Omron EJ1 User Manual page 111

Detecting Current Errors
Normal operation
90
Examples
1. Single-phase Heaters
Example 1 Using a 200-VAC, 1-kW Heater
Normal operation
5 A
200 V
5 A
To CT input
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:
∴ Heater burnout detection current
Example 2 Using Three 200-VAC, 1-kW Heaters
15 A AC line
200 V Load
15 A
CT
To CT input
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
AC line
Load
CT
Normal current value + Burnout current value
=
5 + 0
= = 2.5 A
2
Heater burnout occurred
10 A
Load Load 200 V
10 A
To CT input
Normal current value + Burnout current value
=
15 + 10
=
2
Section 4-5
Heater burnout occurred
AC line
200 V
Burnout
0 A
CT
To CT input
2
AC line
Load Load
Burnout
CT
2
= 12.5 A
Load
Load