Quickly find experience - PLC system failure reasons

by:Coolmay     2020-06-17
In the maintenance and repair of PLC system in recent years,'s summarizes some quickly find PLC system failure reasons of experience, now communicate with people is as follows. A typical PLC system includes a field PLC station, and through the high-speed data line connected to the PC and mimic panel PLC station, PC is used to display a variety of graphics and data, simulation screen PLC station used to drive simulation light-emitting diodes (leds) on the screen. The PLC system and communications equipment, constitutes a automatic control system.

judge ark of PLC I/O terminals, communications equipment, whether the I/O terminals are in conformity with the state signal method is very simple, as long as the dc voltage with a multimeter measuring terminal and public side voltage, 24 v disconnect, no signal; 0 v connected, the signal.

2, the operation of the equipment in a simulated screen no display when a judge is PLC is no signal to running, or to run signal and malfunction with the equipment can not run. We can from the scene of the PLC cabinet, according to the observation in the presence of signal output module address and then check the PLC station is output relay have close, then look at communications equipment electrical cabinets have driven signal. If yes, no operation and equipment, is a malfunction with the equipment, if the normal operation of equipment, should be the input end of the communications equipment, back process is just the reverse of the first failure inspection process. The above process is expressed by the following diagram:

if the device is running, in the following diagram to check.

for analog signal detection, because of the instrument used is 4 ~ 20 ma input, so in tandem with the analog signal input a multimeter, detect current value of the analog signal, and compared with PLC output values do, can know whether value is correct.

there is a kind of simple method can quickly judge is PLC controller failure or electrical equipment failure, is to use short circuit method: disconnect the communications equipment state input line, with a wire connected to the input port and the public line, this means that a switching signal to PLC, PLC if have showed that the PLC is normal; Vice for PLC failure. To find fault point should be dealt with accordingly. In general PLC) are less likely to malfunction, most of the cause of the problem is the connection is loose, or the wrong line, or a fault relay, etc. , also have the PLC template burned, then only to replace PLC template. Remember to power operation, otherwise easy to good template burned, also may be implicated in the PLC processor.


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