Voltage RegulatorsThoma Type



Regulating transformers type Thoma are used to provide an adjustable output voltage to increase and decrease the input voltage of high voltage test systems, such as resonant test systems or conventional high voltage transformer test systems. They are equipped with a grounded tank and are also available for outdoor installation.

Radiators allow an easy and effective cooling under rough environmental conditions.


  • High feeder power available
  • Can be connected directly to the feeding MV grid (such as 20kV)
  • Low noise output (for PD measurement) at high power
  • Rigid and reliable performance over decades


As the regulating winding rotates inside the transformer and the current is running through copper brushes there is some copper dust in this kind of transformers. Mohaupt regulating transformers type STO are especially designed to minimize this effect. However in order to ensure reliable operation throughout decades, periodic maintenance is recommended, which is provided by Mohaupt High Voltage. As a further measure to ensure reliable operation, the input voltage of the regulator is limited to 10kV maximum. In case of necessity for higher input voltages, the use of a step down transformer (can be build optionally into the same tank) is recommended. This can be provided as a complete set together with the regulating transformer.

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