Dongan Electric Manufacturing Buck-Boost Transformer Catalog Page
Buck-Boost Transformer
Terms & Definitions
Buck‑Boost transformers are single phase, four
winding transformers designed for two purposes.
The rst purpose is as a low voltage isolation
transformer for use on 12, 16, 24, 32, or 48 volt
circuits. When used as low voltage transformers,
Buck‑Boost transformers have capacities of .050
kVA to 5.0 kVA. Their second, and more important
use, is as a Buck‑Boost transformer. Buck‑Boost
means that these transformers are used to buck
(lower) or boost (increase) line voltage to match
required load voltage.
Buck‑Boost transformers are used to correct
consistently low or high voltage conditions, where
the voltage difference ranges from approximately
5% to 27%. Variation of the input voltage is passed
through to the output side of the transformer in
the same percentage. This concept is important
because the question is frequently asked if Buck‑
Boost transformers will stabilize variable voltages.
They will not!
When connected as a Buck Boost transformer,
these transformers, with dual primaries of
120 x 240, or 240 x 480, and dual secondaries of
12 / 24, 16 / 32, or 24 / 48 volts, have literally
hundreds of voltage matching applications.
Applications:
The most common applications for these
transformers are boosting 208 volt lines to 230
or 240 volts, and vice‑versa. These applications
include both single and three phase lines and are
particularly common in HVAC applications for air‑
conditioning appliances.
Additionally, Buck‑Boost transformers are very
well suited to motor loads, boosting 240 to 277
for lighting loads and many applications where
nominal voltage is above or below 120 volts. Their
use should be considered where supply line voltage
is found to be consistently above or below desired
nominal values of load voltage.
Single Phase Applications:
Single phase applications require the purchase
of one transformer. Charts are provided on Pages
35 ‑ 37 for sizing and specifying single phase
applications.
Three Phase Applications:
Three phase applications require banking either 2 or
3 Buck‑Boost transformers. Charts are provided on
Pages 38 ‑ 40 for sizing and specifying three phase
applications.
Connection/Configurations to Avoid:
Some line/load distribution system combinations
are to be avoided. For instance, closed delta
connections are not recommended because they
may cause phase shifting to occur on the load
side of the bank. In addition, they require larger
transformers to accomplish similar results and are,
therefore, less efcient and more expensive. Also,
a three phase, 4 wire wye supply line should be
connected to a wye conguration, 3 transformer
bank. This conguration will assure sufcient current
carrying capacity in the neutral of the wye circuit.
The chart below indicates distribution system
restrictions.
Input
(Supply System)
WYE 4 wire WYE 3 or 4 wire OK
WYE 3 or 4 wire OPEN DELTA 3 wire OK
CLOSED DELTA 3 Wire OPEN DELTA 3 wire OK
DELTA 3 Wire WYE 3 or 4 wire
OPEN DELTA 3 wire WYE 3 or 4 wire
WYE 3 or 4 wire CLOSED DELTA 3 Wire
Desired Output
Connection
DO NOT USE
DO NOT USE
DO NOT USE
36 Dongan
®
Electric Manufacturing Company
Single Phase Buck-Boost Sizing Tables
Single Phase Buck-Boost Table, Type M
Single Phase / Single Unit - Type M
Type M
Catalog
Number
35-M005
35-M010
35-M015
85-M020
85-M025
85-M030
85-M035
85-M040
85-M045
85-M050
85-M055
Qty. Required
Connection Dia. Page
Line
Load
Load Amps
kVA
Line Fuse
Load Amps
kVA
Line Fuse
Load Amps
kVA
Line Fuse
Load Amps
kVA
Line Fuse
Load Amps
kVA
Line Fuse
Load Amps
kVA
Line Fuse
Load Amps
kVA
Line Fuse
Load Amps
kVA
Line Fuse
Load Amps
kVA
Line Fuse
Load Amps
kVA
Line Fuse
Load Amps
kVA
Line Fuse
Boost - Increase Voltage Buck - Decrease Voltage
96
100
108
109
216
218
228
208
120
120
120
120
240
240
240
230
2.0 2.0 3.7 4.1 2.0 2.0 4.1 1.9 4.5 2.5 2.1 4.3 2.2
132
120
144
120
230
208
252
240
264
240
0.25 0.25 0.45 0.49 0.50 0.49 1.00 0.45 0.55 0.30 0.45 1.05 0.55
5 5 8 8 5 5 7 5 7 5 5 7 5
4.1 4.1 7.5 8.2 4.1 4.1 8.3 3.9 9.1 5.0 4.3 8.7 4.5
0.50 0.50 0.90 0.99 1.00 0.99 2.00 0.90 1.10 0.60 0.91 2.10 1.10
10 10 15 15 8 8 15 8 15 7 7 15 7
6.2 6.2 11.2 12.3 6.2 6.1 12.5 5.9 13.7 7.5 6.5 13.1 6.8
0.75 0.75 1.35 1.48 1.50 1.48 3.00 1.36 1.65 0.90 1.36 3.15 1.65
15 15 20 20 12 12 20 12 20 12 10 20 12
10.4 10.4 18.7 20.6 10.4 10.3 20.8 9.8 22.9 12.5 10.9 21.8 11.4
1.25 1.25 2.25 2.47 2.50 2.47 5.00 2.26 2.75 1.50 2.27 5.25 2.75
20 20 30 30 15 15 30 15 30 15 15 30 15
20.8 20.8 37.5 41.2 20.8 20.6 41.6 19.7 45.8 25.0 21.8 43.7 22.9
2.50 2.50 4.50 4.95 5.00 4.95 10.00 4.53 5.50 3.00 4.55 10.50 5.50
35 35 60 60 30 30 60 30 60 30 30 60 30
31.2 31.2 56.2 61.9 31.2 30.9 62.5 29.5 68.7 37.5 32.8 65.6 34.3
3.75 3.75 6.75 7.43 7.50 7.43 15.00 6.79 8.25 4.50 6.83 15.75 8.25
50 50 80 90 45 45 80 45 80 40 40 80 40
41.6 41.6 75.0 82.5 41.6 41.2 83.3 39.4 91.6 50.0 43.7 87.5 45.8
5.00 5.00 9.00 9.90 10.00 9.90 20.00 9.06 11.00 6.00 9.10 21.00 11.00
70 70 125 125 60 60 110 60 110 60 60 110 60
62.5 62.5 112.5 123.8 62.5 61.9 125.0 59.1 137.5 75.0 65.6 131.2 68.7
7.5 7.5 13.5 14.8 15.0 14.8 30.0 13.5 16.5 9.0 13.6 31.5 16.5
100 100 175 175 80 80 175 90 175 80 80 175 80
83.3 83.3 150.0 165.1 83.3 82.5 166.6 78.8 183.3 100.0 87.5 175.0 91.6
10.0 10.0 18.0 19.8 20.0 19.8 40.0 18.1 22.0 12.0 18.2 42.0 22.0
150 150 250 250 125 125 225 125 225 110 110 225 110
125.0 125.0 225.0 247.7 125.0 123.8 250.0 118.2 275.0 150.0 131.3 262.5 137.5
15.0 15.0 27.0 29.7 30.0 29.7 60.0 27.1 33.0 18.0 27.3 63.0 33.0
200 200 350 350 175 175 350 175 350 175 150 350 175
208.3 208.3 375.0 412.8 208.3 206.4 416.6 197.0 458.3 250.0 218.9 437.5 229.1
25.0 25.0 45.0 49.5 50.0 49.5 100.0 45.3 55.0 30.0 45.5 105.0 55.0
350 350 600 600 300 300 600 300 600 300 250 600 300
1 1 1 1 1 1 1 1 1 1 1 1 1
SP ‑ 843SP ‑1244SP ‑ 743SP ‑1144SP ‑ 643SP ‑1044SP ‑ 543SP ‑1044SP ‑ 343SP ‑ 443SP ‑ 243SP ‑143SP ‑ 2
43
37
Single Phase Buck-Boost Sizing Tables
Single Phase Buck-Boost Table, Type Y
Single Phase / Single Unit - Type Y
Boost - Increase Voltage Buck - Decrease Voltage
Type Y
Catalog
Number
35-Y005
35-Y010
35-Y015
85-Y020
85-Y025
85-Y030
85-Y035
85-Y040
85-Y045
85-Y050
85-Y055
Line
Load
Load Amps
kVA
Line Fuse
Load Amps
kVA
Line Fuse
Load Amps
kVA
Line Fuse
Load Amps
kVA
Line Fuse
Load Amps
kVA
Line Fuse
Load Amps
kVA
Line Fuse
Load Amps
kVA
Line Fuse
Load Amps
kVA
Line Fuse
Load Amps
kVA
Line Fuse
Load Amps
kVA
Line Fuse
Load Amps
kVA
Line Fuse
Qty. Required
Connection Dia. Page
88
12095120
1.5 1.9 3.1 3.1 1.5 3.1 3.1 1.5 3.5 1.9 3.3 1.7 1.8
0.18 0.23 0.37 0.37 0.37 0.75 0.75 0.37 0.42 0.23 0.80 0.42 0.37
5 5 5 5 5 5 5 5 5 5 5 5 5
3.1 3.9 6.2 6.3 3.1 6.2 6.2 3.1 7.0 3.9 6.6 3.5 3.6
0.37 0.47 0.75 0.75 0.75 1.50 1.50 0.75 0.85 0.47 1.60 0.85 0.75
7 8 12 12 6 10 10 6 10 5 10 5 5
4.6 5.9 9.3 9.4 4.7 9.3 9.3 4.6 10.6 5.9 10.0 5.3 5.4
0.56 0.71 1.12 1.13 1.13 2.25 2.25 1.12 1.27 0.71 2.40 1.27 1.12
10 15 15 15 9 15 15 9 15 8 15 8 8
7.8 9.8 15.6 15.7 7.8 15.6 15.6 7.8 17.7 9.8 16.6 8.8 9.0
0.93 1.18 1.87 1.89 1.89 3.75 3.75 1.87 2.12 1.18 4.00 2.12 1.87
15 25 25 25 15 25 25 15 20 15 20 15 15
15.6 19.7 31.2 31.5 15.7 31.2 31.2 15.6 35.4 19.7 33.3 17.7 18.0
1.87 2.37 3.75 3.78 3.78 7.50 7.50 3.75 4.25 2.37 8.00 4.25 3.75
3.0 35 45 45 25 45 45 25 4 25 40 25 25
23.4 29.6 46.8 47.3 23.6 46.8 46.8 23.4 53.1 29.6 50.0 26.5 27.0
2.81 3.56 5.62 5.67 5.67 11.25 11.25 5.62 6.37 3.56 12.00 6.37 5.62
40 50 70 70 35 70 70 35 60 30 60 35 30
31.2 39.5 62.5 63.0 31.5 62.5 62.5 31.2 70.8 39.5 66.6 35.4 36.0
3.75 4.75 7.50 7.57 7.57 15.00 15.00 7.50 8.50 4.75 16.00 8.50 7.50
60 70 90 90 45 90 90 50 80 40 80 45 40
46.8 59.3 93.7 94.6 47.3 93.7 93.7 46.8 106.2 59.3 100.0 53.1 54.0
5.6 7.1 11.2 11.3 11.3 22.5 22.5 11.2 12.7 7.1 24.0 12.7 11.2
80 100 150 150 70 125 125 70 125 60 125 70 60
62.5 79.1 125.0 126.1 63.0 125.0 125.0 62.5 141.6 79.1 133.3 70.8 72.1
7.5 9.5 15.0 15.1 15.1 30.0 30.0 15.0 17.0 9.5 32.0 17.0 15.0
110 125 200 200 90 175 175 100 175 80 150 90 80
93.7 118.7 187.5 189.2 94.6 187.5 187.5 93.7 212.5 118.7 200.0 106.2 108.1
11.2 14.2 22.5 22.7 22.7 45.0 45.0 22.5 25.5 14.2 48.0 25.5 22.5
175 200 300 300 150 300 300 150 250 125 225 150 125
156.2 197.9 312.5 315.4 157.7 312.5 312.5 156.2 354.1 197.9 333.3 177.0 180.2
18.7 23.7 37.5 37.8 37.8 75.0 75.0 37.5 42.5 23.7 80.0 42.5 37.5
300 350 500 450 250 450 450 250 400 200 400 250 200
1 1 1 1 1 1 1 1 1 1 1 1 1
SP ‑ 8 43SP
104
106
212
224
225
208
120
120
240
240
240
240
‑12 44SP ‑ 7 43SP ‑11 44SP ‑ 10 44SP ‑ 5 43SP ‑ 9 44SP ‑ 643SP ‑ 3 43SP ‑ 4 43SP ‑ 1 43SP ‑ 2 43SP ‑13
136
120
152
120
256
240
272
240
240
208
44
38 Dongan
®
Electric Manufacturing Company
Single Phase Buck-Boost Sizing Tables
Single Phase Buck-Boost Table, Type LM
Single Phase / Single Unit - Type LM
Type LM
Catalog
Number
35-LM010
35-LM015
85-LM020
85-LM025
85-LM030
85-LM035
85-LM040
85-LM045
85-LM050
85-LM055
Qty. Required
Connection Dia. Page
Line
Load
Load Amps
kVA
Line Fuse
Load Amps
kVA
Line Fuse
Load Amps
kVA
Line Fuse
Load Amps
kVA
Line Fuse
Load Amps
kVA
Line Fuse
Load Amps
kVA
Line Fuse
Load Amps
kVA
Line Fuse
Load Amps
kVA
Line Fuse
Load Amps
kVA
Line Fuse
Load Amps
kVA
Line Fuse
Boost - Increase Voltage Buck - Decrease Voltage
192
200
216
218
432
437
456
457
240
240
240
240
480
480
480
480
2.0 2.0 4.1 4.1 2.0 2.1 4.1 4.1 4.5 2.4 4.5 2.5 4.3 2.2
0.50 0.50 1.00 1.00 1.00 1.01 2.00 1.98 1.05 0.56 1.10 0.60 2.10 1.10
5 5 8 7 5 5 7 7 7 5 7 7 5 7
3.1 3.1 6.2 6.2 3.1 3.1 6.2 6.2 6.8 3.6 6.8 3.7 6.5 3.4
0.75 0.75 1.50 1.50 1.50 1.52 3.00 2.98 1.58 0.84 1.65 0.90 3.15 1.65
7 7 10 12 6 6 10 10 10 5 10 5 10 5
5.2 5.2 10.4 10.4 5.2 5.2 10.4 10.3 11.4 6.1 11.4 6.2 10.9 5.7
1.25 1.25 2.50 2.50 2.50 2.54 5.00 4.96 2.63 1.41 2.75 1.50 5.25 2.75
10 10 15 15 10 10 15 15 15 9 15 9 15 9
10.4 10.4 20.8 20.8 10.4 10.5 20.8 20.6 22.9 12.2 22.9 12.5 21.8 11.4
2.50 2.50 5.00 5.00 5.00 5.08 10.00 9.93 5.27 2.82 5.50 3.00 10.50 5.50
20 20 30 30 15 15 30 30 30 15 30 15 30 15
15.6 15.6 31.2 31.2 15.6 15.8 31.2 31.0 34.3 18.4 34.3 18.7 32.8 17.1
3.75 3.75 7.50 7.50 7.50 7.62 15.00 14.90 7.90 4.23 8.25 4.50 15.75 8.25
25 25 45 45 25 25 45 45 40 20 20 20 40 20
20.8 20.8 41.6 41.6 20.8 21.1 41.6 41.3 45.8 24.5 45.8 25.0 43.7 22.9
5.00 5.00 10.00 10.00 10.00 10.16 20.00 19.87 10.54 5.64 11.00 6.00 21.00 11.00
35 35 60 60 30 30 60 60 60 30 60 30 60 30
31.2 31.2 62.5 62.5 31.2 31.7 62. 62.0 68.7 36.8 68.7 37.5 65.6 34.3
7.50 7.50 15.00 15.00 15.00 15.24 30.00 29.80 15.81 8.47 16.50 9.00 31.50 16.50
50 50 90 90 45 45 90 90 80 40 80 40 80 40
41.6 41.6 83.3 83.3 41.6 42.3 83.3 82.7 91.6 49.1 91.6 50.0 87.5 45.8
10.0 10.0 20.0 20.0 20.0 20.3 40.0 39.7 21.0 11.2 22.0 12.0 42.0 22.0
70 70 125 125 60 60 110 110 110 60 110 60 110 60
62.5 62.5 125.0 124.9 62.5 63.5 125.0 124.1 137.5 73.6 137.5 75.0 131.2 68.7
15.0 15.0 30.0 30.0 30.0 30.4 60.0 59.6 31.6 16.9 33.0 18.0 63.0 33.0
100 100 175 175 90 90 175 175 175 80 175 80 175 80
104.1 104.1 208.3 208.3 104.1 105.8 208.3 206.9 229.1 122.7 229.1 125.0 218.7 114.5
25.0 25.0 50.0 50.0 50.0 50.8 100.0 99.3 52.7 28.2 55.0 30.0 105.0 55.0
175 175 300 300 150 150 300 300 300 150 300 150 300 150
1 1 1 1 1 1 1 1 1 1 1 1 1 1
SP ‑ 843SP ‑1244SP ‑ 743SP ‑1144SP ‑ 643SP ‑1044SP ‑ 543SP ‑ 944SP ‑ 343SP ‑ 443SP ‑ 343SP ‑ 443SP ‑ 143SP ‑ 2
253
230
277
230
264
240
288
240
504
480
528
480
43
39
Three Phase Buck-Boost Sizing Tables
Three Phase Buck-Boost Table, Type M
Three Phase / Two or Three Units - Type M
Type M
Catalog
Number
35-M005
35-M010
35-M015
85-M020
85-M025
85-M030
85-M035
85-M040
85-M045
85-M050
85-M055
Qty. Required
Connection Dia. Page
Line
Load
Load Amps
kVA
Line Fuse
Load Amps
kVA
Line Fuse
Load Amps
kVA
Line Fuse
Load Amps
kVA
Line Fuse
Load Amps
kVA
Line Fuse
Load Amps
kVA
Line Fuse
Load Amps
kVA
Line Fuse
Load Amps
kVA
Line Fuse
Load Amps
kVA
Line Fuse
Load Amps
kVA
Line Fuse
Load Amps
kVA
Line Fuse
166
173
208
208
1.6 2.0 3.6 4.1 1.8 3.9 1.8 2.0 3.9 4.1 4.5 2.4 4.3 2.2 4.3 2.2
0.60 0.75 1.30 1.64 0.77 1.64 1.34 1.50 2.85 3.95 1.64 0.90 1.82 0.95 3.12 1.65
5 5 7 8 5 7 5 5 7 7 7 5 7 5 7 5
3.3 4.1 7.2 8.2 3.7 7.8 3.7 4.1 7.9 8.3 9.1 4.9 8.7 4.5 8.6 4.5
1.20 1.49 2.60 3.29 1.55 3.28 2.69 3.00 5.70 5.99 3.29 1.80 3.64 1.90 6.24 3.30
7 8 15 12 7 15 7 7.5 15 15 15 7 15 7 15 7
4.9 6.2 10.8 12.4 5.5 11.8 5.6 6.2 11.8 12.4 13.7 7.4 13.1 6.8 12.9 6.8
1.80 2.24 3.90 4.94 2.32 4.92 4.04 4.50 8.55 8.99 4.94 2.70 5.46 2.86 9.36 4.95
10 12 20 20 10 20 12 10 20 20 20 10 20 10 20 10
8.3 10.4 18.0 20.6 9.3 19.7 9.3 10.4 19.7 20.8 22.8 12.4 21.9 11.4 21.6 11.4
3.00 3.74 6.50 8.23 3.87 8.20 6.74 7.50 14.26 14.99 8.23 4.50 9.10 4.76 15.60 8.25
15 20 30 30 15 30 15 15 30 30 30 15 30 15 30 15
16.6 20.8 36.0 41.3 18.6 39.4 18.7 20.8 39.5 41.6 45.7 24.9 43.8 22.9 43.3 22.9
6.00 7.49 13.00 16.46 7.75 16.40 13.49 15.00 28.52 29.98 16.46 9.00 18.20 9.53 31.21 16.50
30 35 60 60 30 60 30 30 60 60 60 30 60 30 60 30
24.9 31.2 54.1 62.0 27.9 59.1 28.0 31.2 59.3 62.42 68.5 37.4 65.7 34.4 64.9 34.3
9.00 11.24 19.50 24.69 11.62 24.60 20.23 22.50 42.78 44.97 24.69 13.50 27.31 14.30 46.82 24.75
45 50 80 90 45 80 45 45 80 90 80 45 80 45 80 45
33.3 41.6 72.1 82.6 37.2 78.9 37.4 41.6 79.1 83.2 91.4 49.9 87.6 45.8 86.6 45.8
12.00 14.99 26.00 32.93 15.50 32.80 26.98 30.00 57.05 59.97 32.93 18.00 36.41 19.07 62.49 33.00
60 70 110 125 60 110 60 60 110 110 110
49.9 62.4 108.2 124.0 55.9 118.3 56.17 62.45 118.7 124.8 137.1 74.9 131.4 68.8 129.9 68.7
18.00 22.49 39.00 49.39 23.25 49.20 40.47 45.00 85.57 89.95 49.39 27.00 54.62 28.61 93.64 49.50
80 100 175 175 80 175 80 90 175 175 175 80 175 80 175 80
66.6 83.2 144.3 165.3 74.5 157.8 74.8 83.2 158.3 166.4 182.8 99.9 175.2 91.7 173.2 91.6
24.0 29.9 52.0 65.8 31.1 65.6 53.9 60.0 114.1 119.9 65.8 36.0 72.8 38.1 124.8 66.0
110 150 225 250 110 250 110 125 250 250 225 110 225 110 225 110
99.9 124.8 216.5 248.0 111.8 236.7 112.3 124.9 237.5 249.6 274.2 149.9 262.8 137.6 259.9 137.4
36.0 44.9 78.8 98.7 46.5 98.4 80.9 90.00 171.1 179.9 98.7 54.0 109.2 57.2 187.2 99.0
175 200 350 400 175 250 175 175 350 350 350 175 350 175 350 175
166.6 208.1 360.8 413.3 186.4 394.5 187.2 208.1 395.9 416.1 457.0 249.8 438.0 229.4 433.2 229.0
60.0 74.9 130.0 164.6 77.5 164.0 134.9 150.0 285.2 299.8 164.6 90.0 182.0 95.3 312.1 165.0
300 350 600 600 300 600 200 300 600 600 600 300 600 300 600 300
3 3 3 3 2 2 3 3 3 3 3 3 2 2 3 3
TP‑1846TP‑2247TP‑1746TP‑2147TP‑545TP‑645TP‑2047TP‑2447TP‑1947TP‑2347TP‑1346TP‑1446TP‑1046TP‑945TP‑1546TP‑16
Boost - Increase Voltage Buck - Decrease Voltage
187
208
216
228
374
377
395
397
208
230
240
240
416
416
416
416
230
249
252
208
208
240
60 110 60 110 60
264
240
437
416
457
416
46
40 Dongan
®
Electric Manufacturing Company
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