Single-phase variable autotransformers

Single-phase variable autotransformers — also known as "voltage regulators" or "Variac" — are often used for equipment requiring precise voltage adjustment at constant current, such as test laboratories or measuring devices. They are used as step-down units, and can be controlled either manually or electrically.

Please bear in mind that the power of the variable autotransformer changes with the requested output voltage. Do not exceed the rated winding current.

Motorisation is not mandatory for small power ratings below 5 kVA. In this case, the products are manually adjustable with a rotary handle. Conversely, if you wish to electrically control the variable autotransformer remotely or automatically, you will need to opt for the solution controlled by a "0-10VDC" signal. Note that the higher the power rating, the more advantageous electrical control becomes, and it is almost mandatory for high power ratings given the torque required.

Single-phase variable autotransformers are generally supplied bare, as they are often installed in a dedicated cabinet, laboratory or special-purpose machine. From 5 kVA upwards, they are often requested with an enclosure, minimum IP23, with electrical protection and displays.