Answer / ripul ghosh

nowadays 24V DC relays are used compared to 230V what was used before..relays are mainly there to isolate the controller from high power lines,
The signal from the controller will come to the relay and it will get energised to drive the output load.

Answer / nirmalya basu

to energise a output by plc and for its protection purpose
also.

Answer / ganesh

the relay works with AC and DC.
it provide the isolation between controller and devices works on ac and dc.
it is extremely useful when you need to control a large amount of current or voltage with small electrical signal.

Answer / suresh agravat

Example pressure transmitter input showing fiied full with liquid than send singnal through output to relay. When relay deenergised motor contactor not get supply and it will be motor or pump stop. Relay is basically on/off switch

plz send me placement paper of ongc

0 Answers   ONGC,

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0 Answers   ABB, L&T,

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A PLC is programmed to drive three motors A, B and C as follows : After running motor A for an hour, motor B should get ON and motor A should get OFF. And after running motor B for an hour, motor C should get ON and motor B should get OFF. And after running motor C for an hour, motor A should get ON and motor C should get OFF. (That is, a cyclic repetition with time period one hour) Now, the second condition is: If any motor gone faulty and is tripped, the consecutive motor should get ON and the faulty (tripped) motor should be eliminated from cyclic repetition. The remaining two motors should bear the cyclic repetition of one hour each. (For healthy motor take logic as high and for tripped motor take logic as low) Now, the third condition is: When motor A load(Amps) exceeds 60% of its rated load, motor B should get ON in parallel to motor A. And when both motors A & B are running in parallel, and if their load exceeds 60% of their rated load, motor C should also start in parallel to A & B. [Here the cyclic repetition is eliminated, until their loads become normal(40%)] [Take logic high(1) for load at 60% and logic low(0) for load at 40%] Now draw a flow chart or a ladder diagram to fulfill the above condition.

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䑰ҕ䔈ҕ䖠ҕ䘰ҕ䛀ҕ䝐ҕ䟐ҕ䢐ҕ䥐ҕŹ

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What is the three element? And how it work?

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