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Our Rotavolt variable autotransformers provide a continuous linear regulation of AC voltage, with high efficiency, without distorting waveforms significantly.

The Watford Control Rotavolt provides a precise and effective way of controlling current, light, heat, motor speed or any other type of output that has a voltage factor.

Our Rotavolt autotransformers are the backbone of our EM Voltage Stabilisers, renowned for their unrivalled accuracy and reliability, with tens of thousands of systems in operation around the world.

We offer a range of specifications depending on your needs. Here are some key features to help you choose the best option:


  • 9 frame sizes and ratings up to 60kVA
  • Single and three phase models
  • Ideal for high-speed servo applications
  • Multi ganged units available
  • Output voltage continuously variable from 0-115% of input voltage
  • Motorised versions available for remote or automatic operation