Toshiba GRL150-100 Series Instruction Manual page 14

Characteristic A is expressed by the following equation:
I out ≤ (5/7)(I in - DIFI1)
Characteristic B is expressed by the following equation:
I out ≤ DIFI2
2.2.3 Fail-safe Function (Overcurrent Guard Scheme)
GRL150 provides OC5 and OCD elements which provide an overcurrent guard scheme for
fail-safe operation. OC5 is a phase overcurrent element and its sensitivity can be set. OCD is a
phase current change detection element and its sensitivity is fixed.
The scheme logic is shown in Figure 2.2.3.1. The output of DIFFS_OP is connected to DIF-A_FS,
DIF-B_FS, DIF-C_FS respectively by PLC function.
The fail-safe function is disabled by the [DIF-FS] switch. By [DIF-FS], OC5 or OCD or both
elements can be selected. If the switch is set to "OFF", the signal of DIFFS_OP is "1" and the
fail-safe is disabled.
64
OC5-A
65
OC5-B
66
OC5-C
68
OCD-A
69
OCD-B
70
OCD-C
[DIF-FS]
+
≥1
" "
OC
≥1
" "
OCD
" "
BOTH
" "
OFF
I out
DIFI2
DIFI1
0
Figure 2.2.2.2 DIF Element (I in -I out Plane)
265
≥1
& DIFFS-A_OP
266
≥1
&
DIFFS-B_OP
≥1
& DIFFS-C_OP
&
&
&
Figure 2.2.3.1 Fail-safe Logic
⎯ 13 ⎯
I out = I in
B
Operating
Zone
A
264
≥1
DIFFS_OP
267
6 F 2 S 0 8 2 8
I in
By PLC
1584 DIF-A_FS
1585 DIF-B_FS
1586 DIF-C_FS
(see Fig. 2.2.1.1.)