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hubbell-acmeelectric.comTransformer Selection Steps
D r y - T y p e D i s t r i b u t i o n T r a n s f o r m e r s
①
When motor service factor is greater than 1, increase
full load amps proportionally.
Example:
If service factor is
1.15, increase above amp values by 15%.
3 Phase kVA =
Volts x Amps x 1.73
1000
Note:
If motors are started more than once per hour,
increase minimum transformer kVA by 20%.
Table 3
Full Load Current in Amperes–
Three Phase Circuits
Horsepower
208V
230V
460V
575V
Minimum
Transformer
KVA
1/2
2.2
2.0
1.0
0.8
0.9
3/4
3.1
2.8
1.4
1.1
1.2
1
4.0
3.6
1.8
1.4
1.5
2
7.5
6.8
3.4
2.7
2.7
3
10.7
9.6
4.8
3.9
3.8
5
16.7
15.2
7.6
6.1
6.3
10
31
28
14
11
11.2
15
46
42
21
17
16.6
20
59
54
27
22
21.6
25
75
68
34
27
26.6
30
88
80
40
32
32.4
40
114
104
52
41
43.2
50
143
130
65
52
52
60
170
154
77
62
64
75
213
192
96
77
80
100
273
248
124
99
103
125
342
312
156
125
130
150
396
360
180
144
150
200
528
480
240
192
200
Table 4
Full Load Amperes
Three Phase A.C. Motors
①
kVA 208V 240V 380V 440V 480V 600V
3
8.3
7.2
4.6
3.9
3.6
2.9
4.5
12.5 10.8
6.8
5.9
5.4
4.3
6
16.6 14.4
9.1
7.8
7.2
5.8
9
25
21.6 13.7
11.8 10.8
8.6
15
41
36
22.8
19.6 18.0 14.4
22.5
62
54
34.2
29
27
21.6
30
83
72
45.6
39
36
28
45
124
108
68.4
59
54
43
75
208
180
114
98
90
72
112.5 312
270
171
147
135
108
150
416
360
228
196
180
144
225
624
541
342
294
270
216
300
832
721
456
392
360
288
500 1387 1202 760
655
601
481
750 2081 1804 1139 984
902
721
1000 2775 2405 1519 1312 1202 962