Omron E5CN User Manual page 90

Using Heater Burnout, Heater Short, and Heater Overcurrent Alarms
Three-phase Heaters
Burnout
Burnout
200 V
15 A→
200 V
200 V
Product
To CT input
15 A→
Product
To CT input
Current when there is a burnout = 10 A × √3 ×
Delta Connecting Lines
Example: Using Three 200-VAC, 2-kW Heaters
Normal
17.3 A→
200 V
17.3 A→
200 V
200 V
Product
To CT input
17.3 A→
Product
To CT input
The current when each phase is normal is 17.3 A ( ≈ √ 3 × 10 A).
200 V
Load
CT
CT
(√3/2) = 15 A
The heater burnout current when there is a burnout at the load line is as fol-
lows:
(Heater burnout detection current) = (17.3 + 15) / 2 ≈ 16.1 [A]
The heater burnout current when there is a burnout at the load is as follows:
(Heater burnout detection current) = (17.3 + 10) / 2 ≈ 13.65 [A]
To enable detection in either case, use 16.1 A as the heater burnout detection
current.
Load
CT
Burnout
10 A→
200 V
17.3 A→
200 V
Product
To CT input
10 A→
Product
To CT input
Current when there is a burnout = 10 A × √3 ×
Section 3-10
Burnout
Load
CT
CT
(1/√3) = 10 A
65