How to solve the "false alarm" problem of frequency converter?

In the field of industrial control, frequency converters are key devices for regulating motor speeds, and their stability and accuracy are crucial. However, in practical applications, we often encounter the problem of "false alarms" from frequency converters. What exactly is a "false alarm"? In layman's terms, it means that the frequency converter sounds an alarm when it should not. This phenomenon may cause trouble to normal production and maintenance work.

For example, when the bus voltage of the inverter drops, it should issue a "bus undervoltage" alarm. If it does not issue an alarm in this case, it is abnormal. However, sometimes the inverter will report an error, such as an "overheat" alarm, even if the inverter is not running, when there is no problem. In this case, many people may suspect that it is caused by a fan failure, but in fact, if it is a fan problem, the inverter will usually issue a "fan failure" alarm message.

So, what exactly causes false alarms? In fact, false alarms are often caused by problems in the principle circuit that implements a certain function, resulting in the function not achieving the expected effect. This problem may be caused by damage to a component or by external factors. Among the external factors, interference is a problem that needs special attention. Transient interference may cause the inverter to falsely alarm, and this interference is often elusive and difficult to detect and prove.

However, the term "false alarm" is sometimes used as an excuse to shirk responsibility. Whether it is really a false alarm, the relevant personnel actually know it. For example, the "overheat" alarm mentioned above is implemented by detecting the temperature of the IGBT through a thermistor. The resistance of this thermistor changes with the temperature, forming a voltage signal. This signal is compared with a preset voltage signal, and then the result is output to the CPU to determine whether overheating occurs. If the temperature of the IGBT is not high in the shutdown state, but the "overheat" alarm is still issued, it means that there is a problem in a certain link. After careful investigation, it may be that the voltage comparator is faulty, resulting in a high level output under normal circumstances, thereby triggering the alarm.

In summary, false alarms do exist, but we cannot blindly assume that they are false alarms just because they are alarmed. Each alarm message has its reasons and logic behind it, and we should carefully analyze it to find out the real reason. At the same time, we should also pay enough attention to factors such as external interference to ensure the stable operation of the inverter.