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Why you add contactors in PLC controlled system while PLC has built-in contactors?

Mechatronics Electrical Controls
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Question added by محمود الطيب
Date Posted: 2014/04/26
Upvote (1) Views (10) Followers (1) Answers (5) Report Question
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Danyal Shahzad
by Danyal Shahzad , Maintenance Executive , Tapal Tea (Pvt) Ltd

main reason is to isolate PLC

Ali Hassan Ali Osman
by Ali Hassan Ali Osman , Production and Maintenance Manager , Loviseberg Presseri AB

Plc has contactors with low load thats why we isolate the output by external contactors to protect the plcs contact and increase its lifetime. Also in case of running3 phase motors we will only need a single signal from one relay (contactor) to activate that external contactor for that motor.

Md. Noman Ahammed

to run a three phase (high rated) load we must need a3 phase cotactor which can be powered by PLC. single phase low power rated load may be directly powered by PLC.

Ahmed Alam Khan Bangash
by Ahmed Alam Khan Bangash , Senior Manager Electrical & Instrumentation, Reliability Centered Maintenance at (Cement and Power) , MAPLE LEAF CEMENT FACTORY AND POWER PLANT

PLC contact are of very low rating thatswhy external contactor are used, which could be of very high ratings. 

sohail zaman
by sohail zaman , Engineer - Instrumentation and Automation , National Petroleum Services Co.

there is no contactors in PLC .

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