Omron EJ1 User Manual page 108

Detecting Current Errors
Note
Note
(1) In the above diagram, power is considered to be ON (normal) if the heater
current is greater than the heater burnout detection current during the ON
time. If the heater is burned out, the current measured at the current
transformer decreases. When the current falls below the channel's Heat-
er Burnout Detection Value, a heater burnout alarm (HB Alarm) will be
output.
(2) Heater burnouts are not detected if the control output (heating) ON time
is 100 ms or less. Detection is also sometimes not possible if a contactor
is used for the control output.
Variable type
D6/96 (See note 3.) Heater Burnout 1 or 2
Detection
E4/A4 (See note 4.) Heater Burnout 1 or 2 Hys-
teresis
C5/85 Heater Current Value 1 or 2
Monitor
Conditions for use There must be a CT input.
(3) The HB Alarm can be forced OFF or ON, regardless of the actual heater
current value, by setting the Heater Burnout Detection parameter to 0.0
or 100.0. Use the 0.0 and 100.0 settings to check operation.
(4) This parameter can be set only when operation is stopped.
The hysteresis setting prevents chattering at the detection point.
• Turn the heater ON before the EJ1, or turn both ON simultaneously. If the
heater power is turned ON after turning ON the EJ1, the HB Alarm will be
output.
• Control will be continued even when there is an HB Alarm.
• The rated current value may sometimes differ slightly from the actual cur-
rent flowing to the heater. Check the current value in an actual operating
state in the Heater Current Monitor Value 1 or 2 parameter.
• If there is little difference between the current in normal and abnormal
states, detection may become unstable. To stabilize detection, set a cur-
rent value difference of at least 1.0 A for heaters of less than 10.0 A, and
at least 2.5 A for heaters of 10.0 A or more. If the heater current is too low,
loop the load line several times through a CT, as shown in the diagram
below. Looping it through twice will double the detection current.
Load line
Heater Burnout Latch and Latch Cancel
The heater burnout alarm latch can be used to keep the HB Alarm ON once it
goes ON.
The latch can be released by executing an operation command (Reset Error
or Software Reset), cycling the power, or setting the Heater Burnout Detection
Value to 0.0 A. Refer to 6-4-11 Operation Commands for details on the opera-
tion commands.
Variable type
E4/A4 Heater Burnout 1 or 2 Latch
This parameter can be set only when operation is stopped.
Parameter name
0.0: HB Alarm OFF
(I/O) 0.1 to 99.9 A
100.0: HB Alarm ON
0.1 to 100.0 A
(I/O)
0.0 to 110.0 A
(I/O)
CT
Parameter name
(I/O) 0: Disabled
Section 4-5
Setting range Default
0.0
0.1
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Setting range Default
0
1: Enabled
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