Analysis of Common Causes of Frequency Converter Faults

2024-07-10

A frequency converter consists of several parts including the main circuit, power supply circuit, IPM drive and protection circuit, cooling fan, etc. Its structure is mostly unitary or modular. Improper usage methods or unreasonable setting environments can easily cause frequency converter fault or fail to meet expected operational results. To prevent potential issues, it is especially important to carefully analyze the causes of frequency converter fault in advance.

Frequency Converter Fault NO.1: Main Circuit

The main circuit primarily consists of a three-phase or single-phase rectifier bridge, smoothing capacitor, filter capacitor, IPM inverter bridge, current limiting resistor, contactor, and other components. Many common frequency converter faults are caused by electrolytic capacitors. Therefore, on the one hand, it is necessary to consider the appropriate ambient temperature during installation. On the other hand, measures can be taken to reduce ripple current. Using AC or DC reactors to improve power factor can reduce ripple current, thereby extending the life of electrolytic capacitors.

Frequency Converter Fault NO.2: Control Circuit

In the power supply part of the control circuit, particularly the smoothing capacitor and IPM buffer capacitor, their lifespan is affected by temperature and energization time, as the current set value is not affected by the load. The deterioration of capacitors is difficult to measure, and lifespan is mostly estimated based on ambient temperature and usage time. The power circuit board supplies power for control, drive, display, etc., and a short circuit in one path may affect the entire circuit.

Frequency Converter Fault NO.3: Cooling System

The cooling fan in the cooling system has a relatively short lifespan. When nearing the end of its lifespan, the fan generates vibrations, increased noise, and eventually stops rotating, leading to frequency converter faults such as IPM overheating tripping. The lifespan of the cooling fan is dependent on the bearing, approximately 10,000 to 35,000 hours. When the frequency converter operates continuously, the fan or bearing needs to be replaced every 2 to 3 years.

Frequency Converter Fault's Self-Diagnosis and Preventive Functions

Older models of transistor frequency converters have the following drawbacks: easy tripping, difficult to restart, and low overload capacity. Due to the rapid development of IGBT and CPU technology, comprehensive self-diagnosis and fault prevention functions have been added to the internals of frequency converters, significantly improving their reliability. For instance, the frequency converters from MICNO inverter rarely have the above issues due to their high quality.

The causes of frequency converter fault are diverse, and only through constant exploration and summarization in practice can various frequency converter faults be promptly eliminated.