Siemens frequency converter agent diagnoses faults

Siemens frequency converter agent teaches you how to maintain and diagnose frequency converters: In order to ensure the normal operation of the system, it is necessary to regularly inspect and maintain the PLC system, and you must also be familiar with general fault diagnosis and troubleshooting methods.

Siemens frequency converter agent teaches you how to maintain and diagnose faults in frequency converters

In order to ensure the normal operation of the system, it is necessary to regularly inspect and maintain the PLC system, and it is also necessary to be familiar with general fault diagnosis and troubleshooting methods.

1、 Inspection and maintenance

1. Regular inspection of PLC is an industrial control equipment, and although many measures have been taken in terms of reliability, the working environment still has a significant impact on PLC. So, it is usually necessary to conduct regular inspections on the PLC every six months. If the working conditions of the PLC do not meet the specified standards, emergency measures should be taken to ensure that the PLC operates in the designated standard environment.

2. In daily maintenance of PLC, apart from lithium batteries and relay output contacts, there are basically no other vulnerable components. Due to the use of lithium batteries to protect the random access memory (RAM), counters, and auxiliary relays with hold functions that store user programs, the lifespan of lithium batteries is approximately 5 years. When the voltage of the lithium battery gradually decreases to a certain extent, the battery voltage drop indicator light on the PLC basic unit lights up. Reminder to users: Programs supported by lithium batteries can be retained for about a week, and the battery must be replaced, which is the main content of daily maintenance.

Steps for swapping lithium batteries:

① Before disassembly and assembly, the PLC should be powered on for at least 15 seconds (this can charge the capacitor used as a backup power source for the memory. After the lithium battery is disconnected, the capacitor can provide temporary power to the PLC to protect the information in the RAM from being lost);

② Disconnect the AC power supply of the PLC;

③ Open the battery cover of the basic unit;

④ Remove the old battery and install a new one;

⑤ Cover the battery cover and replace the battery as quickly as possible, generally not exceeding 3 minutes. If the time is too long, the program in RAM will disappear.

2、 Fault finding

PLC has strong self diagnostic ability. When the PLC itself or peripheral equipment fails, the light emitting diode with diagnostic indication function on the PLC can be used to diagnose.

To add terminal resistors to the network bus is to eliminate signal reflections in communication cables. During communication, there are two types of signal reflections: impedance discontinuity and impedance mismatch.

Impedance discontinuity, when the signal suddenly encounters a cable with very low or even no impedance at the end of the transmission line, the signal will cause reflection at this location. The principle of signal reflection is similar to the reflection that occurs when light enters another medium from one medium. The method of eliminating this reflection requires a terminal resistor of the same size as the characteristic impedance of the cable to be connected across the end of the cable, making the impedance of the cable continuous.

Due to the bidirectional transmission of signals over cables, a terminal resistor of the same size can be connected across the other end of the communication cable. Another reason for signal reflection is the impedance mismatch between the data transceiver and the transmission cable. The reflection caused by this reason is mainly manifested in the chaos of the entire network data when the communication line is in idle mode. To reduce the impact of reflected signals on communication lines, methods such as noise suppression and adding bias resistors are usually used. In practical applications, for relatively small reflected signals, the method of adding bias resistors is often used for simplicity and convenience.