How to Identify Power Transformers

Small power transformers operate appliances.

Adding the word "power" to the word "transformer" does not narrow down its identity. It only means that the transformer changes voltage from one level to another. Power transformers the size of houses change voltages at hydroelectric dams, and power transformers the size of coins change voltage inside a cell phone charger. But a series of logical steps helps you narrow down your identification. Identify power transformers first by their application and then by their technical specifications. You need enough electrical knowledge to understand the specifications.

Instructions

1. 

   Huge power transformers distribute electricity.

   Identify the application. Electric companies have specific jargon for the hundreds of types of power transformers they use to distribute electricity. You have to be specifically trained to correctly identify them. Appliance manufacturers use power transformers in thousands of applications inside their products. Some applications may identify the transformer more closely, such as an "HVAC transformer" or "doorbell transformer," but that does not totally identify them. Be careful, as a "lighting transformer" for a garden project is far different than a "lighting transformer" for a Las Vegas hotel sign. Be as descriptive as you can when identifying a power transformer's application. Use terms like "an industrial power transformer for a substation," "a power transformer for an antique radio" or "a power transformer for a garden lighting system."

2. Identify the power transformer input in terms of voltage, frequency and phase. For a power company, the input could be thousands or even hundreds of thousands of volts. For an appliance, it could be standard household voltage of 120 or 240 volts alternating current (AC). Specialty transformers could have any input voltage. Also identify the frequency. Standard household AC in the U.S. is 60 hertz, but other countries use 50 hertz. Many aircraft systems run at 400 hertz, and specialty power transformers could run at a wide range of frequencies. Also identify the phase. Many industrial and aircraft generators have three sets of windings on one armature to produce three electric sources at once. The output often connects directly to a three-phase power transformer.

3. Identify the output specifications. Simple transformers have only one output that you must express in both voltage and current in amps or power in watts. A cell phone charger power transformer produces about 5 volts at a half an amp. A power company transformer could produce 10,000 volts at 5,000 watts. Complex power transformers may have several outputs for distribution throughout a building or an appliance. Identify each output in terms of voltage and current or power.

4. Identify specialty features as applicable. Identify such features as oil-filled, pole-mounted, hermetically sealed, high altitude, center tapped, wye or delta wound, special connection details or any other specialty feature needed to identify the transformer and distinguish it from other similar ones. If the power transformer has any specific connection details, include that data in your identification also.

5. Arrange all the identification data in a cohesive description of the transformer. Start with the application and then add the technical specifications as necessary to completely identify it.

Tips & Warnings

• A power transformer cannot change frequency. It operates within its designed frequency range, and the input frequency always remains the same at the output.

• The more data you collect for a power transformer, the better you will identify it. Sometimes using the brand name of the transformer or the equipment in which it is installed helps.

• Some manufacturers use part numbers to specifically identify the power transformers they make. If you can find a part number and know the manufacturer, you can identify it that way.

• Stay away from power company transformers unless you are authorized and know exactly what you are doing. One wrong move could kill you.

• Never attempt to identify a power transformer by just looking at it. Always read the specifications, either from a tag on the transformer or from its technical specifications sheet.

• Don't confuse the term "power transformer" with any type of power supply, power converter, adapter or charger. These devices may contain power transformers but should not be identified solely as such.

References

• Elliott Sound Products: Transformers -- The Basics
• GlobalSpec: Power Transformer Specifications
• Power Transformer Co.: Oil Filled and Power Transformer Information