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8.3
Protection Function
The overload protection function and overheat protection function protect the internal circuit from overcurrent and its heat.
Overload protection function
If the transistor output module and I/O combined module (transistor output part) detect overcurrent, the module performs the
current limiting operation (that imposes a limit on the output current to a constant value and keeps the output).
For the overcurrent detection value and the limited current, refer to the overload protection function in the specifications for
each module.
Page 26 Output module
Page 41 I/O combined module
If the load current becomes equal to the overcurrent detection value or lower, the module returns to normal operation.
Overheat protection function
If the transistor output module and I/O combined module (transistor output part) keep outputting the overcurrent caused by an
overload, heat is generated inside the module. If the module detects a high heat in its inside, it turns off the output.
The multiple points at which the overheat protection function operates depend on the module. Refer to the overheat protection
function in the specifications for each module.
Page 26 Output module
Page 41 I/O combined module
If the heat descends, the module automatically returns to normal operation.
The overload protection function and the overheat protection function do not protect external devices but
protect the internal circuit of the module.
A problem on a load may raise the internal temperature of the module, causing deterioration in output
elements and discoloration on the case and the printed-circuit board. Turn off the corresponding output as
soon as a problem on a load is found, and remove the cause.
8 FUNCTIONS
88
8.3 Protection Function
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Troubleshooting
