What are Air Core Transformers?

Air core transformers, also called antenna coils, are transformers used in electronic radio, radio transmission, and other communications systems. 

How are Air Core Transformers Different from Other Transformers?

Induction between two magnetically linked coils and windings is how an air coil transformer works. These transformers consist of primary and secondary windings constructed from insulated copper wires.

Generally, these coils are wound on a non-magnetized surface such as plastic tubes or cardboards. Unlike electrical and power transformers, in which the cores create a flux, air-core transformers generate flux using the coil windings and the air passing through its hole.

Advantages of using air-core transformers

Air core transformers offer various advantages when used for small sized, portable electronic devices:

  • no loss of signal, there exists no distortion and a noise free operation
  • no losses of hysteresis and eddy currents
  • light in weight due to the absence of a core

Types of Air Coil Transformers 

There are primarily two forms of air core transformers:

  1. Cylindrical Air Core Transformers: Insulated copper wires are wound on a cylindrical, hollow, non-metallic structure which also provides mechanical support to the windings. Tapes are used at specific points when winding the primary coil, while “taps” are used to wind the secondary winding across. The hollow cylinder and the taps allow the flux to flow through the air within the hollow cylinder and air encapsulating the winding.
  2. Toroidal Air Core Transformers: In this type of air-core transformer form, insulated copper wires are wound around a non-metallic ring, usually made from rigid plastic. The coil is then wound around the ring’s periphery. In toroidal air-core transformers, each coil winding is utilized separately. Separate winding ensures that the effect of stray couplings is minimal. For this reason, toroidal air-core transformers are typically installed in high-frequency applications. The primary to secondary winding ratio depends on the type of operation and change in frequency.

Maintaining and Enhancing the Performance of Air Core Transformers

There are specific steps that Engineers and electrical designers can take to maintain or enhance the performance of the transformer:

  • A guard winding can be wound across the primary winding in cylindrical transformers to allow for impedance matching.
  • The guard winding can also be connected to antenna receivers to improve the transformers’ operation.
  • Another method to enhance the performance of the transformer is to connect a capacitor to the winding. A capacitor allows the winding to maintain a constant resonance of the tuning circuit.

It is now clear that air-core antenna coils follow the same working principle as other transformers. However, their lack of cores makes them the perfect solution for small portable radios and other communication devices.

Since 1985, Shreejee Electronics has been a leading provider of reliable, high-performance air-core coils. We are committed to providing the highest quality audio solutions for our customers in a wide range of industries. Contact us today for an RFQ to see how Shreejee can help you in your projects.

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