Working Mechanism of DC Transformers

A transformer is a device that increases or decreases voltage in its most basic form. For example, the output voltage of a step-up transformer is increased, whereas the output voltage of a step-down transformer is dropped. As a result, the output current of the step-up transformer will be reduced, while the output current of the step-down transformer will be increased, keeping the input and output power of the system equal.

A transformer is a voltage control device commonly used in alternating current power distribution and transmission. Michael Faraday first proposed the concept of a transformer in 1831, and several other famous scientists picked it up. The general goal of transformers, on the other hand, is to maintain a balance between electricity generated at very high voltages and electricity used at very low voltages.

What is The Definition of A Transformer?

A transformer is an electronic device that transfers alternating current signals from one circuit to another using electromagnetic induction. These devices do not pass direct current, and they can be utilized to remove the DC voltage (constant voltage) from a signal while maintaining the variable part (the AC voltage). Transformers are essential in the electrical circuit for shifting voltages and reducing energy loss during transmission.

Working Principle of A Transformer

Faraday’s Law of electromagnetic induction and mutual induction governs a transformer’s operation. 

There are usually two coils on the transformer core: 

1. Primary coil 
2. Secondary coil

Strips are used to connect the core lamination. The mutual inductance of the two coils is very high. A changing magnetic flux is created when an alternating current passes through the primary coil. According to Faraday’s Law of electromagnetic induction, the shift in magnetic flux induces an emf (electromotive force) in the secondary coil, which is connected to the primary coil. Hence, it is mutual induction.

In general, a transformer performs the following tasks:

1. Transfers electrical energy from one circuit to another 
2. Transfers electrical power  by electromagnetic induction
3. Transmits electric power with no change in frequency
4. Connects two circuits by means of mutual induction 

A Single-Phase Transformer’s Components

The following are the primary components of a single-phase transformer:

1. Core: The core of the transformer provides support to the transformer’s circuit. It also creates a low-resistance path for magnetic force to travel. The centre of the winding is twisted. The laminated soft iron core reduces transformer losses. Core composition is determined by the operational voltage, current and power parameters. Copper losses are proportional to core diameter, while iron losses are inversely proportional.
2. Windings: Transformer windings are a collection of copper wires that are wound around the transformer’s core. Copper wires are utilized because:

• Copper has high conductivity, which helps in reducing transformer losses –  as conductivity increases resistance to current flow decreases.
• Copper is highly ductile as a metal, which allows it to be manufactured into soft wires.

There are two types of windings: 

• Primary winding: It is the set of winding turns in which the supply current is fed.
• Secondary winding: It is the set of winding turns from which the output is derived.

Insulation coating agents are used to keep the primary and secondary windings separate.

3. Insulating Materials: Transformers require insulation to isolate the windings from one another and prevent short circuits. Mutual induction is made more accessible as a result of this. Insulation agents have an impact on a transformer’s durability and stability.

In a transformer, the following materials are utilised as insulation:

• Wood-based lamination
• Insulating oil
• Insulating tape
• Insulating paper

Transformers on DC Supply

Transformers, as previously stated, require AC power and cannot operate on a DC supply. Therefore, a constant magnitude flux will occur in the transformer’s core if the rated DC voltage is applied across the primary winding, preventing self-induced emf generation. However, an alternating flux, not a constant flux, is necessary for electric field connection with the secondary winding.

Ohm’s Law states that:

Primary Current = DC applied voltage/Resistance of primary winding.

The primary winding resistance is meagre, and the direct current is very high. As a result, this current is substantially higher than the rated primary winding current at full load.

As a result, the amount of heat produced will be more significant, resulting in increased Eddy current loss (I2R). The primary winding insulation will be burnt and will destroy the transformer. 

Turn Ratio

It is the ratio of primary and secondary movements:

Turn ratio = N₁/N₂.

If N2>N1, the transformer is known as a step-up transformer.

The transformer is called a step-down transformer if N₂ < N₁.

Ratio of Transformation

The secondary voltage to primary voltage ratio is known as the transformation ratio denoted by the letter K:

K = E₂/E₁ = N₂/N₁

As (E₂ ∞ N₂and E₁ ∞ N₁).

Conclusion

In ideal conditions, any transformer’s current and voltage fluctuate by a similar ratio. That is the reason behind the similarity in the values of the primary and secondary power values. As one value falls, the other value rises to maintain the power of continuous equilibrium. 

Transformers have the potential to be incredibly efficient. As a result of advances in reducing transformer losses, high-power transformers can achieve efficiencies of up to 99 percent. However, if failures are avoided, a transformer will always produce less power than its input. There will be a small amount of transformer resistance.