Selection Steps
A. Use the following steps below to manually select
a transformer.
B. Findtheelectricalloadrequirements.Theseare:
1. Load operating voltage.
2. Load frequency (expressed in Hz).
3. Determine load size - usually expressed in kVA,
amperage or horsepower.
4. Is the load designed to operate on single phase
or three phase power?
This information is available from the equipment
manufacturer and is typically listed on the nameplate
of the equipment.
C. Know the supply voltage conditions:
1. Available source voltage.
2. Available source frequency (a transformer will not
change frequency. The frequency of the supply
voltage and the needed load voltage must be equal).
3. Number of phases on power source.
D. Determine the transformer kVA rating:
1. If the load is expressed in kVA, select the appropriate
transformer from the following selection charts (make
sure the selected transformer’s kVA rating is equal to
or greater than the required load kVA).
2. If the load is expressed in amperage, use either
the appropriate kVA formula listed below or the
appropriate sizing chart on the next page.
Transformers
3. If the load is expressed in wattage, either utilize the
formula below to convert to kVA or refer to the
equipment nameplate to obtain amperage
requirement.
4. If the load is a motor and expressed in horsepower,
refer to the motor horsepower charts on the
next page.
Some sizes may require an optional weather shield
(order separately) for outdoor use.
kVA =
(1000 x Power Factor of the load)
Wattage
5
kVA (1Ø) =
kVA (3Ø) =
Volts x Amps
1000
Volts x Amps x 1.732
1000
Contact Technical Services at (800) 377-4384 with any questions.
Always size the transformer
to the load requirements.
195
Visit our website at www.solahd.com.
5
Transformers
Single Phase:
Full Load Current Chart
kVA
120 V 208 V 240 V 277 V 480 V 600 V
Rating
Amperes
0.05 0.42 0.24 0.21 0.18 0.1 0.08
0.075 0.63 0.36 0.31 0.27 0.16 0.13
0.1 0.83 0.48 0.42 0.36 0.21 0.17
0.15 1.3 0.72 0.63 0.54 0.31 0.25
0.25 2.1 1.2 1 0.9 0.52 0.42
0.5 4.2 2.4 2.1 1.8 1.4 0.83
0.75 6.3 3.6 3.1 2.7 1.6 1.3
1 8.3 4.8 4.2 3.6 2.1 1.7
1.5 12.5 7.2 6.3 5.4 3.1 2.5
2 16.7 9.6 8.3 7.2 4.2 3.3
3 25 14.4 12.5 10.8 6.3 5
5 41.7 24 20.8 18.1 10.4 8.3
7.5 62.5 36.1 31.3 27.1 15.6 12.5
10 83.3 48.1 41.7 36.1 20.8 16.7
15 125 72.1 62.5 54.2 31.3 25.0
25 208.3 120.2 104.2 90.3 52.1 41.7
37.5 312.5 180.3 156.3 135.4 78.1 62.5
50 416.7 240.4 208.3 180.5 104.2 83.3
75 625 361 313 271 156 125.0
100 833 481 417 361 208 167.0
167 1392 803 696 603 348 278.0
200 1667 962 833 722 417 333.0
250 2083 1202 1042 903 521 417.0
Three Phase: Full Load Current Chart
kVA
Rating
112.5 312 271 135 108.0
150 416 361 180 144.0
225 625 541 271 217.0
300 833 722 361 289.0
500 1388 1203 601 481.0
208 V 240 V 480 V 600 V
Amperes
3 8.3 7.2 3.6 2.9
6 16.7 14.4 7.2 5.8
9 25 21.7 10.8 8.7
15 41.6 36.1 18 14.4
30 83.3 72.2 36.1 28.9
45 125 108.3 54.1 43.3
75 208.2 180.4 90.2 72.2
Single Phase Motor Chart:
AC, Motor Horsepower Amperage
Horse
115 V208 V230 V460 V575
Power
1/6 4.4 2.4 2.2 1.1 0.9 0.53 0.75
¼ 5.8 3.2 2.9 1.4 1.2 0.7 0.75
1/3 7.2 4 3.6 1.8 1.4 0.87 1
½ 9.8 5.4 4.9 2.5 2 1.2 1.5
¾ 13.8 7.6 6.9 3.5 2.8 1.7 2
1 16 8.8 8 4 3.2 1.9 2
1½ 20 11 10 5 4 2.4 3
2 24 13.2 12 6 4.8 2.9 3
3 34 18.7 17 8.5 6.8 4.1 5
5 56 30.8 28 14 11.2 6.7 7.5
7.5 80 44 40 21 16 9.6 10
10 100 55 50 26 20 12 15
Mini
Tfmr.
V
kVA
Three Phase Motor Chart:
AC, Motor Horsepower Amperage
Horse
208 V 230 V 460 V 575 V
Power
½ 2.2 2 1 0.8 0.9 3.0
¾ 3.1 2.8 1.4 1.1 1.2 3.0
1 4 3.6 1.8 1.4 1.5 3.0
1½ 5.7 5.2 2.6 2.1 2.1 3.0
2 7.5 6.8 3.4 2.7 2.7 3.0
3 10.7 9.6 4.8 3.9 3.8 6.0
5 16.7 15.2 7.6 6.1 6.3 9.0
7½ 24 22 11 9 9.2 15.0
10 31 28 14 11 11.2 15.0
15 46 42 21 17 16.6 30.0
20 59 54 27 22 21.6 30.0
25 75 68 34 27 26.6 30.0
30 88 80 40 32 32.4 45.0
40 114 104 52 41 43.2 45.0
50 143 130 65 52 52 75.0
60 170 154 77 62 64 75.0
75 211 192 96 77 80 112.5
100 273 248 124 99 103 112.5
125 342 312 156 125 130 150.0
150 396 360 180 144 150 150.0
200 528 480 240 192 200 225.0
Mini
Tfmr.
kVA
Std.
NEMA
kVA
Size
Std.
NEMA
kVA
Size
Three things to keep in mind:
1. Motor horsepower charts are
based on 1800 RPM squirrel cage
induction motors. If using another
type of motor, check running
amperage against the chart and
adjust as necessary.
2. Increase required transformer kVA
by 20% if motors are started more
than once per hour.
3. If your motor service factor is
greater than 1, proportionally
increase full load amperage. (i.e.
– if service factor is 1.10, increase
full load amperage by 10%).
Are there any special application
considerations?
A. For ambient conditions over 40°C,
derate the transformer nameplate
kVA by 8% for each 10°C above
40°C.
B. For high altitude applications, derate
the transformer nameplate kVA
by 0.3% for every 330 feet over
3300 feet above sea level. This
assures proper transformer
convection cooling.
C. Some applications may require
a transformer design that limits
theBTUoutputoftheunitatfull
load or a design to withstand and
mitigatespecicelectrical
anomalies.
196
Contact Technical Services at (800) 377-4384 with any questions.
Visit our website at www.solahd.com.
Loading...