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Using Heater Burnout, Heater Short, and Heater Overcurrent Alarms Section 3-10
Star Connecting Lines
Example: Using Three 200-VAC, 2-kW Heaters
The current when each phase is normal is 5.8 A (≈ 10 A × (1 /√3)).
The heater burnout detection current for this connecting line is 5.4 A (= (5.8 +
5) / 2).
CT
CT
200 V
200 V
5.8 A→
5.8 A→
5.8 A→
200 V
Load
Load
Load
Normal
Product
To CT input
Product
To CT in
ut
Load (such as a heater)
CT
CT
200 V
200 V
5 A→
5 A→
200 V
Load
Load
CT
CT
200 V
200 V
5 A→
5 A→
200 V
Load
Load
Burnout
Burnout
Load (such as a heater) Load (such as a heater)
Load
Load
Product
To CT input
Product
To CT input
Product
To CT input
Burnout
Current when there is a burnout = 10 A × (1/√3)
× (√3/2) = 5 A
Current when there is a burnout = 10 A × (1/√3)
× (√3/2) = 5 A
Product
To CT input