Common Causes Of Inverter Overheating Failure

Inverter overheating is a common fault in industrial settings. The core reason is that the heat generated inside the inverter cannot be dissipated in time, causing the temperature to exceed the protection threshold. Common causes can be categorized as follows:

I. Installation Environment
1. High Ambient Temperature: The inverter is installed in a high-temperature environment (such as a boiler room, near a kiln, or an outdoor electrical cabinet in direct sunlight), exceeding its nominal operating temperature.

2. Poor Ventilation:
The installation cabinet is too small, preventing air convection.

Insufficient vertical spacing between the inverter and the cabinet affects airflow; hot air rises, so sufficient clearance is needed at the bottom air inlet.

Other heat-generating components inside the cabinet (such as braking resistors and transformers) are too close to the inverter.

3. Dust Accumulation or Blockage Inside the Cabinet: The inverter's cooling fan inlet or radiator fins are blocked by lint, dust, or grease, causing a sharp decrease in airflow.

The cabinet's dust filter has not been cleaned for a long time.

II. Heat Dissipation Failure
1. Fan Not Turning:
The fan motor is burnt out.

The bearing is seized or excessive dust accumulation causes high resistance. 1. The fan control circuit or temperature switch is damaged.

2. Slow fan speed: Wear on the bearings or abnormal voltage leads to insufficient airflow.

3. Fan is running in the wrong direction: This is extremely rare, but if the wiring is reversed when replacing the fan, the DC fan, which has polarity, will draw air outward instead of blowing it inward, disrupting the heat dissipation airflow.

III. Load Operation

1. Long-term Overload Operation: Excessive motor load causes the inverter output current to consistently approach or exceed the rated current.

2. Frequent Starts/Stops or Rapid Acceleration/Deceleration: Excessive acceleration, deceleration, or start/stop operations result in higher current during acceleration and deceleration, increasing average losses.

3. Poor Motor or Cable Insulation: Minor leakage or inter-turn short circuits in the motor or cable cause reactive or fault components to be included in the inverter output current, increasing losses.

4. Carrier Frequency Setting Too High: A carrier frequency setting that is too high, while reducing motor noise, significantly increases the inverter's switching losses and leads to a noticeable increase in heat generation. This is especially noticeable in quiet operation environments.

IV. Hardware Faults

1. False Overheat Alarms from Temperature Detection Circuit: Aging of the temperature sensor, poor contact, or a faulty detection circuit can cause false overheat alarms.

2. Aging of Power Modules: After prolonged use, internal contact resistance or conduction voltage drop increases, leading to increased losses.

3. Dry thermal grease: The thermal grease between the power module and the heatsink dries out and becomes ineffective after prolonged exposure to high temperatures, hindering heat conduction.

4. Loose main circuit screws: Loose screws at the input/output terminals or internal main circuit connections increase contact resistance, causing localized heat generation and conduction, leading to overall overheating.

If overheating is reported immediately upon power-on after cooling down, it is likely due to a faulty temperature sensor or detection circuit. If overheating is reported only after running for some time, it is likely due to poor heat dissipation or excessive load.