Mitsubishi Electric MELSEC iQ-R Series User Manual page 126

■Case 2
Cause When the load current is low (lower than 25mA), the triac does not operate and the load current flows to a phototriac as indicated by the
arrows in the figure below. If an inductive load is connected as a load in this situation, the load may not turn off because the surge at the
time of off is applied to the phototriac.
Triac output module
Control
circuit
Action Connect a resistor across the load so that the load current of approx. 100mA flows and the triac operation becomes stable.
Resistance value  Voltage across the load  100mA
(Example)
When the output voltage is 100VAC, calculate the resistance value by the following formula.
100VAC  100mA = 1k
Resistance value = 1k
The load does not turn off (transistor output).
Cause When a load that operates with a minute current of 0.1mA or lower is connected, the load may not turn off (may turn on) due to a leakage
current of the transistor.
Action Connect a resistor (several tens or hundreds of k) across the load.
9 TROUBLESHOOTING
124
9.3 Output Circuit Troubles and Corrective Actions
Surge suppressor
Phototriac
Triac
Resistor
Load
Resistor
Load
Load