Omron EJ1G, User Manual

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Detecting Current Errors
Section 5-5
• The setting range is 0.1 to 99.9 A. Heater burnout is not detected when
the setting is 0.0 or 100.0. When the set value is 0.0, the HB alarm is
turned OFF. When the set value is 100.0 the HB alarm is turned ON.
• Set the total current value at normal heater operation to 100 A or less.
■
Examples
1. Single-phase Heaters
Example 1 Using a 200-VAC, 1-kW Heater
The heater current is 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:
Example 2 Using Three 200-VAC, 1-kW Heaters
The heater current is 15 A when the current is normal, and 10 A when there is
a burnout, so the heater burnout detection current is calculated as follows:
5-5-2 Heater Short Alarm (HS Alarm)
The HS Alarm detection function measures the heater current when the con-
trol output (heating) is OFF. For details, refer to the following table.
(HS Alarm detection cannot be used with the control output for cooling.)
∴
Heater burnout detection current
=
Normal current value + Burnout current value
2
Normal operation Heater burnout occurred
CT
To CT input
AC line
Load
5 A
5 A
200 V
CT
To CT input
AC line
Load
0 A
200 V
Burnout
=
5 + 0
= 2.5 A
2
Normal operation Heater burnout occurred
CT
To CT input
AC line
Load
15 A
200 V Load Load
15 A
CT
To CT input
AC line
Load
10 A
200 V
Load Load
10 A
Burnout
∴
Heater burnout detection current
=
Normal current value + Burnout current value
2
=
15 + 10
= 12.5 A
2
Control output (heating) Power to heater HS Alarm output
OFF Yes (HS alarm occurred) ON
No (Normal) (See note 1.) OFF