Types of transformers

Voltage transformers, called transformers, are devices that increase or decrease a certain voltage value. The transformer consists of a core and two coils. The transformer core is made of a highly magnetizable material, and the coils are made up of a number of different turns, electrically isolated from each other, called the primary and secondary. The primary is the coil that receives the mains voltage, and the secondary is the coil that the transformed voltage comes out, that is, with a different value.

The vast majority of electronic equipment employ transformers, either as an elevator or a voltage lowered. When the coil is connected to an AC source (alternating current) a variable magnetic field appears around it. Approaching another coil to the first, the variable magnetic field generated in the first coil “cuts” the turns of the second coil. As a consequence of the magnetic field variation on its turns, an induced voltage appears in the second coil. Since the coils are electrically isolated from each other, the passage of energy is made from one to the other exclusively through magnetic force. The tension the secondary of a transformer it is proportional to the number of magnetic lines that cut the secondary coil. For this reason, the primary and secondary of a transformer are mounted on a core of ferromagnetic material. The core decreases the dispersion of the magnetic field, causing the secondary to be cut by as many lines as possible, obtaining a better transfer of energy between the primary and secondary.

Illustration of a transformer.

Types of transformers

Transformers can be classified according to various parameters, such as purpose, type, core material, number of phases, etc.

  • Goal:

Current transformer:

The current transformer, or TC, has the purpose of detecting or measuring the electric current flowing in a cable or power bar, and transforming it into another current of lesser value, to be transmitted to a measuring instrument or electronic circuit. CT is widely used to lower the electrical current of the network to supply electronic devices that do not support high levels of current.

Power transformers:

The name transformer of potential (or TP) denotes that this machine changes the power values, but in fact it changes the voltage values ​​that enter the primary coil. The primary loop receives the primary voltage and conducts a primary current. Because this current is alternating, it generates a variation in the magnetic flux inside it. This flow is channeled through the ferromagnetic core, and into the secondary loop, inducing tension in this loop. If there is no closed circuit connected to the secondary loop, an induced current will be established.

Distribution transformer:

This type of transformer is mainly used by energy distribution concessionaires and in power generation plants. They are used to distribute the generated energy to consumers, with different values ​​than that generated, suitable for each type of consumer. They can be self-protected against overloads and short circuits.

Power Transformers:

They are used for power generation and distribution by concessionaires and plants, and electricity distribution substations, and substations in large industries, including special applications such as induction and arc furnaces, and rectifiers.

Elevator and voltage-lowering transformer:

The value at which the voltage will be after leaving the transformer is directly linked to the number of turns each coil has. In the case of a voltage-boosting transformer, the number of turns on the second coil is greater than the number of turns on the first coil. And on the step-down transformer, the number of turns on the second coil is less than the number of turns on the first coil.

  • Type:

A number of coils:

In the case of two-coil transformers, it is common to call them primary and secondary. When there is a third coil, it is called a tertiary. There are also transformers with only one coil, the so-called autotransformer.

  • Core material:

Magnetic iron:

In the case of a transformer with a ferromagnetic core, laminated steel sheets, generally, silicon steel sheets, are used to reduce the losses due to eddy currents.

Air core:

Air core transformers consist of the location of the coils, which are in direct contact with the atmosphere.

  • A number of phases:


This type of transformer is suitable for supplying control circuits or for industrial use. The transformer used in homes is also single-phase, it transforms 127 V into 220 V and 220 V into 127 V.


This is the type of transformer that we see on the streets, it receives the voltage from the distribution substation and at a voltage level of 13800 V and transforms it into 127 V or 220 V.


It has relatively high efficiency, these transformers supply the voltage for systems that need more phases through the three-phase system. This type of transformer varies from 3 to 6 phases. Those systems that require more phases are especially for full ave measurement rectification due to their components.