72
6
F
2
S
0
8
3
4
onto a system that has previously been loaded to 90% of its capacity.
Thermal Curves (Cold Curve - no
prior load)
0.01
0.1
1
10
100
1000
1
10
Overload Current (Multiple of I
AOL
)
Operate Ti
m
e
(m
inutes)
Thermal Curves (Hot Curve - 90%
prior load)
0.001
0.01
0.1
1
10
100
1000
1
10
Overload Current (Multiple of I
AOL
)
O
p
erate Ti
me (mi
nutes)
Figure 2.4.6.1 Thermal Curves
Scheme Logic
Figure 2.4.6.2 shows the scheme logic of the thermal overload protection.
The thermal overload element THM has independent thresholds for alarm and trip, and outputs
alarm signal THM_ALARM and trip signal THM_TRIP. The alarming threshold level is set as a
percentage of the tripping threshold.
The alarming and tripping can be disabled by the scheme switches [THMAL] and [THMT]
respectively or binary input signals THMA_BLOCK and THM_BLOCK.
&
THM_ALARM
+
"ON"
[THMAL]
+
"ON"
[THMT]
THM_TRIP
&
&
&
T
A
THM
1
THMA_BLOCK
1615
1
THM_BLOCK
1631
560
556
690
691
Figure 2.4.6.2 Thermal Overload Protection Scheme Logic
Setting
The table below shows the setting elements necessary for the thermal overload protection and their
setting ranges.
τ
100
50
20
10
5
2
1
τ
100
50
20
10
5
2
1
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Summary of Contents for GRZ100-211B
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