Learn about the scientific principles behind the functioning of transformers and how they step-up and step-down voltage to facilitate the distribution of electricity.
What Do Transformers Do?
Transformers are devices that use electromagnetic induction to change electrical current properties from one circuit to another. Virtually all the electrical power we use daily processed through a transformer at some point. Utility companies rely on transformers to increase voltages for transfer from the power station to the distribution grid, then back to voltages that are usable in for our everyday electrical applications.
Application of Faraday’s Law: How Transformers Work
So, how do transformers work? Let’s get into the details.
Transformers contain a pair of windings, and they function by applying Faraday’s law of induction.
- AC passes through the primary winding, which creates a varying magnetic flux.
- The magnetic field that results strikes the second winding and generates an AC voltage in that winding via electromagnetic induction.
In a theoretical, ideal transformer, no energy escapes between the circuits; the two circuits couple perfectly with infinitely high magnetic permeability. Here are the equations describing this theoretical transformer:
VP = -NP (dɸ / dt)
VS = -NS (dɸ / dt)
The symbols in these equations have the following values:
- V is the instantaneous voltage.
- N the number of turns in the winding.
- dɸ / dt is the change in magnetic flux (ɸ) through the windings over time.
- P and S refer to the primary and secondary windings respectively.
The ratio of initial voltage to output voltage is equal to the ratio of turns in the primary winding to the turns in the secondary. For instance, a secondary winding with twice as many turns as the primary winding will output a voltage twice that of the original voltage.
In real life, we’ll always experience some loss of efficiency due to heating in the core, reactive impedance, or other variables. Still, electromagnetic induction is a useful method for changing voltages as needed for different applications.
Working Principle: Step-Up and Step-Down Transformers
Here’s the ratio between windings and voltages we described above:
VP/VS = NP/NS
Transformers are capable of drastically changing voltages. Transformers that increase voltage are called “step-up transformers” while those that decrease voltage are “step-down transformers.” Step-up transformers are crucial to distributing electricity to the public. These transformers enable the power station to increase its supply voltage levels high enough to travel efficiently over long distances. Once the current arrives at the distribution grid, a step-down transformer changes the current back to a level appropriate to end users’ demands.
Other Types of Transformers
Step-up and step-down transformers illustrate the basic principles of electromagnetic induction and voltage changes. However, many other types of transformers exist for specific applications, including audio, electrical, instrumentation, and others. All these transformers work on the principle of induction in AC power, but they vary in construction to allow for their specific functions. These functions may include balancing voltages or precisely down-converting huge voltage to enable delicate instruments to read current and voltage.
