The invention relates to an AC voltage conversion and switching device comprising a main circuit and a switching circuit. The input of the device is connected to the power supply, and the output to the consumer. In the main circuit a controlled transformer (T) is inserted. The essence of the invention lies in that the secondary coil (6) of the transformer (T) is connected in series between the input (8) and the output (10) for decreasing the voltage at the consumer (F) during operation, and the secondary coil (6) of the transformer (T) is bridged by a first controlled switch (12), whereas the primary coil (7) of the transformer (T) is connected in series with a second controlled switch (18), and the serial circuit formed by the primary coil (7) and the second controlled switch (18) is connected parallel with the consumer (F), the switches (12; 18) are in an operational connection with a central control unit (K).