TOHO ELECTRONICS TTM200 - Manual (Page 112)

48-7009-E 5-42
■ For 3-phase
■ Delta connection
Example: Where 3 heaters of 200 V and 2 kW are used
[When normal]
To equipment
CT input
To equipment
CT input
Load
Load Load
Normal current is 17.3 A (≒√3 × 10 A) for each phase.
[When disconnected in between phases]
To equipment
CT input
To equipment
CT input
Load
Load Load
To equipment
CT input
To equipment
CT input
Load
Load Load
[When disconnected on load side]
Disconnected
Current when disconnected = 10A
 √3 
(√3/2)
= 15A
Disconnected
Current when disconnected = 10A
 √3 
(1/√3)
= 10A
The heater disconnection detection current value when disconnection occurs in between phases is as
follows.
CT 1 abnormal current value setting value = (17.3 + 15)/2 ≒ 16.1 [A]
The heater disconnection detection current value when disconnection occurs on the load side is as follows.
CT 1 abnormal current value setting value = (17.3 + 10)/2 ≒ 13.65 [A]
For detection in both cases, the CT 1 abnormal current value setting value is to be 16.1 A.