Transformer Types

Types of Transformers

Industrial Control and General Purpose Enclosed Transformers

A control transformer is an isolation transformer designed to provide a high degree of secondary voltage stability (regulation) during a brief period of overload condition (also referred to as "Inrush Current"). Control transformers are usually rated for 600 volts or less.

Buck-Boost Transformers

Buck-Boost transformers are control transformers with low voltage secondary windings. By field connecting the primary and secondary windings in an autotransformer configuration, they offer an economical solution to the adjustment of line voltages that are slightly above or below normal.

Buck-Boost transformers can be used to adjust stable voltages only. Fluctuating line voltages should be regulated with a voltage conditioner.


Air core

They are used primarily as current or voltage limiting devices, particulary where large currents can enter a system that uses small amounts of power. An example is the telephone system which uses very small voltages where the currenty in a fault condition needs to be kept to a minimum.

Iron core

An iron core reactor provides the same current or voltage control on a system as its air core counterpart. Iron core units tend to be used on smaller applications where the variables need greater or more sensitive control.

Drive Isolation Transformers

Drive isolation transformers are designed to supply power to AC and DC variable speed drives. The harmonics created by SCR type drives requires careful designing to match the rated hp of each drive system. The duty cycle included is approximately one start every 2 hours. The windings are designed for an overcurrent of 150% for 60 seconds, or 200% for 30 seconds.

Motor Starting Autotransformers

Motors have a large inrush current component that requires a special design. Motor starting autotransformers are designed to withstand an inrush of upwards of 25 times normal current. Typically, they are tapped on larger sizes to soft-start the motor until it is up to full RPM.

Low Voltage General Purpose Transformers

Low voltage general purpose transformers provide a safe, long lasting, highly reliable power source. They are designed for general lighting and other low voltage applications. They are UL listed and CSA certified.

Energy Efficient Transformers

There is a growing movement in the electrical industry towards energy efficient products in all sectors including dry-type transformers. In addition to the benefits to the environment, energy efficient transformers also can realize substantial savings in operating costs thereby having a direct impact on the initial investment evaluated over a period of time.

The standards covering 600 volt class energy efficient in dry-type transformers in North America are outline in DOE 10 CFR Part 431, "Energy Conservation Program for Commercial Equipment: Distribution Transformers Energy Conservation Standards; Final Rule." These specifications have carefully considered the total owning cost unique for industrial or commercial installations where the load factor is an integral part of the efficiency rating.

Energy Efficient General Purpose Transformers

Energy efficient general purpose transformers are designed for linear loads and are most frequently used for applications such as commercial buildings which will supply a variety of general loads.

Energy Efficient K-Factor Transformers

Energy efficient k-factor transformers are designed to tolerate heating due to harmonics associated with non-linear loads. Harmonics can indicate their presence in a number of ways: overheating, device malfunctions, telephone interference, equipment vibration, and breakers tripping.

Energy Efficient Harmonic Mitigating Transformers

Energy efficient harmonic mitigating transformers with zero sequence flux cancellation technology are specifically designed to treat the harmonics generated by computer equipment and other non-linear, power electronic loads. Combining zero sequence flux cancellation with phase shifting treats 3rd, 5th, 7th, 9th, 15th, 17th, and 19th harmonics within its secondary windings. Typical applications of severe non-linear loading conditions include data centers, internet-service prodivders, telecom sites, call centers, broadcast centers, etc.

Encapsulated (Potted) Transformers

Here are two complete lines of encapsulated transformers to meet both a commercial and industrial environment. These units are encapsulated and completely enclosed.

Encapsulated Transformers for Commercial Use

Encapsulated transformers for commercial use are designed to provide the ideal solution for commercial applications. All units are encapsulated with electrical grade silica sand and resin compounds, which completely enclose the core and coil to seal out moisture and airborne contaminants. This also eliminates corrosion and deterioration.

Encapsulated Transformers for Harsh Environments and Hazardous Locations

Encapsulated transformers for harsh environments and hazardous locations are especially suited for areas which may contain dangerous gasses, liquids, dust, lint, moisture and where corrosive contaminants are present. Typical applications inculde: institutional, commercial, industrial, petrochemical, pulp and paper; food processing, mines, marine and shipboard installations. They are designed to meet both UL Standard 1604 entitled "Electrical Equipment for use in Class I and Class II, Division 2 and Class III Hazardous (Classified) Locations" and ABS Type Approval for "Marine Duty Service and Offshore Applications - Electrical Distribution and Propulsion".


Autotransformers are similar to Buck-Boost transformers in that they are also an economical means of adjusting output voltage. Autotransformers are designed to adjust the suply voltage when isolation from the line is not necessary and where local electrical codes permit. Units are designed in either a step-up or step-down application and meet motor inrush currents.

Energy Efficient Medium Voltage Distribution Transformers

As of January 1, 2010, all dry-type medium voltage distribution transformers manufactured or imported into North America must comply with the new DOE 10 CFR Part 431/NRCan standards. These standards were put in place to reduce additional energy consumption, as well as reduce greenhouse gases.

These transformers are really 5kV class dry-type energy efficient distribution transformers. They are designed primarily for use in stepping down medium voltage power (i.e. 4160V or 2400V primary) to a lower voltage for commercial, institutional, or industrial applications.