Autotransformers

Important: The essential characteristic that distinguishes electrical autotransformers from transformers is the absence of galvanic isolation between the input and output of the autotransformer. These products therefore cannot be used in all installations, and they do not allow network separation or changes to the neutral earthing system.

The autotransformer is a reliable, cost-effective and energy-efficient solution for changing the value of a network voltage. And of course, thanks to our local production, we can adapt our products to your specific use very rapidly.

Depending on the environment where the autotransformer will be installed, the appropriate protection rating must be selected. If the autotransformer is installed in a secure cabinet, an IP00 protection rating (bare) is sufficient — an enclosure is not necessary. In a technical room, a minimum IP21 protective enclosure is required to protect people. In environments subject to water splashes, a higher protection rating such as IP54 should be considered.

We also offer single-phase and three-phase variable autotransformers, also known as "voltage regulators", "Alternostat" or "Variac". These allow adjustment of the output voltage across a wide operating range for a given maximum current. Control can be either manual or electrically driven.

Single-phase autotransformers

Single-phase autotransformers are typically used for low or moderate power installations or inside electrical cabinets. They can be either step-down or step-up transformers.

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Three-phase autotransformers

Three-phase autotransformers are often used as step-up or step-down transformers for higher power installations that do not require galvanic isolation.

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Variables

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.

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Three-phase variable autotransformers

Three-phase variable autotransformers — also known as "voltage regulators", "Alternostat" or "Variac" — are often used for equipment requiring precise voltage adjustment at constant current, such as test laboratories or measuring devices.

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There are particularly compelling use cases for autotransformers when galvanic isolation is not required. For example, in the case of high-power electrical lines over long distances: using a pair of autotransformers — a 400V / 990V step-up and then a 990V / 400V step-down — can prove especially cost-effective. Indeed, increasing the voltage over the long distance reduces Joule losses by the square of the current. This has a very significant impact on the cable cross-section and therefore on its cost.

Please note that for most of these products, we can adapt the input and output voltages, produce reversible autotransformers, add adjustment taps, supply silent blocks or rollers, thermal sensors, adapt the IP ratings of enclosures, and many more options besides.