5 installation precautions, 5 installation precautions -13 – Proface LT3300 - 5.7 All-in-One HMI" User Manual

Page 80

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Chapter 4 Installation and Wiring

4-13

4.2.5

Installation Precautions

External power failure or failure of the LT unit may cause abnormal behavior.

To prevent such abnormal behavior from leading to the abnormal operation of the entire system, and to ensure

fail-safe operation, configure circuits which may lead to machine damage or accident due to abnormal

operation (emergency stop circuit, protection circuit, interlock circuit, etc.) externally to the LT.

This section describes examples of the system circuit design to improve system reliability and to ensure

optimum performance.

„

Fail-safe Design of the Electric Circuit

Design the electric circuit with consideration to equipment malfunctions caused when the LT is turned on by

a delay among the startup times of the control equipment connected to the LT output unit (especially the one

operated by a DC power supply), the LT unit itself, and the program. When remote I/O is used, create a

program that checks the status of the terminal with a logic program.

For example, connect voltage relay coils to the power supply circuit of the LT output unit and the power

supply circuit of the connected control equipment, and connect the contact to the LT input unit. Configure the

circuit to check the ON signal from the voltage relay in the logic program before executing the ladder of the

control equipment connected to the LT output unit.

„

Rated Voltage

Be sure to supply an appropriate power supply voltage to your LT that is within the specified range.

„

Power-down

LT unit enters power-down status when an instantaneous power interruption of the rated voltage continues for

10ms or longer.

When the LT unit enters power-down status, it stops the calculation even if the instruction is not finished.

For example, when the LT unit enters power-down status while 100 words of data are being transferred by an

FMOV instruction, the transfer stops midway.

Consequently, design your program with consideration to power-down occurrences.

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