GE Power Break II Manual page 46

Application
General ly, electrical power system engineers calculate the
></R ratios of circuit rather than power factor. The procedures
for calcu lating short-circuit current and X/R ratios a re de­
scribed in Publication G ET-3 550.
Oscillogram of typical short circuit
Asymmetrical ac waveform
The fi g u res below show the initial fault current displacement
of a pure circuit (sym metrical) and a reactive circuit with a
high X/R ratio. The actua l current d isplacement of a reac­
tive circuit depends on the exact moment the short circuit is
a ppl ies. There is a simple relationship between power factor
and X/R of a faulted circuit:
z
R
PF = - x 100 And: Z
R
+
Therefore PF =
PF = Power factor, %
R = Resistance i n ohms
I nterrupting Rati ngs - Sta ndard A n d Hi-Break® Brea kers
Power Break® I I brea kers a re available i n two classifications
of interrupting rati ngs: Standard and H i-Break breakers. All
ratings a re without the need for external fuses or current
l i miters. Hi-B reak b reakers' interrupting rati ngs a re for those
circuits with unusually high levels of available fa ult current.
46
Envelopes o f peaks a r e not
symmetri c a l about zero axis
Zero axis
+
(X JZ
=
x 100
Z I m pedance i n ohms
=
>< = Reactance i n ohms
Table 46.1
Interrupting Rating Breaker Performance I n RMS Symmetrical kA
U L 489
50/60 Hz
800A
Standard
240V 65
480V 65
600V 50
H i-Break'"'
240V 100
480V 100
65
600V
Short Time
25
10 5 sec.)
IEC 947 - 2 Ratings
415V, 50/60 Hz
leu
-
lcs
-
lew (1 sec)
-
Q) Req u i res 4000A construction
Table 46.2
Estimated 400 Hz Interrupting Ratings
RMS Symmetrical Amperes - Not UL Listed
Standard Break
Frame Size Max. Rating Plug
(Amps) Ampacity@
800 600
1600 1000
2000 1200
2500 1600
Hi-Break
(Amps) Am pocity@
Frame Size Max. Rating Plug
800 600
1000
1600
1200
2000
1600
2500
@ No additional thermal derating is required for above-maximum rating
plug ratings far frame sizes noted. Note: 400Hz interrupting ratings ore
based on engineering judgment, taking into consideration the operating
cha racteristics of insulated case circuit breakers and the worldwide lack
of test facilities to verify performance. Power+™ trip units and the energy
ma nagement functions in MicroVersaTrip PM™ trip u nits are suitable for
50/60 Hz a p plications only.
Frame Size
1600 - 2500 -
2000A 3000 4000A
85 100 100
65 100 100
50 85 85
1 2 5 200 200
100 150 150
65 100 100
40 42 42
7 5 Q)
7 5 85
45 Q)
25
56
50 Q)
40 50
120/240 277/480 346/600
6500 5000 4200
8500 6500 5000
8500 6500 5000
10000 10000 8500
277/480 346/600
120/140
10000 10000 6500
1 2 500 10000 6500
1 2 500 10000 6500
20000 15000 10000