How Transformers Work


Transformers are very basic electrical devices that, according to, “take electricity that’s one voltage and changes it into electricity that’s another voltage.” Sounds right to us. (Voltage, FYI, is the amount of pressure, or strength, that an electrical current has.)

If you search the internet for electrical transformers, you’ll discover a mind-boggling and vast assortment of examples that reflect the way electricity exists in our lives; transformers are within the walls of our homes, in hospitals, universities, factories, machine shops, and transportation grids, emanating from the landscape as much as trees do. And, the huge voltage requirements needed for the modern world attest to the thousands of different transformer types that exist.

ACUPWR’s voltage transformers are relatively unsophisticated, step-up and step-down types that convert different basic household electricity (known as line or mains electricity, or voltage) up or down to higher or lower voltages so appliances and electrical devices can work in a country that has a different line electricity. FYI, most countries in the world—two-thirds, actually—have a native line voltage of 220 to 240 volts. The USA, Canada, Taiwan, and some other countries rely on a 110 to 120-volt standard. Mexico, Brazil, Bonaire, Surinam, and Curacao use a 127 to 130-volt standard. And then there’s Japan, the lone holdout that uses a 100-volt standard.

 As far as how transformers work, there’s no great, complicated circuitry involved, only—in our case at least—two coils of wire that are wrapped around a ring-shaped iron core, as you can see in the infographic below.

The wire coming into the transformer is referred to as the primary. Wrapped around the opposite side of the iron core is the second wire, known as the secondary. Thanks to basic electromagnetics, the primary’s current creates a magnetic field that travels across the iron core to the secondary. Note that transformers do not work with DC, or direct current. That’s because they rely on something called magnetic flux, which is caused by the constant forward-backward motion of the current when it is alternating, or AC (alternating current). If you want to try and visualize magnetic flux, think of the electrons that make up electricity as a bunch of school kids running amok in a playground. This activity creates the electromagnetic energy, or flux. The flux then flows around the core

In the case of a 220/240V to 110/120V step-down, the primary will have more windings (or turns) around the core than the secondary. Actually, in the scenario outlined above, the secondary will have exactly half the turns as the primary. The voltage in the secondary core is related to the primary voltage as determined by the number of turns that the primary coil is wrapped around the core. If the primary has 10 turns and the secondary has 5, the voltage in the secondary will be exactly half of the primary. This relationship is measured by the turns ratio. In this case the ratio is 2:1. If the voltage transformer was a step-up type that converts 110/120V up to 220/240, the scenario is reversed with the ratio now 1:2.

So, that’s what goes on inside a transformer—at least essentially. Remember that there are thousands of different types of transformers and they get radically bigger and more complicated with extensive cooling apparatuses, numerous secondary coils and cores to handle dual- and triple-phase current, and otherworldly things sticking outward, as demonstrated in the picture below. Crazy stuff…

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  • Mike Bieber
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