Toroidal vs Square Transformers: Key Differences

What Is a Toroidal Transformer?

A toroidal transformer is a major type of electronic transformer that has been widely used in household appliances and other electronic equipment with higher technical requirements. Its primary applications are as a power transformer and an isolation transformer. Abroad, toroidal transformers are already available in complete series and are extensively used in computers, medical equipment, telecommunications, instruments, and lighting applications.

In China, toroidal transformers have developed from nothing to a considerable production scale over the past decade. They now not only meet domestic demand but are also exported in large quantities. Domestically, they are mainly used in audio equipment for home appliances, automatic control equipment, and quartz lamp lighting, among other applications.

Characteristics of Toroidal Transformers

• High electrical efficiency: The core has no air gap, and the stacking factor can reach over 95%.

• Low vibration and noise: The absence of an air gap in the core reduces vibration-induced noise. The windings are uniformly and tightly wrapped around the toroidal core, effectively minimizing the "humming" sound caused by magnetostriction.

• Low operating temperature: Core loss can be as low as 1.1 W/kg, resulting in minimal iron losses and low core temperature rise. The windings dissipate heat well on the relatively cool core, leading to low overall transformer temperature rise.

• Easy installation: A toroidal transformer has only one central mounting bolt, making it especially easy to install and remove quickly in electronic equipment.

Differences Between Toroidal Transformers and Square (Laminated) Transformers

Both toroidal and square transformers belong to the category of electronic transformers. Visually, toroidal transformers are ring-shaped, with cores made by rolling silicon steel sheets, whereas square transformers use E-type and I-type silicon steel laminations stacked alternately to form the core. Aside from differences in physical structure, what other distinctions exist between them?

• Efficiency: At the same power rating (e.g., 50W), a toroidal transformer achieves an efficiency of 86%–90%, while a square transformer operates at 80%–84% efficiency.

• Temperature rise: At the same power (e.g., 50W), toroidal transformers exhibit much lower temperature rise compared to square transformers, which run hotter.

• Cost: For power ratings above 200W, toroidal transformers are lower in cost, whereas square transformers become relatively more expensive.

• Electromagnetic interference: Toroidal transformers have very low leakage flux, while square transformers exhibit noticeable leakage flux and generate low-frequency interference.

• Service life: Although neither type uses materials that significantly degrade over time, toroidal transformers generally offer a longer service life.

• Low-temperature performance: Toroidal transformers can operate normally at temperatures as low as -30°C, making them well-suited for outdoor use in northern winters.

• Design flexibility: The size of toroidal transformers can be customized according to customer requirements. Multiple windings can also be tailored to specific needs without requiring molds, and installation is convenient.