Omron E5AN-H

75
Using Heater Burnout, Heater Short, and Heater Overcurrent Alarms Section 3-10
Three-phase Heaters Delta Connecting Lines
Example: Using Three 200-VAC, 2-kW Heaters
The current when each phase is normal is 17.3 A (≈ √3 × 10 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.
Heater burnout detection current =
(Normal current) + (Heater burnout current)
2
=
15 + 10
2
= 12.5 [A]
CT
Load
Load
200 V
200 V
17.3 A→
17.3 A→
17.3 A→
200 V
Normal
Product
To CT input
Product
To CT input
Load
CT
CT
Load
Load
200 V
200 V
15 A→
15 A→
200 V
CT
CT
Load
Load
200 V
200 V
10 A→
17.3 A→
10 A→
200 V
Burnout Burnout
Burnout
Load
Load
Product
To CT input
Product
To CT input
Product
To CT input
Product
To CT input
Current when there is a burnout = 10 A × √3 ×
(√3/2) = 15 A
Current when there is a burnout = 10 A × √3 ×
(1/√3) = 10 A
Burnout