher power inverter.

2. Carrier Frequency: Check whether the "carrier frequency" parameter is set too high (e.g., >8kHz). The higher the carrier frequency, the more heat the inverter generates. Appropriately reduce the carrier frequency. 3. Motor Abnormality: Poor motor insulation or stalled motor can also cause excessive inverter output current. Disconnect the motor wires and test the machine under no-load to see if the alarm persists.

(IV) Sensors and Hardware

1. Temperature Sensor: Check if the thermistor mounted on the heat sink is open-circuited or short-circuited (measure with a multimeter in resistance mode; at room temperature, it is typically a few kΩ to tens of kΩ).

2. Control Board Fault: If the sensor resistance is normal but the displayed temperature is abnormally high, the mainboard detection circuit may be damaged.