Pole Mounted Transformers - Electric Utility Workhorse

By Gerry Fox - ET Editor

Pole Mounted Transformers
Utility Distribution Transformation

Pole mounted transformers are electric utility distribution transformers that are mounted on an electrical service pole (wood or concrete) and are usually at the level of the overhead cables. Pole mounted transformers are the common breadbox transformers used for converting distribution voltage to the 120/240 volt power used by homes and low-volume commercial installations.

Pole mounted electrical transformers are used in extensive rural area. These transformers range from 16 kVA to 100kVA and transform 11,000 to 33,000 volts down to a low voltage of 400 volts. Pole mounted transformers are reasonably small in size and mass so that it is easy to install them on single pole structures, and larger units on two-pole structures, approximately 5 meters above the ground. This makes the transformers inaccessible, reducing the risk of injury to animals and people and minimizing vandalism.

With exposure to harsh climate conditions and situated in remote areas, reliability has been built into the specification of these electrical transformers. Tanks are shaped to reduce accumulation of water and corrosive materials. Protective coatings are applied to tanks to reduce corrosion. In the coastal regions tanks are zinc sprayed. In highly corrosive areas tanks are made from Stainless or 3CR12 steel.

Pole mounted transformers are typically single-phase. However, vector designations determine the number of primary bushings and how the transformers can be connected in a three-phase bank.


  • 7620/13200Y - indicates a two-bushing primary; the transformer's primary winding is rated for 7620V; used individually, it should be connected between one phase and the neutral of a 13200Y system; can be connected with two identical transformers in a three-phase bank in two ways; (1) the most common is a 13200Y bank, (2) but can also be connected 7620 Delta.
  • 13200GY/7200 - indicates a one-bushing primary; the transformer's primary winding is rated for 7620V; should be connected between one phase and the neutral of a 13200Y system.
  • 13200 - This is the most common way voltages are designated but it does not indicate how the transformer will be connected. If the vector cannot be clarified, we will quote the transformer based on a voltage of 13200/22900Y.

Pole mounted transformers that have primary and secondary windings of the transformer, can either be copper or aluminum or one can be copper and the other aluminum. The industry standard, since the early 1970's, has been aluminum.

The vector sum of resistance and reactance which limits the current flow in an alternating current circuit; when banking single-phase pole mount transformers, impedance can be critical to ensure proper balanced loading of the three transformers in the bank and when pole mounted transformers are used in parallel operation.

Read Our Other Utility Transformer Pages: Padmount Transformers, Electrical Power Transformers, Power Transformers Explained, Transformer Manufacturers, Step Up Transformer, High Voltage Transformers Explained, What is an Auto Transformer? Three Phase Transformers Explained