Three Phase Isolation Transformer Selection Guide

Three Phase Isolation Transformer Selection Guide

TEMCo Three Phase Isolation Transformers are 50/60 Hz rated and come in a NEMA 3R enclosure for indoor use as well as outdoor protection against rain and sleet. Our transformers are built to last, guaranteed. That's why we back these with a decade long warranty. For single phase copper or aluminum windings in other sizes, please refer to the Single Phase Isolation Transformer Selection Guide.


  • 50/60 Hz
  • NEMA 3R
  • 150°C rise UL Listed and CSA Certified 10 Year Warranty
TEMCO 3 Phase Isolation Transformer

How to Select a Transformer

Selecting the right voltage transformer is simple. Review the following considerations to determine the best fit for your application. Then, select a transformer from one of the tables below.

Input Voltage

Select a transformer that will operate on the supply voltage available at your facility (Example: 120V, 240V, or 480V). To ensure compatibility, check the wiring diagram by clicking a part number and viewing its product page.


All the transformers in this section are rated for both 50 and 60 Hz, for use worldwide.


Copper wound models cost more than the equivalent aluminum wound versions. The primary advantage of copper is its superior corrosion resistance. Copper wound transformers are commonly used for corrosive or high humidity environments like marine applications, and when cost is not a factor.

kVA or Amp Output

Select a transformer with kVA based on your load requirements. It is fine to oversize significantly, but never to undersize for your load. For motor loads, do not exceed 60% of the maximum capacity of the transformer, because electric motors have start up requirements significantly higher than their running requirements.

3 Phase Isolation Transformer Product Selection

Below is a list of all the TEMCo three phase isolation transformer configurations we offer. First, find the primary voltage you need. Then, click on the primary voltage you need to view the full product selection of secondary voltage configurations.

Transformer sizes offered from 3 to 330 kVA.

Primary (Input) Voltage
A. 600 » K. 230 »
B. 575 » L. 220 »
C. 550 » M. 216 »
D. 480 » N. 208 »
E. 460 » O. 200 »
F. 440 » P. 190 »
G. 416 » Q. 120 »
H. 400 » R. 115 »
I. 380 » S. 110 »
J. 240 » T. 100 »