- 12 -
Output protections (recommended values for selectivity)
Table 13
Normal fuses (GI) In (Nominal current)/4
Normal switches (C curve) In (Nominal current)/4
Ultra-fast fuses (GF) In (Nominal current)/2
SHORT CIRCUIT PROTECTION
If a failure at the output occurs, the CSS protects itself by limiting the value and duration of the output current (short-circuit current).
These values also depend on the operating status of the CSS at the time of the failure; there are two different scenarios:
CSS in NORMAL OPERATION with a bypass supply: the load is instantly switched to the bypass line (I
2
t see table below):
the input line is connected to the output without any internal protection (blocked after t > 500ms).
CSS (kVA) I
2
t [A
2
s]
Table 14
6 - 8 - 10 20000
15 - 20 35000
CSS in BATTERY OPERATION or in NORMAL OPERATION without a bypass supply: the CSS protects itself by supplying
2.7 times the nominal current to the output for the first 200ms, which is then reduced to 1.5 times nominal for 300 ms. After
this time (500 ms) it switches off.
SHORT CIRCUIT WITHSTANDING
This equipment is rated for use in a circuit capable of delivering no more than the current as per the table below at 240V maximum.
CSS (kVA) Short circuit symmetrical amperes WITHSTANDING
Table 15
6 - 8 - 10 6000 (6 kA)
15- 20 10000 (10 kA)
INTERNAL PROTECTIVE DEVICES
The table below shows the sizes of the switch disconnectors of the CSS and the sizes of the battery fuses: these devices are accessible
either from the front.
There is also data in relation to the rating of the internal fuses (not accessible) which protect the input and output lines, along with the
maximum input and rated output currents.
Fuses must be replaced with ones of the same size and the characteristics as indicated in the table below.
Switches and internal protective devices
Table 16
Disconnect switches and fuse holders Internal Fuses
CSS
model
SWIN
SWOUT / SWBYP
/ SWMB
SWBATT
(
*
)
Rectifier input fuses
Battery stage
fuses
Output fuses
3P+N P+N
6 63A (4P) 63A (2P)
32A gG 400V
(10x38)
25A FF 500V
(6.3x32)
3x25A FF 500V
(6.3x32)
20A FF 500Vdc
(6.3x32)
2x20A FF 500V
(6.3x32)
8 63A (4P) 63A (2P)
32A gG 400V
(10x38)
25A FF 500V
(6.3x32)
3x25A FF 500V
(6.3x32)
20A FF 500Vdc
(6.3x32)
2x25A FF 500V
(6.3x32)
10 63A (4P) 63A (2P)
32A gG 400V
(10x38)
25A FF 500V
(6.3x32)
3x25A FF 500V
(6.3x32)
20A FF 500Vdc
(6.3x32)
4x20A FF 500V
(6.3x32)
15 125A (4P) 100A (2P)
50A gG 400V
(14x51)
2x25A FF 500V
(6.3x32)
6x25A FF 500V
(6.3x32)
32A gR 500V
(10x38)
6x20A FF 500V
(6.3x32)
20 125A (4P) 100A (2P)
50A gG 400V
(14x51)
2x25A FF 500V
(6.3x32)
6x25A FF 500V
(6.3x32)
32A gR 500V
(10x38)
6x20A FF 500V
(6.3x32)
(
*
)
Warning: SWBATT disconnect only the batteries contained in the CSS cabinet
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