What is a Toroidal Power Transformer?

A toroidal transformer has its primary and secondary windings wrapped around a torus or donut-shaped core made of ferromagnetic material such as banded iron, magnetite, ferrite, or iron oxides, separated by an insulating material. Because of this nature, a toroidal transformer features lower winding losses, increased efficiency &effectiveness, decreased eddy current, less magnetic flux leakage, and less humming noise than typical types. The electrical characteristics make toroid transformers perfect for sensitive and critical electronic circuits.

Toroidal transformers are widely used in amplifiers, inverters, computers, power supplies, medical equipment, telecommunications, instruments, lighting, etc. In electrical circuits, toroidal transformers are used to transmit electricity between two regions of the circuit, enabling isolation while altering the current and voltage. In comparison to conventional EI transformers, their size is small, making them excellent for use in other comparable devices.


What Is a Toroidal Inverter?

Toroidal inverters receive electricity from a battery and convert it from direct current to alternating current. Toroidal inverters feature high efficiency, silent operation, minimum heat output, and a small footprint. Toroidal inverters are widely used in solar inverters, power suppliers, and control equipment, among other electronic and electrical systems.

The Advantages of Using Toroidal Transformers

A toroidal transformer is used to step up or down a voltage, as well as to isolate equipment from primary winding. Toroidal transformers are well-suited for important equipment due to their higher efficiency, low power dissipation, silent operation, and durability. These transformers are readily fitted into medical equipment when space and weight limits are significant design concerns.

  • Electromagnetic shielding and Low magnetic field, which is about one-tenth that of EI transformers. This way, power transfer from input to output will obviate the need for further shielding. Because of the effective containment of the magnetic flux, toroid cores inherently shield adjacent components from electromagnetic interference (EMI). This feature makes them suitable for use in electronic devices with sensitive components.
  • Toroidal transformers feature smaller sizes and weights than conventional transformers because they use less material for construction. A short wire is achievable due to the windings being equally dispersed throughout the core. Therefore, these types of transformers are widely used in compact electrical equipment and miniature power supply.
  • Highly effective and has a high efficiency of 90-95%, higher than traditional types below 90%. This enhanced efficiency is due to the high-quality steel in the core, lower leakage flux, and the balanced winding distribution around the whole toroid core.
  • Low humming and quiet operation. For traditional transformers constructed with laminated iron cores,  the hum got louder and louder as the lamination started to separate due to vibration caused by magnetostriction. Plus, EI core is not a continuous structure, thus having air gaps. For toroidal types, the core is uniquely constructed to eliminate air gaps, resulting in the absence of loose layers that may vibrate, finally leading to a decrease in hum. If you notice a hum whenever the power is turned on, it will subside after several seconds of operation to a reasonable level.
  • Low temperature rise. Toroidal transformers run at a lower temperature and generate lower heat owing to lower eddy current, lower hysteresis loss, and lower iron loss, obviating the need to use cooling fans and heat dispersion components like heat sinks.
  • Minimal signal distortion. Leakage flux or stray magnetic fields can induce stray currents when their magnetic field lines cross nearby conductors. This allows unwanted signals to appear or interfere with other sensitive signals. That is why toroidal transformers with low signal distortion are widely applied in audio systems, medical devices, measuring instruments, and power analyzers, where high signal resolution is required.
  • Lower Off-load Losses: Off-load losses are caused by magnetizing the core even when there is no load connected to the secondary circuit. Transformers tend to consume power even in standby mode. Because of their unique construction, core losses in toroidal transformers are lower than in traditional transformers.
  • No air gap: Toroidal cores have the characteristics of a continuous construction, leaving no air gap. Air gap could lead to magnetic flux leakage which passes through adjacent components. For example, the EI core has 3 air gaps.

The Disadvantages of Using Toroidal Transformers

  • Expensive to manufacture: Despite the smaller dimensions and using fewer materials, toroidal transformers are more expensive to make for mass production compared to other traditional types. This is because of the difficulty of winding the coils around the entire toroid tore.
  • Higher inrush current: Inrush current is the current spike when the transformer is turned on. The amount of inrush current is greater in highly efficient transformers such as toroid transformers. High inrush current can cause serious damage if not managed correctly. It can trip circuit breakers, cause fuses to blow, and lead to the failure of a transformer. You could use current limiters or electrical resistors to protect from the effects of inrush current.

What Materials Does The Core of Toroidal Transformers Use

A transformer core is made from magnetic materials. These materials can vary in levels of effective magnetic permeability, electrical resistivity, hysteresis, and so on. The efficiency of the transformer is mainly determined by the qualities of magnetic materials, as the core has to do with most transformer losses. We list the types of cores used in toroidal transformers as follows:

Ferrite Cores: Ferrite cores are made from a metal-oxide ceramic, iron oxide, mixed with other metals such as cobalt, copper, nickel, manganese, and zinc. The two common types of ferrite cores are manganese-zinc ferrite and nickel-zinc ferrite cores. Ferrite cores characterize low permeability, low saturation flux density, and low Curie temperature. The good thing about these cores is their high electrical resistivity which could lower the eddy currents.

Laminated Iron Cores: Laminated iron cores are used in traditional transformers running at low to medium frequencies. The lamination features could reduce the generation of eddy current. Silicon iron core and nickel-iron core are two types of laminated cores. They feature high resistivity and high permeability with thickness ranging from 0.35mm to 0.5mm. They are stacked or overlapped in the manufacturing process of transformers.

Tape Wound Cores: Tape wound cores are the same as laminated cores. Instead of stacking, tape-wound cores are made from insulated metal ribbons wound into a spiral. It is then encapsulated by a thin sheet made from aluminum, or plastic.

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