User manual

Chapter 3 – Installation and Wiring
3–12 LT Series User Manual
LT
After the LT or external device runs the program, the timing of
the ON/OFF signals to the output device is carried out simulta-
neously.
For example, an electromagnetic switch for forward and reverse motor rota-
tion could be turned ON and OFF at the same time. Therefore, when the
main contact for the power circuits of both the forward and the reverse motor
rotation are turned ON and OFF at the same time, there is a possibility that
an R Phase and a T Phase short circuit will occur. Please use the above
interlock, or a mechanical interlock equipped with an electromagnetic switch,
when designing a forward/reverse rotation circuit.
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 Interlock Circuit 2
If there is a possibility that an LT failure could cause an accident, use an external
hardware device to include a failsafe element in the design of the interlock circuit.
For example, if the system first needs to stop the Travel Motor whenever the Unit
Travel Limit Switch is activated, include the Unit Travel Limit Switch in the LT
input. The following circuit uses a hardware method to ensure that the Travel
Motor is stopped.
This applies to hardware; do NOT rely on software to process the interlock design.
1 When the LT discovers major errors such as Watchdog Timer Error, set up the LT unit's
alarm so that it turns all relay output OFF.
2 The relay output remains OFF until the LT system starts. In this case, the external
supervisory monitoring circuit has to recognize that the LT is not yet operating.
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 Interlock Circuit 1
Create an interlock circuit outside the LT (below), to control a motor’s forward/
reverse rotation circuit using an LT or external device connection.
Auxiliary B contact of electromagnetic
switch for motor reverse rotation
Motor rotation signal
(forward)
Auxiliary B contact of electro-
magnetic switch for motor forward
rotation
Error monitoring circuit
LT
Unit Travel
Limit Switch
Emergency
Stop Switch
LT Alarm Interpolation Circuit
*2
LT Unit alarm connection
*1
Unit Travel
Limit Switch
Travel Motor Control Signal
Travel Motor
Control Circuit
Electromagnetic
switch for motor
forward rotation
Electromagnetic
switch for motor
reverse rotation
Motor rotation signal
(reverse)