Omron EJ1

91
Detecting Current Errors Section 4-5
2. Three-phase Heaters
a. Delta Connection
Example: Using Three 200-VAC, 2-kW Heaters
When each phase's current is normal, the current is:
17.3 A (
≅ × 10 A).
The heater burnout current when there is a burnout at the load line is as fol-
lows:
Heater burnout detection current =
≅ 16.15 [A]
The heater burnout current when there is a burnout at the load is as follows:
Heater burnout detection current =
≅ 13.65 [A]
To enable detection in either case, use 16.1 A as the heater burnout detection
current.
Normal Operation
CT
To CT input
To CT input
Load
Load
Load
17.3 A
200 V
200 V
17.3 A
17.3 A
200 V
CT
Load: Heater (example)
3
Heater Burnout Occurred
CT
To CT input
To CT input
Load
Load
Load
200 V
200 V
200 V 15 A
15 A
CT
Burnout
CT
To CT input
To CT input
Load
Load
Load
200 V
200 V
200 V
10 A
CT
Burnout
17.3 A
10 A
Load: Heater
(example)
Load: Heater
(example)
Current when there is a burnout = 10 A × ×
= 15 A
3



3
2
-------



Current when there is a burnout = 10 A × ×
= 10 A
3



1
3
-------



17.3 15+
2
------------------------
17.3 10+
2
------------------------