Omron E5ZE Operation Manual page 50

Heater Burnout Detection
Heater Burnout Detection
Current Value Calculation
• Set the control points for which HB alarms will be enabled. The factory setting
is for the HB alarm to be disabled for all control points. The HB alarm is set by
executing the HB Alarm/HS Alarm Effective Control Point Setting (WU) com-
mand. If DeviceNet communications are being used, set the HB alarm with
FINS messages.
• Set the heater burnout detection current value. The setting range is between
0.0 and 50.0 A.
• If the HB alarm is set to 0.0, it will always be OFF, and if it is set to 50.0, it will
always be ON. The default is 0.0 (always OFF).
• To check the CT current, read the values for the heater current and SSR leak-
age current.
• If the HB alarm is output, it will turn OFF again once the heater current in-
creases to a value greater than or equal to the heater burnout detection cur-
rent.
• For direct operation, set the heater current to 50 A max. for each control point.
If the heater current exceeds 50 A, heater burnout cannot be detected.
• Turn ON the heater power either at the same time as or before turning ON the
power to the E5ZE. The HB alarm output will turn ON if the power to the E5ZE is
turned ON before turning ON the heater power.
• Temperature control will continue even when the HB alarm turns ON. (The
E5ZE will attempt to control the temperature for the heater that has burnt out.)
• The heater burnout detection function operates when the control output is con-
tinuously ON for more than 100 ms.
• If the heater's rated current does not match the actual current flowing through
the heater, check the actual current being applied by reading the values for the
heater current and the SSR leakage current.
• If the difference between normal heater current and heater burnout current is
small, the detection function will not operate properly. For reliable detection,
use a heater that will give a current difference of at least 1.0 A for heaters that
are less than 10.0 A, and at least 2.5 A for heaters that are 10.0 A or more.
• The heater burnout detection function cannot be used when the heater is being
controlled by phase control or cycle control, or if a 3-phase heater is being
used.
• The heater burnout detection delay is 10 control periods max.
• The HB alarm will not operate for a control point during auto-tuning.
Use the K2CU-FjjA-jGS Heater Burnout Alarm Unit, which has gate input
terminals, to detect heater burnout when using 3-phase heaters. (Refer to the
relevant datasheets for further details.)
Calculate the set value for the heater burnout detection current using the follow-
ing formula.
Heater burnout detection current set value =
• If more than two heaters are passed through the CT, set the heater burnout
detection current to that for the heater with the smaller heater burnout detec-
tion current value. (If the heater burnout detection current is the same for all
heaters, set the value to the heater burnout detection current for one heater.)
• Heater burnout will be detected under the following conditions.
If heater current consumption is less than 10.0 A:
Normal heater current – Heater burnout current y 1 A
Heater burnout may not be detected if the difference is less than 1 A.
Section 3-10
Normal heater current + Heater burnout current
2
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