User`s manual

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MELSEC-Q
11 I/O MODULE TROUBLESHOOTING
Table 11.2 Output Circuit Problems and Corrective Actions (Continued)
Condition Cause Corrective Action
Example 3
The load is
not turned
OFF. (Triac
output)
• The load current is lower than the minimum
load current.
Triac
Surge suppresso
r
Phototriac
QY22
Control
circuit
Load
• When the load current is lower than the
minimum load current of the output module,
the triac does not operate since the load
current flows into a phototriac as shown
below.
When an inductive load is connected, the load
may not be turned OFF since surge at the
time of OFF is applied to the phototriac.
• Connect a resistor to both ends of a load so
that the load current is higher than the
minimum load current.
Load
Resistor