
11. TROUBLESHOOTING
11 - 18
MELSEC-A
11.4.2
Output circuit failures and corrective action
Table 11.3 Output circuit failures and corrective action
Condition
Cause
Corrective action
Example
1
When the
output is OFF,
excessive
voltage is
applied to the
load.
•
Load is half-wave rectified inside (in some cases,
this is true of a solenoid).
A1SY22
Output module
Load
D1
(1)
(2)
When the polarity of the power supply is as shown in
[1], C is charged. When the polarity is as shown in
[2], the voltage charged in C plus the line voltage are
applied across D1. Max. voltage is approx. 2.2E.
•
Connect a resistor of 10 to 99 k
Ω
.
across the load.
If a resistor is used in this way, it does not
pose a problem to the output element. But
it may cause the diode, which is built into
the load, to deteriorate, resulting in a fire, etc.
Resistor
Load
Example
2
The load does
not turn OFF
(triac output)
•
Leakage current due to built-in noise suppression
A1SY22
Output module
Load
Leakage current
•
Connect C and R across the load.
When the wiring distance from the output
card to the load is long, there may be a
leakage current due to the line capacity.
Resistor
Load
Example
3
When the load
is a CR type
timer, time
constant
fluctuates
(triac output).
A1SY22
Output module
CR timer
Leakage current
•
Drive the relay using a contact and drive the
CR type timer using the same contact.
Some timers have half-wave rectified internal
circuits. Therefore, take the precautions
indicated in the Example1.
Resistor
CR timer
Calculate the CR constant
depending on the load.
Содержание A1SH
Страница 15: ...MEMO...