Mitsubishi Melsec-Q Series User Manual page 478

12.5.2 Output circuit troubleshooting
This section explains trouble examples and troubleshooting in the output circuit.
Condition
Excessive
voltage is applied
to load when
output turns off.
Load does not
turn off.(Triac
output)
The load is not
turned off. (Triac
output)
12 - 183
Table12.10 Output circuit troubleshooting
Cause
• When load is half-wave rectified inside (This is
typical of some solenoids.)
QY22
Output module
Load
• When the polarity of the power supply is [1], the
capacitor C is charged. When the polarity is [2], the
voltage charged in C plus the power supply voltage
is applied to across D1. The maximum value of the
voltage is approx. 2.2E.
(This usage does not pose problems to the output
components but may deteriorate the diode built in
the load, causing burnout, etc.)
• Leakage current due to the built-in surge
suppressor
QY22
Output module
Leakage current
• The load current is lower than the minimum load
current.
• When the load current is lower than the minimum
load current of the output module, the triac does not
operate and the load current flows into a phototriac
as shown by the arrow in the following figure. When
an inductive load is being connected, the load may
not be turned off since surge at the time of off is
applied to the phototriac.
QY22
Phototriac
Control
circuit
• Connect a resistor of several ten K
hundred K
[1]
D1
[2]
• Connect a resistor at both ends of the load.
(If the wiring from the output module to the load is
long, be careful since there may be a leakage
current due to the line capacity.)
Load
• Connect a resistor to both ends of a load so that the
load current is higher than the minimum load
current.
Surge suppressor
Load
Triac
Corrective Action
to several
at both ends of the load.
Resistor
Load
Resistor
Load
Resistor
Load