Power Circuit Breaker Selection Tables - GE AKD-10 Application Manual

Power circuit breaker selection tables

Table 25.1 Transformer forced cooled ratings
Self-cooled
Transformer type
Liquid filled: 65° C rise 750-2000
2500-5000
Liquid filled: 55/65° C rise 750-2000
2500-5000
Ventilated dry 750-2500
Cast coil 500-2500
3000-5000
Table 25.2 208 volts, three phase
Transformer
rating 3-phase Max short-circuit Full load
kVA and MVA available continuous
impedance from primary current
(amperes) Œ Ž
percent system
50
100
300 150
4.5% 250
500
750
Unlimited
50
100
500 150
4.5% 250
500
750
Unlimited
50
100
750 150
Ž (2915)
5.75% 250
500
750
Unlimited
50
100
1000 150
Ž (3886)
5.75% 250
500
750
Unlimited
50
100
1500 150
5.75% 250
500
Ž (5830)
750
Unlimited
ΠWith transformer operating on base temperature rise, without fans. Larger frame
size main breaker may be required when dual temperature rise for forced cooled
transformers are used.
 Minimum impedance.
Ž Maximum forced cooled rating indicated in parentheses.
L = Long-time delay trip (overload tripping)
S = Short-time delay trip (selective fault tripping)
I = Instantaneous trip (high fault current fast tripping)
kVA % increase with fans
15%
25%
15% (fans) + 12% (65° C)
25% (fans) + 12% (65° C)
33%
40%
25%
Short-circuit rating sym current (A)
Transformer 100%
alone Motor load
16300
17300
17700
833 18000 1700
18300
18300
18500
25200
27800
28700
1388 29500 2800
30200
30400
30800
28700
32000
2082 33300
34400 4200
35300
35600
36200
35800
41100
2776 43300
45100 5600
46700
47200
48300
47600
57400
61700
4164 65600 8300
68800
70000
72400
Main
Fully rated or
selective Selective
Fully rated
arrangement
LI
LS
LS
Selectively
coordinated
arrangements
Distribution or motor control center
Long-time inst.
or long-time Long-time
short-time Œ
Combined short-time
18000
19000
19400
19700 WPS-16 WPS-08
20000
20000
20200
28000 WPS-08
30600
31500
32300 WPS-16 WPH-08
33000
33200
33600
32900
36200
37500
38600 WPS-32 WPH-08
39500
39800
40400
41400 WPH-08
46700
48900
50700 WPS-32 WPX-08
52300
52800
53900
55900 WPX-08
65700
70000
73900 WPS-50 WPH-32
77100
78300
80700
Feeder circuit breakers
Zone
selective Fully rated
LI
LSI LI
Long-time
short-time Long-time
inst. inst.
WPS-08 WPS-08
WPS-08 WPS-08
WPS-08 WPS-08
WPS-08 WPS-08
WPH-08 WPH-08
WPX-08 WPX-08
WPX-08 WPX-08
WPS-32 WPS-32
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