Output Off-Time Current Error Detection Function (Available For The Q64Tcttbw And Q64Tcrtbw Only); Loop Disconnection Detection Function - Mitsubishi Electric MELSEC Q Series User Manual

3 SPECIFICATIONS
3.2.8 Output off-time current error detection function (available for the Q64TCTTBW and
Q64TCRTBW only)

3.2.9 Loop disconnection detection function

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(1) Using the reference heater current value (load current value detected by the
current sensor (CT)), this function checks for a transistor output off-time current
error when the transistor output is off.
(2) The transistor output off-time current error detection function compares the
reference heater current value and the current value of the heater disconnection
alert, and judges it as an output off-time current error if the reference heater current
value is higher than the current value of the output off-time current alert.
Note that output off-time current error detection will not be made if the transistor
output off period is within 0.5 seconds.
The loop disconnection detection function detects errors in the control system (control
loop) caused by a load (heater) disconnection, external operation device (e.g.
magnetic relay) fault, input disconnection and others.
When the PID operation value has reached 100% or 0%, this function starts monitoring
the variation of the process value per loop disconnection detection judgment time to
detect a heater or input disconnection.
(1) When the heater is disconnected, when the input is disconnected or shorted, or
when the external operation device contact does not turn on, it is judged as an
error since the temperature will not rise despite the control output provided.
In this case, an alert is output if a temperature rise of 2°C or more is not observed
within the preset loop disconnection detection judgment time after the control
output is provided 100%.
(2) When the input is disconnected or when the external operation device contact is
welded, it is judged as an error since the temperature will rise though the control
output is not provided.
In this case, an alert is output if a temperature fall of 2°C or more is not observed
within the preset loop disconnection detection judgment time after the control
output has dropped to 0%.
(In either case, inverse operation will be performed for forward action: cooling
control.)
POINT
(1) When not using the loop disconnection detection function, set the loop
disconnection detection judgment time to "0".
(2) Setting the loop disconnection detection dead band will not cause a loop
disconnection if there is no temperature variation of 2°C or more when the
control output is provided 100% or 0% at the set value. (Refer to Section
3.5.32.)
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