Mitsubishi Electric MELSEC-L Series User Manual page 24

(2) Precaution for using the transistor output module
(a) Action against reverse current
If a transistor output module is wired as shown below, reverse current flows in an output element, causing a
failure of the element.
When wiring a transistor output module, connect a diode as shown below.
• When connecting transistor output modules in parallel
• When incorporating an additional circuit parallel to a transistor output module
(b) Measures against back EMF
When an inductive load is connected, connect a diode in parallel with the load.
Use a diode that meets the following conditions.
• Reverse breakdown voltage is equal to or more than 10 times as large as the circuit voltage.
• Forward current is equal to or more than 2 times as large as the load current.
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Diode
Load
OUT1
Diode
Load
OUT2
COM
Diode
OUT1
Diode
OUT2
COM
Sink type
Additional circuit
OUT
Diode
COM
Sink type
Inductive
OUT
load
Diode
COM
Sink type
Diode
Load
OUT1
Diode
Load
OUT2
COM
Diode
OUT1
Diode
OUT2
COM
Source type
Additional circuit
OUT
Diode
COM
Source type
Inductive
OUT
load
Diode
COM
Source type