Common Causes Of Inverter Overload Faults

Inverter overload faults are a common problem in industrial settings. Essentially, the inverter detects that the output current continuously exceeds its rated load capacity protection value. The causes can be mainly categorized into mechanical, electrical, parameter-related, and inverter-related factors.

I. Mechanical Load Causes
This is the most direct cause: the actual load driven by the motor is too large.

1. Mechanical jamming or stall: The current will rise sharply, leading to instantaneous overload.

2. Overload: Incorrect selection, the motor operating under overload conditions for extended periods.

3. Motor Body Faults:
Winding damage: Insulation aging, inter-turn short circuits, resulting in excessively high no-load current.
Bearing damage: Worn, insufficient lubrication, or damaged bearings in the motor or load machinery, leading to a significant increase in frictional resistance.

Poor heat dissipation: Damaged fan, blocked air ducts, causing the motor to overheat.

II. Electrical Motor Causes
1. Motor problems:
Deteriorated motor insulation: Decreased insulation between windings or to ground, leading to increased current.

Inter-turn short circuit: A slight inter-turn short circuit can increase motor current, reduce output, and lead to overload.

Poor heat dissipation: A damaged motor fan or blocked air ducts can cause the motor to overheat and reduce its thermal load capacity.

2. Power supply issues:

Low input voltage: When the mains voltage is too low, the inverter needs to increase current to maintain output power, leading to overload.

Input phase loss: This causes a drop in DC bus voltage and an increase in unbalanced output current.

III. Improper Parameter Settings
Improper parameter settings prevent the inverter from correctly matching the load.

1. Incorrect Motor Parameter Settings: The motor's rated current is set too low, causing the inverter to trigger protection prematurely.

2. Insufficient Acceleration Time: Too rapid motor acceleration requires excessive acceleration torque, easily triggering overload.

3. Inappropriate V/F Curve or Torque Boost: Excessive low-frequency torque boost causes a sharp increase in current, leading to overload. An unsuitable V/F curve.

4. Inappropriate Overload Protection Level Settings: The setting is too sensitive.

IV. Inverter Malfunctions

1. Current Detection Unit Malfunction: A faulty Hall sensor or abnormal related circuitry causes the detected current value to be higher than the actual value, resulting in a false overload alarm.

2. Cooling System Malfunction: A damaged cooling fan, blocked air ducts, or dust accumulation on the heat sink leads to internal overheating, performance degradation, or false alarms.

3. Aging Main Circuit Components: For example, a decrease in the capacitance of the filter capacitor affects the stability of the DC bus and the accuracy of current detection.