A power transformer is an electrical device that converts alternating power from one voltage to another. Because there are no rotating or moving components a transformer is usually modeled as a stationary device.
In the majority of cases, power transformers are used to “step down” voltage from a higher level to a lower level to make the power usable in factories, offices, and homes. Their main purpose is to make electricity safer and more efficient to be used in a wide array of electrical machines and appliances by regulating the voltage as needed. As such, they can be found in a wide variety of electrical devices such as microwaves, televisions, computers, and so forth. Their use is however more pronounced in the distribution of power through cables across long distances.
How Power Transformers Work
Electrical transformers rely on Faraday’s law of electromagnetic induction to work. The law states that the intensity of the electromagnetic force that’s induced is identical to the rate at which the current changes.
To explain this law in layman’s terms, consider the following scenario: Whenever a current flows through a conductor, an electromagnetic force is created along the current’s path. The strength of the electromagnetic force, which has the technical name “magnetic flux density,” is proportional, or equal, to the amount of the electric current that’s flowing through the material. The stronger the current the greater the surrounding electromagnetic field and vice-versa.
Now, this assumes the current is stable and traveling at a constant pace. However, alternating current, the type found in power lines, consists of electrons whose flow and polarity constantly changes.
Faraday noted that when the current was fluctuating it caused the magnetic field that was generated to also fluctuate, and this gave birth to another electric current. Case in point, if we put another conductor next to our first conductor that’s receiving fluctuating electric current, the first conductor’s electromagnetic field will generate current and transmit it to the second conductor.
The current flowing through the first conductor is called primary current and the one that’s newly generated and flowing in the second conductor is called secondary current. The secondary current is essentially passed through empty space (air) from one conductor to another.
Transformers employ this concept of secondary current to regulate power. Please note that the application may vary depending on the type of transformer e.g. step up or step down transformers.
To make the transfer of electrical power between the two aforementioned conductors more seamless, a load (i.e. another conductor) is usually inserted between the two existing conductors.
This load also plays the role of helping to regulate the secondary current output.
In cases where there is no load installed the voltage will be less on the transformer’s secondary side. In cases where a load is used other factors such as the material, and the power factor of the load can be used to regulate the secondary current output.