Omron G3ZA - MANUAL 2 User Manual page 58

Detecting Heater Burnouts (4-channel Models Only)
Burnout current = 20 A ×
Wire
break
200 V
200 V
15 A
200 V
15 A
3
×
3
2
= 30 A
The following formula yields the heater burnout current when there is a break
in the load wiring.
Heater burnout detection value =
The following formula yields the heater burnout current when there is a break
in the load itself.
Heater burnout detection value =
To detect a wire break at either location, set a heater burnout detection value
of 32 A.
b. Star Wiring
Example: Using three 6-kW heaters (200 V AC)
Normal Operation:
17.3 A
200 V
200 V
17.3 A
200 V
To CT
input
17.3 A
Each phase's normal current is 17.3 A.
1
30 A ×
17.3 A
3
Burnout Occurred:
Load such
as a heater
CT
To CT input
CT
To CT input
Burnout current = 20 A ×
= 20 A
34.6 + 30
= 32.3 → 32 [A]
2
34.6 + 20
= 27.3 → 27 [A]
2
Load such
as a heater
CT
CT
To CT
input
15 A
200 V
200 V
15 A
200 V
To CT input
To CT input
Section 4-5
1
×
3
3
Load such
as a heater
CT
Wire
break
CT
41