J.H. Larson Company  
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FPE Buck-Boost Transformer Selection Chart
240x480 Volts Primary–24/48 Volts Secondary
 Three Phase BOOSTING BUCKING
Line Voltage (Available)  399Y
230		 380 430 440 460 460 480 480 440 440 460 460 460 480 500 500
Load Voltage (Available)  480Y
277		 418 473 462 506 483 528 504 400 419 438 418 457 436 455 476
Catalog Number Connection
Diagram		 E G G H G H G H G H H G H G G H
SB24N.050F
0.05 KVA		 KVA
Amps
Fuse**		 0.86
1.04
2*		 0.75
1.04
1.5*		 0.85
1.04
1.5*		 1.67
2.08
3		 0.91
1.04
1.5*		 1.74
2.08
3		 0.95
1.04
1.5*		 1.82
2.08
3		 0.79
1.15
1.5*		 1.59
2.19
3		 1.66
2.19
3		 0.83
1.15
1.5*		 1.73
2.19
3		 0.87
1.15
1.5*		 0.90
1.15
1.5*		 1.80
2.19
3
SB24N.100F
0.10 KVA		 KVA
Amps
Fuse**		 1.73
2.08
4*		 1.51
2.08
3		 1.71
2.08
3		 3.33
4.17
6		 1.83
2.08
3		 3.49
4.17
6		 1.91
2.08
3		 3.64
4.17
6		 1.59
2.29
3		 3.18
4.38
6		 3.32
4.38
6		 1.66
2.29
3		 3.46
4.38
6		 1.73
2.29
3		 1.80
2.29
3		 3.61
4.38
6
SB24N.150F
0.15 KVA		 KVA
Amps
Fuse**		 2.59
3.13
6		 2.26
3.13
5*		 2.56
3.13
5*		 5.00
6.25
10		 2.74
3.13
5*		 5.23
6.25
10		 2.86
3.13
5*		 5.46
6.25
10		 2.38
3.44
5*		 4.76
6.56
10		 4.98
6.56
10		 2.49
3.44
5*		 5.20
6.56
10		 2.60
3.44
5*		 2.71
3.44
5*		 5.41
6.56
10
SB24N.250F
0.25 KVA		 KVA
Amps
Fuse**		 4.32
5.21
10		 3.77
5.21
8*		 4.27
5.21
8*		 8.34
10.42
15		 4.56
5.21
8*		 8.71
10.42
15		 4.76
5.21
8*		 9.09
10.42
15		 3.97
5.73
8*		 7.94
10.94
15		 8.30
10.94
15		 4.15
5.73
8*		 8.66
10.94
15		 4.33
5.73
8*		 4.51
5.73
8*		 9.02
10.94
15
SB24N.500F
0.50 KVA		 KVA
Amps
Fuse**		 8.64
10.42
20		 7.54
10.42
15		 8.53
10.42
15		 16.67
20.83
30		 9.13
10.42
15		 17.43
20.83
30		 9.53
10.42
15		 18.19
20.83
30		 7.94
11.46
15		 15.88
21.88
30		 16.60
21.88
15		 8.30
11.46
15		 17.32
21.88
30		 8.66
11.46
15		 9.02
11.46
15		 18.04
21.88
30
SB24N.750F
0.75 KVA		 KVA
Amps
Fuse**		 12.96
15.62
25		 11.31
15.63
25		 12.80
15.63
25		 25.01
31.25
45		 13.69
15.63
25		 26.14
31.25
45		 14.29
15.63
25		 27.28
31.25
45		 11.91
17.19
20		 23.82
32.81
40		 24.90
32.81
40		 12.45
17.19
20		 25.98
32.81
40		 12.99
17.19
20		 13.53
17.19
20		 27.06
32.81
40
SB24N1F
1.00 KVA		 KVA
Amps
Fuse**		 17.28
20.83
35		 15.08
20.83
30		 17.07
20.83
30		 33.34
41.67
60		 18.26
20.83
30		 34.86
41.67
60		 19.05
20.83
30		 36.37
41.67
60		 15.88
22.92
30		 31.75
43.75
60		 33.20
43.75
60		 16.60
22.92
30		 34.64
43.75
60		 17.32
22.92
30		 18.04
22.92
30		 36.08
43.75
60
SB24N1.5F
1.50 KVA		 KVA
Amps
Fuse**		 25.92
31.25
50		 22.62
31.25
45		 25.60
31.25
45		 50.01
62.50
90		 27.39
31.25
45		 52.29
62.50
90		 28.58
31.25
45		 54.66
62.50
90		 23.82
34.38
40		 47.63
65.63
80		 49.80
65.63
80		 24.90
34.38
40		 51.96
65.63
80		 25.98
34.37
40		 27.06
34.37
40		 54.13
65.63
80
SB24N2F
2.00 KVA		 KVA
Amps
Fuse**		 34.55
41.67
70		 30.17
41.67
60		 34.14
41.67
60		 66.68
83.33
70		 36.52
41.67
60		 69.72
83.33
70		 38.11
41.67
60		 72.75
83.33
70		 31.75
45.83
60		 63.51
87.50
70		 66.40
87.50
70		 33.20
45.83
60		 69.28
87.50
70		 34.64
45.83
60		 36.08
45.83
60		 72.17
87.50
70
SB24N3F
3.00 KVA		 KVA
Amps
Fuse**		 51.83
62.50
100		 45.25
62.50
90		 51.20
62.50
90		 100.03
125.00
175		 54.78
62.50
90		 104.57
125.00
175		 57.16
62.50
90		 109.12
125.00
175		 47.63
68.75
80		 95.26
131.25
175		 99.59
131.25
175		 49.80
68.75
80		 103.92
131.25
175		 51.96
68.75
80		 54.13
68.75
80		 108.25
131.25
175
SB24N5F
5.00 KVA		 KVA
Amps
Fuse**		 86.39
104.17
175		 75.42
104.17
150		 85.34
104.17
150		 166.71
208.33
300		 91.29
104.17
150		 174.29
208.33
300		 95.26
104.17
150		 181.87
208.33
300		 79.39
114.58
150		 158.77
218.75
300		 165.99
218.75
300		 82.99
114.58
150		 173.21
218.75
300		 86.60
114.58
150		 90.21
114.58
150		 180.42
218.75
300
No. of Transformers 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2
Catalog Number Connection
Diagram		 E G G H G H G H G H H G H G G H
 * Non-NEC standard fuse size (NEC 240-6), check with local authorities for use of next larger size.
 ** Maximum fuse or circuit breaker size per NEC 450-4.
 
  Output for lower voltage can be found by:  Rated Output Voltage
Rated Input Voltage		 x  Input Actual Voltage = Output New Voltage.
 
Output KVA available at reduced voltage can be found by:  Actual Input Voltage
Rated Input Voltage		 x  Output KVA = New KVA Rating.
 

 Other Selection Charts
 120x240V - 12/24V 1Ø Phase
 120x240V - 12/24V 3Ø Phase
 120x240V - 16/32V 1Ø Phase
 120x240V - 16/32V 3Ø Phase
 240x480V - 24/48V 1Ø Phase
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