Test Your Knowledge: Instrument Logic Diagram Quiz Based on Real DCS to MCC Logic Diagram

The diagram remark says that when the reset PB is pressed on the drive pop-up screen, RUN TIME ERROR FF resets.

The NOT bubble flips the AUTO SEL input, which is commonly done to make sure that logic branches are only turned on when AUTO SEL is off.

This signal is transferred from the logic to the Motor Control Center (MCC) as a digital start command.

When AND/OR gates certify that there is a legitimate START logic path, the S input is triggered. This makes sure that the system works safely.

Even if AUTO START is on, the drive won’t start since the START PERMISSIVE AND gate condition fails.

“ON RUN TIME ERROR” usually lights up when the drive doesn’t start up within a certain amount of time after an RUN command is given.

Without AUTO SEL, the OR gate can’t send the AUTO START signal forward, which means that start logic is turned off.

FBOF stands for Field Breaker OFF Feedback, which means that the breaker is either not closed or has tripped.

TRIP EQUIP., being normally closed, when broken, leads to logic reset (STOP) and interrupts operation.

An OR gate sends these signals through it, making sure that any one of them can send a STOP signal.

START PERM is a permissive condition that lets AUTO or MANUAL START logic turn on if other logic conditions are met.

When engaged, thermal OL (overload) in NC (normally closed) condition disrupts the READY TO START route.

“RUNNING” means the drive is working under the START instruction, and feedback shows that it is ON.

According to the legend, the STOP ERROR FF resets only when the reset pushbutton (PB) is pressed on the drive pop-up.

When REMOTE SELECT is on, the START button sends a valid remote START signal, which turns on the logic.

The NOT RUNNING output means that the drive isn’t working, which helps with diagnostics and sequencing.

The tag XX-OL-YYY plainly means thermal overload, which is a safety feature that causes STOP/TRIP circumstances.

The 5-second TDO (time delay ON) makes sure that a controlled pulse is supplied to the S/R flip-flop, which is utilized for dependable switching.

The signal XX-FBON-YYY means that the field breaker is ON, which means that the breaker is closed.

When you press STOP or AUTO STOP, the OR gate turns on, which sets the STOP signal and resets the S/R latch.

The tag XX-ON-MYYY is connected to the START Command, which means that the drive has been told to start.

The label “LOC Selected” on XX-LOC-MYYY implies that the drive is in local mode and can’t be started from a distance.

The S/R block is a set/reset flip-flop that keeps the drive in either RUN or STOP mode based on logic inputs.

This AND gate makes sure that AUTO START is only allowed when START PERMISSIVE is activated, which means that the process conditions are ready.

The AUTO START signal is made by an OR gate that takes the AUTO SELECT and AUTO START criteria and combines them.