Mitsubishi Electric MELSEC-L Series User Manual page 80

(4) A load momentarily turns on from off when the system is powered off
(transistor output).
When an inductive load is connected, 2) Load may turn on from off due to a diversion of back EMF at 1) Shutoff.
Cause
Take one of two actions shown below.
Action 1: To suppress the back EMF, connect a diode to 3) parallel to the load where back EMF is generated.
Action 2: Configure another current path by connecting a diode across positive and negative of the external power supply. When taking the
action described in "A load momentarily turns on when powering on the external power supply" (Page 77, Section 8.2 (3)) at a time,
connect a diode parallel to C1 and R1.
For the following source output modules, take Action 1 on the above due to no effect of Action 2 by the characteristics of the external power
supply circuit.
• LY40PT5P
• LY41PT1P
• LY42PT1P
• LH42C4PT1P
Action
Sink type output
ON
OFF
78
Transistor
output module
Sink type output
Back EMF
Y0
ON
2)
Y1
OFF
12/24VDC
COM
Sink type
output
Back EMF
Load
Y0
2)
Load
Y1
R1
12/24VDC
D1
C1
COM
Case
Transistor
output module
Source type output
3)
Load
ON
Load
OFF
1) Shut off
Source type
Back EMF
output
Load
3)
D1 is in the following status.
Reverse voltage VR (VRM)
Example 24 VDC
Forward current IF (IFM)
Example
2A/1 common
1) Shut off
Back EMF
3)
Y0 Load
2)
Load
Y1
1) Shut off
COM
0V
Back EMF
Load
Approximately 10times higher than
the rated voltage in the specifications
Approximately 200V
More than twice as much as
the maximum load current (common)
in the specifications
4A or more