Proface LT3300 - 5.7 All-in-One HMI" Manuale Utente Scaricare il pdf (Pagina 82)

Chapter 4 Installation and Wiring

4-15

 Interlock Circuit 2

If there is a possibility that the abnormal operation of the LT may lead to an accident, design a fail-safe

measure to configure an interlock circuit with external hardware devices.

For a system which requires the running motor to stop before all other processes when the travel limit switch

is activated, never design a system in which the signals from the travel limit switch are input to the input

terminals of the LT and then processed using software.

Configure a circuit that reliably stops the running motor using hardware as shown below.

• After executing an internal program, the LT outputs ON/OFF information to the output

devices at the same time. For example, the electromagnetic switches for forward and

reverse rotation of a motor are turned on and off at the same time.

Consequently, a situation may arise in which both of the main contacts of the motor cir-

cuits for the electromagnetic switches for forward and reverse rotation may turn on, caus-

ing a short-circuit of the R and T phases. To avoid this situation, you need to provide the

interlock circuit shown above or use an electromagnetic switch equipped with a mechani-

cal interlock for a forward/reverse circuit.

Running motor control signal

Travel limit switch

Running motor

control circuit

Emergency

stop switch

Travel limit

switch

Direct input to the emer-

gency stop circuit of the

control unit

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Proface LT3300 - 5.7 All-in-One HMI" Manuale Utente Pagina 82