GE AKD-10 - Transformer Ratings and Breaker Selection; Transformer Forced Cooled Ratings

25
M
ain Feeder circuit breakers
F
ully rated or Zone
selective Selective selective Fully rated
Table 25.2 208 volts, three phase
T
ransformer
rating 3-phase Max short-circuit Full load
Short-circuit rating sym current (A)
kVA and MVA available continuous Long-time inst. Long-time
i
mpedance from primary current Transformer 100% or long-time Long-time short-time Long-time
p
ercent system (amperes)
À
Â
a
lone Motor load Combined short-time
À
s
hort-time inst. inst.
50 16300 18000
100 17300 19000
300 150 17700 19400
4
.5%Á 2
50 833 18000 1700 19700 WPS-16 WPS-08 WPS-08 WPS-08
500 18300 20000
750 18300 2
0000
Unlimited 18500 20200
50 25200 28000 WPS-08
100 27800 30600
500 150 28700 31500
4.5%
Á 250 1388 29500 2800 32300 WPS-16 WPH-08 WPS-08 WPS-08
500 30200 33000
750 30400 33200
Unlimited 30800 33600
50 28700 32900
100 32000 36200
750 150 2082 33300 37500
5.75% 250
 (2915) 34400 4200 38600 WPS-32 WPH-08 WPS-08 WPS-08
500 35300 39500
750 35600 39800
Unlimited 36200 40400
50 35800 41400 WPH-08 WPS-08 WPS-08
100 41100 46700
1000 150 2776 43300 48900
WPH-08 WPH-08
5.75% 250
 (3886) 45100 5600 50700
WPS-32
WPX-08
500 46700 52300 WPX-08 WPX-08
750 47200 52800
Unlimited 48300 53900
50 47600 55900 WPX-08 WPX-08 WPX-08
100 57400 65700
1500
150
61700 70000
5.75% 250 4164 65600 8300 73900 WPS-50 WPH-32 WPS-32 WPS-32
500 68800 77100
750
 (5830)
70000
78300
Unlimited 72400 80700
À With 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.
Á Minimum impedance.
 Maximum forced cooled rating indicated in parentheses.
L
=
Long-time delay trip (ov
erload tripping)
S = Short-time delay trip (selective fault tripping)
I
= Instantaneous trip (high fault current fast tripping)
Fully rated
a
rrangement
S
elf-cooled
Transformer type kVA % increase with fans
L
iquid filled: 65° C rise 750-2000 15%
2500-5000 25%
L
iquid filled: 55/65° C rise 750-2000 15% (fans) + 12% (65° C)
2500-5000 25% (fans) + 12% (65° C)
V
entilated dry 750-2500 33%
C
ast coil 500-2500 40%
3000-5000 25%
Power circuit breaker selection tables
T
able 25.1
T
ransformer forced cooled ratings
L
S
L
S LSI LI
LI
L
I
D
istribution or motor control center
S
electively
coordinated
a
rrangements