7.3.4 Transformers HT

In this lesson, we will examine the basic structure of transformers, the voltage ratio relationship, and the power conversionThe act of changing someone's religion. principles involved.

The Structure of a Transformer

Transformers are essential devices in electrical systems that facilitate the efficient transfer of electrical energy between different voltage levels.

• A transformer comprises a primary coil and a secondary coil wound on an iron core.
• The primary coil is connected to the power source, while the secondary coil is connected to the load or the device receiving the transformed electrical energy.
• Iron is commonly used as the core material due to its high magnetic permeability and ease of magnetisation.

Voltage Ratio in Transformers

The voltage ratio in a transformer is determined by the ratio of the number of turns on the primary coil (n_p) to the number of turns on the secondary coil (n_s). Mathematically, the voltage ratio is expressed as:

v_p / v_s = n_p / n_s

Variables:

• v_p = Potential difference across the primary coil in volts, V
• v_s = Potential difference across the secondary coil in volts, V
• n_p = Number of turns on the primary coil
• n_s = Number of turns on the secondary coil

Step-Up and Step-Down Transformers

• A step-up transformer is designed to increase the voltage level from the primary coil to the secondary coil. In this case, v_s > v_p.
• Conversely, a step-down transformer reduces the voltage level from the primary coil to the secondary coil. Here, v_s < v_p.

Efficiency and Losses

In practice, transformers exhibit some energy losses due to factors such as resistive heating, hysteresis, and eddy currents. These losses reduce the efficiency of the transformer.

If transformers were 100% efficient, the electrical power output would equal the electrical power input.

Power Conversion in Transformers

Transformers are highly efficient devices, where the power output is nearly equal to the power input, neglecting losses.

• The power input (primary side) is given by Vp × Ip, where Vp is the potential difference across the primary coil and Ip is the current flowing through it.
• Similarly, the power output (secondary side) is calculated as Vs × Is, where Vs is the potential difference across the secondary coil, and Is is the current flowing through it.

V_s x I_s = V_p x I_p

Variables:

• V_p = Potential difference across the primary coil in volts, V
• V_s = Potential difference across the secondary coil in volts, V
• I_p = Current through the primary coil in amperes, A
• I_s = Current through the secondary coil in amperes, A

Power Transfer and Advantages of High Potential Differences

• Transformers allow for efficient power transfer by increasing or decreasing the voltage levels according to the application's requirements.
• Higher voltage transmission reduces current, minimising energy losses due to resistance and heat dissipation.
• This enables power transmission over long distances, as high-voltage transmission lines experience lower energy losses.

Conclusion

Transformers play a crucial role in electrical power systems by efficiently converting electrical energy between different voltage levels. Their structure, voltage ratio relationship, and power conversion principles enable the transmission of electrical power over long distances and facilitate the use of various devices at appropriate voltage levels.