Omron E5C User Manual page 144

4 Basic Operation
Example: Using Three 200-VAC, 1-kW Heaters
Normal
Product
To CT input
The heater power supply provides 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 =
15 + 10
=
(2) Three-phase Heaters
(a) Delta Connecting Lines
4 - 46
15 A
Load
200 V
15 A
CT
= 12.5 [A]
2
Example: Using Three 200-VAC, 2-kW Heaters
Normal
17.3 A
200 V
17.3 A
200 V
Product
200 V
To CT input
17.3 A
Product
To CT input
The current when each phase is normal is 17.3 A (≈ √3 × 10 A).
Normal
Burnout
200 V
15 A
200 V
Product
200 V
To CT input
15 A
Product
To CT input
Current when there is a burnout =
10 A × √3 × (√3/2) = 15 A
The heater burnout current when there is a burnout at the load line is as follows:
(Heater burnout detection current) = (17.3 + 15) / 2
Burnout
10 A
Load Load
200 V
10 A
Product
To CT input
(Normal current) + (Heater burnout current)
2
Load
CT
CT
Burnout
200 V
200 V
Load
CT
200 V
CT
Current when there is a burnout =
10 A × √3 × (1/√3) = 10 A
E5@C Digital Temperature Controllers User's Manual (H174)
Load Load Load
Burnout
CT
Burnout
15 A
Load
Product
CT
To CT input
15 A
CT
Product
To CT input
16.15 [A]
=