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Single phase pad mounted transformers
25 to 167 kVA at 120/240 volts, the units that feed houses, small commercial services and pumps. Smaller, lighter and cheaper than the three phase equivalents, and a different product line rather than a smaller version of the same thing.
| Rating | Cabinet, in | Weight, lb | Impedance | Secondary at 240 V | Typical use |
|---|---|---|---|---|---|
| 25 kVA | 30 x 32 x 38 | 470 | 2.2 % | 104 A | One or two houses on an underground lateral, a small well pump, a lift station |
| 50 kVA | 32 x 34 x 40 | 610 | 2.3 % | 208 A | Three to five houses, a small commercial unit, a irrigation pump |
| 75 kVA | 34 x 36 x 42 | 780 | 2.4 % | 313 A | Five to eight houses, a small strip unit, a convenience store |
| 100 kVA | 36 x 38 x 44 | 950 | 2.5 % | 417 A | Eight to twelve houses, a small apartment building, a fast food unit |
| 167 kVA | 40 x 42 x 48 | 1,240 | 2.6 % | 696 A | A large single phase service, a rural commercial load, an agricultural pump station |
Dimensions and weights are typical and vary between manufacturers. Free to cite with a link to this page.
Common questions
What is the difference between a single phase and a three phase pad mounted transformer
A single phase unit has one high voltage bushing set and delivers 120/240 volts to houses and small services. A three phase unit has three and delivers 480Y/277 or 208Y/120 to commercial and industrial loads. Single phase units are smaller, lighter and far cheaper, and most residential subdivisions run entirely on them.
How many houses can one single phase pad mounted transformer serve
It depends on the utility and the local load, but a rough working figure is one house per 10 to 15 kVA. A 50 kVA unit commonly serves three to five houses and a 100 kVA unit eight to twelve. The utility makes the final call from its own load study.
What is the secondary current of a 75 kVA single phase transformer
About 313 amps at 240 volts. Single phase current is kVA times 1000 divided by the voltage, with no square root of three, which is why the figure is much higher than people expect if they are used to three phase numbers.
Why is 167 kVA a standard rating
Because it is one third of 500 kVA. Three 167 kVA single phase units make a 500 kVA three phase bank, which is how utilities build larger capacity from single phase stock.
Need three phase instead. See the 45 to 2500 kVA three phase range, or ask for a quote.