Electrical supply is used in bringing electrical energy to central processing unit. Most PLC controllers work either at 24 VDC or 220 VAC. On some PLC controllers you’ll find electrical supply as a separate module. Those are usually bigger PLC controllers, while small and medium series already contain the supply module. User has to determine how much current to take from I/O module to ensure that electrical supply provides appropriate amount of current. Different types of modules use different amounts of electrical current.    

This electrical supply is usually not used to start external input or output. User has to provide separate supplies in starting PLC controller inputs because then you can ensure so called “pure” supply for the PLC controller. With pure supply we mean supply where industrial environment can not affect it damagingly. Some of the smaller PLC controllers supply their inputs with voltage from a small supply source already incorporated into a PLC.

PLC which should pay attention in the application is specially the control device which serves for the industrial production, usually does not need to take any measure, may use directly in the industry environment. But, when the production environment is too bad, the electromagnetic interference is special intense, or installs uses improper, cannot guarantee PLC the normal operation, therefore should pay attention to the following question in the use. 

First, Siemens PLC maintenance 

1, maintenance procedures, equipment, periodic testing, adjustment provisions 

(1) half-yearly or quarterly inspection PLC cabinet terminal connections, and if time to re-loose strong local connection; 

(2) of the cabinet to the host power supply voltage of the monthly re-survey work; 

         2, the provisions of cleaning equipment on a regular basis 

(1) every six months or a quarter of the PLC to clean, cut off power to the PLC power supply to the power rack, CPU board and input / output board in turn be removed to purge, clean and then in turn installed in situ, will all link to resume evacuation call and start the host PLC. PLC box carefully sweeping health; 

        (2) every three months to replace the power rack below the filter; 

3,maintenance preparation, maintenance of order (1) ready before maintenance tools; (2) To protect the components and the template does not function no fault damage, must be protection devices and serious preparations for anti-static; 

(3) maintenance scheduling and operator contact before and well, be linked to overhaul licensing office hung maintenance card; 

4, equipment and method of disassembly sequence 

(1) downtime, must be two or more monitoring operation; 

(2) the way the CPU on the front panel select switch from the "Run" to "stop" position; 

         (3) Close the PLC power supply mains, and then close the other to the power supply module Osaka; 

(4) connected to the power supply rack power cord clear line number in mind and remove the link location, then remove the power rack and rack screws connected, power rack can be removed; 

(5) CPU motherboard and I / 0 board in the bottom of the screw rotation after template removed; 

(6) installed in reverse order; 

5, maintenance process and technical requirements 

(1) measure voltage, use a digital voltmeter or accuracy of 1% of the multimeter, measure 

(2) the power rack, CPU board can only be removed when the main power cut off; 

(3) RAM module to remove or insert the CPU from the CPU prior to disconnect the PC's power supply, so as to ensure the data is not confused; 

(4) before removing RAM modules, check the battery module is working correctly, if the battery fault light is removed when the PAM module content will be lost;