What is resonant transformer? structure and application?

In Electric transformers, maybe you know many types like oil immersed transformer, dry-type transformer, three phase transformer, single phase transformer, but resonant transformers may be new to you. In this article, we will introduce you to the definition, usage as well as working principle of resonant transformer. 

Keep reading for more information!



1. What is a resonant transformer? Construction of resonant transformer?

2. Working principle of a resonant transformer

3. Purpose of resonant transformer


Whenever required of test voltage too high, a unit transformer can not generate such high voltage, because high voltage measure, building a single transformer became difficult and expensive due to insulation problems. Furthermore, it becomes difficult to transport and install large transformers. Overcome these disadvantages, cascading of the transformer is an option


But cascading of transformers also has some disadvantages such as

(1) Design is complicated

(2) bulky size.

(3) costly.

(4) more losses (sum of individual transformers) and thus efficiency reduce.


Resonant transformers are among the best choice for generating high voltage works on resonance phenomenon

1. What is a resonant transformer? Construction of resonant transformer?

A resonant transformer is a transformer in which one or both windings have a capacitor across it and act as a regulator circuit.


Resonant transformer 


Used at radio frequencies, resonant transformers can act as high Q-factor bandpass filters. The transformer windings have an air core or a ferrite core and the bandwidth can be adjusted by varying the coupling (mutual inductance). One common form is the IF (intermediate frequency) transformer, which is used in superheterodyne radio receivers. They are also used in radio transmitters

2. Working principle of a resonant transformer

Resonant transformers work on the principle that the capacitance of the load can be varied, and for certain loads, when the capacitance equals the inductance of the circuit, resonance may occur.

In this condition then, the current will be very large and limited only by the resistance of the circuit. The waveform of the voltage across the test object will be purely sinusoidal

Resonant transformer and equivalent circuit

3. Application of resonant transformer

Resonant transformer is used in many applications, we introduce you some typical cases that resonant transformer is commonly used

One common form of resonant transformer is the IF transformer (mean intermediate frequency) which is used in superheterodyne radio receivers as well as radio transmitters..

The transformers are also used in electronic ballasts for gas discharge lamps, high voltage power supplies. They also applied for switching power supplies.


Other applications of resonant transformer are:

  • Intermediate frequency (IF) transformer in superheterodyne radio receiver

  • Tank transformers in radio transmitters

  • Tesla coil

  • CCFL inverter

  • Oudin coil (or Oudin resonator; named after its inventor Paul Oudin)

  • D'Arsonval apparatus

  • Ignition coil or induction coil used in the ignition system of a petrol engine

  • Electrical breakdown and insulation testing of high voltage equipment and cables. In the latter case, the transformer's secondary is resonated with the cable's capacitance.



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