J.H. Larson Company  
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FPE Buck-Boost Transformer Selection Chart
240x480 Volts Primary–24/48 Volts Secondary
 Single Phase BOOSTING BUCKING
Line Voltage (Available)  230 380 416 425 430 435 440 450 465 132 277 480 480 504
Load Voltage (Output)  276 418 458 468 473 457 462 495 483 126 231 436 457 480
Catalog Number Connection
Diagram		 B D D D D C C D C C B D C C
SB24N.050F
0.05 KVA		 KVA
Amps
Fuse**		 0.29
1.04
2*		 0.44
1.04
1.5*		 0.48
1.04
1.5*		 0.49
1.04
1.5*		 0.49
1.04
1.5*		 0.95
2.08
3		 0.96
2.08
3		 0.52
1.04
1.5*		 1.01
2.08
3		 0.28
2.19
3		 0.29
1.25
1.5*		 0.50
1.15
1.5*		 1.02
2.19
3		 1.05
2.19
3
SB24N.100F
0.10 KVA		 KVA
Amps
Fuse**		 0.58
2.08
4*		 0.87
2.08
3		 0.95
2.08
3		 0.97
2.08
3		 0.99
2.08
3		 1.90
4.17
6		 1.93
4.17
6		 1.03
2.08
3		 2.01
4.17
6		 0.55
4.38
6		 0.58
2.50
3		 1.00
2.29
3		 2.00
4.38
6		 2.10
4.38
6
SB24N.150F
0.15 KVA		 KVA
Amps
Fuse**		 0.86
3.13
6		 1.31
3.13
5*		 1.43
3.13
5*		 1.46
3.13
5*		 1.48
3.13
5*		 2.85
6.25
10		 2.89
6.25
10		 1.55
3.13
5*		 3.02
6.25
10		 0.83
6.56
10		 0.87
3.75
5*		 1.50
3.44
5*		 3.00
6.56
10		 3.15
6.56
10
SB24N.250F
0.25 KVA		 KVA
Amps
Fuse**		 1.44
5.21
10		 2.18
5.21
8*		 2.38
5.21
8*		 2.43
5.21
8*		 2.46
5.21
8*		 4.76
10.42
15		 4.81
10.42
15		 2.58
5.21
8*		 5.03
10.42
15		 1.38
10.94
15		 1.44
6.25
8*		 2.50
5.73
8*		 5.00
10.94
15		 5.25
10.94
15
SB24N.500F
0.50 KVA		 KVA
Amps
Fuse**		 2.88
10.42
20		 4.35
10.42
15		 4.77
10.42
15		 4.87
10.42
15		 4.93
10.42
15		 9.52
20.83
30		 9.63
20.83
30		 5.16
10.42
15		 10.06
20.83
30		 2.75
21.88
30		 2.89
12.50
15		 5.00
11.46
15		 10.00
21.88
30		 10.50
21.88
30
SB24N.750F
0.75 KVA		 KVA
Amps
Fuse**		 4.31
15.63
25		 6.53
15.63
25		 7.15
15.62
25		 7.30
15.63
25		 7.39
15.63
25		 14.27
31.25
45		 14.44
31.25
45		 7.73
15.63
25		 15.09
31.25
45		 4.13
32.81
40		 4.33
18.75
20		 7.50
17.91
20		 15.00
32.81
40		 15.75
17.19
40
SB24N1F
1.00 KVA		 KVA
Amps
Fuse**		 5.75
20.83
35		 8.71
20.83
30		 9.53
20.83
30		 9.74
20.83
30		 9.85
20.83
30		 19.03
41.67
60		 19.25
41.67
60		 10.31
20.83
30		 20.13
41.67
60		 5.50
43.75
60		 5.77
25.00
30		 10.00
22.92
30		 20.00
43.75
60		 21.00
43.75
60
SB24N1.5F
1.50 KVA		 KVA
Amps
Fuse**		 8.63
31.25
50		 13.06
31.25
45		 14.30
31.25
45		 14.61
31.25
45		 14.78
31.25
45		 28.55
62.50
90		 28.88
62.50
90		 15.47
31.25
45		 30.19
62.50
90		 8.25
65.63
80		 8.66
37.50
40		 15.00
34.37
40		 30.00
65.63
80		 31.50
65.63
80
SB24N2F
2.00 KVA		 KVA
Amps
Fuse**		 11.50
41.67
70		 17.42
41.67
60		 19.07
41.67
60		 19.48
41.67
60		 19.71
41.67
60		 38.06
83.33
110		 38.50
83.33
110		 20.63
41.67
60		 40.25
83.33
110		 11.00
87.50
110		 11.54
50.00
60		 20.00
45.83
60		 40.00
87.50
110		 42.00
87.50
110
SB24N3F
3.00 KVA		 KVA
Amps
Fuse**		 17.25
62.50
100		 26.13
62.50
90		 28.60
62.50
90		 29.22
62.50
90		 29.56
62.50
90		 57.09
125.00
175		 57.75
125.00
175		 30.94
62.50
90		 60.38
125.00
175		 16.50
131.25
175		 17.31
75.00
80		 30.00
68.75
80		 60.00
131.25
175		 63.00
131.25
175
SB24N5F
5.00 KVA		 KVA
Amps
Fuse**		 28.75
104.17
175		 43.54
104.17
150		 47.67
104.17
150		 48.70
104.17
150		 49.27
104.17
150		 95.16
208.33
300		 96.25
208.33
300		 51.56
104.17
150		 100.63
208.33
300		 27.50
218.75
300		 28.85
125.00
150		 50.00
114.58
150		 100.00
218.75
300		 105.00
218.75
300
Catalog Number Connection
Diagram		 B D D D D C C D C C B D C C
 * 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 3Ø Phase
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