89
Detecting Current Errors
Section 5-5
• 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 once will double the detection current.
■
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.
Note
Set this parameter in the TC2/4 Unit.
Installing Current
Transformers (CT)
(HB Alarm)
Connect the CT in advance to terminals A8 and A9 (CT1) or A7 and A9 (CT2),
and pass the heater power line through the CT's hole. Refer to Current Trans-
former on page 172 for details on compatible CT specifications, models, and
dimensions.
Single-phase Heaters
Install the CT as shown below.
Calculating the Heater
Burnout Detection
Current Value
Calculate the set value with the following equation:
• To set the value of the heater burnout when two or more heaters are con-
nected through the CT, use the current value of the smallest heater con-
nected. (When all of the heaters have the same current value, use the
current value when one of the heaters has burned out.)
• Be sure that the following conditions are satisfied:
Heater with a current of less than 10.0 A:
Current value at normal operation
−
Current value at heater burnout
≥
1 A
When the difference is less than 1 A, detection is unstable.
Heater of current 10.0 A or more:
Current value at normal operation
−
Current value at heater burnout
≥
2.5 A
When the difference is less than 2.5 A, detection is unstable.
CT
Load line
Variable type
Parameter name
Setting range Default
E4/A4
Heater Burnout 1 or 2 Latch
(I/O) 0: Disabled
1: Enabled
0
CT
To CT input
AC line
Load
Load: Heater (example)
Set value =
Normal current value + Burnout current value
2
Summary of Contents for EJ1G
Page 3: ...iv ...
Page 17: ...xviii ...
Page 21: ...xxii ...
Page 53: ...32 Unit Configuration Examples Section 2 4 ...
Page 69: ...48 Changing SPs During Operation Section 3 3 ...
Page 81: ...60 Other Functions Section 4 5 ...
Page 145: ...124 Other HFU Functions Section 5 7 ...
Page 167: ...146 Detailed Description of Services Section 6 4 ...
Page 229: ...208 Parameters That Can Be Allocated for Programless Communications Appendix ...
Page 237: ......