Page 29 - SACE Tmax XT - Technical Catalogue

INSTALL ATION 1/25
01

Example 4 - XT4N 250 Ekip M-LIU
Cold trip / hot trip curves
The first curve shows the time of intervention of the trip Once the cold trip time has been identified on the first graph
unit in case of fault under cold conditions. Each curve is re- in relation to a fault current, the hot trip time can be calcu-
lated to a single operating class defined by Standard IEC lated on the second graph, based on t-off and class of inter-
60947-4-1 (3E, 5E, 10E or 10E). The second curve, hot trip, vention. For a XT4N 250 In=200A in the operating class 10E,
must be read in relation to the previous one. Considering given a fault current of 0.8kA (4xIn), the cold trip time for in-
the time the circuit-breaker has remained open after the tervention is 7s. If we consider a t off = 90s, t-hot/t-cold = 0.4,
first trip (t-off on the x-axis), the t-hot/t-cold ratio can be the hot trip time results 2.8s.
identified on the y-axis.

t [s] t-hot/t-cold
10 4 1.2
0.4...1
0.4 1
10 3 1
3E 5E 10E 20E
10 2 0.8
20EC 20EC
7s
10 0.6
3EC 3EC
0.4
1 0.4

0.8kA
10 -1 0.2 90s

10 -2 0
10 -1 1 10 10 2 1 10 10 2 10 3
x In Time [s]