What Is an Auto Transformer?
An auto transformer follows the same principles as a regular transformer with one important advantage. An auto transformer is typically 30 to 70 percent smaller than a regular transformer because the primary and secondary windings share turns (and mutual currents). This type of transformer is ideal when a smaller, lighter transformer is needed. Because of the decrease in size, this type of transformer is considered the most cost-effective solution when you only need to step up or step down a voltage.
Unlike an isolation transformer, an auto transformer does not offer isolation between the input and output windings. An additional isolation transformer will be necessary if other components in your equipment have isolation requirements. (This is critical when sending products to UL for safety approvals).
Advantages of a Toroidal Auto Transformer
- They’re considerably smaller than standard auto transformers.
- They make a cost-effective solution to step up/down a voltage, when isolation is not required.
- The combination of their compact size and low noise output makes them an ideal solution for an audio application.
- Because of their ring shape, they have a nearly ideal magnetic circuit and are 90 to 95 percent efficient. Meanwhile, EI transformers may lose 40 to 50 percent of their core power.
- They have low leakage losses and run cooler than standard transformers.