What is a transformer?
A transformer is an electrical device that is used in AC power distribution systems to safely “step up” or “step down” voltages to meet the incoming power requirements of connected equipment. Transformers achieve this goal without modifying the frequency or amount of electrical power to help ensure connected devices can operate reliably.
Transformers are static devices, meaning they contain no continuously moving mechanical parts. This contributes to their long lifecycle and minimal maintenance requirements. They can range in size from enormous devices that weighs several tons, commonly used in power substations, to very small devices that weigh only a few ounces and are commonly found in compact electrical equipment.
Thanks to their design flexibility and critical role in the electrical system, transformers are used in nearly every power distribution system application including commercial buildings, schools, healthcare & institutions, water/wastewater, industrial, oil & gas and data centers.
How do transformers work?
The typical transformer has several secondary windings or coils of insulated wire conductor wrapped around a laminated steel core. When voltage is introduced to one coil, called the primary, it magnetizes the iron core. A voltage is then induced in the other coil, called the secondary or output coil. The change of voltage (or voltage ratio) between the primary and secondary depends on the ratio of the turns in the two coils.
There are two primary types of transformers that are defined by the insulation used within the enclosure: dry-type and liquid-filled. On this page, we will explore the basics of dry-type transformers and their most common configurations.
Features & Benefits:
Ratings available from 0.25 through 167 kVA 1-phase and 3 through 1000 kVA 3-phase
Designed to ANSI, UL, and NEMA Standards
Available in a wide variety of ratings
For general purpose, lighting and power loads in commercial and industrial applications
Dry type transformers are air-cooled by natural convection
Meets the demands of AC and DC variable speed drives
Horsepower rating and voltage changes for motor drive systems
Cores designed with reduced flux density for drive applications
What is a low voltage dry type transformer?
“Dry-type” is a reference to the type of insulation medium, which means that the core and coil is cooled and insulated by air, as opposed to “liquid immersed” transformers that use oil as the coolant/insulant. “Low-voltage” means that it has an input voltage of 600 volts or less.
THE PRODUCT:
Low-voltage dry-type transformers (LVDT) are generally used inside buildings to reduce voltage to the values necessary to power appliances, lighting and other products. Unlike liquid-immersed transformers, these are generally owned by the building owner. The customer purchases electricity at a voltage level that must be stepped down for use. “Dry-type” is a reference to the type of insulation medium, which means that the core and coil is cooled and insulated by air, as opposed to “liquid immersed” transformers that use oil as the coolant/insulant. “Low-voltage” means that it has an input voltage of 600 volts or less.
THE STANDARD:
Initial standards for low-voltage dry type transformers were set in EPAct 2005 and became effective in 2007. In March 2010, DOE began a new rulemaking to update standards for the three main categories of distribution transformers: liquid-immersed, low-voltage dry-type and medium-voltage dry-type. In February 2012, DOE proposed a very modest increase in efficiency for LVDT, below the level agreed to by manufacturers in 2011 transformer negotiations facilitated by DOE. However, in the final rule published in April 2013, DOE improved the standard, reducing electrical losses by about 18 percent compared to products meeting the current standard. The standard for dry-type transformers is based on a voluntary industry level called “NEMA Premium”, developed by the National Electrical Manufacturers Association.The standards went into effect on January 1, 2016.
KEY FACTS:
Transformers are generally very efficient — electricity losses are usually below 1 or 2%. However, since all power generated goes through one or more transformers, even small improvements can yield very large national savings benefits. In general, transformers can be made more efficient by using better quality windings (which can be aluminum or copper) and through improved core designs, material (electrical grade steel), and construction. Amorphous core material offers the biggest step up in efficiency.