The design of a transformer involves a careful consideration of the turns ratio between the primary and secondary coils. The primary coil has more turns than the secondary coil to achieve the desired voltage transformation and power transfer characteristics.
The fundamental principle behind this lies in the conservation of energy and the relationship between voltage and turns in a transformer. According to Faraday’s Law of electromagnetic induction, the induced voltage in a coil is directly proportional to the rate of change of magnetic flux linking the coil. The equation expressing this relationship is given by:
�=−��Φ��E=−NdtdΦ
Here, �E is the induced voltage, �N is the number of turns in the coil, ΦΦ is the magnetic flux, and �t is time.
When a voltage is applied to the primary coil, it creates a changing magnetic field in the transformer’s core. This changing magnetic field induces a voltage in both the primary and secondary coils. The ratio of the number of turns in the primary coil (�1N1) to the number of turns in the secondary coil (�2N2) directly determines the voltage transformation ratio:
�1�2=�1�2V2V1=N2N1
Where �1V1 is the voltage in the primary coil and �2V2 is the voltage in the secondary coil.
To step down the voltage from the primary to the secondary, the secondary coil must have fewer turns. Conversely, to step up the voltage, the secondary coil needs more turns than the primary. This is because the product of the number of turns and the induced voltage remains constant, assuming ideal transformer conditions (negligible losses):
�1⋅�1=�2⋅�2N1⋅V1=N2⋅V2
Having more turns in the primary allows for efficient energy transfer and voltage transformation across the transformer. It enables the device to match the impedance between the source and load, facilitating optimal power transfer while meeting the desired voltage requirements. Therefore, the turns ratio is a critical aspect of transformer design, ensuring the efficient and effective conversion of electrical energy between different voltage levels.
