Small-sized transformers used in the electronics domain come with precision engineering, low breakdown rates and a long life.
By Potshangbam July
Small-sized transformers are in use in countless electronic products and appliances, ranging from camcorders to air-conditioning systems. These handy devices, which are integrated into electronic circuits to obtain the right voltage, are known to be energy-efficient and flexible. The transformer market has been divided into the small power, medium power and large power categories, based on the power rating. Among them, the small power category is leading in the market because of its many benefits, such as effective three windings, special cooling, being single phase, low noise generation, etc. They are commonly used in all sorts of household appliances, as these require low voltage (around 5V to 50V) to operate, with minimal current consumption.
Types of small-sized transformers
Toroidal transformers: These are up to 50 per cent smaller and lighter than other conventional transformers. They have a simple cabinet design and their mechanics is less complicated. They can be mounted very easily as they require only one centre screw, whereas other transformers need around four screws. Thus, it reduces the assembly time.
Pulse transformers: These are some of the most used small-sized transformers in electronic devices. They essentially isolate a digital load circuit and supply pulses of constant amplitude to it.
Audio transformers: These work at frequencies from 20Hz to 20kHz. They can be step-up and step-down transformers, and are commonly used in the electronics industry. They are specifically used in audio related applications, where impedance matching is needed, and are designed to offer almost zero reactance. Audio transformers can have various primary and secondary coils, which are either separated or centre-tapped.
RF transformers: These are used at radio frequencies ranging from 30kHz to 30MHz.
They are widely used in electronic equipment to either step up or step down voltage. They are also used for isolating DC from two circuits at the same time, while maintaining AC continuity. Besides, they are required for impedance matching, so that they can transfer maximum power. They are also effective in reducing or suppressing unwanted signal reflection. RF transformers come as connector packages, surface mount packages and in various other configurations.
According to Balram Sharma, assistant general manager – product & business development, WingsAuto, “There are mainly two types of small-sized transformers—iron core and ferrite core. Iron core transformers are normally used for small DC power supplies, with various electronic appliances. But these are being replaced by high frequency switched ferrite core transformers, which are smaller in size, cost less and are more efficient. One more application is voltage sensing, for which the smallest possible transformer is used to step down the voltage to be read by electronic circuits. The reason for this is isolation from mains high voltage and stepping it down to a voltage that is comfortable enough to be handled by the electronic circuit. Ferrite core transformers are used in SMPS power supplies, DC-DC converters, frequency and voltage conversion.”
Sharma adds that ferrite core transformers can be used at high frequencies only (normally in the kHz range), so the 50Hz mains supply is first converted to DC and then again switched to high frequency AC in order to use these transformers. Hence, the complexity of the devices increases. But now chips are available to handle this entire operation and are being commonly used in the chargers for mobiles, tablets and PCs; and in adapters, etc.
Advantages of small-sized transformers
When it comes to efficiency, small-sized transformers rank high. Another factor that makes them more attractive is that they are cost-effective. Small-sized transformers are not only lightweight but also require less space. Their small and compact size makes them ideal to be integrated and fitted anywhere in electrical and electronic products; they can often be directly integrated into a light fixture or other electronic device instead of being installed as a separate piece of equipment. Even when they cannot be integrated properly into the devices, their tiny size makes it possible to hide them successfully.
Small-sized transformers have low electromagnetic fields in comparison with other transformers and hence operate more efficiently. Therefore, they are considered to be the appropriate choice for sensitive electronic systems. There are noise issues with transformers, caused by high magnetostriction, but small variants like toroidal transformers release no disturbing humming sound. The uniform winding around the core ensures no air gaps and loose sheets that vibrate. Besides, they are manufactured from a continuous strip of high-grade steel, which helps in noise reduction. Therefore, they are preferred in hospitals, which require a quiet environment.
The installation process for small transformers is a lot easier. Since they are tiny in size, it does not take time to assemble and install them. Most small transformers offer significant energy savings, and therefore have a lower impact on the environment.
Standard features of small-sized transformers
Core: The main difference between the various types of transformers is the kind of core used and the number of turns in primary and secondary coils. Advancements in the field of electronics have influenced changes in design and the use of new types of core materials in small-sized transformers.
Windings: The conductor material used in the windings of small-sized transformers can be aluminium or copper. The conductor can be in the form of a foil, strip or a continuously transposed cable.
Insulating oil: Oil is used in these transformers for its chemical properties and dielectric strength. It has high insulating properties that help to minimise power outages. It is also used for cooling purposes and assists in dissipating the heat of the transformer. In addition, it prevents oxidation. It also ensures a low impact on the environment by curbing carbon emissions.
|Benefits of small-sized transformers|
Inputs from K. Manoj Kumar, manager, Raytech Electronics
To ensure that transformers deliver a high level of performance over a long period, thorough maintenance is required. Small-sized transformers do not require heavy maintenance like other transformers do. They come with fewer switches (almost ten times less), which reduces the complexity. As intermediate DC-conversion steps are not needed, no bulky capacitor is used.
Care and maintenance should not be overlooked despite the fact that small-sized transformers do not require as much attention as other equipment. As Sharma puts it, “Small-sized transformers are maintenance-free, but routine dusting and cleaning can be done to maintain the pace of heat transfer to the atmosphere.”