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