Technical Data
Effective: May 1998 Page 23
TD.44A.01.T.E
Cutler-Hammer
Magnum DS
Metal-Enclosed
Low-Voltage Switchgear
Application
Application of Magnum DS Power Circuit Breakers
With Standard Three-Phase Transformers – Fluid Filled and Ventilated Dry Types
Transformer Base
(100%) Rating
Secondary Short-Circuit Currents
RMS Symmetrical Amperes
Minimum Size Breakers for Selective
Trip Systems
kVA and
Percent
Impedance
Amperes➀ Maximum Short Circuit
kVA Available from
Primary System
Through
Transformer
Only
Motor
Contribution
Combined Main
Breaker
Short Delay
Trip
Feeder
Breaker
Short Delay
Trip
Feeder
Breaker
Instantaneous
Trip
Table A1 – 208 Volts Three-Phase — 50% Motor Load
300
5.0%
833 50000
100000
150000
250000
500000
Unlimited
14900
15700
16000
16300
16500
16700
1700 16600
17400
17700
18000
18200
18400
MDS-616 MDS-408
MDS-408
MDS-408
MDS-408
MDS-408
MDS-408
MDS-408
MDS-408
MDS-408
MDS-408
MDS-408
MDS-408
500
5.0%
1389 50000
100000
150000
250000
500000
Unlimited
23100
25200
26000
26700
27200
27800
2800 25900
28000
28800
29500
30000
30600
MDS-616
➁ MDS-408
MDS-408
MDS-408
MDS-408
MDS-408
MDS-408
MDS-408
MDS-408
MDS-408
MDS-408
MDS-408
MDS-408
750
5.75%
2083 50000
100000
150000
250000
500000
Unlimited
28700
32000
33300
34400
35200
36200
4200 32900
36200
37500
38600
39400
40400
MDS-632 MDS-408
MDS-408
MDS-408
MDS-608
MDS-608
MDS-608
MDS-408
MDS-408
MDS-408
MDS-408
MDS-408
MDS-408
1000
5.75%
2778 50000
100000
150000
250000
500000
Unlimited
35900
41200
43300
45200
46700
48300
5600 41500
46800
48900
50800
52300
53900
MDS-632
➁ MDS-408
MDS-608
MDS-608
MDS-608
MDS-608
MDS-608
MDS-408
MDS-608
MDS-608
MDS-608
MDS-608
MDS-608
Table A2 – 240 Volts Three-Phase — 100% Motor Load
300
5.0%
722 50000
100000
150000
250000
500000
Unlimited
12900
13600
13900
14100
14300
14400
2900 15800
16500
16800
17000
17200
17300
MDS-408
➁ MDS-408
MDS-408
MDS-408
MDS-408
MDS-408
MDS-408
MDS-408
MDS-408
MDS-408
MDS-408
MDS-408
MDS-408
500
5.0%
1203 50000
100000
150000
250000
500000
Unlimited
20000
21900
22500
23100
23600
24100
4800 24800
26700
27300
27900
28400
28900
MDS-616
➁ MDS-408
MDS-408
MDS-408
MDS-408
MDS-408
MDS-408
MDS-08
MDS-408
MDS-408
MDS-408
MDS-408
MDS-408
750
5.75%
1804 50000
100000
150000
250000
500000
Unlimited
24900
27800
28900
29800
30600
31400
7200 32100
35000
36100
37000
37800
38600
MDS-620
➁ MDS-408
MDS-408
MDS-408
MDS-408
MDS-408
MDS-408
MDS-408
MDS-408
MDS-408
MDS-408
MDS-408
MDS-408
1000
5.75%
2406 50000
100000
150000
250000
500000
Unlimited
31000
35600
37500
39100
40400
41800
9600 40600
45200
47100
48700
50000
51400
MDS-632
➁ MDS-408
MDS-608
MDS-608
MDS-608
MDS-608
MDS-608
MDS-408
MDS-608
MDS-608
MDS-608
MDS-608
MDS-608
➀ At transformer self-cooled rating.
➁ Next larger frame size main breaker may be
required for 55/65°C rise and/or forced air-
cooled (FA) transformer. Check Transformer
Secondary Ampere Rating.
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