4 Basic Operation
4 - 46
E5@C Digital Temperature Controllers User’s Manual (H174)
Calculate the set value using the following equation:
• To set the current for heater burnout when two or more heaters are connected through the CT, use
the value from when the heater with the smallest current burns out. If all of the heaters have the same
current, use the value from when any one of them burns out.
Example:
• Make sure that the following conditions are satisfied:
Heater with a current of less than 10.0 A:
(Normal current value) − (Burnout current value) ≥ 1A
When the difference is less than 1 A, detection is unstable.
Heater with a current of 10.0 A or more:
(Normal current value) − (Burnout current value) ≥ 2.5 A
When the difference is less than 2.5 A, detection is unstable.
• The setting range is 0.1 to 49.9 A. Heater burnouts and heater shorts are not detected when the set
value is 0.0 or 50.0. When the set value is 0.0, the HB alarm is always OFF and the HS alarm is
always ON. When the set value is 50.0, the HB alarm is always ON and the HS alarm is always OFF.
• Set the total current value for normal heater operation to 50 A or less. When a current value of 55.0 A
is exceeded, ffff is displayed in the Heater Current 1 (or 2) Value Monitor and Leakage Current 1
(or 2) Monitor parameters.
(1) Single-phase Heaters
Example: Using a 200-VAC, 1-kW Heater
The heater power supply provides 5 A when the current is normal, and 0 A when there is a
burnout, so the heater burnout detection current is calculated as follows:
4-12-4 Calculating Detection Current Values
4-12-5 Application Examples
Normal Burnout
Heater Burnout Detection 1/2 set value =
Normal current value + Burnout current value
2
HS Alarm 1/2 set value =
Leakage current value (output OFF) + HS current value
2
Heater Burnout Detection 1/2 set value =
(Normal current value + Burnout current value)
×
Number of turns
2
CT
5 A
5 A
Load
AC line
200 V
Product
To CT input
CT
0 A
Load
Load (such as a heater)
AC line
Burnout
200 V
Product
To CT input
Heater burnout detection current =
(Normal current) + (Heater burnout current)
2
=
5 + 0
2
= 2.5 [A]
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