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FX2N-2LC Temperature Control Block
5.5
Heater disconnection detection function
The heater disconnection detection function detects the current flowing in the load using a cur-
rent detector (CT), it compares the detected value (heater current measured value) with the
current value set for heater disconnection alarm, and issues an alarm when the measured
value is more than or less than the current set value for the heater disconnection alarm.
The heater current can be measured using buffer memories (BFM #7, BFM #8).
Connection example
Temperature
control block
FX
-2LC
2N
Measured
value (PV)
Alarm operation
The heater disconnection detection function issues an alarm in the following cases.
1) When the heater current does not flow
... Caused by heater disconnection, error in operating machine, etc.
When the reference heater current value is equivalent to or less than the current set value
for the heater disconnection alarm while the control output is ON, an alarm is issued.
However, if the control output ON time is 0.5 sec or less, heater disconnection alarm is not
issued.
2) When the heater current does not turn off
... Caused by a molten relay, etc.
When the reference heater current value is more than the current set value for the heater
disconnection alarm while the control output is OFF, an alarm is issued.
However, if the control output OFF time is 0.5 sec or less, heater disconnection alarm is not
issued.
Current detector
CTL-12-S36-8 (Applicable current range: 0.0 to 100.0 A)
CTL-6-P-H (Applicable current range: 0.0 to 30.0 A)
Manufacturer: U.R.D. Co., Ltd.
Control output
Current detector
Current detector input
Sensor
Power supply
Operating
machine SSR
Heater
Control target
Introduction of Functions 5
5-8
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