Omron EJ1

90
Detecting Current Errors Section 4-5
■ 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:
∴ 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