The inverter circuit module's function is to systematically control the on/off switching of the main switching devices in the inverter to obtain three-phase AC power of any frequency; the intermediate DC link module is used to buffer reactive power. The control circuit module is the command center of the frequency converter, mainly composed of operational circuits, detection circuits, control signal input and output circuits, and drive circuits. It mainly performs switching control of the inverter, voltage control of the rectifier, and various protection functions, and is also the part that frequently experiences failures.
I. Fault Types
When the frequency converter fails to work properly, it may malfunction, and the following types of faults may occur depending on its location:
1. Power supply failure: refers to the fault in the power grid to which the frequency converter is connected, such as overvoltage, undervoltage, three-phase imbalance, poor contact or damage of the main switch, and phase loss caused by fuse blowing.
2. Internal faults: These refer to faults inherent in the inverter itself, which may occur in the DC link, such as short circuits, DC overvoltage, and undervoltage; in the inverter link, such as output overvoltage, undervoltage, imbalance, and overcurrent; and in the control link, where more faults may occur.
3. Load fault: refers to motor faults, such as phase loss, overload, short circuit, etc.
When a fault occurs, the frequency converter will refuse certain operations, mainly due to its protection circuitry kicking in.
II. Causes of the Fault
Inverters can experience various malfunctions during operation. The causes of these malfunctions are numerous, but can be broadly categorized into two main reasons:
1. External causes: Caused by external factors of the frequency converter, such as operation error, incorrect parameter setting, excessive load, damage to external cooling fan, excessive temperature, external interference, and problems with the power grid itself.
2. Internal causes: Caused by internal factors of the frequency converter, such as short circuit, damaged grounding components, insulation damage, poor contact of connectors, module damage, etc.
When dealing with faults, take corresponding solutions for different causes.
